Breaking changes in .NET Core 3.0

If you're migrating to version 3.0 of .NET Core, ASP.NET Core, or EF Core, the breaking changes listed in this article may affect your app.

ASP.NET Core

Obsolete Antiforgery, CORS, Diagnostics, MVC, and Routing APIs removed

Obsolete members and compatibility switches in ASP.NET Core 2.2 were removed.

Version introduced

3.0

Reason for change

Improvement of API surface over time.

While targeting .NET Core 2.2, follow the guidance in the obsolete build messages to adopt new APIs instead.

Category

ASP.NET Core

Affected APIs

The following types and members were marked as obsolete for ASP.NET Core 2.1 and 2.2:

Types

  • Microsoft.AspNetCore.Diagnostics.Views.WelcomePage
  • Microsoft.AspNetCore.DiagnosticsViewPage.Views.AttributeValue
  • Microsoft.AspNetCore.DiagnosticsViewPage.Views.BaseView
  • Microsoft.AspNetCore.DiagnosticsViewPage.Views.HelperResult
  • Microsoft.AspNetCore.Mvc.Formatters.Xml.ProblemDetails21Wrapper
  • Microsoft.AspNetCore.Mvc.Formatters.Xml.ValidationProblemDetails21Wrapper
  • Microsoft.AspNetCore.Mvc.Razor.Compilation.ViewsFeatureProvider
  • Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.PageArgumentBinder
  • Microsoft.AspNetCore.Routing.IRouteValuesAddressMetadata
  • Microsoft.AspNetCore.Routing.RouteValuesAddressMetadata

Constructors

  • Microsoft.AspNetCore.Cors.Infrastructure.CorsService(IOptions{CorsOptions})
  • Microsoft.AspNetCore.Routing.Tree.TreeRouteBuilder(ILoggerFactory,UrlEncoder,ObjectPool{UriBuildingContext},IInlineConstraintResolver)
  • Microsoft.AspNetCore.Mvc.Formatters.OutputFormatterCanWriteContext
  • Microsoft.AspNetCore.Mvc.ApiExplorer.DefaultApiDescriptionProvider(IOptions{MvcOptions},IInlineConstraintResolver,IModelMetadataProvider)
  • Microsoft.AspNetCore.Mvc.ApiExplorer.DefaultApiDescriptionProvider(IOptions{MvcOptions},IInlineConstraintResolver,IModelMetadataProvider,IActionResultTypeMapper)
  • Microsoft.AspNetCore.Mvc.Formatters.FormatFilter(IOptions{MvcOptions})
  • Microsoft.AspNetCore.Mvc.ModelBinding.Binders.ArrayModelBinder`1(IModelBinder)
  • Microsoft.AspNetCore.Mvc.ModelBinding.Binders.ByteArrayModelBinder
  • Microsoft.AspNetCore.Mvc.ModelBinding.Binders.CollectionModelBinder`1(IModelBinder)
  • Microsoft.AspNetCore.Mvc.ModelBinding.Binders.ComplexTypeModelBinder(IDictionary`2)
  • Microsoft.AspNetCore.Mvc.ModelBinding.Binders.DictionaryModelBinder`2(IModelBinder,IModelBinder)
  • Microsoft.AspNetCore.Mvc.ModelBinding.Binders.DoubleModelBinder(System.Globalization.NumberStyles)
  • Microsoft.AspNetCore.Mvc.ModelBinding.Binders.FloatModelBinder(System.Globalization.NumberStyles)
  • Microsoft.AspNetCore.Mvc.ModelBinding.Binders.FormCollectionModelBinder
  • Microsoft.AspNetCore.Mvc.ModelBinding.Binders.FormFileModelBinder
  • Microsoft.AspNetCore.Mvc.ModelBinding.Binders.HeaderModelBinder
  • Microsoft.AspNetCore.Mvc.ModelBinding.Binders.KeyValuePairModelBinder`2(IModelBinder,IModelBinder)
  • Microsoft.AspNetCore.Mvc.ModelBinding.Binders.SimpleTypeModelBinder(System.Type)
  • Microsoft.AspNetCore.Mvc.ModelBinding.ModelAttributes(IEnumerable{System.Object})
  • Microsoft.AspNetCore.Mvc.ModelBinding.ModelAttributes(IEnumerable{System.Object},IEnumerable{System.Object})
  • Microsoft.AspNetCore.Mvc.ModelBinding.ModelBinderFactory(IModelMetadataProvider,IOptions{MvcOptions})
  • Microsoft.AspNetCore.Mvc.ModelBinding.ParameterBinder(IModelMetadataProvider,IModelBinderFactory,IObjectModelValidator)
  • Microsoft.AspNetCore.Mvc.Routing.KnownRouteValueConstraint()
  • Microsoft.AspNetCore.Mvc.Formatters.XmlDataContractSerializerInputFormatter
  • Microsoft.AspNetCore.Mvc.Formatters.XmlDataContractSerializerInputFormatter(System.Boolean)
  • Microsoft.AspNetCore.Mvc.Formatters.XmlDataContractSerializerInputFormatter(MvcOptions)
  • Microsoft.AspNetCore.Mvc.Formatters.XmlSerializerInputFormatter
  • Microsoft.AspNetCore.Mvc.Formatters.XmlSerializerInputFormatter(System.Boolean)
  • Microsoft.AspNetCore.Mvc.Formatters.XmlSerializerInputFormatter(MvcOptions)
  • Microsoft.AspNetCore.Mvc.TagHelpers.ImageTagHelper(IHostingEnvironment,IMemoryCache,HtmlEncoder,IUrlHelperFactory)
  • Microsoft.AspNetCore.Mvc.TagHelpers.LinkTagHelper(IHostingEnvironment,IMemoryCache,HtmlEncoder,JavaScriptEncoder,IUrlHelperFactory)
  • Microsoft.AspNetCore.Mvc.TagHelpers.ScriptTagHelper(IHostingEnvironment,IMemoryCache,HtmlEncoder,JavaScriptEncoder,IUrlHelperFactory)
  • Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.RazorPageAdapter(RazorPageBase)

Properties

  • Microsoft.AspNetCore.Antiforgery.AntiforgeryOptions.CookieDomain
  • Microsoft.AspNetCore.Antiforgery.AntiforgeryOptions.CookieName
  • Microsoft.AspNetCore.Antiforgery.AntiforgeryOptions.CookiePath
  • Microsoft.AspNetCore.Antiforgery.AntiforgeryOptions.RequireSsl
  • Microsoft.AspNetCore.Mvc.ApiBehaviorOptions.AllowInferringBindingSourceForCollectionTypesAsFromQuery
  • Microsoft.AspNetCore.Mvc.ApiBehaviorOptions.SuppressUseValidationProblemDetailsForInvalidModelStateResponses
  • Microsoft.AspNetCore.Mvc.CookieTempDataProviderOptions.CookieName
  • Microsoft.AspNetCore.Mvc.CookieTempDataProviderOptions.Domain
  • Microsoft.AspNetCore.Mvc.CookieTempDataProviderOptions.Path
  • Microsoft.AspNetCore.Mvc.DataAnnotations.MvcDataAnnotationsLocalizationOptions.AllowDataAnnotationsLocalizationForEnumDisplayAttributes
  • Microsoft.AspNetCore.Mvc.Formatters.Xml.MvcXmlOptions.AllowRfc7807CompliantProblemDetailsFormat
  • Microsoft.AspNetCore.Mvc.MvcOptions.AllowBindingHeaderValuesToNonStringModelTypes
  • Microsoft.AspNetCore.Mvc.MvcOptions.AllowCombiningAuthorizeFilters
  • Microsoft.AspNetCore.Mvc.MvcOptions.AllowShortCircuitingValidationWhenNoValidatorsArePresent
  • Microsoft.AspNetCore.Mvc.MvcOptions.AllowValidatingTopLevelNodes
  • Microsoft.AspNetCore.Mvc.MvcOptions.InputFormatterExceptionPolicy
  • Microsoft.AspNetCore.Mvc.MvcOptions.SuppressBindingUndefinedValueToEnumType
  • Microsoft.AspNetCore.Mvc.MvcViewOptions.AllowRenderingMaxLengthAttribute
  • Microsoft.AspNetCore.Mvc.MvcViewOptions.SuppressTempDataAttributePrefix
  • Microsoft.AspNetCore.Mvc.RazorPages.RazorPagesOptions.AllowAreas
  • Microsoft.AspNetCore.Mvc.RazorPages.RazorPagesOptions.AllowDefaultHandlingForOptionsRequests
  • Microsoft.AspNetCore.Mvc.RazorPages.RazorPagesOptions.AllowMappingHeadRequestsToGetHandler

Methods


"Pubternal" APIs removed

To better maintain the public API surface of ASP.NET Core, most of the types in *.Internal namespaces (referred to as "pubternal" APIs) have become truly internal. Members in these namespaces were never meant to be supported as public-facing APIs. The APIs could break in minor releases and often did. Code that depends on these APIs breaks when updating to ASP.NET Core 3.0.

For more information, see dotnet/aspnetcore#4932 and dotnet/aspnetcore#11312.

Version introduced

3.0

Old behavior

The affected APIs are marked with the public access modifier and exist in *.Internal namespaces.

New behavior

The affected APIs are marked with the internal access modifier and can no longer be used by code outside that assembly.

Reason for change

The guidance for these "pubternal" APIs was that they:

  • Could change without notice.
  • Weren't subject to .NET policies to prevent breaking changes.

Leaving the APIs public (even in the *.Internal namespaces) was confusing to customers.

Stop using these "pubternal" APIs. If you have questions about alternate APIs, open an issue in the dotnet/aspnetcore repository.

For example, consider the following HTTP request buffering code in an ASP.NET Core 2.2 project. The EnableRewind extension method exists in the Microsoft.AspNetCore.Http.Internal namespace.

HttpContext.Request.EnableRewind();

In an ASP.NET Core 3.0 project, replace the EnableRewind call with a call to the EnableBuffering extension method. The request buffering feature works as it did in the past. EnableBuffering calls the now internal API.

HttpContext.Request.EnableBuffering();

Category

ASP.NET Core

Affected APIs

All APIs in the Microsoft.AspNetCore.* and Microsoft.Extensions.* namespaces that have an Internal segment in the namespace name. For example:

  • Microsoft.AspNetCore.Authentication.Internal
  • Microsoft.AspNetCore.Builder.Internal
  • Microsoft.AspNetCore.DataProtection.Cng.Internal
  • Microsoft.AspNetCore.DataProtection.Internal
  • Microsoft.AspNetCore.Hosting.Internal
  • Microsoft.AspNetCore.Http.Internal
  • Microsoft.AspNetCore.Mvc.Core.Infrastructure
  • Microsoft.AspNetCore.Mvc.Core.Internal
  • Microsoft.AspNetCore.Mvc.Cors.Internal
  • Microsoft.AspNetCore.Mvc.DataAnnotations.Internal
  • Microsoft.AspNetCore.Mvc.Formatters.Internal
  • Microsoft.AspNetCore.Mvc.Formatters.Json.Internal
  • Microsoft.AspNetCore.Mvc.Formatters.Xml.Internal
  • Microsoft.AspNetCore.Mvc.Internal
  • Microsoft.AspNetCore.Mvc.ModelBinding.Internal
  • Microsoft.AspNetCore.Mvc.Razor.Internal
  • Microsoft.AspNetCore.Mvc.RazorPages.Internal
  • Microsoft.AspNetCore.Mvc.TagHelpers.Internal
  • Microsoft.AspNetCore.Mvc.ViewFeatures.Internal
  • Microsoft.AspNetCore.Rewrite.Internal
  • Microsoft.AspNetCore.Routing.Internal
  • Microsoft.AspNetCore.Server.Kestrel.Core.Adapter.Internal
  • Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
  • Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Infrastructure
  • Microsoft.AspNetCore.Server.Kestrel.Https.Internal

Authentication: Google+ deprecated and replaced

Google is starting to shut down Google+ Sign-in for apps as early as January 28, 2019.

Change description

ASP.NET 4.x and ASP.NET Core have been using the Google+ Sign-in APIs to authenticate Google account users in web apps. The affected NuGet packages are Microsoft.AspNetCore.Authentication.Google for ASP.NET Core and Microsoft.Owin.Security.Google for Microsoft.Owin with ASP.NET Web Forms and MVC.

Google's replacement APIs use a different data source and format. The mitigations and solutions provided below account for the structural changes. Apps should verify the data itself still satisfies their requirements. For example, names, email addresses, profile links, and profile photos may provide subtly different values than before.

Version introduced

All versions. This change is external to ASP.NET Core.

Owin with ASP.NET Web Forms and MVC

For Microsoft.Owin 3.1.0 and later, a temporary mitigation is outlined here. Apps should complete testing with the mitigation to check for changes in the data format. There are plans to release Microsoft.Owin 4.0.1 with a fix. Apps using any prior version should update to version 4.0.1.

ASP.NET Core 1.x

The mitigation in Owin with ASP.NET Web Forms and MVC can be adapted to ASP.NET Core 1.x. NuGet package patches aren't planned because 1.x has reached end of life status.

ASP.NET Core 2.x

For Microsoft.AspNetCore.Authentication.Google version 2.x, replace your existing call to AddGoogle in Startup.ConfigureServices with the following code:

.AddGoogle(o =>
{
    o.ClientId = Configuration["Authentication:Google:ClientId"];
    o.ClientSecret = Configuration["Authentication:Google:ClientSecret"];
    o.UserInformationEndpoint = "https://www.googleapis.com/oauth2/v2/userinfo";
    o.ClaimActions.Clear();
    o.ClaimActions.MapJsonKey(ClaimTypes.NameIdentifier, "id");
    o.ClaimActions.MapJsonKey(ClaimTypes.Name, "name");
    o.ClaimActions.MapJsonKey(ClaimTypes.GivenName, "given_name");
    o.ClaimActions.MapJsonKey(ClaimTypes.Surname, "family_name");
    o.ClaimActions.MapJsonKey("urn:google:profile", "link");
    o.ClaimActions.MapJsonKey(ClaimTypes.Email, "email");
});

The February 2.1 and 2.2 patches incorporated the preceding reconfiguration as the new default. No patch is planned for ASP.NET Core 2.0 since it has reached end of life.

ASP.NET Core 3.0

The mitigation given for ASP.NET Core 2.x can also be used for ASP.NET Core 3.0. In future 3.0 previews, the Microsoft.AspNetCore.Authentication.Google package may be removed. Users would be directed to Microsoft.AspNetCore.Authentication.OpenIdConnect instead. The following code shows how to replace AddGoogle with AddOpenIdConnect in Startup.ConfigureServices. This replacement can be used with ASP.NET Core 2.0 and later and can be adapted for ASP.NET Core 1.x as needed.

.AddOpenIdConnect("Google", o =>
{
    o.ClientId = Configuration["Authentication:Google:ClientId"];
    o.ClientSecret = Configuration["Authentication:Google:ClientSecret"];
    o.Authority = "https://accounts.google.com";
    o.ResponseType = OpenIdConnectResponseType.Code;
    o.CallbackPath = "/signin-google"; // Or register the default "/sigin-oidc"
    o.Scope.Add("email");
});
JwtSecurityTokenHandler.DefaultInboundClaimTypeMap.Clear();

Category

ASP.NET Core

Affected APIs

Microsoft.AspNetCore.Authentication.Google


Authentication: HttpContext.Authentication property removed

The deprecated Authentication property on HttpContext has been removed.

Change description

As part of dotnet/aspnetcore#6504, the deprecated Authentication property on HttpContext has been removed. The Authentication property has been deprecated since 2.0. A migration guide was published to migrate code using this deprecated property to the new replacement APIs. The remaining unused classes / APIs related to the old ASP.NET Core 1.x authentication stack were removed in commit dotnet/aspnetcore@d7a7c65.

For discussion, see dotnet/aspnetcore#6533.

Version introduced

3.0

Reason for change

ASP.NET Core 1.0 APIs have been replaced by extension methods in Microsoft.AspNetCore.Authentication.AuthenticationHttpContextExtensions.

See the migration guide.

Category

ASP.NET Core

Affected APIs


Authentication: Newtonsoft.Json types replaced

In ASP.NET Core 3.0, Newtonsoft.Json types used in Authentication APIs have been replaced with System.Text.Json types. Except for the following cases, basic usage of the Authentication packages remains unaffected:

  • Classes derived from the OAuth providers, such as those from aspnet-contrib.
  • Advanced claim manipulation implementations.

For more information, see dotnet/aspnetcore#7105. For discussion, see dotnet/aspnetcore#7289.

Version introduced

3.0

For derived OAuth implementations, the most common change is to replace JObject.Parse with JsonDocument.Parse in the CreateTicketAsync override as shown here. JsonDocument implements IDisposable.

The following list outlines known changes:

Category

ASP.NET Core

Affected APIs


Authentication: OAuthHandler ExchangeCodeAsync signature changed

In ASP.NET Core 3.0, the signature of OAuthHandler.ExchangeCodeAsync was changed from:

protected virtual System.Threading.Tasks.Task<Microsoft.AspNetCore.Authentication.OAuth.OAuthTokenResponse> ExchangeCodeAsync(string code, string redirectUri) { throw null; }

To:

protected virtual System.Threading.Tasks.Task<Microsoft.AspNetCore.Authentication.OAuth.OAuthTokenResponse> ExchangeCodeAsync(Microsoft.AspNetCore.Authentication.OAuth.OAuthCodeExchangeContext context) { throw null; }

Version introduced

3.0

Old behavior

The code and redirectUri strings were passed as separate arguments.

New behavior

Code and RedirectUri are properties on OAuthCodeExchangeContext that can be set via the OAuthCodeExchangeContext constructor. The new OAuthCodeExchangeContext type is the only argument passed to OAuthHandler.ExchangeCodeAsync.

Reason for change

This change allows additional parameters to be provided in a non-breaking manner. There's no need to create new ExchangeCodeAsync overloads.

Construct an OAuthCodeExchangeContext with the appropriate code and redirectUri values. An AuthenticationProperties instance must be provided. This single OAuthCodeExchangeContext instance can be passed to OAuthHandler.ExchangeCodeAsync instead of multiple arguments.

Category

ASP.NET Core

Affected APIs

OAuthHandler<TOptions>.ExchangeCodeAsync(String, String)


Authorization: AddAuthorization overload moved to different assembly

The core AddAuthorization methods that used to reside in Microsoft.AspNetCore.Authorization were renamed to AddAuthorizationCore. The old AddAuthorization methods still exist, but are in the Microsoft.AspNetCore.Authorization.Policy assembly instead. Apps using both methods should see no impact. Note that Microsoft.AspNetCore.Authorization.Policy now ships in the shared framework rather than a standalone package as discussed in Shared framework: Assemblies removed from Microsoft.AspNetCore.App.

Version introduced

3.0

Old behavior

AddAuthorization methods existed in Microsoft.AspNetCore.Authorization.

New behavior

AddAuthorization methods exist in Microsoft.AspNetCore.Authorization.Policy. AddAuthorizationCore is the new name for the old methods.

Reason for change

AddAuthorization is a better method name for adding all common services needed for authorization.

Either add a reference to Microsoft.AspNetCore.Authorization.Policy or use AddAuthorizationCore instead.

Category

ASP.NET Core

Affected APIs

Microsoft.Extensions.DependencyInjection.AuthorizationServiceCollectionExtensions.AddAuthorization(IServiceCollection, Action<AuthorizationOptions>)


Authorization: IAllowAnonymous removed from AuthorizationFilterContext.Filters

As of ASP.NET Core 3.0, MVC doesn't add AllowAnonymousFilters for [AllowAnonymous] attributes that were discovered on controllers and action methods. This change is addressed locally for derivatives of AuthorizeAttribute, but it's a breaking change for IAsyncAuthorizationFilter and IAuthorizationFilter implementations. Such implementations wrapped in a [TypeFilter] attribute are a popular and supported way to achieve strongly-typed, attribute-based authorization when both configuration and dependency injection are required.

Version introduced

3.0

Old behavior

IAllowAnonymous appeared in the AuthorizationFilterContext.Filters collection. Testing for the interface's presence was a valid approach to override or disable the filter on individual controller methods.

New behavior

IAllowAnonymous no longer appears in the AuthorizationFilterContext.Filters collection. IAsyncAuthorizationFilter implementations that are dependent on the old behavior typically cause intermittent HTTP 401 Unauthorized or HTTP 403 Forbidden responses.

Reason for change

A new endpoint routing strategy was introduced in ASP.NET Core 3.0.

Search the endpoint metadata for IAllowAnonymous. For example:

var endpoint = context.HttpContext.GetEndpoint();
if (endpoint?.Metadata?.GetMetadata<IAllowAnonymous>() != null)
{
}

An example of this technique is seen in this HasAllowAnonymous method.

Category

ASP.NET Core

Affected APIs

None


Authorization: IAuthorizationPolicyProvider implementations require new method

In ASP.NET Core 3.0, a new GetFallbackPolicyAsync method was added to IAuthorizationPolicyProvider. This fallback policy is used by the authorization middleware when no policy is specified.

For more information, see dotnet/aspnetcore#9759.

Version introduced

3.0

Old behavior

Implementations of IAuthorizationPolicyProvider didn't require a GetFallbackPolicyAsync method.

New behavior

Implementations of IAuthorizationPolicyProvider require a GetFallbackPolicyAsync method.

Reason for change

A new method was needed for the new AuthorizationMiddleware to use when no policy is specified.

Add the GetFallbackPolicyAsync method to your implementations of IAuthorizationPolicyProvider.

Category

ASP.NET Core

Affected APIs

Microsoft.AspNetCore.Authorization.IAuthorizationPolicyProvider


Caching: CompactOnMemoryPressure property removed

The ASP.NET Core 3.0 release removed the obsolete MemoryCacheOptions APIs.

Change description

This change is a follow-up to aspnet/Caching#221. For discussion, see dotnet/extensions#1062.

Version introduced

3.0

Old behavior

MemoryCacheOptions.CompactOnMemoryPressure property was available.

New behavior

The MemoryCacheOptions.CompactOnMemoryPressure property has been removed.

Reason for change

Automatically compacting the cache caused problems. To avoid unexpected behavior, the cache should only be compacted when needed.

To compact the cache, downcast to MemoryCache and call Compact when needed.

Category

ASP.NET Core

Affected APIs

MemoryCacheOptions.CompactOnMemoryPressure


Caching: Microsoft.Extensions.Caching.SqlServer uses new SqlClient package

The Microsoft.Extensions.Caching.SqlServer package will use the new Microsoft.Data.SqlClient package instead of System.Data.SqlClient package. This change could cause slight behavioral breaking changes. For more information, see Introducing the new Microsoft.Data.SqlClient.

Version introduced

3.0

Old behavior

The Microsoft.Extensions.Caching.SqlServer package used the System.Data.SqlClient package.

New behavior

Microsoft.Extensions.Caching.SqlServer is now using the Microsoft.Data.SqlClient package.

Reason for change

Microsoft.Data.SqlClient is a new package that is built off of System.Data.SqlClient. It's where all new feature work will be done from now on.

Customers shouldn't need to worry about this breaking change unless they were using types returned by the Microsoft.Extensions.Caching.SqlServer package and casting them to System.Data.SqlClient types. For example, if someone was casting a DbConnection to the old SqlConnection type, they would need to change the cast to the new Microsoft.Data.SqlClient.SqlConnection type.

Category

ASP.NET Core

Affected APIs

None


Caching: ResponseCaching "pubternal" types changed to internal

In ASP.NET Core 3.0, "pubternal" types in ResponseCaching have been changed to internal.

In addition, default implementations of IResponseCachingPolicyProvider and IResponseCachingKeyProvider are no longer added to services as part of the AddResponseCaching method.

Change description

In ASP.NET Core, "pubternal" types are declared as public but reside in a namespace suffixed with .Internal. While these types are public, they have no support policy and are subject to breaking changes. Unfortunately, accidental use of these types has been common, resulting in breaking changes to these projects and limiting the ability to maintain the framework.

Version introduced

3.0

Old behavior

These types were publicly visible, but unsupported.

New behavior

These types are now internal.

Reason for change

The internal scope better reflects the unsupported policy.

Copy types that are used by your app or library.

Category

ASP.NET Core

Affected APIs


Data Protection: DataProtection.Blobs uses new Azure Storage APIs

Azure.Extensions.AspNetCore.DataProtection.Blobs depends on the Azure Storage libraries. These libraries renamed their assemblies, packages, and namespaces. Starting in ASP.NET Core 3.0, Azure.Extensions.AspNetCore.DataProtection.Blobs uses the new Azure.Storage.-prefixed APIs and packages.

For questions about the Azure Storage APIs, use https://github.com/Azure/azure-storage-net. For discussion on this issue, see dotnet/aspnetcore#19570.

Version introduced

3.0

Old behavior

The package referenced the WindowsAzure.Storage NuGet package. The package references the Microsoft.Azure.Storage.Blob NuGet package.

New behavior

The package references the Azure.Storage.Blob NuGet package.

Reason for change

This change allows Azure.Extensions.AspNetCore.DataProtection.Blobs to migrate to the recommended Azure Storage packages.

If you still need to use the older Azure Storage APIs with ASP.NET Core 3.0, add a direct dependency to the package WindowsAzure.Storage or Microsoft.Azure.Storage. This package can be installed alongside the new Azure.Storage APIs.

In many cases, the upgrade only involves changing the using statements to use the new namespaces:

- using Microsoft.WindowsAzure.Storage;
- using Microsoft.WindowsAzure.Storage.Blob;
- using Microsoft.Azure.Storage;
- using Microsoft.Azure.Storage.Blob;
+ using Azure.Storage;
+ using Azure.Storage.Blobs;

Category

ASP.NET Core

Affected APIs

None


Hosting: AspNetCoreModule V1 removed from Windows Hosting Bundle

Starting with ASP.NET Core 3.0, the Windows Hosting Bundle won't contain AspNetCoreModule (ANCM) V1.

ANCM V2 is backwards compatible with ANCM OutOfProcess and is recommended for use with ASP.NET Core 3.0 apps.

For discussion, see dotnet/aspnetcore#7095.

Version introduced

3.0

Old behavior

ANCM V1 is included in the Windows Hosting Bundle.

New behavior

ANCM V1 isn't included in the Windows Hosting Bundle.

Reason for change

ANCM V2 is backwards compatible with ANCM OutOfProcess and is recommended for use with ASP.NET Core 3.0 apps.

Use ANCM V2 with ASP.NET Core 3.0 apps.

If ANCM V1 is required, it can be installed using the ASP.NET Core 2.1 or 2.2 Windows Hosting Bundle.

This change will break ASP.NET Core 3.0 apps that:

  • Explicitly opted into using ANCM V1 with <AspNetCoreModuleName>AspNetCoreModule</AspNetCoreModuleName>.
  • Have a custom web.config file with <add name="aspNetCore" path="*" verb="*" modules="AspNetCoreModule" resourceType="Unspecified" />.

Category

ASP.NET Core

Affected APIs

None


Hosting: Generic host restricts Startup constructor injection

The only types the generic host supports for Startup class constructor injection are IHostEnvironment, IWebHostEnvironment, and IConfiguration. Apps using WebHost are unaffected.

Change description

Prior to ASP.NET Core 3.0, constructor injection could be used for arbitrary types in the Startup class's constructor. In ASP.NET Core 3.0, the web stack was replatformed onto the generic host library. You can see the change in the Program.cs file of the templates:

ASP.NET Core 2.x:

https://github.com/dotnet/aspnetcore/blob/5cb615fcbe8559e49042e93394008077e30454c0/src/Templating/src/Microsoft.DotNet.Web.ProjectTemplates/content/EmptyWeb-CSharp/Program.cs#L20-L22

ASP.NET Core 3.0:

https://github.com/dotnet/aspnetcore/blob/b1ca2c1155da3920f0df5108b9fedbe82efaa11c/src/ProjectTemplates/Web.ProjectTemplates/content/EmptyWeb-CSharp/Program.cs#L19-L24

Host uses one dependency injection (DI) container to build the app. WebHost uses two containers: one for the host and one for the app. As a result, the Startup constructor no longer supports custom service injection. Only IHostEnvironment, IWebHostEnvironment, and IConfiguration can be injected. This change prevents DI issues such as the duplicate creation of a singleton service.

Version introduced

3.0

Reason for change

This change is a consequence of replatforming the web stack onto the generic host library.

Inject services into the Startup.Configure method signature. For example:

public void Configure(IApplicationBuilder app, IOptions<MyOptions> options)

Category

ASP.NET Core

Affected APIs

None


Hosting: HTTPS redirection enabled for IIS out-of-process apps

Version 13.0.19218.0 of the ASP.NET Core Module (ANCM) for hosting via IIS out-of-process enables an existing HTTPS redirection feature for ASP.NET Core 3.0 and 2.2 apps.

For discussion, see dotnet/AspNetCore#15243.

Version introduced

3.0

Old behavior

The ASP.NET Core 2.1 project template first introduced support for HTTPS middleware methods like UseHttpsRedirection and UseHsts. Enabling HTTPS redirection required the addition of configuration, since apps in development don't use the default port of 443. HTTP Strict Transport Security (HSTS) is active only if the request is already using HTTPS. Localhost is skipped by default.

New behavior

In ASP.NET Core 3.0, the IIS HTTPS scenario was enhanced. With the enhancement, an app could discover the server's HTTPS ports and make UseHttpsRedirection work by default. The in-process component accomplished port discovery with the IServerAddresses feature, which only affects ASP.NET Core 3.0 apps because the in-process library is versioned with the framework. The out-of-process component changed to automatically add the ASPNETCORE_HTTPS_PORT environment variable. This change affected both ASP.NET Core 2.2 and 3.0 apps because the out-of-process component is shared globally. ASP.NET Core 2.1 apps aren't affected because they use a prior version of ANCM by default.

The preceding behavior was modified in ASP.NET Core 3.0.1 and 3.1.0 Preview 3 to reverse the behavior changes in ASP.NET Core 2.x. These changes only affect IIS out-of-process apps.

As detailed above, installing ASP.NET Core 3.0.0 had the side effect of also activating the UseHttpsRedirection middleware in ASP.NET Core 2.x apps. A change was made to ANCM in ASP.NET Core 3.0.1 and 3.1.0 Preview 3 such that installing them no longer has this effect on ASP.NET Core 2.x apps. The ASPNETCORE_HTTPS_PORT environment variable that ANCM populated in ASP.NET Core 3.0.0 was changed to ASPNETCORE_ANCM_HTTPS_PORT in ASP.NET Core 3.0.1 and 3.1.0 Preview 3. UseHttpsRedirection was also updated in these releases to understand both the new and old variables. ASP.NET Core 2.x won't be updated. As a result, it reverts to the previous behavior of being disabled by default.

Reason for change

Improved ASP.NET Core 3.0 functionality.

No action is required if you want all clients to use HTTPS. To allow some clients to use HTTP, take one of the following steps:

  • Remove the calls to UseHttpsRedirection and UseHsts from your project's Startup.Configure method, and redeploy the app.

  • In your web.config file, set the ASPNETCORE_HTTPS_PORT environment variable to an empty string. This change can occur directly on the server without redeploying the app. For example:

    <aspNetCore processPath="dotnet" arguments=".\WebApplication3.dll" stdoutLogEnabled="false" stdoutLogFile="\\?\%home%\LogFiles\stdout" >
        <environmentVariables>
        <environmentVariable name="ASPNETCORE_HTTPS_PORT" value="" />
        </environmentVariables>
    </aspNetCore>
    

UseHttpsRedirection can still be:

  • Activated manually in ASP.NET Core 2.x by setting the ASPNETCORE_HTTPS_PORT environment variable to the appropriate port number (443 in most production scenarios).
  • Deactivated in ASP.NET Core 3.x by defining ASPNETCORE_ANCM_HTTPS_PORT with an empty string value. This value is set in the same fashion as the preceding ASPNETCORE_HTTPS_PORT example.

Machines running ASP.NET Core 3.0.0 apps should install the ASP.NET Core 3.0.1 runtime before installing the ASP.NET Core 3.1.0 Preview 3 ANCM. Doing so ensures that UseHttpsRedirection continues to operate as expected for the ASP.NET Core 3.0 apps.

In Azure App Service, ANCM deploys on a separate schedule from the runtime because of its global nature. ANCM was deployed to Azure with these changes after ASP.NET Core 3.0.1 and 3.1.0 were deployed.

Category

ASP.NET Core

Affected APIs

HttpsPolicyBuilderExtensions.UseHttpsRedirection(IApplicationBuilder)


Hosting: IHostingEnvironment and IApplicationLifetime types marked obsolete and replaced

New types have been introduced to replace existing IHostingEnvironment and IApplicationLifetime types.

Version introduced

3.0

Old behavior

There were two different IHostingEnvironment and IApplicationLifetime types from Microsoft.Extensions.Hosting and Microsoft.AspNetCore.Hosting.

New behavior

The old types have been marked as obsolete and replaced with new types.

Reason for change

When Microsoft.Extensions.Hosting was introduced in ASP.NET Core 2.1, some types like IHostingEnvironment and IApplicationLifetime were copied from Microsoft.AspNetCore.Hosting. Some ASP.NET Core 3.0 changes cause apps to include both the Microsoft.Extensions.Hosting and Microsoft.AspNetCore.Hosting namespaces. Any use of those duplicate types causes an "ambiguous reference" compiler error when both namespaces are referenced.

Replaced any usages of the old types with the newly introduced types as below:

Obsolete types (warning):

New types:

The new IHostEnvironment IsDevelopment and IsProduction extension methods are in the Microsoft.Extensions.Hosting namespace. That namespace may need to be added to your project.

Category

ASP.NET Core

Affected APIs


Hosting: ObjectPoolProvider removed from WebHostBuilder dependencies

As part of making ASP.NET Core more pay for play, the ObjectPoolProvider was removed from the main set of dependencies. Specific components relying on ObjectPoolProvider now add it themselves.

For discussion, see dotnet/aspnetcore#5944.

Version introduced

3.0

Old behavior

WebHostBuilder provides ObjectPoolProvider by default in the DI container.

New behavior

WebHostBuilder no longer provides ObjectPoolProvider by default in the DI container.

Reason for change

This change was made to make ASP.NET Core more pay for play.

If your component requires ObjectPoolProvider, it needs to be added to your dependencies via the IServiceCollection.

Category

ASP.NET Core

Affected APIs

None


HTTP: DefaultHttpContext extensibility removed

As part of ASP.NET Core 3.0 performance improvements, the extensibility of DefaultHttpContext was removed. The class is now sealed. For more information, see dotnet/aspnetcore#6504.

If your unit tests use Mock<DefaultHttpContext>, use Mock<HttpContext> or new DefaultHttpContext() instead.

For discussion, see dotnet/aspnetcore#6534.

Version introduced

3.0

Old behavior

Classes can derive from DefaultHttpContext.

New behavior

Classes can't derive from DefaultHttpContext.

Reason for change

The extensibility was provided initially to allow pooling of the HttpContext, but it introduced unnecessary complexity and impeded other optimizations.

If you're using Mock<DefaultHttpContext> in your unit tests, begin using Mock<HttpContext> instead.

Category

ASP.NET Core

Affected APIs

Microsoft.AspNetCore.Http.DefaultHttpContext


HTTP: HeaderNames constants changed to static readonly

Starting in ASP.NET Core 3.0 Preview 5, the fields in Microsoft.Net.Http.Headers.HeaderNames changed from const to static readonly.

For discussion, see dotnet/aspnetcore#9514.

Version introduced

3.0

Old behavior

These fields used to be const.

New behavior

These fields are now static readonly.

Reason for change

The change:

  • Prevents the values from being embedded across assembly boundaries, allowing for value corrections as needed.
  • Enables faster reference equality checks.

Recompile against 3.0. Source code using these fields in the following ways can no longer do so:

  • As an attribute argument
  • As a case in a switch statement
  • When defining another const

To work around the breaking change, switch to using self-defined header name constants or string literals.

Category

ASP.NET Core

Affected APIs

Microsoft.Net.Http.Headers.HeaderNames


HTTP: Response body infrastructure changes

The infrastructure backing an HTTP response body has changed. If you're using HttpResponse directly, you shouldn't need to make any code changes. Read further if you're wrapping or replacing HttpResponse.Body or accessing HttpContext.Features.

Version introduced

3.0

Old behavior

There were three APIs associated with the HTTP response body:

  • IHttpResponseFeature.Body
  • IHttpSendFileFeature.SendFileAsync
  • IHttpBufferingFeature.DisableResponseBuffering

New behavior

If you replace HttpResponse.Body, it replaces the entire IHttpResponseBodyFeature with a wrapper around your given stream using StreamResponseBodyFeature to provide default implementations for all of the expected APIs. Setting back the original stream reverts this change.

Reason for change

The motivation is to combine the response body APIs into a single new feature interface.

Use IHttpResponseBodyFeature where you previously were using IHttpResponseFeature.Body, IHttpSendFileFeature, or IHttpBufferingFeature.

Category

ASP.NET Core

Affected APIs


SameSite is an option for cookies that can help mitigate some Cross-Site Request Forgery (CSRF) attacks. When this option was initially introduced, inconsistent defaults were used across various ASP.NET Core APIs. The inconsistency has led to confusing results. As of ASP.NET Core 3.0, these defaults are better aligned. You must opt in to this feature on a per-component basis.

Version introduced

3.0

Old behavior

Similar ASP.NET Core APIs used different default SameSiteMode values. An example of the inconsistency is seen in HttpResponse.Cookies.Append(String, String) and HttpResponse.Cookies.Append(String, String, CookieOptions), which defaulted to SameSiteMode.None and SameSiteMode.Lax, respectively.

New behavior

All the affected APIs default to SameSiteMode.None.

Reason for change

The default value was changed to make SameSite an opt-in feature.

Each component that emits cookies needs to decide if SameSite is appropriate for its scenarios. Review your usage of the affected APIs and reconfigure SameSite as needed.

Category

ASP.NET Core

Affected APIs


HTTP: Synchronous IO disabled in all servers

Starting with ASP.NET Core 3.0, synchronous server operations are disabled by default.

Change description

AllowSynchronousIO is an option in each server that enables or disables synchronous IO APIs like HttpRequest.Body.Read, HttpResponse.Body.Write, and Stream.Flush. These APIs have long been a source of thread starvation and app hangs. Starting in ASP.NET Core 3.0 Preview 3, these synchronous operations are disabled by default.

Affected servers:

  • Kestrel
  • HttpSys
  • IIS in-process
  • TestServer

Expect errors similar to:

  • Synchronous operations are disallowed. Call ReadAsync or set AllowSynchronousIO to true instead.
  • Synchronous operations are disallowed. Call WriteAsync or set AllowSynchronousIO to true instead.
  • Synchronous operations are disallowed. Call FlushAsync or set AllowSynchronousIO to true instead.

Each server has an AllowSynchronousIO option that controls this behavior and the default for all of them is now false.

The behavior can also be overridden on a per-request basis as a temporary mitigation. For example:

var syncIOFeature = HttpContext.Features.Get<IHttpBodyControlFeature>();
if (syncIOFeature != null)
{
    syncIOFeature.AllowSynchronousIO = true;
}

If you have trouble with a TextWriter or another stream calling a synchronous API in Dispose, call the new DisposeAsync API instead.

For discussion, see dotnet/aspnetcore#7644.

Version introduced

3.0

Old behavior

HttpRequest.Body.Read, HttpResponse.Body.Write, and Stream.Flush were allowed by default.

New behavior

These synchronous APIs are disallowed by default:

Expect errors similar to:

  • Synchronous operations are disallowed. Call ReadAsync or set AllowSynchronousIO to true instead.
  • Synchronous operations are disallowed. Call WriteAsync or set AllowSynchronousIO to true instead.
  • Synchronous operations are disallowed. Call FlushAsync or set AllowSynchronousIO to true instead.

Reason for change

These synchronous APIs have long been a source of thread starvation and app hangs. Starting in ASP.NET Core 3.0 Preview 3, the synchronous operations are disabled by default.

Use the asynchronous versions of the methods. The behavior can also be overridden on a per-request basis as a temporary mitigation.

var syncIOFeature = HttpContext.Features.Get<IHttpBodyControlFeature>();
if (syncIOFeature != null)
{
    syncIOFeature.AllowSynchronousIO = true;
}

Category

ASP.NET Core

Affected APIs


Identity: AddDefaultUI method overload removed

Starting with ASP.NET Core 3.0, the IdentityBuilderUIExtensions.AddDefaultUI(IdentityBuilder,UIFramework) method overload no longer exists.

Version introduced

3.0

Reason for change

This change was a result of adoption of the static web assets feature.

Call IdentityBuilderUIExtensions.AddDefaultUI(IdentityBuilder) instead of the overload that takes two arguments. If you're using Bootstrap 3, also add the following line to a <PropertyGroup> element in your project file:

<IdentityUIFrameworkVersion>Bootstrap3</IdentityUIFrameworkVersion>

Category

ASP.NET Core

Affected APIs

IdentityBuilderUIExtensions.AddDefaultUI(IdentityBuilder,UIFramework)


Identity: Default Bootstrap version of UI changed

Starting in ASP.NET Core 3.0, Identity UI defaults to using version 4 of Bootstrap.

Version introduced

3.0

Old behavior

The services.AddDefaultIdentity<IdentityUser>().AddDefaultUI(); method call was the same as services.AddDefaultIdentity<IdentityUser>().AddDefaultUI(UIFramework.Bootstrap3);

New behavior

The services.AddDefaultIdentity<IdentityUser>().AddDefaultUI(); method call is the same as services.AddDefaultIdentity<IdentityUser>().AddDefaultUI(UIFramework.Bootstrap4);

Reason for change

Bootstrap 4 was released during ASP.NET Core 3.0 timeframe.

You're impacted by this change if you use the default Identity UI and have added it in Startup.ConfigureServices as shown in the following example:

services.AddDefaultIdentity<IdentityUser>().AddDefaultUI();

Take one of the following actions:

  • Migrate your app to use Bootstrap 4 using their migration guide.

  • Update Startup.ConfigureServices to enforce usage of Bootstrap 3. For example:

    services.AddDefaultIdentity<IdentityUser>().AddDefaultUI(UIFramework.Bootstrap3);
    

Category

ASP.NET Core

Affected APIs

None


Identity: SignInAsync throws exception for unauthenticated identity

By default, SignInAsync throws an exception for principals / identities in which IsAuthenticated is false.

Version introduced

3.0

Old behavior

SignInAsync accepts any principals / identities, including identities in which IsAuthenticated is false.

New behavior

By default, SignInAsync throws an exception for principals / identities in which IsAuthenticated is false. There's a new flag to suppress this behavior, but the default behavior has changed.

Reason for change

The old behavior was problematic because, by default, these principals were rejected by [Authorize] / RequireAuthenticatedUser().

In ASP.NET Core 3.0 Preview 6, there's a RequireAuthenticatedSignIn flag on AuthenticationOptions that is true by default. Set this flag to false to restore the old behavior.

Category

ASP.NET Core

Affected APIs

None


Identity: SignInManager constructor accepts new parameter

Starting with ASP.NET Core 3.0, a new IUserConfirmation<TUser> parameter was added to the SignInManager constructor. For more information, see dotnet/aspnetcore#8356.

Version introduced

3.0

Reason for change

The motivation for the change was to add support for new email / confirmation flows in Identity.

If manually constructing a SignInManager, provide an implementation of IUserConfirmation or grab one from dependency injection to provide.

Category

ASP.NET Core

Affected APIs

SignInManager<TUser>


Identity: UI uses static web assets feature

ASP.NET Core 3.0 introduced a static web assets feature, and Identity UI has adopted it.

Change description

As a result of Identity UI adopting the static web assets feature:

  • Framework selection is accomplished by using the IdentityUIFrameworkVersion property in your project file.
  • Bootstrap 4 is the default UI framework for Identity UI. Bootstrap 3 has reached end of life, and you should consider migrating to a supported version.

Version introduced

3.0

Old behavior

The default UI framework for Identity UI was Bootstrap 3. The UI framework could be configured using a parameter to the AddDefaultUI method call in Startup.ConfigureServices.

New behavior

The default UI framework for Identity UI is Bootstrap 4. The UI framework must be configured in your project file, instead of in the AddDefaultUI method call.

Reason for change

Adoption of the static web assets feature required that the UI framework configuration move to MSBuild. The decision on which framework to embed is a build-time decision, not a runtime decision.

Review your site UI to ensure the new Bootstrap 4 components are compatible. If necessary, use the IdentityUIFrameworkVersion MSBuild property to revert to Bootstrap 3. Add the property to a <PropertyGroup> element in your project file:

<IdentityUIFrameworkVersion>Bootstrap3</IdentityUIFrameworkVersion>

Category

ASP.NET Core

Affected APIs

IdentityBuilderUIExtensions.AddDefaultUI(IdentityBuilder, UIFramework)


Kestrel: Connection adapters removed

As part of the move to move "pubternal" APIs to public, the concept of an IConnectionAdapter was removed from Kestrel. Connection adapters are being replaced with connection middleware (similar to HTTP middleware in the ASP.NET Core pipeline, but for lower-level connections). HTTPS and connection logging have moved from connection adapters to connection middleware. Those extension methods should continue to work seamlessly, but the implementation details have changed.

For more information, see dotnet/aspnetcore#11412. For discussion, see dotnet/aspnetcore#11475.

Version introduced

3.0

Old behavior

Kestrel extensibility components were created using IConnectionAdapter.

New behavior

Kestrel extensibility components are created as middleware.

Reason for change

This change is intended to provide a more flexible extensibility architecture.

Convert any implementations of IConnectionAdapter to use the new middleware pattern as shown here.

Category

ASP.NET Core

Affected APIs

Microsoft.AspNetCore.Server.Kestrel.Core.Adapter.Internal.IConnectionAdapter


Kestrel: Empty HTTPS assembly removed

The assembly Microsoft.AspNetCore.Server.Kestrel.Https has been removed.

Version introduced

3.0

Reason for change

In ASP.NET Core 2.1, the contents of Microsoft.AspNetCore.Server.Kestrel.Https were moved to Microsoft.AspNetCore.Server.Kestrel.Core. This change was done in a non-breaking way using [TypeForwardedTo] attributes.

  • Libraries referencing Microsoft.AspNetCore.Server.Kestrel.Https 2.0 should update all ASP.NET Core dependencies to 2.1 or later. Otherwise, they may break when loaded into an ASP.NET Core 3.0 app.
  • Apps and libraries targeting ASP.NET Core 2.1 and later should remove any direct references to the Microsoft.AspNetCore.Server.Kestrel.Https NuGet package.

Category

ASP.NET Core

Affected APIs

None


Kestrel: Request trailer headers moved to new collection

In prior versions, Kestrel added HTTP/1.1 chunked trailer headers into the request headers collection when the request body was read to the end. This behavior caused concerns about ambiguity between headers and trailers. The decision was made to move the trailers to a new collection.

HTTP/2 request trailers were unavailable in ASP.NET Core 2.2 but are now also available in this new collection in ASP.NET Core 3.0.

New request extension methods have been added to access these trailers.

HTTP/1.1 trailers are available once the entire request body has been read.

HTTP/2 trailers are available once they're received from the client. The client won't send the trailers until the entire request body has been at least buffered by the server. You may need to read the request body to free up buffer space. Trailers are always available if you read the request body to the end. The trailers mark the end of the body.

Version introduced

3.0

Old behavior

Request trailer headers would be added to the HttpRequest.Headers collection.

New behavior

Request trailer headers aren't present in the HttpRequest.Headers collection. Use the following extension methods on HttpRequest to access them:

  • GetDeclaredTrailers() - Gets the request "Trailer" header that lists which trailers to expect after the body.
  • SupportsTrailers() - Indicates if the request supports receiving trailer headers.
  • CheckTrailersAvailable() - Determines if the request supports trailers and if they're available for reading.
  • GetTrailer(string trailerName) - Gets the requested trailing header from the response.

Reason for change

Trailers are a key feature in scenarios like gRPC. Merging the trailers in to request headers was confusing to users.

Use the trailer-related extension methods on HttpRequest to access trailers.

Category

ASP.NET Core

Affected APIs

HttpRequest.Headers


Kestrel: Transport abstractions removed and made public

As part of moving away from "pubternal" APIs, the Kestrel transport layer APIs are exposed as a public interface in the Microsoft.AspNetCore.Connections.Abstractions library.

Version introduced

3.0

Old behavior

  • Transport-related abstractions were available in the Microsoft.AspNetCore.Server.Kestrel.Transport.Abstractions library.
  • The ListenOptions.NoDelay property was available.

New behavior

  • The IConnectionListener interface was introduced in the Microsoft.AspNetCore.Connections.Abstractions library to expose the most used functionality from the ...Transport.Abstractions library.
  • The NoDelay is now available in transport options (LibuvTransportOptions and SocketTransportOptions).
  • SchedulingMode is no longer available.

Reason for change

ASP.NET Core 3.0 has moved away from "pubternal" APIs.

Category

ASP.NET Core

Affected APIs

None


Localization: ResourceManagerWithCultureStringLocalizer and WithCulture marked obsolete

The ResourceManagerWithCultureStringLocalizer class and WithCulture interface member are often sources of confusion for users of localization, especially when creating their own IStringLocalizer implementation. These items give the user the impression that an IStringLocalizer instance is "per-language, per-resource". In reality, the instances should only be "per-resource". The language searched for is determined by the CultureInfo.CurrentUICulture at execution time. To eliminate the source of confusion, the APIs were marked as obsolete in ASP.NET Core 3.0 Preview 3. The APIs will be removed in a future release.

For context, see dotnet/aspnetcore#3324. For discussion, see dotnet/aspnetcore#7756.

Version introduced

3.0

Old behavior

Methods weren't marked as Obsolete.

New behavior

Methods are marked Obsolete.

Reason for change

The APIs represented a use case that isn't recommended. There was confusion about the design of localization.

The recommendation is to use ResourceManagerStringLocalizer instead. Let the culture be set by the CurrentCulture. If that isn't an option, create and use a copy of ResourceManagerWithCultureStringLocalizer.

Category

ASP.NET Core

Affected APIs


Logging: DebugLogger class made internal

Prior to ASP.NET Core 3.0, DebugLogger's access modifier was public. In ASP.NET Core 3.0, the access modifier changed to internal.

Version introduced

3.0

Reason for change

The change is being made to:

  • Enforce consistency with other logger implementations such as ConsoleLogger.
  • Reduce the API surface.

Use the AddDebug ILoggingBuilder extension method to enable debug logging. DebugLoggerProvider is also still public in the event the service needs to be registered manually.

Category

ASP.NET Core

Affected APIs

Microsoft.Extensions.Logging.Debug.DebugLogger


MVC: Async suffix trimmed from controller action names

As part of addressing dotnet/aspnetcore#4849, ASP.NET Core MVC trims the suffix Async from action names by default. Starting with ASP.NET Core 3.0, this change affects both routing and link generation.

Version introduced

3.0

Old behavior

Consider the following ASP.NET Core MVC controller:

public class ProductController : Controller
{
    public async IActionResult ListAsync()
    {
        var model = await DbContext.Products.ToListAsync();
        return View(model);
    }
}

The action is routable via Product/ListAsync. Link generation requires specifying the Async suffix. For example:

<a asp-controller="Product" asp-action="ListAsync">List</a>

New behavior

In ASP.NET Core 3.0, the action is routable via Product/List. Link generation code should omit the Async suffix. For example:

<a asp-controller="Product" asp-action="List">List</a>

This change doesn't affect names specified using the [ActionName] attribute. The new behavior can be disabled by setting MvcOptions.SuppressAsyncSuffixInActionNames to false in Startup.ConfigureServices:

services.AddMvc(options =>
{
   options.SuppressAsyncSuffixInActionNames = false;
});

Reason for change

By convention, asynchronous .NET methods are suffixed with Async. However, when a method defines an MVC action, it's undesirable to use the Async suffix.

If your app depends on MVC actions preserving the name's Async suffix, choose one of the following mitigations:

  • Use the [ActionName] attribute to preserve the original name.
  • Disable the renaming entirely by setting MvcOptions.SuppressAsyncSuffixInActionNames to false in Startup.ConfigureServices:
services.AddMvc(options =>
{
   options.SuppressAsyncSuffixInActionNames = false;
});

Category

ASP.NET Core

Affected APIs

None


MVC: JsonResult moved to Microsoft.AspNetCore.Mvc.Core

JsonResult has moved to the Microsoft.AspNetCore.Mvc.Core assembly. This type used to be defined in Microsoft.AspNetCore.Mvc.Formatters.Json. An assembly-level [TypeForwardedTo] attribute was added to Microsoft.AspNetCore.Mvc.Formatters.Json to address this issue for the majority of users. Apps that use third-party libraries may encounter issues.

Version introduced

3.0 Preview 6

Old behavior

An app using a 2.2-based library builds successfully.

New behavior

An app using a 2.2-based library fails compilation. An error containing a variation of the following text is provided:

The type 'JsonResult' exists in both 'Microsoft.AspNetCore.Mvc.Core, Version=3.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60' and 'Microsoft.AspNetCore.Mvc.Formatters.Json, Version=2.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60'

For an example of such an issue, see dotnet/aspnetcore#7220.

Reason for change

Platform-level changes to the composition of ASP.NET Core as described at aspnet/Announcements#325.

Libraries compiled against the 2.2 version of Microsoft.AspNetCore.Mvc.Formatters.Json may need to recompile to address the problem for all consumers. If affected, contact the library author. Request recompilation of the library to target ASP.NET Core 3.0.

Category

ASP.NET Core

Affected APIs

Microsoft.AspNetCore.Mvc.JsonResult


MVC: Precompilation tool deprecated

In ASP.NET Core 1.1, the Microsoft.AspNetCore.Mvc.Razor.ViewCompilation (MVC precompilation tool) package was introduced to add support for publish-time compilation of Razor files (.cshtml files). In ASP.NET Core 2.1, the Razor SDK was introduced to expand upon features of the precompilation tool. The Razor SDK added support for build- and publish-time compilation of Razor files. The SDK verifies the correctness of .cshtml files at build time while improving on app startup time. The Razor SDK is on by default, and no gesture is required to start using it.

In ASP.NET Core 3.0, the ASP.NET Core 1.1-era MVC precompilation tool was removed. Earlier package versions will continue receiving important bug and security fixes in the patch release.

Version introduced

3.0

Old behavior

The Microsoft.AspNetCore.Mvc.Razor.ViewCompilation package was used to pre-compile MVC Razor views.

New behavior

The Razor SDK natively supports this functionality. The Microsoft.AspNetCore.Mvc.Razor.ViewCompilation package is no longer updated.

Reason for change

The Razor SDK provides more functionality and verifies the correctness of .cshtml files at build time. The SDK also improves app startup time.

For users of ASP.NET Core 2.1 or later, update to use the native support for precompilation in the Razor SDK. If bugs or missing features prevent migration to the Razor SDK, open an issue at dotnet/aspnetcore.

Category

ASP.NET Core

Affected APIs

None


MVC: "Pubternal" types changed to internal

In ASP.NET Core 3.0, all "pubternal" types in MVC were updated to either be public in a supported namespace or internal as appropriate.

Change description

In ASP.NET Core, "pubternal" types are declared as public but reside in a .Internal-suffixed namespace. While these types are public, they have no support policy and are subject to breaking changes. Unfortunately, accidental use of these types has been common, resulting in breaking changes to these projects and limiting the ability to maintain the framework.

Version introduced

3.0

Old behavior

Some types in MVC were public but in a .Internal namespace. These types had no support policy and were subject to breaking changes.

New behavior

All such types are updated either to be public in a supported namespace or marked as internal.

Reason for change

Accidental use of the "pubternal" types has been common, resulting in breaking changes to these projects and limiting the ability to maintain the framework.

If you're using types that have become truly public and have been moved into a new, supported namespace, update your references to match the new namespaces.

If you're using types that have become marked as internal, you'll need to find an alternative. The previously "pubternal" types were never supported for public use. If there are specific types in these namespaces that are critical to your apps, file an issue at dotnet/aspnetcore. Considerations may be made for making the requested types public.

Category

ASP.NET Core

Affected APIs

This change includes types in the following namespaces:

  • Microsoft.AspNetCore.Mvc.Cors.Internal
  • Microsoft.AspNetCore.Mvc.DataAnnotations.Internal
  • Microsoft.AspNetCore.Mvc.Formatters.Internal
  • Microsoft.AspNetCore.Mvc.Formatters.Json.Internal
  • Microsoft.AspNetCore.Mvc.Formatters.Xml.Internal
  • Microsoft.AspNetCore.Mvc.Internal
  • Microsoft.AspNetCore.Mvc.ModelBinding.Internal
  • Microsoft.AspNetCore.Mvc.Razor.Internal
  • Microsoft.AspNetCore.Mvc.RazorPages.Internal
  • Microsoft.AspNetCore.Mvc.TagHelpers.Internal
  • Microsoft.AspNetCore.Mvc.ViewFeatures.Internal

MVC: Web API compatibility shim removed

Starting with ASP.NET Core 3.0, the Microsoft.AspNetCore.Mvc.WebApiCompatShim package is no longer available.

Change description

The Microsoft.AspNetCore.Mvc.WebApiCompatShim (WebApiCompatShim) package provides partial compatibility in ASP.NET Core with ASP.NET 4.x Web API 2 to simplify migrating existing Web API implementations to ASP.NET Core. However, apps using the WebApiCompatShim don't benefit from the API-related features shipping in recent ASP.NET Core releases. Such features include improved Open API specification generation, standardized error handling, and client code generation. To better focus the API efforts in 3.0, WebApiCompatShim was removed. Existing apps using the WebApiCompatShim should migrate to the newer [ApiController] model.

Version introduced

3.0

Reason for change

The Web API compatibility shim was a migration tool. It restricts user access to new functionality added in ASP.NET Core.

Remove usage of this shim and migrate directly to the similar functionality in ASP.NET Core itself.

Category

ASP.NET Core

Affected APIs

Microsoft.AspNetCore.Mvc.WebApiCompatShim


Razor: RazorTemplateEngine API removed

The RazorTemplateEngine API was removed and replaced with RazorProjectEngine.

For discussion, see GitHub issue dotnet/aspnetcore#25215.

Version introduced

3.0

Old behavior

A template engine can be created and used to parse and generate code for Razor files.

New behavior

RazorProjectEngine can be created and provided the same type of information as RazorTemplateEngine to parse and generate code for Razor files. RazorProjectEngine also provides extra levels of configuration.

Reason for change

RazorTemplateEngine was too tightly coupled to the existing implementations. This tight coupling led to more questions when trying to properly configure a Razor parsing/generation pipeline.

Use RazorProjectEngine instead of RazorTemplateEngine. Consider the following examples.

Create and configure the RazorProjectEngine
RazorProjectEngine projectEngine =
    RazorProjectEngine.Create(RazorConfiguration.Default,
        RazorProjectFileSystem.Create(@"C:\source\repos\ConsoleApp4\ConsoleApp4"),
        builder =>
        {
            builder.ConfigureClass((document, classNode) =>
            {
                classNode.ClassName = "MyClassName";

                // Can also configure other aspects of the class here.
            });

            // More configuration can go here
        });
Generate code for a Razor file
RazorProjectItem item = projectEngine.FileSystem.GetItem(
    @"C:\source\repos\ConsoleApp4\ConsoleApp4\Example.cshtml",
    FileKinds.Legacy);
RazorCodeDocument output = projectEngine.Process(item);

// Things available
RazorSyntaxTree syntaxTree = output.GetSyntaxTree();
DocumentIntermediateNode intermediateDocument =
    output.GetDocumentIntermediateNode();
RazorCSharpDocument csharpDocument = output.GetCSharpDocument();

Category

ASP.NET Core

Affected APIs


Razor: Runtime compilation moved to a package

Support for runtime compilation of Razor views and Razor Pages has moved to a separate package.

Version introduced

3.0

Old behavior

Runtime compilation is available without needing additional packages.

New behavior

The functionality has been moved to the Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation package.

The following APIs were previously available in Microsoft.AspNetCore.Mvc.Razor.RazorViewEngineOptions to support runtime compilation. The APIs are now available via Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation.MvcRazorRuntimeCompilationOptions.

  • RazorViewEngineOptions.FileProviders is now MvcRazorRuntimeCompilationOptions.FileProviders
  • RazorViewEngineOptions.AdditionalCompilationReferences is now MvcRazorRuntimeCompilationOptions.AdditionalReferencePaths

In addition, Microsoft.AspNetCore.Mvc.Razor.RazorViewEngineOptions.AllowRecompilingViewsOnFileChange has been removed. Recompilation on file changes is enabled by default by referencing the Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation package.

Reason for change

This change was necessary to remove the ASP.NET Core shared framework dependency on Roslyn.

Apps that require runtime compilation or recompilation of Razor files should take the following steps:

  1. Add a reference to the Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation package.

  2. Update the project's Startup.ConfigureServices method to include a call to AddRazorRuntimeCompilation. For example:

    services.AddMvc()
        .AddRazorRuntimeCompilation();
    

Category

ASP.NET Core

Affected APIs

Microsoft.AspNetCore.Mvc.Razor.RazorViewEngineOptions


Session state: Obsolete APIs removed

Obsolete APIs for configuring session cookies were removed. For more information, see aspnet/Announcements#257.

Version introduced

3.0

Reason for change

This change enforces consistency across APIs for configuring features that use cookies.

Migrate usage of the removed APIs to their newer replacements. Consider the following example in Startup.ConfigureServices:

public void ConfigureServices(ServiceCollection services)
{
    services.AddSession(options =>
    {
        // Removed obsolete APIs
        options.CookieName = "SessionCookie";
        options.CookieDomain = "contoso.com";
        options.CookiePath = "/";
        options.CookieHttpOnly = true;
        options.CookieSecure = CookieSecurePolicy.Always;

        // new API
        options.Cookie.Name = "SessionCookie";
        options.Cookie.Domain = "contoso.com";
        options.Cookie.Path = "/";
        options.Cookie.HttpOnly = true;
        options.Cookie.SecurePolicy = CookieSecurePolicy.Always;
    });
}

Category

ASP.NET Core

Affected APIs


Shared framework: Assemblies removed from Microsoft.AspNetCore.App

Starting in ASP.NET Core 3.0, the ASP.NET Core shared framework (Microsoft.AspNetCore.App) only contains first-party assemblies that are fully developed, supported, and serviceable by Microsoft.

Change description

Think of the change as the redefining of boundaries for the ASP.NET Core "platform." The shared framework will be source-buildable by anybody via GitHub and will continue to offer the existing benefits of .NET Core shared frameworks to your apps. Some benefits include smaller deployment size, centralized patching, and faster startup time.

As part of the change, some notable breaking changes are introduced in Microsoft.AspNetCore.App.

Version introduced

3.0

Old behavior

Projects referenced Microsoft.AspNetCore.App via a <PackageReference> element in the project file.

Additionally, Microsoft.AspNetCore.App contained the following subcomponents:

  • Json.NET (Newtonsoft.Json)
  • Entity Framework Core (assemblies prefixed with Microsoft.EntityFrameworkCore.)
  • Roslyn (Microsoft.CodeAnalysis)

New behavior

A reference to Microsoft.AspNetCore.App no longer requires a <PackageReference> element in the project file. The .NET Core SDK supports a new element called <FrameworkReference>, which replaces the use of <PackageReference>.

For more information, see dotnet/aspnetcore#3612.

Entity Framework Core ships as NuGet packages. This change aligns the shipping model with all other data access libraries on .NET. It provides Entity Framework Core the simplest path to continue innovating while supporting the various .NET platforms. The move of Entity Framework Core out of the shared framework has no impact on its status as a Microsoft-developed, supported, and serviceable library. The .NET Core support policy continues to cover it.

Json.NET and Entity Framework Core continue to work with ASP.NET Core. They won't, however, be included in the shared framework.

For more information, see The future of JSON in .NET Core 3.0. Also see the complete list of binaries removed from the shared framework.

Reason for change

This change simplifies the consumption of Microsoft.AspNetCore.App and reduces the duplication between NuGet packages and shared frameworks.

For more information on the motivation for this change, see this blog post.

It won't be necessary for projects to consume assemblies in Microsoft.AspNetCore.App as NuGet packages. To simplify the targeting and usage of the ASP.NET Core shared framework, many NuGet packages shipped since ASP.NET Core 1.0 are no longer produced. The APIs those packages provide are still available to apps by using a <FrameworkReference> to Microsoft.AspNetCore.App. Common API examples include Kestrel, MVC, and Razor.

This change doesn't apply to all binaries referenced via Microsoft.AspNetCore.App in ASP.NET Core 2.x. Notable exceptions include:

  • Microsoft.Extensions libraries that continue to target .NET Standard will be available as NuGet packages (see https://github.com/dotnet/extensions).
  • APIs produced by the ASP.NET Core team that aren't part of Microsoft.AspNetCore.App. For example, the following components are available as NuGet packages:
  • Extensions to MVC that maintain support for Json.NET. An API will be provided as a NuGet package to support using Json.NET and MVC.
  • The SignalR .NET client will continue to support .NET Standard and ship as a NuGet package. It's intended for use on many .NET runtimes, such as Xamarin and UWP.

For more information, see Stop producing packages for shared framework assemblies in 3.0. For discussion, see dotnet/aspnetcore#3757.

Category

ASP.NET Core

Affected APIs


Shared framework: Removed Microsoft.AspNetCore.All

Starting in ASP.NET Core 3.0, the Microsoft.AspNetCore.All metapackage and the matching Microsoft.AspNetCore.All shared framework are no longer produced. This package is available in ASP.NET Core 2.2 and will continue to receive servicing updates in ASP.NET Core 2.1.

Version introduced

3.0

Old behavior

Apps could use the Microsoft.AspNetCore.All metapackage to target the Microsoft.AspNetCore.All shared framework on .NET Core.

New behavior

.NET Core 3.0 doesn't include a Microsoft.AspNetCore.All shared framework.

Reason for change

The Microsoft.AspNetCore.All metapackage included a large number of external dependencies.

Migrate your project to use the Microsoft.AspNetCore.App framework. Components that were previously available in Microsoft.AspNetCore.All are still available on NuGet. Those components are now deployed with your app instead of being included in the shared framework.

Category

ASP.NET Core

Affected APIs

None


SignalR: HandshakeProtocol.SuccessHandshakeData replaced

The HandshakeProtocol.SuccessHandshakeData field was removed and replaced with a helper method that generates a successful handshake response given a specific IHubProtocol.

Version introduced

3.0

Old behavior

HandshakeProtocol.SuccessHandshakeData was a public static ReadOnlyMemory<byte> field.

New behavior

HandshakeProtocol.SuccessHandshakeData has been replaced by a static GetSuccessfulHandshake(IHubProtocol protocol) method that returns a ReadOnlyMemory<byte> based on the specified protocol.

Reason for change

Additional fields were added to the handshake response that are non-constant and change depending on the selected protocol.

None. This type isn't designed for use from user code. It's public, so it can be shared between the SignalR server and client. It may also be used by customer SignalR clients written in .NET. Users of SignalR shouldn't be affected by this change.

Category

ASP.NET Core

Affected APIs

HandshakeProtocol.SuccessHandshakeData


SignalR: HubConnection ResetSendPing and ResetTimeout methods removed

The ResetSendPing and ResetTimeout methods were removed from the SignalR HubConnection API. These methods were originally intended only for internal use but were made public in ASP.NET Core 2.2. These methods won't be available starting in the ASP.NET Core 3.0 Preview 4 release. For discussion, see dotnet/aspnetcore#8543.

Version introduced

3.0

Old behavior

APIs were available.

New behavior

APIs are removed.

Reason for change

These methods were originally intended only for internal use but were made public in ASP.NET Core 2.2.

Don't use these methods.

Category

ASP.NET Core

Affected APIs


SignalR: HubConnectionContext constructors changed

SignalR's HubConnectionContext constructors changed to accept an options type, rather than multiple parameters, to future-proof adding options. This change replaces two constructors with a single constructor that accepts an options type.

Version introduced

3.0

Old behavior

HubConnectionContext has two constructors:

public HubConnectionContext(ConnectionContext connectionContext, TimeSpan keepAliveInterval, ILoggerFactory loggerFactory);
public HubConnectionContext(ConnectionContext connectionContext, TimeSpan keepAliveInterval, ILoggerFactory loggerFactory, TimeSpan clientTimeoutInterval);

New behavior

The two constructors were removed and replaced with one constructor:

public HubConnectionContext(ConnectionContext connectionContext, HubConnectionContextOptions contextOptions, ILoggerFactory loggerFactory)

Reason for change

The new constructor uses a new options object. Consequently, the features of HubConnectionContext can be expanded in the future without making more constructors and breaking changes.

Instead of using the following constructor:

HubConnectionContext connectionContext = new HubConnectionContext(
    connectionContext,
    keepAliveInterval: TimeSpan.FromSeconds(15),
    loggerFactory,
    clientTimeoutInterval: TimeSpan.FromSeconds(15));

Use the following constructor:

HubConnectionContextOptions contextOptions = new HubConnectionContextOptions()
{
    KeepAliveInterval = TimeSpan.FromSeconds(15),
    ClientTimeoutInterval = TimeSpan.FromSeconds(15)
};
HubConnectionContext connectionContext = new HubConnectionContext(connectionContext, contextOptions, loggerFactory);

Category

ASP.NET Core

Affected APIs


SignalR: JavaScript client package name changed

In ASP.NET Core 3.0 Preview 7, the SignalR JavaScript client package name changed from @aspnet/signalr to @microsoft/signalr. The name change reflects the fact that SignalR is useful in more than just ASP.NET Core apps, thanks to the Azure SignalR Service.

To react to this change, change references in your package.json files, require statements, and ECMAScript import statements. No API will change as part of this rename.

For discussion, see dotnet/aspnetcore#11637.

Version introduced

3.0

Old behavior

The client package was named @aspnet/signalr.

New behavior

The client package is named @microsoft/signalr.

Reason for change

The name change clarifies that SignalR is useful beyond ASP.NET Core apps, thanks to the Azure SignalR Service.

Switch to the new package @microsoft/signalr.

Category

ASP.NET Core

Affected APIs

None


SignalR: UseSignalR and UseConnections methods marked obsolete

The methods UseConnections and UseSignalR and the classes ConnectionsRouteBuilder and HubRouteBuilder are marked as obsolete in ASP.NET Core 3.0.

Version introduced

3.0

Old behavior

SignalR hub routing was configured using UseSignalR or UseConnections.

New behavior

The old way of configuring routing has been obsoleted and replaced with endpoint routing.

Reason for change

Middleware is being moved to the new endpoint routing system. The old way of adding middleware is being obsoleted.

Replace UseSignalR with UseEndpoints:

Old code:

app.UseSignalR(routes =>
{
    routes.MapHub<SomeHub>("/path");
});

New code:

app.UseEndpoints(endpoints =>
{
    endpoints.MapHub<SomeHub>("/path");
});

Category

ASP.NET Core

Affected APIs


SPAs: SpaServices and NodeServices marked obsolete

The contents of the following NuGet packages have all been unnecessary since ASP.NET Core 2.1. Consequently, the following packages are being marked as obsolete:

For the same reason, the following npm modules are being marked as deprecated:

The preceding packages and npm modules will later be removed in .NET 5.

Version introduced

3.0

Old behavior

The deprecated packages and npm modules were intended to integrate ASP.NET Core with various Single-Page App (SPA) frameworks. Such frameworks include Angular, React, and React with Redux.

New behavior

A new integration mechanism exists in the Microsoft.AspNetCore.SpaServices.Extensions NuGet package. The package remains the basis of the Angular and React project templates since ASP.NET Core 2.1.

Reason for change

ASP.NET Core supports integration with various Single-Page App (SPA) frameworks, including Angular, React, and React with Redux. Initially, integration with these frameworks was accomplished with ASP.NET Core-specific components that handled scenarios like server-side prerendering and integration with Webpack. As time went on, industry standards changed. Each of the SPA frameworks released their own standard command-line interfaces. For example, Angular CLI and create-react-app.

When ASP.NET Core 2.1 was released in May 2018, the team responded to the change in standards. A newer and simpler way to integrate with the SPA frameworks' own toolchains was provided. The new integration mechanism exists in the package Microsoft.AspNetCore.SpaServices.Extensions and remains the basis of the Angular and React project templates since ASP.NET Core 2.1.

To clarify that the older ASP.NET Core-specific components are irrelevant and not recommended:

  • The pre-2.1 integration mechanism is marked as obsolete.
  • The supporting npm packages are marked as deprecated.

If you're using these packages, update your apps to use the functionality:

  • In the Microsoft.AspNetCore.SpaServices.Extensions package.
  • Provided by the SPA frameworks you're using

To enable features like server-side prerendering and hot module reload, see the documentation for the corresponding SPA framework. The functionality in Microsoft.AspNetCore.SpaServices.Extensions is not obsolete and will continue to be supported.

Category

ASP.NET Core

Affected APIs


SPAs: SpaServices and NodeServices no longer fall back to console logger

Microsoft.AspNetCore.SpaServices and Microsoft.AspNetCore.NodeServices won't display console logs unless logging is configured.

Version introduced

3.0

Old behavior

Microsoft.AspNetCore.SpaServices and Microsoft.AspNetCore.NodeServices used to automatically create a console logger when logging isn't configured.

New behavior

Microsoft.AspNetCore.SpaServices and Microsoft.AspNetCore.NodeServices won't display console logs unless logging is configured.

Reason for change

There's a need to align with how other ASP.NET Core packages implement logging.

If the old behavior is required, to configure console logging, add services.AddLogging(builder => builder.AddConsole()) to your Setup.ConfigureServices method.

Category

ASP.NET Core

Affected APIs

None


Target framework: .NET Framework support dropped

Starting with ASP.NET Core 3.0, .NET Framework is an unsupported target framework.

Change description

.NET Framework 4.8 is the last major version of .NET Framework. New ASP.NET Core apps should be built on .NET Core. Starting with the .NET Core 3.0 release, you can think of ASP.NET Core 3.0 as being part of .NET Core.

Customers using ASP.NET Core with .NET Framework can continue in a fully supported fashion using the 2.1 LTS release. Support and servicing for 2.1 continues until at least August 21, 2021. This date is three years after declaration of the LTS release per the .NET Support Policy. Support for ASP.NET Core 2.1 packages on .NET Framework will extend indefinitely, similar to the servicing policy for other package-based ASP.NET frameworks.

For more information about porting from .NET Framework to .NET Core, see Porting to .NET Core.

Microsoft.Extensions packages (such as logging, dependency injection, and configuration) and Entity Framework Core aren't affected. They'll continue to support .NET Standard.

For more information on the motivation for this change, see the original blog post.

Version introduced

3.0

Old behavior

ASP.NET Core apps could run on either .NET Core or .NET Framework.

New behavior

ASP.NET Core apps can only be run on .NET Core.

Take one of the following actions:

  • Keep your app on ASP.NET Core 2.1.
  • Migrate your app and dependencies to .NET Core.

Category

ASP.NET Core

Affected APIs

None


Core .NET libraries

APIs that report version now report product and not file version

Many of the APIs that return versions in .NET Core now return the product version rather than the file version.

Change description

In .NET Core 2.2 and previous versions, methods such as Environment.Version, RuntimeInformation.FrameworkDescription, and the file properties dialog for .NET Core assemblies reflect the file version. Starting with .NET Core 3.0, they reflect the product version.

The following figure illustrates the difference in version information for the System.Runtime.dll assembly for .NET Core 2.2 (on the left) and .NET Core 3.0 (on the right) as displayed by the Windows Explorer file properties dialog.

Difference in product version information

Version introduced

3.0

None. This change should make version detection intuitive rather than obtuse.

Category

Core .NET libraries

Affected APIs


Custom EncoderFallbackBuffer instances cannot fall back recursively

Custom EncoderFallbackBuffer instances cannot fall back recursively. The implementation of EncoderFallbackBuffer.GetNextChar() must result in a character sequence that is convertible to the destination encoding. Otherwise, an exception occurs.

Change description

During a character-to-byte transcoding operation, the runtime detects ill-formed or nonconvertible UTF-16 sequences and provides those characters to the EncoderFallbackBuffer.Fallback method. The Fallback method determines which characters should be substituted for the original nonconvertible data, and these characters are drained by calling EncoderFallbackBuffer.GetNextChar in a loop.

The runtime then attempts to transcode these substitution characters to the target encoding. If this operation succeeds, the runtime continues transcoding from where it left off in the original input string.

Previously, custom implementations of EncoderFallbackBuffer.GetNextChar() can return character sequences that are not convertible to the destination encoding. If the substituted characters cannot be transcoded to the target encoding, the runtime invokes the EncoderFallbackBuffer.Fallback method once again with the substitution characters, expecting the EncoderFallbackBuffer.GetNextChar() method to return a new substitution sequence. This process continues until the runtime eventually sees a well-formed, convertible substitution, or until a maximum recursion count is reached.

Starting with .NET Core 3.0, custom implementations of EncoderFallbackBuffer.GetNextChar() must return character sequences that are convertible to the destination encoding. If the substituted characters cannot be transcoded to the target encoding, an ArgumentException is thrown. The runtime will no longer make recursive calls into the EncoderFallbackBuffer instance.

This behavior only applies when all three of the following conditions are met:

  • The runtime detects an ill-formed UTF-16 sequence or a UTF-16 sequence that cannot be converted to the target encoding.
  • A custom EncoderFallback has been specified.
  • The custom EncoderFallback attempts to substitute a new ill-formed or nonconvertible UTF-16 sequence.

Version introduced

3.0

Most developers needn't take any action.

If an application uses a custom EncoderFallback and EncoderFallbackBuffer class, ensure the implementation of EncoderFallbackBuffer.Fallback populates the fallback buffer with well-formed UTF-16 data that is directly convertible to the target encoding when the Fallback method is first invoked by the runtime.

Category

Core .NET libraries

Affected APIs


Floating-point formatting and parsing behavior changed

Floating point parsing and formatting behavior (by the Double and Single types) are now IEEE-compliant.

Change description

In .NET Core 2.2 and earlier versions, formatting with Double.ToString and Single.ToString, and parsing with Double.Parse, Double.TryParse, Single.Parse, and Single.TryParse are not IEEE-compliant. As a result, it is impossible to guarantee that a value will roundtrip with any supported standard or custom format string. For some inputs, the attempt to parse a formatted value can fail, and for others, the parsed value doesn't equal the original value.

Starting with .NET Core 3.0, parsing and formatting operations are IEEE 754-compliant. This ensures that the behavior of floating-point types in .NET matches that of IEEE-compliant languages such as C#. For more information, see the Floating-point parsing and formatting improvements in .NET Core 3.0 blog post.

Version introduced

3.0

The "Potential impact to existing code" section of the Floating-point parsing and formatting improvements in .NET Core 3.0 blog post suggests changes to your code if you observe a change of behavior when compared to .NET Core 2.2 applications Generally, this involves using a different standard or custom format string to enforce the desired behavior. Some results may not have a workaround if they were previously incorrect.

Category

Core .NET libraries

Affected APIs


Floating-point parsing operations no longer fail or throw an OverflowException

The floating-point parsing methods no longer throw an OverflowException or return false when they parse a string whose numeric value is outside the range of the Single or Double floating-point type.

Change description

In .NET Core 2.2 and earlier versions, the Double.Parse and Single.Parse methods throw an OverflowException for values that outside the range of their respective type. The Double.TryParse and Single.TryParse methods return false for the string representations of out-of-range numeric values.

Starting with .NET Core 3.0, the Double.Parse, Double.TryParse, Single.Parse, and Single.TryParse methods no longer fail when parsing out-of-range numeric strings. Instead, the Double parsing methods return Double.PositiveInfinity for values that exceed Double.MaxValue, and they return Double.NegativeInfinity for values that are less than Double.MinValue. Similarly, the Single parsing methods return Single.PositiveInfinity for values that exceed Single.MaxValue, and they return Single.NegativeInfinity for values that are less than Single.MinValue.

This change was made for improved IEEE 754:2008 compliance.

Version introduced

3.0

This change can affect your code in either of two ways:

  • Your code depends on the handler for the OverflowException to execute when an overflow occurs. In this case, you should remove the catch statement and place any necessary code in an If statement that tests whether Double.IsInfinity or Single.IsInfinity is true.

  • Your code assumes that floating-point values are not Infinity. In this case, you should add the necessary code to check for floating-point values of PositiveInfinity and NegativeInfinity.

Category

Core .NET libraries

Affected APIs


InvalidAsynchronousStateException moved to another assembly

The InvalidAsynchronousStateException class has been moved.

Change description

In .NET Core 2.2 and earlier versions, the InvalidAsynchronousStateException class is found in the System.ComponentModel.TypeConverter assembly.

Starting with .NET Core 3.0, it is found in the System.ComponentModel.Primitives assembly.

Version introduced

3.0

This change only affects applications that use reflection to load the InvalidAsynchronousStateException by calling a method such as Assembly.GetType or an overload of Activator.CreateInstance that assumes the type is in a particular assembly. If that is the case, update the assembly referenced in the method call to reflect the type's new assembly location.

Category

Core .NET libraries

Affected APIs

None.


Replacing ill-formed UTF-8 byte sequences follows Unicode guidelines

When the UTF8Encoding class encounters an ill-formed UTF-8 byte sequence during a byte-to-character transcoding operation, it replaces that sequence with a '�' (U+FFFD REPLACEMENT CHARACTER) character in the output string. .NET Core 3.0 differs from previous versions of .NET Core and the .NET Framework by following the Unicode best practice for performing this replacement during the transcoding operation.

This is part of a larger effort to improve UTF-8 handling throughout .NET, including by the new System.Text.Unicode.Utf8 and System.Text.Rune types. The UTF8Encoding type was given improved error handling mechanics so that it produces output consistent with the newly introduced types.

Change description

Starting with .NET Core 3.0, when transcoding bytes to characters, the UTF8Encoding class performs character substitution based on Unicode best practices. The substitution mechanism used is described by The Unicode Standard, Version 12.0, Sec. 3.9 (PDF) in the heading titled U+FFFD Substitution of Maximal Subparts.

This behavior only applies when the input byte sequence contains ill-formed UTF-8 data. Additionally, if the UTF8Encoding instance has been constructed with throwOnInvalidBytes: true, the UTF8Encoding instance will continue to throw on invalid input rather than perform U+FFFD replacement. For more information about the UTF8Encoding constructor, see UTF8Encoding(Boolean, Boolean).

The following table illustrates the impact of this change with an invalid 3-byte input:

Ill-formed 3-byte input Output before .NET Core 3.0 Output starting with .NET Core 3.0
[ ED A0 90 ] [ FFFD FFFD ] (2-character output) [ FFFD FFFD FFFD ] (3-character output)

The 3-char output is the preferred output, according to Table 3-9 of the previously linked Unicode Standard PDF.

Version introduced

3.0

No action is required on the part of the developer.

Category

Core .NET libraries

Affected APIs


TypeDescriptionProviderAttribute moved to another assembly

The TypeDescriptionProviderAttribute class has been moved.

Change description

In .NET Core 2.2 and earlier versions, The TypeDescriptionProviderAttribute class is found in the System.ComponentModel.TypeConverter assembly.

Starting with .NET Core 3.0, it is found in the System.ObjectModel assembly.

Version introduced

3.0

This change only affects applications that use reflection to load the TypeDescriptionProviderAttribute type by calling a method such as Assembly.GetType or an overload of Activator.CreateInstance that assumes the type is in a particular assembly. If that is the case, the assembly referenced in the method call should be updated to reflect the type's new assembly location.

Category

Windows Forms

Affected APIs

None.


ZipArchiveEntry no longer handles archives with inconsistent entry sizes

Zip archives list both compressed size and uncompressed size in the central directory and local header. The entry data itself also indicates its size. In .NET Core 2.2 and earlier versions, these values were never checked for consistency. Starting with .NET Core 3.0, they now are.

Change description

In .NET Core 2.2 and earlier versions, ZipArchiveEntry.Open() succeeds even if the local header disagrees with the central header of the zip file. Data is decompressed until the end of the compressed stream is reached, even if its length exceeds the uncompressed file size listed in the central directory/local header.

Starting with .NET Core 3.0, the ZipArchiveEntry.Open() method checks that local header and central header agree on compressed and uncompressed sizes of an entry. If they do not, the method throws an InvalidDataException if the archive's local header and/or data descriptor list sizes that disagree with the central directory of the zip file. When reading an entry, decompressed data is truncated to the uncompressed file size listed in the header.

This change was made to ensure that a ZipArchiveEntry correctly represents the size of its data and that only that amount of data is read.

Version introduced

3.0

Repackage any zip archive that exhibits these problems.

Category

CoreFx

Affected APIs


FieldInfo.SetValue throws exception for static, init-only fields

Starting in .NET Core 3.0, an exception is thrown when you attempt to set a value on a static, InitOnly field by calling System.Reflection.FieldInfo.SetValue.

Change description

In .NET Framework and versions of .NET Core prior to 3.0, you could set the value of a static field that's constant after it is initialized (readonly in C#) by calling System.Reflection.FieldInfo.SetValue. However, setting such a field in this way resulted in unpredictable behavior based on the target framework and optimization settings.

In .NET Core 3.0 and later versions, when you call SetValue on a static, InitOnly field, a System.FieldAccessException exception is thrown.

Tip

An InitOnly field is one that can only be set at the time it's declared or in the constructor for the containing class. In other words, it's constant after it is initialized.

Version introduced

3.0

Initialize static, InitOnly fields in a static constructor. This applies to both dynamic and non-dynamic types.

Alternatively, you can remove the FieldAttributes.InitOnly attribute from the field, and then call FieldInfo.SetValue.

Category

Core .NET libraries

Affected APIs


Cryptography

"BEGIN TRUSTED CERTIFICATE" syntax no longer supported for root certificates on Linux

Root certificates on Linux and other Unix-like systems (but not macOS) can be presented in two forms: the standard BEGIN CERTIFICATE PEM header, and the OpenSSL-specific BEGIN TRUSTED CERTIFICATE PEM header. The latter syntax allows for additional configuration that has caused compatibility issues with .NET Core's System.Security.Cryptography.X509Certificates.X509Chain class. BEGIN TRUSTED CERTIFICATE root certificate contents are no longer loaded by the chain engine starting in .NET Core 3.0.

Change description

Previously, both the BEGIN CERTIFICATE and BEGIN TRUSTED CERTIFICATE syntaxes were used to populate the root trust list. If the BEGIN TRUSTED CERTIFICATE syntax was used and additional options were specified in the file, X509Chain may have reported that the chain trust was explicitly disallowed (X509ChainStatusFlags.ExplicitDistrust). However, if the certificate was also specified with the BEGIN CERTIFICATE syntax in a previously loaded file, the chain trust was allowed.

Starting in .NET Core 3.0, BEGIN TRUSTED CERTIFICATE contents are no longer read. If the certificate is not also specified via a standard BEGIN CERTIFICATE syntax, the X509Chain reports that the root is not trusted (X509ChainStatusFlags.UntrustedRoot).

Version introduced

3.0

Most applications are unaffected by this change, but applications that cannot see both root certificate sources because of permissions problems may experience unexpected UntrustedRoot errors after upgrading.

Many Linux distributions (or distros) write root certificates into two locations: a one-certificate-per-file directory, and a one-file concatenation. On some distros, the one-certificate-per-file directory uses the BEGIN TRUSTED CERTIFICATE syntax while the file concatenation uses the standard BEGIN CERTIFICATE syntax. Ensure that any custom root certificates are added as BEGIN CERTIFICATE in at least one of these locations, and that both locations can be read by your application.

The typical directory is /etc/ssl/certs/ and the typical concatenated file is /etc/ssl/cert.pem. Use the command openssl version -d to determine the platform-specific root, which may differ from /etc/ssl/. For example, on Ubuntu 18.04, the directory is /usr/lib/ssl/certs/ and the file is /usr/lib/ssl/cert.pem. However, /usr/lib/ssl/certs/ is a symlink to /etc/ssl/certs/ and /usr/lib/ssl/cert.pem does not exist.

$ openssl version -d
OPENSSLDIR: "/usr/lib/ssl"
$ ls -al /usr/lib/ssl
total 12
drwxr-xr-x  3 root root 4096 Dec 12 17:10 .
drwxr-xr-x 73 root root 4096 Feb 20 15:18 ..
lrwxrwxrwx  1 root root   14 Mar 27  2018 certs -> /etc/ssl/certs
drwxr-xr-x  2 root root 4096 Dec 12 17:10 misc
lrwxrwxrwx  1 root root   20 Nov 12 16:58 openssl.cnf -> /etc/ssl/openssl.cnf
lrwxrwxrwx  1 root root   16 Mar 27  2018 private -> /etc/ssl/private

Category

Cryptography

Affected APIs


EnvelopedCms defaults to AES-256 encryption

The default symmetric encryption algorithm used by EnvelopedCms has changed from TripleDES to AES-256.

Change description

In previous versions, when EnvelopedCms is used to encrypt data without specifying a symmetric encryption algorithm via a constructor overload, the data is encrypted with the TripleDES/3DES/3DEA/DES3-EDE algorithm.

Starting with .NET Core 3.0 (via version 4.6.0 of the System.Security.Cryptography.Pkcs NuGet package), the default algorithm has been changed to AES-256 for algorithm modernization and to improve the security of default options. If a message recipient certificate has a (non-EC) Diffie-Hellman public key, the encryption operation may fail with a CryptographicException due to limitations in the underlying platform.

In the following sample code, the data is encrypted with TripleDES if running on .NET Core 2.2 or earlier. If running on .NET Core 3.0 or later, it's encrypted with AES-256.

EnvelopedCms cms = new EnvelopedCms(content);
cms.Encrypt(recipient);
return cms.Encode();

Version introduced

3.0

If you are negatively impacted by the change, you can restore TripleDES encryption by explicitly specifying the encryption algorithm identifier in an EnvelopedCms constructor that includes a parameter of type AlgorithmIdentifier, such as:

Oid tripleDesOid = new Oid("1.2.840.113549.3.7", null);
AlgorithmIdentifier tripleDesIdentifier = new AlgorithmIdentifier(tripleDesOid);
EnvelopedCms cms = new EnvelopedCms(content, tripleDesIdentifier);

cms.Encrypt(recipient);
return cms.Encode()l

Category

Cryptography

Affected APIs


Minimum size for RSAOpenSsl key generation has increased

The minimum size for generating new RSA keys on Linux has increased from 384-bit to 512-bit.

Change description

Starting with .NET Core 3.0, the minimum legal key size reported by the LegalKeySizes property on RSA instances from RSA.Create, RSAOpenSsl, and RSACryptoServiceProvider on Linux has increased from 384 to 512.

As a result, in .NET Core 2.2 and earlier versions, a method call such as RSA.Create(384) succeeds. In .NET Core 3.0 and later versions, the method call RSA.Create(384) throws an exception indicating the size is too small.

This change was made because OpenSSL, which performs the cryptographic operations on Linux, raised its minimum between versions 1.0.2 and 1.1.0. .NET Core 3.0 prefers OpenSSL 1.1.x to 1.0.x, and the minimum reported version was raised to reflect this new higher dependency limitation.

Version introduced

3.0

If you call any of the affected APIs, ensure that the size of any generated keys is not less than the provider minimum.

Note

384-bit RSA is already considered insecure (as is 512-bit RSA). Modern recommendations, such as NIST Special Publication 800-57 Part 1 Revision 4, suggest 2048-bit as the minimum size for newly generated keys.

Category

Cryptography

Affected APIs


.NET Core 3.0 prefers OpenSSL 1.1.x to OpenSSL 1.0.x

.NET Core for Linux, which works across multiple Linux distributions, can support both OpenSSL 1.0.x and OpenSSL 1.1.x. .NET Core 2.1 and .NET Core 2.2 look for 1.0.x first, then fall back to 1.1.x; .NET Core 3.0 looks for 1.1.x first. This change was made to add support for new cryptographic standards.

This change may impact libraries or applications that do platform interop with the OpenSSL-specific interop types in .NET Core.

Change description

In .NET Core 2.2 and earlier versions, the runtime prefers loading OpenSSL 1.0.x over 1.1.x. This means that the IntPtr and SafeHandle types for interop with OpenSSL are used with libcrypto.so.1.0.0 / libcrypto.so.1.0 / libcrypto.so.10 by preference.

Starting with .NET Core 3.0, the runtime prefers loading OpenSSL 1.1.x over OpenSSL 1.0.x, so the IntPtr and SafeHandle types for interop with OpenSSL are used with libcrypto.so.1.1 / libcrypto.so.11 / libcrypto.so.1.1.0 / libcrypto.so.1.1.1 by preference. As a result, libraries and applications that interoperate with OpenSSL directly may have incompatible pointers with the .NET Core-exposed values when upgrading from .NET Core 2.1 or .NET Core 2.2.

Version introduced

3.0

Libraries and applications that do direct operations with OpenSSL need to be careful to ensure they are using the same version of OpenSSL as the .NET Core runtime.

All libraries or applications that use IntPtr or SafeHandle values from the .NET Core cryptographic types directly with OpenSSL should compare the version of the library they use with the new SafeEvpPKeyHandle.OpenSslVersion property to ensure the pointers are compatible.

Category

Cryptography

Affected APIs


CryptoStream.Dispose transforms final block only when writing

The CryptoStream.Dispose method, which is used to finish CryptoStream operations, no longer attempts to transform the final block when reading.

Change description

In previous .NET versions, if a user performed an incomplete read when using CryptoStream in Read mode, the Dispose method could throw an exception (for example, when using AES with padding). The exception was thrown because the final block was attempted to be transformed but the data was incomplete.

In .NET Core 3.0 and later versions, Dispose no longer tries to transform the final block when reading, which allows for incomplete reads.

Reason for change

This change enables incomplete reads from the crypto stream when a network operation is canceled, without the need to catch an exception.

Version introduced

3.0

Most apps should not be affected by this change.

If your application previously caught an exception in case of an incomplete read, you can delete that catch block. If your app used transforming of the final block in hashing scenarios, you might need to ensure that the entire stream is read before it's disposed.

Category

Cryptography

Affected APIs


Entity Framework Core

Entity Framework Core breaking changes

Globalization

"C" locale maps to the invariant locale

.NET Core 2.2 and earlier versions depend on the default ICU behavior, which maps the "C" locale to the en_US_POSIX locale. The en_US_POSIX locale has an undesirable collation behavior, because it doesn't support case-insensitive string comparisons. Because some Linux distributions set the "C" locale as the default locale, users were experiencing unexpected behavior.

Change description

Starting with .NET Core 3.0, the "C" locale mapping has changed to use the Invariant locale instead of en_US_POSIX. The "C" locale to Invariant mapping is also applied to Windows for consistency.

Mapping "C" to en_US_POSIX culture caused customer confusion, because en_US_POSIX doesn't support case insensitive sorting/searching string operations. Because the "C" locale is used as a default locale in some of the Linux distros, customers experienced this undesired behavior on these operating systems.

Version introduced

3.0

Nothing specific more than the awareness of this change. This change affects only applications that use the "C" locale mapping.

Category

Globalization

Affected APIs

All collation and culture APIs are affected by this change.


MSBuild

Resource manifest file name change

Starting in .NET Core 3.0, in the default case, MSBuild generates a different manifest file name for resource files.

Version introduced

3.0

Change description

Prior to .NET Core 3.0, if no LogicalName, ManifestResourceName, or DependentUpon metadata was specified for an EmbeddedResource item in the project file, MSBuild generated a manifest file name in the pattern <RootNamespace>.<ResourceFilePathFromProjectRoot>.resources. If RootNamespace is not defined in the project file, it defaults to the project name. For example, the generated manifest name for a resource file named Form1.resx in the root project directory was MyProject.Form1.resources.

Starting in .NET Core 3.0, if a resource file is colocated with a source file of the same name (for example, Form1.resx and Form1.cs), MSBuild uses type information from the source file to generate the manifest file name in the pattern <Namespace>.<ClassName>.resources. The namespace and class name are extracted from the first type in the colocated source file. For example, the generated manifest name for a resource file named Form1.resx that's colocated with a source file named Form1.cs is MyNamespace.Form1.resources. The key thing to note is that the first part of the file name is different to prior versions of .NET Core (MyNamespace instead of MyProject).

Note

If you have LogicalName, ManifestResourceName, or DependentUpon metadata specified on an EmbeddedResource item in the project file, then this change does not affect that resource file.

This breaking change was introduced with the addition of the EmbeddedResourceUseDependentUponConvention property to .NET Core projects. By default, resource files aren't explicitly listed in a .NET Core project file, so they have no DependentUpon metadata to specify how to name the generated .resources file. When EmbeddedResourceUseDependentUponConvention is set to true, which is the default, MSBuild looks for a colocated source file and extracts a namespace and class name from that file. If you set EmbeddedResourceUseDependentUponConvention to false, MSBuild generates the manifest name according to the previous behavior, which combines RootNamespace and the relative file path.

In most cases, no action is required on the part of the developer, and your app should continue to work. However, if this change breaks your app, you can either:

  • Change your code to expect the new manifest name.

  • Opt out of the new naming convention by setting EmbeddedResourceUseDependentUponConvention to false in your project file.

    <PropertyGroup>
      <EmbeddedResourceUseDependentUponConvention>false</EmbeddedResourceUseDependentUponConvention>
    </PropertyGroup>
    

Category

MSBuild

Affected APIs

N/A


Networking

Default value of HttpRequestMessage.Version changed to 1.1

The default value of the System.Net.Http.HttpRequestMessage.Version property has changed from 2.0 to 1.1.

Version introduced

3.0

Change description

In .NET Core 1.0 through 2.0, the default value of the System.Net.Http.HttpRequestMessage.Version property is 1.1. Starting with .NET Core 2.1, it was changed to 2.1.

Starting with .NET Core 3.0, the default version number returned by the System.Net.Http.HttpRequestMessage.Version property is once again 1.1.

Update your code if it depends on the System.Net.Http.HttpRequestMessage.Version property returning a default value of 2.0.

Category

Networking

Affected APIs


Visual Basic

Microsoft.VisualBasic.Constants.vbNewLine is obsolete

The Microsoft.VisualBasic.Constants.vbNewLine constant is marked as [Obsolete] starting with .NET Core 3.0.

Version introduced

3.0

Change description

Starting with .NET Core 3.0, the Obsolete attribute has been applied to the Microsoft.VisualBasic.Constants.vbNewLine constant. Use of the constant produces a compiler warning. In .NET Framework and previous releases of .NET Core, it was not marked as obsolete.

This change was made to support Visual Basic as a language for multi-platform development. The vbNewLine constant is equivalent to \r\n, the newline character sequence on Windows. On Unix-based systems, the newline character is \n.

The Obsolete attribute message for vbNewLine includes the following recommendation:

For a carriage return and line feed, use vbCrLf. For the current platform's newline, use Environment.NewLine.

Category

Visual Basic

Affected APIs