ASP.NET Core Blazor authentication and authorization
This article describes ASP.NET Core's support for the configuration and management of security in Blazor apps.
Security scenarios differ between Blazor Server and Blazor WebAssembly apps. Because Blazor Server apps run on the server, authorization checks are able to determine:
- The UI options presented to a user (for example, which menu entries are available to a user).
- Access rules for areas of the app and components.
Blazor WebAssembly apps run on the client. Authorization is only used to determine which UI options to show. Since client-side checks can be modified or bypassed by a user, a Blazor WebAssembly app can't enforce authorization access rules.
Razor Pages authorization conventions don't apply to routable Razor components. If a non-routable Razor component is embedded in a page, the page's authorization conventions indirectly affect the Razor component along with the rest of the page's content.
Note
SignInManager<TUser> and UserManager<TUser> aren't supported in Razor components. Blazor Server apps use ASP.NET Core Identity. For more information, see the following guidance:
Authentication
Blazor uses the existing ASP.NET Core authentication mechanisms to establish the user's identity. The exact mechanism depends on how the Blazor app is hosted, Blazor WebAssembly or Blazor Server.
Blazor WebAssembly authentication
In Blazor WebAssembly apps, authentication checks can be bypassed because all client-side code can be modified by users. The same is true for all client-side app technologies, including JavaScript SPA frameworks or native apps for any operating system.
Add the following:
A package reference for
Microsoft.AspNetCore.Components.Authorization
.Note
For guidance on adding packages to .NET apps, see the articles under Install and manage packages at Package consumption workflow (NuGet documentation). Confirm correct package versions at NuGet.org.
The
Microsoft.AspNetCore.Components.Authorization
namespace to the app's_Imports.razor
file.
To handle authentication, use of a built-in or custom AuthenticationStateProvider service is covered in the following sections.
For more information on creating apps and configuration, see Secure ASP.NET Core Blazor WebAssembly.
Blazor Server authentication
Blazor Server apps operate over a real-time connection that's created using SignalR. Authentication in SignalR-based apps is handled when the connection is established. Authentication can be based on a cookie or some other bearer token.
The built-in AuthenticationStateProvider service for Blazor Server apps obtains authentication state data from ASP.NET Core's HttpContext.User
. This is how authentication state integrates with existing ASP.NET Core authentication mechanisms.
For more information on creating apps and configuration, see Secure ASP.NET Core Blazor Server apps.
AuthenticationStateProvider service
AuthenticationStateProvider is the underlying service used by the AuthorizeView component and CascadingAuthenticationState component to get the authentication state.
You don't typically use AuthenticationStateProvider directly. Use the AuthorizeView
component or Task<AuthenticationState>
approaches described later in this article. The main drawback to using AuthenticationStateProvider directly is that the component isn't notified automatically if the underlying authentication state data changes.
The AuthenticationStateProvider service can provide the current user's ClaimsPrincipal data, as shown in the following example:
@page "/"
@using System.Security.Claims
@using Microsoft.AspNetCore.Components.Authorization
@inject AuthenticationStateProvider AuthenticationStateProvider
<h3>ClaimsPrincipal Data</h3>
<button @onclick="GetClaimsPrincipalData">Get ClaimsPrincipal Data</button>
<p>@authMessage</p>
@if (claims.Count() > 0)
{
<ul>
@foreach (var claim in claims)
{
<li>@claim.Type: @claim.Value</li>
}
</ul>
}
<p>@surnameMessage</p>
@code {
private string authMessage;
private string surnameMessage;
private IEnumerable<Claim> claims = Enumerable.Empty<Claim>();
private async Task GetClaimsPrincipalData()
{
var authState = await AuthenticationStateProvider.GetAuthenticationStateAsync();
var user = authState.User;
if (user.Identity.IsAuthenticated)
{
authMessage = $"{user.Identity.Name} is authenticated.";
claims = user.Claims;
surnameMessage =
$"Surname: {user.FindFirst(c => c.Type == ClaimTypes.Surname)?.Value}";
}
else
{
authMessage = "The user is NOT authenticated.";
}
}
}
If user.Identity.IsAuthenticated
is true
and because the user is a ClaimsPrincipal, claims can be enumerated and membership in roles evaluated.
For more information on dependency injection (DI) and services, see ASP.NET Core Blazor dependency injection and Dependency injection in ASP.NET Core.
Expose the authentication state as a cascading parameter
If authentication state data is required for procedural logic, such as when performing an action triggered by the user, obtain the authentication state data by defining a cascading parameter of type Task<
AuthenticationState>
:
@page "/"
<button @onclick="LogUsername">Log username</button>
<p>@authMessage</p>
@code {
[CascadingParameter]
private Task<AuthenticationState> authenticationStateTask { get; set; }
private string authMessage;
private async Task LogUsername()
{
var authState = await authenticationStateTask;
var user = authState.User;
if (user.Identity.IsAuthenticated)
{
authMessage = $"{user.Identity.Name} is authenticated.";
}
else
{
authMessage = "The user is NOT authenticated.";
}
}
}
If user.Identity.IsAuthenticated
is true
, claims can be enumerated and membership in roles evaluated.
Set up the Task<
AuthenticationState>
cascading parameter using the AuthorizeRouteView and CascadingAuthenticationState components in the App
component (App.razor
):
<CascadingAuthenticationState>
<Router AppAssembly="@typeof(Program).Assembly">
<Found Context="routeData">
<AuthorizeRouteView RouteData="@routeData"
DefaultLayout="@typeof(MainLayout)" />
</Found>
<NotFound>
<LayoutView Layout="@typeof(MainLayout)">
<p>Sorry, there's nothing at this address.</p>
</LayoutView>
</NotFound>
</Router>
</CascadingAuthenticationState>
In a Blazor WebAssembly App, add services for options and authorization to Program.cs
:
builder.Services.AddOptions();
builder.Services.AddAuthorizationCore();
In a Blazor Server app, services for options and authorization are already present, so no further action is required.
Authorization
After a user is authenticated, authorization rules are applied to control what the user can do.
Access is typically granted or denied based on whether:
- A user is authenticated (signed in).
- A user is in a role.
- A user has a claim.
- A policy is satisfied.
Each of these concepts is the same as in an ASP.NET Core MVC or Razor Pages app. For more information on ASP.NET Core security, see the articles under ASP.NET Core Security and Identity.
AuthorizeView component
The AuthorizeView component selectively displays UI content depending on whether the user is authorized. This approach is useful when you only need to display data for the user and don't need to use the user's identity in procedural logic.
The component exposes a context
variable of type AuthenticationState, which you can use to access information about the signed-in user:
<AuthorizeView>
<h1>Hello, @context.User.Identity.Name!</h1>
<p>You can only see this content if you're authenticated.</p>
</AuthorizeView>
You can also supply different content for display if the user isn't authorized:
<AuthorizeView>
<Authorized>
<h1>Hello, @context.User.Identity.Name!</h1>
<p>You can only see this content if you're authorized.</p>
<button @onclick="SecureMethod">Authorized Only Button</button>
</Authorized>
<NotAuthorized>
<h1>Authentication Failure!</h1>
<p>You're not signed in.</p>
</NotAuthorized>
</AuthorizeView>
@code {
private void SecureMethod() { ... }
}
The content of <Authorized>
and <NotAuthorized>
tags can include arbitrary items, such as other interactive components.
A default event handler for an authorized element, such as the SecureMethod
method for the <button>
element in the preceding example, can only be invoked by an authorized user.
Authorization conditions, such as roles or policies that control UI options or access, are covered in the Authorization section.
If authorization conditions aren't specified, AuthorizeView uses a default policy and treats:
- Authenticated (signed-in) users as authorized.
- Unauthenticated (signed-out) users as unauthorized.
The AuthorizeView component can be used in the NavMenu
component (Shared/NavMenu.razor
) to display a NavLink
component (NavLink), but note that this approach only removes the list item from the rendered output. It doesn't prevent the user from navigating to the component.
Apps created from a Blazor project template that include authentication use a LoginDisplay
component that depends on an AuthorizeView
component. The AuthorizeView
component selectively displays content to users for Identity-related work. The following example is from the Blazor WebAssembly project template.
Shared/LoginDisplay.razor
:
@using Microsoft.AspNetCore.Components.Authorization
@using Microsoft.AspNetCore.Components.WebAssembly.Authentication
@inject NavigationManager Navigation
@inject SignOutSessionStateManager SignOutManager
<AuthorizeView>
<Authorized>
Hello, @context.User.Identity.Name!
<button class="nav-link btn btn-link" @onclick="BeginLogout">Log out</button>
</Authorized>
<NotAuthorized>
<a href="authentication/login">Log in</a>
</NotAuthorized>
</AuthorizeView>
@code{
private async Task BeginLogout(MouseEventArgs args)
{
await SignOutManager.SetSignOutState();
Navigation.NavigateTo("authentication/logout");
}
}
The following example is from the Blazor Server project template and uses ASP.NET Core Identity endpoints in the Identity
area of the app to process Identity-related work.
Shared/LoginDisplay.razor
:
<AuthorizeView>
<Authorized>
<a href="Identity/Account/Manage">Hello, @context.User.Identity.Name!</a>
<form method="post" action="Identity/Account/LogOut">
<button type="submit" class="nav-link btn btn-link">Log out</button>
</form>
</Authorized>
<NotAuthorized>
<a href="Identity/Account/Register">Register</a>
<a href="Identity/Account/Login">Log in</a>
</NotAuthorized>
</AuthorizeView>
Role-based and policy-based authorization
The AuthorizeView component supports role-based or policy-based authorization.
For role-based authorization, use the Roles parameter:
<AuthorizeView Roles="admin, superuser">
<p>You can only see this if you're an admin or superuser.</p>
</AuthorizeView>
For more information, see Role-based authorization in ASP.NET Core.
For policy-based authorization, use the Policy parameter:
<AuthorizeView Policy="content-editor">
<p>You can only see this if you satisfy the "content-editor" policy.</p>
</AuthorizeView>
Claims-based authorization is a special case of policy-based authorization. For example, you can define a policy that requires users to have a certain claim. For more information, see Policy-based authorization in ASP.NET Core.
These APIs can be used in either Blazor Server or Blazor WebAssembly apps.
If neither Roles nor Policy is specified, AuthorizeView uses the default policy.
Content displayed during asynchronous authentication
Blazor allows for authentication state to be determined asynchronously. The primary scenario for this approach is in Blazor WebAssembly apps that make a request to an external endpoint for authentication.
While authentication is in progress, AuthorizeView displays no content by default. To display content while authentication occurs, use the <Authorizing>
tag:
<AuthorizeView>
<Authorized>
<h1>Hello, @context.User.Identity.Name!</h1>
<p>You can only see this content if you're authenticated.</p>
</Authorized>
<Authorizing>
<h1>Authentication in progress</h1>
<p>You can only see this content while authentication is in progress.</p>
</Authorizing>
</AuthorizeView>
This approach isn't normally applicable to Blazor Server apps. Blazor Server apps know the authentication state as soon as the state is established. Authorizing content can be provided in a Blazor Server app's AuthorizeView component, but the content is never displayed.
[Authorize] attribute
The [Authorize]
attribute can be used in Razor components:
@page "/"
@attribute [Authorize]
You can only see this if you're signed in.
Important
Only use [Authorize]
on @page
components reached via the Blazor Router. Authorization is only performed as an aspect of routing and not for child components rendered within a page. To authorize the display of specific parts within a page, use AuthorizeView instead.
The [Authorize]
attribute also supports role-based or policy-based authorization. For role-based authorization, use the Roles parameter:
@page "/"
@attribute [Authorize(Roles = "admin, superuser")]
<p>You can only see this if you're in the 'admin' or 'superuser' role.</p>
For policy-based authorization, use the Policy parameter:
@page "/"
@attribute [Authorize(Policy = "content-editor")]
<p>You can only see this if you satisfy the 'content-editor' policy.</p>
If neither Roles nor Policy is specified, [Authorize]
uses the default policy, which by default is to treat:
- Authenticated (signed-in) users as authorized.
- Unauthenticated (signed-out) users as unauthorized.
Resource authorization
To authorize users for resources, pass the request's route data to the Resource parameter of AuthorizeRouteView.
In the Router.Found content for a requested route in the App
component (App.razor
):
<AuthorizeRouteView Resource="@routeData" RouteData="@routeData"
DefaultLayout="@typeof(MainLayout)" />
For more information on how authorization state data is passed and used in procedural logic, see the Expose the authentication state as a cascading parameter section.
When the AuthorizeRouteView receives the route data for the resource, authorization policies have access to RouteData.PageType and RouteData.RouteValues that permit custom logic to make authorization decisions.
In the following example, an EditUser
policy is created in AuthorizationOptions for the app's authorization service configuration (AddAuthorizationCore) with the following logic:
- Determine if a route value exists with a key of
id
. If the key exists, the route value is stored invalue
. - In a variable named
id
, storevalue
as a string or set an empty string value (string.Empty
). - If
id
isn't an empty string, assert that the policy is satisfied (returntrue
) if the string's value starts withEMP
. Otherwise, assert that the policy fails (returnfalse
).
In either Program.cs
or Startup.cs
(depending on the hosting model and framework version):
Add namespaces for Microsoft.AspNetCore.Components and System.Linq:
using Microsoft.AspNetCore.Components; using System.Linq;
Add the policy:
options.AddPolicy("EditUser", policy => policy.RequireAssertion(context => { if (context.Resource is RouteData rd) { var routeValue = rd.RouteValues.TryGetValue("id", out var value); var id = Convert.ToString(value, System.Globalization.CultureInfo.InvariantCulture) ?? string.Empty; if (!string.IsNullOrEmpty(id)) { return id.StartsWith("EMP", StringComparison.InvariantCulture); } } return false; }) );
The preceding example is an oversimplified authorization policy, merely used to demonstrate the concept with a working example. For more information on creating and configuring authorization policies, see Policy-based authorization in ASP.NET Core.
In the following EditUser
component, the resource at /users/{id}/edit
has a route parameter for the user's identifier ({id}
). The component uses the preceding EditUser
authorization policy to determine if the route value for id
starts with EMP
. If id
starts with EMP
, the policy succeeds and access to the component is authorized. If id
starts with a value other than EMP
or if id
is an empty string, the policy fails, and the component doesn't load.
Pages/EditUser.razor
:
@page "/users/{id}/edit"
@using Microsoft.AspNetCore.Authorization
@attribute [Authorize(Policy = "EditUser")]
<h1>Edit User</h1>
<p>The 'EditUser' policy is satisfied! <code>Id</code> starts with 'EMP'.</p>
@code {
[Parameter]
public string Id { get; set; }
}
Customize unauthorized content with the Router component
The Router component, in conjunction with the AuthorizeRouteView component, allows the app to specify custom content if:
- The user fails an
[Authorize]
condition applied to the component. The markup of the<NotAuthorized>
element is displayed. The[Authorize]
attribute is covered in the[Authorize]
attribute section. - Asynchronous authorization is in progress, which usually means that the process of authenticating the user is in progress. The markup of the
<Authorizing>
element is displayed. - Content isn't found. The markup of the
<NotFound>
element is displayed.
In the default Blazor Server project template, the App
component (App.razor
) demonstrates how to set custom content:
<CascadingAuthenticationState>
<Router AppAssembly="@typeof(Program).Assembly">
<Found Context="routeData">
<AuthorizeRouteView RouteData="@routeData"
DefaultLayout="@typeof(MainLayout)">
<NotAuthorized>
<h1>Sorry</h1>
<p>You're not authorized to reach this page.</p>
<p>You may need to log in as a different user.</p>
</NotAuthorized>
<Authorizing>
<h1>Authorization in progress</h1>
<p>Only visible while authorization is in progress.</p>
</Authorizing>
</AuthorizeRouteView>
</Found>
<NotFound>
<LayoutView Layout="@typeof(MainLayout)">
<h1>Sorry</h1>
<p>Sorry, there's nothing at this address.</p>
</LayoutView>
</NotFound>
</Router>
</CascadingAuthenticationState>
The content of <NotFound>
, <NotAuthorized>
, and <Authorizing>
tags can include arbitrary items, such as other interactive components.
If the <NotAuthorized>
tag isn't specified, the AuthorizeRouteView uses the following fallback message:
Not authorized.
Procedural logic
If the app is required to check authorization rules as part of procedural logic, use a cascaded parameter of type Task<
AuthenticationState>
to obtain the user's ClaimsPrincipal. Task<
AuthenticationState>
can be combined with other services, such as IAuthorizationService
, to evaluate policies.
@using Microsoft.AspNetCore.Authorization
@inject IAuthorizationService AuthorizationService
<button @onclick="@DoSomething">Do something important</button>
@code {
[CascadingParameter]
private Task<AuthenticationState> authenticationStateTask { get; set; }
private async Task DoSomething()
{
var user = (await authenticationStateTask).User;
if (user.Identity.IsAuthenticated)
{
// Perform an action only available to authenticated (signed-in) users.
}
if (user.IsInRole("admin"))
{
// Perform an action only available to users in the 'admin' role.
}
if ((await AuthorizationService.AuthorizeAsync(user, "content-editor"))
.Succeeded)
{
// Perform an action only available to users satisfying the
// 'content-editor' policy.
}
}
}
Note
In a Blazor WebAssembly app component, add the Microsoft.AspNetCore.Authorization and Microsoft.AspNetCore.Components.Authorization namespaces:
@using Microsoft.AspNetCore.Authorization
@using Microsoft.AspNetCore.Components.Authorization
These namespaces can be provided globally by adding them to the app's _Imports.razor
file.
Troubleshoot errors
Common errors:
Authorization requires a cascading parameter of type
Task<AuthenticationState>
. Consider usingCascadingAuthenticationState
to supply this.null
value is received forauthenticationStateTask
It's likely that the project wasn't created using a Blazor Server template with authentication enabled. Wrap a <CascadingAuthenticationState>
around some part of the UI tree, for example in the App
component (App.razor
) as follows:
<CascadingAuthenticationState>
<Router AppAssembly="@typeof(Program).Assembly">
...
</Router>
</CascadingAuthenticationState>
The CascadingAuthenticationState supplies the Task<
AuthenticationState>
cascading parameter, which in turn it receives from the underlying AuthenticationStateProvider DI service.
Additional resources
- Microsoft identity platform documentation
- ASP.NET Core security topics
- Configure Windows Authentication in ASP.NET Core
- Build a custom version of the Authentication.MSAL JavaScript library
- ASP.NET Core Blazor Hybrid authentication and authorization
- Awesome Blazor: Authentication community sample links
Security scenarios differ between Blazor Server and Blazor WebAssembly apps. Because Blazor Server apps run on the server, authorization checks are able to determine:
- The UI options presented to a user (for example, which menu entries are available to a user).
- Access rules for areas of the app and components.
Blazor WebAssembly apps run on the client. Authorization is only used to determine which UI options to show. Since client-side checks can be modified or bypassed by a user, a Blazor WebAssembly app can't enforce authorization access rules.
Razor Pages authorization conventions don't apply to routable Razor components. If a non-routable Razor component is embedded in a page, the page's authorization conventions indirectly affect the Razor component along with the rest of the page's content.
Note
SignInManager<TUser> and UserManager<TUser> aren't supported in Razor components. Blazor Server apps use ASP.NET Core Identity. For more information, see the following guidance:
Authentication
Blazor uses the existing ASP.NET Core authentication mechanisms to establish the user's identity. The exact mechanism depends on how the Blazor app is hosted, Blazor WebAssembly or Blazor Server.
Blazor WebAssembly authentication
In Blazor WebAssembly apps, authentication checks can be bypassed because all client-side code can be modified by users. The same is true for all client-side app technologies, including JavaScript SPA frameworks or native apps for any operating system.
Add the following:
A package reference for
Microsoft.AspNetCore.Components.Authorization
.Note
For guidance on adding packages to .NET apps, see the articles under Install and manage packages at Package consumption workflow (NuGet documentation). Confirm correct package versions at NuGet.org.
The
Microsoft.AspNetCore.Components.Authorization
namespace to the app's_Imports.razor
file.
To handle authentication, use of a built-in or custom AuthenticationStateProvider service is covered in the following sections.
For more information on creating apps and configuration, see Secure ASP.NET Core Blazor WebAssembly.
Blazor Server authentication
Blazor Server apps operate over a real-time connection that's created using SignalR. Authentication in SignalR-based apps is handled when the connection is established. Authentication can be based on a cookie or some other bearer token.
The built-in AuthenticationStateProvider service for Blazor Server apps obtains authentication state data from ASP.NET Core's HttpContext.User
. This is how authentication state integrates with existing ASP.NET Core authentication mechanisms.
For more information on creating apps and configuration, see Secure ASP.NET Core Blazor Server apps.
AuthenticationStateProvider service
AuthenticationStateProvider is the underlying service used by the AuthorizeView component and CascadingAuthenticationState component to get the authentication state.
You don't typically use AuthenticationStateProvider directly. Use the AuthorizeView
component or Task<AuthenticationState>
approaches described later in this article. The main drawback to using AuthenticationStateProvider directly is that the component isn't notified automatically if the underlying authentication state data changes.
The AuthenticationStateProvider service can provide the current user's ClaimsPrincipal data, as shown in the following example:
@page "/"
@using System.Security.Claims
@using Microsoft.AspNetCore.Components.Authorization
@inject AuthenticationStateProvider AuthenticationStateProvider
<h3>ClaimsPrincipal Data</h3>
<button @onclick="GetClaimsPrincipalData">Get ClaimsPrincipal Data</button>
<p>@authMessage</p>
@if (claims.Count() > 0)
{
<ul>
@foreach (var claim in claims)
{
<li>@claim.Type: @claim.Value</li>
}
</ul>
}
<p>@surnameMessage</p>
@code {
private string authMessage;
private string surnameMessage;
private IEnumerable<Claim> claims = Enumerable.Empty<Claim>();
private async Task GetClaimsPrincipalData()
{
var authState = await AuthenticationStateProvider.GetAuthenticationStateAsync();
var user = authState.User;
if (user.Identity.IsAuthenticated)
{
authMessage = $"{user.Identity.Name} is authenticated.";
claims = user.Claims;
surnameMessage =
$"Surname: {user.FindFirst(c => c.Type == ClaimTypes.Surname)?.Value}";
}
else
{
authMessage = "The user is NOT authenticated.";
}
}
}
If user.Identity.IsAuthenticated
is true
and because the user is a ClaimsPrincipal, claims can be enumerated and membership in roles evaluated.
For more information on dependency injection (DI) and services, see ASP.NET Core Blazor dependency injection and Dependency injection in ASP.NET Core.
Expose the authentication state as a cascading parameter
If authentication state data is required for procedural logic, such as when performing an action triggered by the user, obtain the authentication state data by defining a cascading parameter of type Task<
AuthenticationState>
:
@page "/"
<button @onclick="LogUsername">Log username</button>
<p>@authMessage</p>
@code {
[CascadingParameter]
private Task<AuthenticationState> authenticationStateTask { get; set; }
private string authMessage;
private async Task LogUsername()
{
var authState = await authenticationStateTask;
var user = authState.User;
if (user.Identity.IsAuthenticated)
{
authMessage = $"{user.Identity.Name} is authenticated.";
}
else
{
authMessage = "The user is NOT authenticated.";
}
}
}
If user.Identity.IsAuthenticated
is true
, claims can be enumerated and membership in roles evaluated.
Set up the Task<
AuthenticationState>
cascading parameter using the AuthorizeRouteView and CascadingAuthenticationState components in the App
component (App.razor
):
<CascadingAuthenticationState>
<Router AppAssembly="@typeof(Program).Assembly">
<Found Context="routeData">
<AuthorizeRouteView RouteData="@routeData"
DefaultLayout="@typeof(MainLayout)" />
</Found>
<NotFound>
<LayoutView Layout="@typeof(MainLayout)">
<p>Sorry, there's nothing at this address.</p>
</LayoutView>
</NotFound>
</Router>
</CascadingAuthenticationState>
Note
With the release of ASP.NET Core 5.0.1 and for any additional 5.x releases, the Router
component includes the PreferExactMatches
parameter set to @true
. For more information, see Migrate from ASP.NET Core 3.1 to 5.0.
In a Blazor WebAssembly App, add services for options and authorization to Program.cs
:
builder.Services.AddOptions();
builder.Services.AddAuthorizationCore();
In a Blazor Server app, services for options and authorization are already present, so no further action is required.
Authorization
After a user is authenticated, authorization rules are applied to control what the user can do.
Access is typically granted or denied based on whether:
- A user is authenticated (signed in).
- A user is in a role.
- A user has a claim.
- A policy is satisfied.
Each of these concepts is the same as in an ASP.NET Core MVC or Razor Pages app. For more information on ASP.NET Core security, see the articles under ASP.NET Core Security and Identity.
AuthorizeView component
The AuthorizeView component selectively displays UI content depending on whether the user is authorized. This approach is useful when you only need to display data for the user and don't need to use the user's identity in procedural logic.
The component exposes a context
variable of type AuthenticationState, which you can use to access information about the signed-in user:
<AuthorizeView>
<h1>Hello, @context.User.Identity.Name!</h1>
<p>You can only see this content if you're authenticated.</p>
</AuthorizeView>
You can also supply different content for display if the user isn't authorized:
<AuthorizeView>
<Authorized>
<h1>Hello, @context.User.Identity.Name!</h1>
<p>You can only see this content if you're authorized.</p>
<button @onclick="SecureMethod">Authorized Only Button</button>
</Authorized>
<NotAuthorized>
<h1>Authentication Failure!</h1>
<p>You're not signed in.</p>
</NotAuthorized>
</AuthorizeView>
@code {
private void SecureMethod() { ... }
}
The content of <Authorized>
and <NotAuthorized>
tags can include arbitrary items, such as other interactive components.
A default event handler for an authorized element, such as the SecureMethod
method for the <button>
element in the preceding example, can only be invoked by an authorized user.
Authorization conditions, such as roles or policies that control UI options or access, are covered in the Authorization section.
If authorization conditions aren't specified, AuthorizeView uses a default policy and treats:
- Authenticated (signed-in) users as authorized.
- Unauthenticated (signed-out) users as unauthorized.
The AuthorizeView component can be used in the NavMenu
component (Shared/NavMenu.razor
) to display a NavLink
component (NavLink), but note that this approach only removes the list item from the rendered output. It doesn't prevent the user from navigating to the component.
Apps created from a Blazor project template that include authentication use a LoginDisplay
component that depends on an AuthorizeView
component. The AuthorizeView
component selectively displays content to users for Identity-related work. The following example is from the Blazor WebAssembly project template.
Shared/LoginDisplay.razor
:
@using Microsoft.AspNetCore.Components.Authorization
@using Microsoft.AspNetCore.Components.WebAssembly.Authentication
@inject NavigationManager Navigation
@inject SignOutSessionStateManager SignOutManager
<AuthorizeView>
<Authorized>
Hello, @context.User.Identity.Name!
<button class="nav-link btn btn-link" @onclick="BeginLogout">Log out</button>
</Authorized>
<NotAuthorized>
<a href="authentication/login">Log in</a>
</NotAuthorized>
</AuthorizeView>
@code{
private async Task BeginLogout(MouseEventArgs args)
{
await SignOutManager.SetSignOutState();
Navigation.NavigateTo("authentication/logout");
}
}
The following example is from the Blazor Server project template and uses ASP.NET Core Identity endpoints in the Identity
area of the app to process Identity-related work.
Shared/LoginDisplay.razor
:
<AuthorizeView>
<Authorized>
<a href="Identity/Account/Manage">Hello, @context.User.Identity.Name!</a>
<form method="post" action="Identity/Account/LogOut">
<button type="submit" class="nav-link btn btn-link">Log out</button>
</form>
</Authorized>
<NotAuthorized>
<a href="Identity/Account/Register">Register</a>
<a href="Identity/Account/Login">Log in</a>
</NotAuthorized>
</AuthorizeView>
Role-based and policy-based authorization
The AuthorizeView component supports role-based or policy-based authorization.
For role-based authorization, use the Roles parameter:
<AuthorizeView Roles="admin, superuser">
<p>You can only see this if you're an admin or superuser.</p>
</AuthorizeView>
For more information, see Role-based authorization in ASP.NET Core.
For policy-based authorization, use the Policy parameter:
<AuthorizeView Policy="content-editor">
<p>You can only see this if you satisfy the "content-editor" policy.</p>
</AuthorizeView>
Claims-based authorization is a special case of policy-based authorization. For example, you can define a policy that requires users to have a certain claim. For more information, see Policy-based authorization in ASP.NET Core.
These APIs can be used in either Blazor Server or Blazor WebAssembly apps.
If neither Roles nor Policy is specified, AuthorizeView uses the default policy.
Content displayed during asynchronous authentication
Blazor allows for authentication state to be determined asynchronously. The primary scenario for this approach is in Blazor WebAssembly apps that make a request to an external endpoint for authentication.
While authentication is in progress, AuthorizeView displays no content by default. To display content while authentication occurs, use the <Authorizing>
tag:
<AuthorizeView>
<Authorized>
<h1>Hello, @context.User.Identity.Name!</h1>
<p>You can only see this content if you're authenticated.</p>
</Authorized>
<Authorizing>
<h1>Authentication in progress</h1>
<p>You can only see this content while authentication is in progress.</p>
</Authorizing>
</AuthorizeView>
This approach isn't normally applicable to Blazor Server apps. Blazor Server apps know the authentication state as soon as the state is established. Authorizing content can be provided in a Blazor Server app's AuthorizeView component, but the content is never displayed.
[Authorize] attribute
The [Authorize]
attribute can be used in Razor components:
@page "/"
@attribute [Authorize]
You can only see this if you're signed in.
Important
Only use [Authorize]
on @page
components reached via the Blazor Router. Authorization is only performed as an aspect of routing and not for child components rendered within a page. To authorize the display of specific parts within a page, use AuthorizeView instead.
The [Authorize]
attribute also supports role-based or policy-based authorization. For role-based authorization, use the Roles parameter:
@page "/"
@attribute [Authorize(Roles = "admin, superuser")]
<p>You can only see this if you're in the 'admin' or 'superuser' role.</p>
For policy-based authorization, use the Policy parameter:
@page "/"
@attribute [Authorize(Policy = "content-editor")]
<p>You can only see this if you satisfy the 'content-editor' policy.</p>
If neither Roles nor Policy is specified, [Authorize]
uses the default policy, which by default is to treat:
- Authenticated (signed-in) users as authorized.
- Unauthenticated (signed-out) users as unauthorized.
Resource authorization
To authorize users for resources, pass the request's route data to the Resource parameter of AuthorizeRouteView.
In the Router.Found content for a requested route in the App
component (App.razor
):
<AuthorizeRouteView Resource="@routeData" RouteData="@routeData"
DefaultLayout="@typeof(MainLayout)" />
For more information on how authorization state data is passed and used in procedural logic, see the Expose the authentication state as a cascading parameter section.
When the AuthorizeRouteView receives the route data for the resource, authorization policies have access to RouteData.PageType and RouteData.RouteValues that permit custom logic to make authorization decisions.
In the following example, an EditUser
policy is created in AuthorizationOptions for the app's authorization service configuration (AddAuthorizationCore) with the following logic:
- Determine if a route value exists with a key of
id
. If the key exists, the route value is stored invalue
. - In a variable named
id
, storevalue
as a string or set an empty string value (string.Empty
). - If
id
isn't an empty string, assert that the policy is satisfied (returntrue
) if the string's value starts withEMP
. Otherwise, assert that the policy fails (returnfalse
).
In either Program.cs
or Startup.cs
(depending on the hosting model and framework version):
Add namespaces for Microsoft.AspNetCore.Components and System.Linq:
using Microsoft.AspNetCore.Components; using System.Linq;
Add the policy:
options.AddPolicy("EditUser", policy => policy.RequireAssertion(context => { if (context.Resource is RouteData rd) { var routeValue = rd.RouteValues.TryGetValue("id", out var value); var id = Convert.ToString(value, System.Globalization.CultureInfo.InvariantCulture) ?? string.Empty; if (!string.IsNullOrEmpty(id)) { return id.StartsWith("EMP", StringComparison.InvariantCulture); } } return false; }) );
The preceding example is an oversimplified authorization policy, merely used to demonstrate the concept with a working example. For more information on creating and configuring authorization policies, see Policy-based authorization in ASP.NET Core.
In the following EditUser
component, the resource at /users/{id}/edit
has a route parameter for the user's identifier ({id}
). The component uses the preceding EditUser
authorization policy to determine if the route value for id
starts with EMP
. If id
starts with EMP
, the policy succeeds and access to the component is authorized. If id
starts with a value other than EMP
or if id
is an empty string, the policy fails, and the component doesn't load.
Pages/EditUser.razor
:
@page "/users/{id}/edit"
@using Microsoft.AspNetCore.Authorization
@attribute [Authorize(Policy = "EditUser")]
<h1>Edit User</h1>
<p>The 'EditUser' policy is satisfied! <code>Id</code> starts with 'EMP'.</p>
@code {
[Parameter]
public string Id { get; set; }
}
Customize unauthorized content with the Router component
The Router component, in conjunction with the AuthorizeRouteView component, allows the app to specify custom content if:
- The user fails an
[Authorize]
condition applied to the component. The markup of the<NotAuthorized>
element is displayed. The[Authorize]
attribute is covered in the[Authorize]
attribute section. - Asynchronous authorization is in progress, which usually means that the process of authenticating the user is in progress. The markup of the
<Authorizing>
element is displayed. - Content isn't found. The markup of the
<NotFound>
element is displayed.
In the default Blazor Server project template, the App
component (App.razor
) demonstrates how to set custom content:
<CascadingAuthenticationState>
<Router AppAssembly="@typeof(Program).Assembly">
<Found Context="routeData">
<AuthorizeRouteView RouteData="@routeData"
DefaultLayout="@typeof(MainLayout)">
<NotAuthorized>
<h1>Sorry</h1>
<p>You're not authorized to reach this page.</p>
<p>You may need to log in as a different user.</p>
</NotAuthorized>
<Authorizing>
<h1>Authorization in progress</h1>
<p>Only visible while authorization is in progress.</p>
</Authorizing>
</AuthorizeRouteView>
</Found>
<NotFound>
<LayoutView Layout="@typeof(MainLayout)">
<h1>Sorry</h1>
<p>Sorry, there's nothing at this address.</p>
</LayoutView>
</NotFound>
</Router>
</CascadingAuthenticationState>
Note
With the release of ASP.NET Core 5.0.1 and for any additional 5.x releases, the Router
component includes the PreferExactMatches
parameter set to @true
. For more information, see Migrate from ASP.NET Core 3.1 to 5.0.
The content of <NotFound>
, <NotAuthorized>
, and <Authorizing>
tags can include arbitrary items, such as other interactive components.
If the <NotAuthorized>
tag isn't specified, the AuthorizeRouteView uses the following fallback message:
Not authorized.
Procedural logic
If the app is required to check authorization rules as part of procedural logic, use a cascaded parameter of type Task<
AuthenticationState>
to obtain the user's ClaimsPrincipal. Task<
AuthenticationState>
can be combined with other services, such as IAuthorizationService
, to evaluate policies.
@using Microsoft.AspNetCore.Authorization
@inject IAuthorizationService AuthorizationService
<button @onclick="@DoSomething">Do something important</button>
@code {
[CascadingParameter]
private Task<AuthenticationState> authenticationStateTask { get; set; }
private async Task DoSomething()
{
var user = (await authenticationStateTask).User;
if (user.Identity.IsAuthenticated)
{
// Perform an action only available to authenticated (signed-in) users.
}
if (user.IsInRole("admin"))
{
// Perform an action only available to users in the 'admin' role.
}
if ((await AuthorizationService.AuthorizeAsync(user, "content-editor"))
.Succeeded)
{
// Perform an action only available to users satisfying the
// 'content-editor' policy.
}
}
}
Note
In a Blazor WebAssembly app component, add the Microsoft.AspNetCore.Authorization and Microsoft.AspNetCore.Components.Authorization namespaces:
@using Microsoft.AspNetCore.Authorization
@using Microsoft.AspNetCore.Components.Authorization
These namespaces can be provided globally by adding them to the app's _Imports.razor
file.
Troubleshoot errors
Common errors:
Authorization requires a cascading parameter of type
Task<AuthenticationState>
. Consider usingCascadingAuthenticationState
to supply this.null
value is received forauthenticationStateTask
It's likely that the project wasn't created using a Blazor Server template with authentication enabled. Wrap a <CascadingAuthenticationState>
around some part of the UI tree, for example in the App
component (App.razor
) as follows:
<CascadingAuthenticationState>
<Router AppAssembly="@typeof(Program).Assembly">
...
</Router>
</CascadingAuthenticationState>
Note
With the release of ASP.NET Core 5.0.1 and for any additional 5.x releases, the Router
component includes the PreferExactMatches
parameter set to @true
. For more information, see Migrate from ASP.NET Core 3.1 to 5.0.
The CascadingAuthenticationState supplies the Task<
AuthenticationState>
cascading parameter, which in turn it receives from the underlying AuthenticationStateProvider DI service.
Additional resources
- Microsoft identity platform documentation
- ASP.NET Core security topics
- Configure Windows Authentication in ASP.NET Core
- Build a custom version of the Authentication.MSAL JavaScript library
- Awesome Blazor: Authentication community sample links
Security scenarios differ between Blazor Server and Blazor WebAssembly apps. Because Blazor Server apps run on the server, authorization checks are able to determine:
- The UI options presented to a user (for example, which menu entries are available to a user).
- Access rules for areas of the app and components.
Blazor WebAssembly apps run on the client. Authorization is only used to determine which UI options to show. Since client-side checks can be modified or bypassed by a user, a Blazor WebAssembly app can't enforce authorization access rules.
Razor Pages authorization conventions don't apply to routable Razor components. If a non-routable Razor component is embedded in a page, the page's authorization conventions indirectly affect the Razor component along with the rest of the page's content.
Note
SignInManager<TUser> and UserManager<TUser> aren't supported in Razor components. Blazor Server apps use ASP.NET Core Identity. For more information, see the following guidance:
Authentication
Blazor uses the existing ASP.NET Core authentication mechanisms to establish the user's identity. The exact mechanism depends on how the Blazor app is hosted, Blazor WebAssembly or Blazor Server.
Blazor WebAssembly authentication
In Blazor WebAssembly apps, authentication checks can be bypassed because all client-side code can be modified by users. The same is true for all client-side app technologies, including JavaScript SPA frameworks or native apps for any operating system.
Add the following:
A package reference for
Microsoft.AspNetCore.Components.Authorization
.Note
For guidance on adding packages to .NET apps, see the articles under Install and manage packages at Package consumption workflow (NuGet documentation). Confirm correct package versions at NuGet.org.
The
Microsoft.AspNetCore.Components.Authorization
namespace to the app's_Imports.razor
file.
To handle authentication, use of a built-in or custom AuthenticationStateProvider service is covered in the following sections.
For more information on creating apps and configuration, see Secure ASP.NET Core Blazor WebAssembly.
Blazor Server authentication
Blazor Server apps operate over a real-time connection that's created using SignalR. Authentication in SignalR-based apps is handled when the connection is established. Authentication can be based on a cookie or some other bearer token.
The built-in AuthenticationStateProvider service for Blazor Server apps obtains authentication state data from ASP.NET Core's HttpContext.User
. This is how authentication state integrates with existing ASP.NET Core authentication mechanisms.
For more information on creating apps and configuration, see Secure ASP.NET Core Blazor Server apps.
AuthenticationStateProvider service
AuthenticationStateProvider is the underlying service used by the AuthorizeView component and CascadingAuthenticationState component to get the authentication state.
You don't typically use AuthenticationStateProvider directly. Use the AuthorizeView
component or Task<AuthenticationState>
approaches described later in this article. The main drawback to using AuthenticationStateProvider directly is that the component isn't notified automatically if the underlying authentication state data changes.
The AuthenticationStateProvider service can provide the current user's ClaimsPrincipal data, as shown in the following example:
@page "/"
@using System.Security.Claims
@using Microsoft.AspNetCore.Components.Authorization
@inject AuthenticationStateProvider AuthenticationStateProvider
<h3>ClaimsPrincipal Data</h3>
<button @onclick="GetClaimsPrincipalData">Get ClaimsPrincipal Data</button>
<p>@authMessage</p>
@if (claims.Count() > 0)
{
<ul>
@foreach (var claim in claims)
{
<li>@claim.Type: @claim.Value</li>
}
</ul>
}
<p>@surnameMessage</p>
@code {
private string authMessage;
private string surnameMessage;
private IEnumerable<Claim> claims = Enumerable.Empty<Claim>();
private async Task GetClaimsPrincipalData()
{
var authState = await AuthenticationStateProvider.GetAuthenticationStateAsync();
var user = authState.User;
if (user.Identity.IsAuthenticated)
{
authMessage = $"{user.Identity.Name} is authenticated.";
claims = user.Claims;
surnameMessage =
$"Surname: {user.FindFirst(c => c.Type == ClaimTypes.Surname)?.Value}";
}
else
{
authMessage = "The user is NOT authenticated.";
}
}
}
If user.Identity.IsAuthenticated
is true
and because the user is a ClaimsPrincipal, claims can be enumerated and membership in roles evaluated.
For more information on dependency injection (DI) and services, see ASP.NET Core Blazor dependency injection and Dependency injection in ASP.NET Core.
Expose the authentication state as a cascading parameter
If authentication state data is required for procedural logic, such as when performing an action triggered by the user, obtain the authentication state data by defining a cascading parameter of type Task<
AuthenticationState>
:
@page "/"
<button @onclick="LogUsername">Log username</button>
<p>@authMessage</p>
@code {
[CascadingParameter]
private Task<AuthenticationState> authenticationStateTask { get; set; }
private string authMessage;
private async Task LogUsername()
{
var authState = await authenticationStateTask;
var user = authState.User;
if (user.Identity.IsAuthenticated)
{
authMessage = $"{user.Identity.Name} is authenticated.";
}
else
{
authMessage = "The user is NOT authenticated.";
}
}
}
If user.Identity.IsAuthenticated
is true
, claims can be enumerated and membership in roles evaluated.
Set up the Task<
AuthenticationState>
cascading parameter using the AuthorizeRouteView and CascadingAuthenticationState components in the App
component (App.razor
):
<CascadingAuthenticationState>
<Router AppAssembly="@typeof(Program).Assembly">
<Found Context="routeData">
<AuthorizeRouteView RouteData="@routeData"
DefaultLayout="@typeof(MainLayout)" />
</Found>
<NotFound>
<LayoutView Layout="@typeof(MainLayout)">
<p>Sorry, there's nothing at this address.</p>
</LayoutView>
</NotFound>
</Router>
</CascadingAuthenticationState>
In a Blazor WebAssembly App, add services for options and authorization to Program.cs
:
builder.Services.AddOptions();
builder.Services.AddAuthorizationCore();
In a Blazor Server app, services for options and authorization are already present, so no further action is required.
Authorization
After a user is authenticated, authorization rules are applied to control what the user can do.
Access is typically granted or denied based on whether:
- A user is authenticated (signed in).
- A user is in a role.
- A user has a claim.
- A policy is satisfied.
Each of these concepts is the same as in an ASP.NET Core MVC or Razor Pages app. For more information on ASP.NET Core security, see the articles under ASP.NET Core Security and Identity.
AuthorizeView component
The AuthorizeView component selectively displays UI content depending on whether the user is authorized. This approach is useful when you only need to display data for the user and don't need to use the user's identity in procedural logic.
The component exposes a context
variable of type AuthenticationState, which you can use to access information about the signed-in user:
<AuthorizeView>
<h1>Hello, @context.User.Identity.Name!</h1>
<p>You can only see this content if you're authenticated.</p>
</AuthorizeView>
You can also supply different content for display if the user isn't authorized:
<AuthorizeView>
<Authorized>
<h1>Hello, @context.User.Identity.Name!</h1>
<p>You can only see this content if you're authorized.</p>
<button @onclick="SecureMethod">Authorized Only Button</button>
</Authorized>
<NotAuthorized>
<h1>Authentication Failure!</h1>
<p>You're not signed in.</p>
</NotAuthorized>
</AuthorizeView>
@code {
private void SecureMethod() { ... }
}
The content of <Authorized>
and <NotAuthorized>
tags can include arbitrary items, such as other interactive components.
A default event handler for an authorized element, such as the SecureMethod
method for the <button>
element in the preceding example, can only be invoked by an authorized user.
Authorization conditions, such as roles or policies that control UI options or access, are covered in the Authorization section.
If authorization conditions aren't specified, AuthorizeView uses a default policy and treats:
- Authenticated (signed-in) users as authorized.
- Unauthenticated (signed-out) users as unauthorized.
The AuthorizeView component can be used in the NavMenu
component (Shared/NavMenu.razor
) to display a NavLink
component (NavLink), but note that this approach only removes the list item from the rendered output. It doesn't prevent the user from navigating to the component.
Apps created from a Blazor project template that include authentication use a LoginDisplay
component that depends on an AuthorizeView
component. The AuthorizeView
component selectively displays content to users for Identity-related work. The following example is from the Blazor WebAssembly project template.
Shared/LoginDisplay.razor
:
@using Microsoft.AspNetCore.Components.Authorization
@using Microsoft.AspNetCore.Components.WebAssembly.Authentication
@inject NavigationManager Navigation
@inject SignOutSessionStateManager SignOutManager
<AuthorizeView>
<Authorized>
Hello, @context.User.Identity.Name!
<button class="nav-link btn btn-link" @onclick="BeginLogout">Log out</button>
</Authorized>
<NotAuthorized>
<a href="authentication/login">Log in</a>
</NotAuthorized>
</AuthorizeView>
@code{
private async Task BeginLogout(MouseEventArgs args)
{
await SignOutManager.SetSignOutState();
Navigation.NavigateTo("authentication/logout");
}
}
The following example is from the Blazor Server project template and uses ASP.NET Core Identity endpoints in the Identity
area of the app to process Identity-related work.
Shared/LoginDisplay.razor
:
<AuthorizeView>
<Authorized>
<a href="Identity/Account/Manage">Hello, @context.User.Identity.Name!</a>
<form method="post" action="Identity/Account/LogOut">
<button type="submit" class="nav-link btn btn-link">Log out</button>
</form>
</Authorized>
<NotAuthorized>
<a href="Identity/Account/Register">Register</a>
<a href="Identity/Account/Login">Log in</a>
</NotAuthorized>
</AuthorizeView>
Role-based and policy-based authorization
The AuthorizeView component supports role-based or policy-based authorization.
For role-based authorization, use the Roles parameter:
<AuthorizeView Roles="admin, superuser">
<p>You can only see this if you're an admin or superuser.</p>
</AuthorizeView>
For more information, see Role-based authorization in ASP.NET Core.
For policy-based authorization, use the Policy parameter:
<AuthorizeView Policy="content-editor">
<p>You can only see this if you satisfy the "content-editor" policy.</p>
</AuthorizeView>
Claims-based authorization is a special case of policy-based authorization. For example, you can define a policy that requires users to have a certain claim. For more information, see Policy-based authorization in ASP.NET Core.
These APIs can be used in either Blazor Server or Blazor WebAssembly apps.
If neither Roles nor Policy is specified, AuthorizeView uses the default policy.
Content displayed during asynchronous authentication
Blazor allows for authentication state to be determined asynchronously. The primary scenario for this approach is in Blazor WebAssembly apps that make a request to an external endpoint for authentication.
While authentication is in progress, AuthorizeView displays no content by default. To display content while authentication occurs, use the <Authorizing>
tag:
<AuthorizeView>
<Authorized>
<h1>Hello, @context.User.Identity.Name!</h1>
<p>You can only see this content if you're authenticated.</p>
</Authorized>
<Authorizing>
<h1>Authentication in progress</h1>
<p>You can only see this content while authentication is in progress.</p>
</Authorizing>
</AuthorizeView>
This approach isn't normally applicable to Blazor Server apps. Blazor Server apps know the authentication state as soon as the state is established. Authorizing content can be provided in a Blazor Server app's AuthorizeView component, but the content is never displayed.
[Authorize] attribute
The [Authorize]
attribute can be used in Razor components:
@page "/"
@attribute [Authorize]
You can only see this if you're signed in.
Important
Only use [Authorize]
on @page
components reached via the Blazor Router. Authorization is only performed as an aspect of routing and not for child components rendered within a page. To authorize the display of specific parts within a page, use AuthorizeView instead.
The [Authorize]
attribute also supports role-based or policy-based authorization. For role-based authorization, use the Roles parameter:
@page "/"
@attribute [Authorize(Roles = "admin, superuser")]
<p>You can only see this if you're in the 'admin' or 'superuser' role.</p>
For policy-based authorization, use the Policy parameter:
@page "/"
@attribute [Authorize(Policy = "content-editor")]
<p>You can only see this if you satisfy the 'content-editor' policy.</p>
If neither Roles nor Policy is specified, [Authorize]
uses the default policy, which by default is to treat:
- Authenticated (signed-in) users as authorized.
- Unauthenticated (signed-out) users as unauthorized.
Customize unauthorized content with the Router component
The Router component, in conjunction with the AuthorizeRouteView component, allows the app to specify custom content if:
- The user fails an
[Authorize]
condition applied to the component. The markup of the<NotAuthorized>
element is displayed. The[Authorize]
attribute is covered in the[Authorize]
attribute section. - Asynchronous authorization is in progress, which usually means that the process of authenticating the user is in progress. The markup of the
<Authorizing>
element is displayed. - Content isn't found. The markup of the
<NotFound>
element is displayed.
In the default Blazor Server project template, the App
component (App.razor
) demonstrates how to set custom content:
<CascadingAuthenticationState>
<Router AppAssembly="@typeof(Program).Assembly">
<Found Context="routeData">
<AuthorizeRouteView RouteData="@routeData"
DefaultLayout="@typeof(MainLayout)">
<NotAuthorized>
<h1>Sorry</h1>
<p>You're not authorized to reach this page.</p>
<p>You may need to log in as a different user.</p>
</NotAuthorized>
<Authorizing>
<h1>Authorization in progress</h1>
<p>Only visible while authorization is in progress.</p>
</Authorizing>
</AuthorizeRouteView>
</Found>
<NotFound>
<LayoutView Layout="@typeof(MainLayout)">
<h1>Sorry</h1>
<p>Sorry, there's nothing at this address.</p>
</LayoutView>
</NotFound>
</Router>
</CascadingAuthenticationState>
The content of <NotFound>
, <NotAuthorized>
, and <Authorizing>
tags can include arbitrary items, such as other interactive components.
If the <NotAuthorized>
tag isn't specified, the AuthorizeRouteView uses the following fallback message:
Not authorized.
Procedural logic
If the app is required to check authorization rules as part of procedural logic, use a cascaded parameter of type Task<
AuthenticationState>
to obtain the user's ClaimsPrincipal. Task<
AuthenticationState>
can be combined with other services, such as IAuthorizationService
, to evaluate policies.
@using Microsoft.AspNetCore.Authorization
@inject IAuthorizationService AuthorizationService
<button @onclick="@DoSomething">Do something important</button>
@code {
[CascadingParameter]
private Task<AuthenticationState> authenticationStateTask { get; set; }
private async Task DoSomething()
{
var user = (await authenticationStateTask).User;
if (user.Identity.IsAuthenticated)
{
// Perform an action only available to authenticated (signed-in) users.
}
if (user.IsInRole("admin"))
{
// Perform an action only available to users in the 'admin' role.
}
if ((await AuthorizationService.AuthorizeAsync(user, "content-editor"))
.Succeeded)
{
// Perform an action only available to users satisfying the
// 'content-editor' policy.
}
}
}
Note
In a Blazor WebAssembly app component, add the Microsoft.AspNetCore.Authorization and Microsoft.AspNetCore.Components.Authorization namespaces:
@using Microsoft.AspNetCore.Authorization
@using Microsoft.AspNetCore.Components.Authorization
These namespaces can be provided globally by adding them to the app's _Imports.razor
file.
Troubleshoot errors
Common errors:
Authorization requires a cascading parameter of type
Task<AuthenticationState>
. Consider usingCascadingAuthenticationState
to supply this.null
value is received forauthenticationStateTask
It's likely that the project wasn't created using a Blazor Server template with authentication enabled. Wrap a <CascadingAuthenticationState>
around some part of the UI tree, for example in the App
component (App.razor
) as follows:
<CascadingAuthenticationState>
<Router AppAssembly="@typeof(Program).Assembly">
...
</Router>
</CascadingAuthenticationState>
The CascadingAuthenticationState supplies the Task<
AuthenticationState>
cascading parameter, which in turn it receives from the underlying AuthenticationStateProvider DI service.
Additional resources
Feedback
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