Retargeting Changes for Migration from .NET Framework 4.0 to 4.6.2

• DbParameter.Precision
• DbParameter.Scale

• HtmlTextWriter.RenderBeginTag(String)
• HtmlTextWriter.RenderBeginTag(HtmlTextWriterTag)

• Handle the T:System.NullReferenceException if you application is running on the .NET Framework 4.6.2.
• Upgrade to the .NET Framework 4.7, which restores the previous behavior and throws an T:System.ArgumentNullException.

• HttpRuntime.AppDomainAppPath

• MachineKey.Encode(Byte[], MachineKeyProtection)
• MachineKey.Decode(String, MachineKeyProtection)

• WebUtility.HtmlEncode(String)
• WebUtility.HtmlEncode(String, TextWriter)

<runtime>
<AppContextSwitchOverrides value="Switch.System.Security.Cryptography.AesCryptoServiceProvider.DontCorrectlyResetDecryptor=true"/>
</runtime>

<runtime>
<AppContextSwitchOverrides value="Switch.System.Security.Cryptography.AesCryptoServiceProvider.DontCorrectlyResetDecryptor=false"/>
</runtime>

• AesCryptoServiceProvider.CreateDecryptor()

<configuration>
<runtime>
<AppContextSwitchOverrides value="Switch.System.Security.ClaimsIdentity.SetActorAsReferenceWhenCopyingClaimsIdentity=true" />
</runtime>
</configuration>

• ClaimsIdentity.ClaimsIdentity(IIdentity)
• ClaimsIdentity.ClaimsIdentity(IIdentity, IEnumerable<Claim>)
• ClaimsIdentity.ClaimsIdentity(IIdentity, IEnumerable<Claim>, String, String, String)

<runtime>
<AppContextSwitchOverrides value="Switch.System.IO.Compression.ZipFile.UseBackslash=true" />
</runtime>

<runtime>
<AppContextSwitchOverrides value="Switch.System.IO.Compression.ZipFile.UseBackslash=false" />
</runtime>

• ZipFile.CreateFromDirectory(String, String)
• ZipFile.CreateFromDirectory(String, String, CompressionLevel, Boolean)
• ZipFile.CreateFromDirectory(String, String, CompressionLevel, Boolean, Encoding)

• Canonicalizing component and directory separators.
• Applying the current directory to a relative path.
• Evaluating the relative directory (.) or the parent directory (..) in a path.
• Trimming specified characters.

• The runtime defers to the operating system's GetFullPathName function to normalize paths.
• Normalization no longer involves trimming the end of directory segments (such as a space at the end of a directory name).
• Support for device path syntax in full trust, including \\.\ and, for file I/O APIs in mscorlib.dll, \\?\.
• The runtime does not validate device syntax paths.
• The use of device syntax to access alternate data streams is supported.

<runtime>
<AppContextSwitchOverrides value="Switch.System.IO.UseLegacyPathHandling=true" />
</runtime>

<runtime>
<AppContextSwitchOverrides value="Switch.System.IO.UseLegacyPathHandling=false" />
</runtime>

• TaskFactory.FromAsync(IAsyncResult, Action<IAsyncResult>)
• TaskFactory.FromAsync(IAsyncResult, Action<IAsyncResult>, TaskCreationOptions)
• TaskFactory.FromAsync(IAsyncResult, Action<IAsyncResult>, TaskCreationOptions, TaskScheduler)
• TaskFactory.FromAsync<TResult>(IAsyncResult, Func<IAsyncResult,TResult>)
• TaskFactory.FromAsync(Func<AsyncCallback,Object,IAsyncResult>, Action<IAsyncResult>, Object)
• TaskFactory.FromAsync(Func<AsyncCallback,Object,IAsyncResult>, Action<IAsyncResult>, Object, TaskCreationOptions)
• TaskFactory.FromAsync<TArg1>(Func<TArg1,AsyncCallback,Object,IAsyncResult>, Action<IAsyncResult>, TArg1, Object)
• TaskFactory.FromAsync<TArg1>(Func<TArg1,AsyncCallback,Object,IAsyncResult>, Action<IAsyncResult>, TArg1, Object, TaskCreationOptions)
• TaskFactory.FromAsync<TResult>(Func<AsyncCallback,Object,IAsyncResult>, Func<IAsyncResult,TResult>, Object)
• TaskFactory.FromAsync<TResult>(Func<AsyncCallback,Object,IAsyncResult>, Func<IAsyncResult,TResult>, Object, TaskCreationOptions)
• TaskFactory.FromAsync<TResult>(IAsyncResult, Func<IAsyncResult,TResult>, TaskCreationOptions)
• TaskFactory.FromAsync<TResult>(IAsyncResult, Func<IAsyncResult,TResult>, TaskCreationOptions, TaskScheduler)
• TaskFactory.FromAsync<TArg1,TArg2>(Func<TArg1,TArg2,AsyncCallback,Object,IAsyncResult>, Action<IAsyncResult>, TArg1, TArg2, Object)
• TaskFactory.FromAsync<TArg1,TArg2>(Func<TArg1,TArg2,AsyncCallback,Object,IAsyncResult>, Action<IAsyncResult>, TArg1, TArg2, Object, TaskCreationOptions)
• TaskFactory.FromAsync<TArg1,TResult>(Func<TArg1,AsyncCallback,Object,IAsyncResult>, Func<IAsyncResult,TResult>, TArg1, Object)
• TaskFactory.FromAsync<TArg1,TResult>(Func<TArg1,AsyncCallback,Object,IAsyncResult>, Func<IAsyncResult,TResult>, TArg1, Object, TaskCreationOptions)
• TaskFactory.FromAsync<TArg1,TArg2,TResult>(Func<TArg1,TArg2,AsyncCallback,Object,IAsyncResult>, Func<IAsyncResult,TResult>, TArg1, TArg2, Object)
• TaskFactory.FromAsync<TArg1,TArg2,TArg3>(Func<TArg1,TArg2,TArg3,AsyncCallback,Object,IAsyncResult>, Action<IAsyncResult>, TArg1, TArg2, TArg3, Object)
• TaskFactory.FromAsync<TArg1,TArg2,TArg3>(Func<TArg1,TArg2,TArg3,AsyncCallback,Object,IAsyncResult>, Action<IAsyncResult>, TArg1, TArg2, TArg3, Object, TaskCreationOptions)
• TaskFactory.FromAsync<TArg1,TArg2,TResult>(Func<TArg1,TArg2,AsyncCallback,Object,IAsyncResult>, Func<IAsyncResult,TResult>, TArg1, TArg2, Object, TaskCreationOptions)
• TaskFactory.FromAsync<TArg1,TArg2,TArg3,TResult>(Func<TArg1,TArg2,TArg3,AsyncCallback,Object,IAsyncResult>, Func<IAsyncResult,TResult>, TArg1, TArg2, TArg3, Object)
• TaskFactory.FromAsync<TArg1,TArg2,TArg3,TResult>(Func<TArg1,TArg2,TArg3,AsyncCallback,Object,IAsyncResult>, Func<IAsyncResult,TResult>, TArg1, TArg2, TArg3, Object, TaskCreationOptions)

• List<T>.ForEach(Action<T>)

• The length of the path is greater than MaxValue (32,767) characters.
• The operating system returns COR_E_PATHTOOLONG or its equivalent.

<runtime>
<AppContextSwitchOverrides value="Switch.System.IO.BlockLongPaths=true" />
</runtime>

<runtime>
<AppContextSwitchOverrides value="Switch.System.IO.BlockLongPaths=false" />
</runtime>

• Remove the scheme from URLs manually (e.g. remove file:// from URLs)
• Pass the URI to the Uri class and use LocalPath

• Path.GetDirectoryName(String)
• Path.GetPathRoot(String)

• URI parsing will perform normalization and character checking according to the latest IRI rules in RFC 3987.
• Unicode normalization form C will only be performed on the host portion of the URI.
• Invalid mailto: URIs will now cause an exception.
• Trailing dots at the end of a path segment are now preserved.
• file:// URIs do not escape the ? character.
• Unicode control characters U+0080 through U+009F are not supported.
• Comma characters , or %2c are not automatically unescaped.

• Uri.Uri(String)
• Uri.Uri(String, Boolean)
• Uri.Uri(String, UriKind)
• Uri.Uri(Uri, String)
• Uri.TryCreate(String, UriKind, Uri)
• Uri.TryCreate(Uri, String, Uri)
• Uri.TryCreate(Uri, Uri, Uri)

• Uri.IsWellFormedUriString(String, UriKind)

• Under certain conditions, an unboxing operation may throw a NullReferenceException in Release builds with optimization turned on.
• In some cases, execution of production code in a large method body may throw a StackOverflowException.
• Under certain conditions, structures passed to a method are treated as reference types rather than as value types in Release builds. One of the manifestations of this issue is that the individual items in a collection appear in an unexpected order.
• Under certain conditions, the comparison of UInt16 values with their high bit set is incorrect if optimization is enabled.
• Under certain conditions, particularly when initializing array values, memory initialization by the OpCodes.Initblk IL instruction may initialize memory with an incorrect value. This can result either in an unhandled exception or incorrect output.
• Under certain rare conditions, a conditional bit test can return the incorrect Boolean value or throw an exception if compiler optimizations are enabled.
• Under certain conditions, if an if statement is used to test for a condition before entering a try block and in the exit from the try block, and the same condition is evaluated in the catch or finally block, the new 64-bit JIT compiler removes the if condition from the catch or finally block when it optimizes code. As a result, code inside the if statement in the catch or finally block is executed unconditionally.

• Upgrade to the .NET Framework 4.6.2. The new 64-bit compiler included with the .NET Framework 4.6.2 addresses each of these known issues.
• Ensure that your version of Windows is up to date by running Windows Update. Service updates to the .NET Framework 4.6 and 4.6.1 address each of these issues except the NullReferenceException in an unboxing operation.
• Compile with the older 64-bit JIT compiler. See the Mitigation of other issues section for more information on how to do this.

• On a per-application basis, you can add the < element to your application's configuration file. The following disables compilation with the new 64-bit JIT compiler and instead uses the legacy 64-bit JIT compiler.

<?xml version ="1.0"?>
<configuration>
<runtime>
<useLegacyJit enabled="1" />
</runtime>
</configuration>

• On a per-user basis, you can add a REG_DWORD value named useLegacyJit to the HKEY_CURRENT_USER\SOFTWARE\Microsoft.NETFramework key of the registry. A value of 1 enables the legacy 64-bit JIT compiler; a value of 0 disables it and enables the new 64-bit JIT compiler.
• On a per-machine basis, you can add a REG_DWORD value named useLegacyJit to the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft.NETFramework key of the registry. A value of 1 enables the legacy 64-bit JIT compiler; a value of 0 disables it and enables the new 64-bit JIT compiler.

• Recompilation generates warnings that did not appear when the app was compiled under a previous version of MSBuild. However, because the warning identifies a possible source of runtime failure, it should be investigated and addressed.
• If warnings are treated as errors, the app will fail to compile.

<runtime>
<AppContextSwitchOverrides
value="Switch.System.Net.DontCheckCertificateEKUs=true" />
</runtime>

[!IMPORTANT] This setting is provided for backward compatibility only. Its use is otherwise not recommended.

• System.Net.Security.SslStream
• System.Net.ServicePointManager
• System.Net.Http.HttpClient
• System.Net.Mail.SmtpClient
• System.Net.HttpWebRequest
• System.Net.FtpWebRequest

1. By programmatically setting compat switches on the AppContext, as explained here.
2. By adding the following line to the <runtime> section of the app.config file:

<AppContextSwitchOverrides value="Switch.System.Net.DontEnableSchUseStrongCrypto=true"/>

• SecurityProtocolType.Ssl3
• SslProtocols.None
• SslProtocols.Ssl2
• SslProtocols.Ssl3

<runtime>
<AppContextSwitchOverrides
value="Switch.System.Net.DontEnableSchSendAuxRecord=true" />
</runtime>

[!IMPORTANT] This setting is provided for backward compatibility only. Its use is otherwise not recommended.

• System.Net.Security.SslStream
• System.Net.ServicePointManager
• System.Net.Http.HttpClient
• System.Net.Mail.SmtpClient
• System.Net.HttpWebRequest
• System.Net.FtpWebRequest

• RSA.ImportParameters(RSAParameters)
• RSACng.ImportParameters(RSAParameters)
• RSACertificateExtensions.GetRSAPrivateKey(X509Certificate2)
• RSACertificateExtensions.GetRSAPublicKey(X509Certificate2)

<AppContextSwitchOverrides value="Switch.System.Security.Cryptography.Xml.SignedXmlUseLegacyCertificatePrivateKey=true" />

• SignedXml.CheckSignatureReturningKey(AsymmetricAlgorithm)

1. Recompile your app to target an earlier version of the .NET Framework than 4.6. For IIS-hosted services, use the <httpRuntime targetFramework="x.x" /> element to target an earlier version of the .NET Framework.
2. Add the following line to the <appSettings> section of your app.config file: <add key="appContext.SetSwitch:Switch.System.IdentityModel.EnableCachedEmptyDefaultAuthorizationContext" value="true" />

• AuthorizationContext.CreateDefaultAuthorizationContext(IList<IAuthorizationPolicy>)

[ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Reentrant)]

• Set the service's concurrency mode to ConcurrencyMode.Single or <System.ServiceModel.ConcurrencyMode.Multiple?displayProperty=nameWithType>. For example:

[ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Single)]

• Install the latest update to the .NET Framework 4.6.2, or upgrade to a later version of the .NET Framework. This disables the flow of the ExecutionContext in OperationContext.Current. This behavior is configurable; it is equivalent to adding the following app setting to your configuration file:

<appSettings>
<add key="Switch.System.ServiceModel.DisableOperationContextAsyncFlow" value="true" />
</appSettings>

• System.ServiceModel.ServiceBehaviorAttribute
• ConcurrencyMode.Reentrant

• You retrieve the value of the OperationContext.Current property in a method that returns a Task or Task<TResult>.
• You instantiate the OperationContextScope object in a using clause.
• You retrieve the value of the OperationContext.Current property within the using statement. For example:

using (new OperationContextScope(OperationContext.Current))
{
OperationContext context = OperationContext.Current;      // OperationContext.Current is null.
// ...
}

• Modify your code as follows to instantiate a new non-null Current object:

OperationContext ocx = OperationContext.Current;
using (new OperationContextScope(OperationContext.Current))
{
OperationContext.Current = new OperationContext(ocx.Channel);
// ...
}

• Install the latest update to the .NET Framework 4.6.2, or upgrade to a later version of the .NET Framework. This disables the flow of the ExecutionContext in OperationContext.Current and restores the behavior of WCF applications in the .NET Framework 4.6.1 and earlier versions. This behavior is configurable; it is equivalent to adding the following app setting to your configuration file:

<appSettings>
<add key="Switch.System.ServiceModel.DisableOperationContextAsyncFlow" value="true" />
</appSettings>

<appSettings>
<add key="Switch.System.ServiceModel.DisableOperationContextAsyncFlow" value="false" />
</appSettings>

• OperationContext.Current

<runtime>
<AppContextSwitchOverrides value="Switch.System.ServiceModel.AllowUnsignedToHeader=true" />
</runtime>

• BasicHttpSecurityMode.TransportWithMessageCredential
• BasicHttpsSecurityMode.TransportWithMessageCredential
• SecurityMode.TransportWithMessageCredential
• WSFederationHttpSecurityMode.TransportWithMessageCredential

<runtime>
<AppContextSwitchOverrides value="Switch.System.ServiceModel.DisableCngCertificates=false" />
</runtime>

private const string DisableCngCertificates = @"Switch.System.ServiceModel.DisableCngCertificate";
AppContext.SetSwitch(disableCngCertificates, false);

Const DisableCngCertificates As String = "Switch.System.ServiceModel.DisableCngCertificates"
AppContext.SetSwitch(disableCngCertificates, False)

• X509CertificateClaimSet.FindClaims(String, String)

Beginning with applications targeting the .NET Framework 4.6.1, this exception is no longer thrown, and re-entrant filters as described above may be used.

• Application.FilterMessage(Message)

For apps that target the .NET Framework 4.5 or later and run on the .NET Framework 4.5.2, DataObject.GetData retrieves HTML-formatted data as UTF-8, which represents characters greater than 0x7F correctly.

• DataObject.GetData(String)
• DataObject.GetData(Type)
• DataObject.GetData(String, Boolean)

• EncoderParameter.EncoderParameter(Encoder, Int32, Int32, Int32, Int32)

In apps that target the .NET Framework 4.5.2 and earlier versions, the Icon.ToBitmap method throws an ArgumentOutOfRangeException exception if the Icon object has PNG frames.

This change affects apps that are recompiled to target the .NET Framework 4.6 and that implement special handling for the ArgumentOutOfRangeException that is thrown when an Icon object has PNG frames. When running under the .NET Framework 4.6, the conversion is successful, an ArgumentOutOfRangeException is no longer thrown, and therefore the exception handler is no longer invoked.

<AppContextSwitchOverrides
value="Switch.System.Drawing.DontSupportPngFramesInIcons=true" />

<AppContextSwitchOverrides
value="Switch.System.Drawing.DontSupportPngFramesInIcons=true;<previous key>=<previous value>" />

• Icon.ToBitmap()

1. Make code changes to compare the Category and Description fields manually in addition to calling the MemberDescriptor.Equals method.
2. Opt out of this change by adding the following value to the app.config file:

<runtime>
<AppContextSwitchOverrides value="Switch.System.MemberDescriptorEqualsReturnsFalseIfEquivalent=true" />
</runtime>

<runtime>
<AppContextSwitchOverrides value="Switch.System.MemberDescriptorEqualsReturnsFalseIfEquivalent=false" />
</runtime>

• MemberDescriptor.Equals(Object)

• BindingMode.TwoWay

• The width or height of elements may grow or shrink by at most one pixel.
• The placement of an object can move by at most one pixel.
• Centered elements can be vertically or horizontally off center by at most one pixel.

<AppContextSwitchOverrides value="Switch.MS.Internal.DoNotApplyLayoutRoundingToMarginsAndBorderThickness=false" />'

<AppContextSwitchOverrides value="Switch.MS.Internal.DoNotApplyLayoutRoundingToMarginsAndBorderThickness=true" />'.

• TextBox.Text

• If an exception occurs, the UnhandledExceptionFilter and UnhandledException events are not raised. Instead, exceptions are handled by the UnobservedTaskException event.
• Calls to some members, such as Result, block until the operation has completed.

• Dispatcher.Invoke(Delegate, Object[])
• Dispatcher.Invoke(Delegate, TimeSpan, Object[])
• Dispatcher.Invoke(Delegate, TimeSpan, DispatcherPriority, Object[])
• Dispatcher.Invoke(Delegate, DispatcherPriority, Object[])

• DragDropHelper.DoDragMove(WorkflowViewElement, Point)
• DragDropHelper.GetCompositeView(DragEventArgs)
• DragDropHelper.GetDraggedModelItem(DragEventArgs)
• DragDropHelper.GetDroppedObject(DependencyObject, DragEventArgs, EditingContext)

• XmlWriter.WriteAttributeString(String, String)
• XmlWriter.WriteAttributeString(String, String, String)
• XmlWriter.WriteAttributeString(String, String, String, String)
• XmlWriter.WriteAttributeStringAsync(String, String, String, String)
• XmlWriter.WriteCData(String)
• XmlWriter.WriteCDataAsync(String)
• XmlWriter.WriteChars(Char[], Int32, Int32)
• XmlWriter.WriteCharsAsync(Char[], Int32, Int32)
• XmlWriter.WriteComment(String)
• XmlWriter.WriteCommentAsync(String)
• XmlWriter.WriteEntityRef(String)
• XmlWriter.WriteEntityRefAsync(String)
• XmlWriter.WriteRaw(Char[], Int32, Int32)
• XmlWriter.WriteProcessingInstruction(String, String)
• XmlWriter.WriteProcessingInstructionAsync(String, String)
• XmlWriter.WriteRaw(String)
• XmlWriter.WriteRawAsync(Char[], Int32, Int32)
• XmlWriter.WriteRawAsync(String)
• XmlWriter.WriteString(String)
• XmlWriter.WriteStringAsync(String)
• XmlWriter.WriteSurrogateCharEntity(Char, Char)
• XmlWriter.WriteSurrogateCharEntityAsync(Char, Char)
• XmlWriter.WriteValue(String)