Runtime Changes for Migration from .NET Framework 4.5.2 to 4.6

If you are migrating from the .NET Framework 4.5.2 to 4.6, review the following topics for application compatibility issues that may affect your app:

ASP.NET

GridViews with AllowCustomPaging set to true may fire the PageIndexChanging event when leaving the final page of the view

Details

A bug in the .NET Framework 4.5 causes System.Web.UI.WebControls.GridView.PageIndexChanging to sometimes not fire for System.Web.UI.WebControls.GridViews that have enabled System.Web.UI.WebControls.GridView.AllowCustomPaging.

Suggestion

This issue has been fixed in the .NET Framework 4.6 and may be addressed by upgrading to that version of the .NET Framework. As a work-around, the app can do an explicit BindGrid on any Page_Load that would hit these conditions (the System.Web.UI.WebControls.GridView is on the last page and LastSystem.Web.UI.WebControls.GridView.PageSize is different from System.Web.UI.WebControls.GridView.PageSize). Alternatively, the app can be modified to allow paging (instead of custom paging), as that scenario does not demonstrate the problem.

Name Value
Scope Minor
Version 4.5
Type Runtime

Affected APIs

-GridView.AllowCustomPaging|

Core

A ConcurrentDictionary serialized in .NET Framework 4.5 with NetDataContractSerializer cannot be deserialized by .NET Framework 4.5.1 or 4.5.2

Details

Due to internal changes to the type, ConcurrentDictionary<TKey,TValue> objects that are serialized with the .NET Framework 4.5 using the System.Runtime.Serialization.NetDataContractSerializer cannot be deserialized in the .NET Framework 4.5.1 or in the .NET Framework 4.5.2.Note that moving in the other direction (serializing with the .NET Framework 4.5.x and deserializing with the .NET Framework 4.5) works. Similarly, all 4.x cross-version serialization works with the .NET Framework 4.6.Serializing and deserializing with a single version of the .NET Framework is not affected.

Suggestion

If it is necessary to serialize and deserialize a System.Collections.Concurrent.ConcurrentDictionary<TKey,TValue> between the .NET Framework 4.5 and .NET Framework 4.5.1/4.5.2, an alternate serializer like the System.Runtime.Serialization.DataContractSerializer or System.Runtime.Serialization.Formatters.Binary.BinaryFormatter serializer should be used instead of the System.Runtime.Serialization.NetDataContractSerializer.Alternatively, because this issue is addressed in the .NET Framework 4.6, it may be solved by upgrading to that version of the .NET Framework.

Name Value
Scope Minor
Version 4.5.1
Type Runtime

AppDomainSetup.DynamicBase is no longer randomized by UseRandomizedStringHashAlgorithm

Details

Prior to the .NET Framework 4.6, the value of DynamicBase would be randomized between application domains, or between processes, if UseRandomizedStringHashAlgorithm was enabled in the app's config file. Beginning in the .NET Framework 4.6, DynamicBase will return a stable result between different instances of an app running, and between different app domains. Dynamic bases will still differ for different apps; this change only removes the random naming element for different instances of the same app.

Suggestion

Be aware that enabling UseRandomizedStringHashAlgorithm will not result in DynamicBase being randomized. If a random base is needed, it must be produced in your app's code rather than via this API.

Name Value
Scope Edge
Version 4.6
Type Runtime

Affected APIs

-AppDomainSetup.DynamicBase|

Calling Attribute.GetCustomAttributes on an indexer property no longer throws AmbiguousMatchException if the ambiguity can be resolved by index's type

Details

Prior to the .NET Framework 4.6, calling GetCustomAttribute(s) on an indexer property which differed from another property only by the type of the index would result in an System.Reflection.AmbiguousMatchException. Beginning in the .NET Framework 4.6, the property's attributes will be correctly returned.

Suggestion

Be aware that GetCustomAttribute(s) will work more frequently now. If an app was previously relying on the System.Reflection.AmbiguousMatchException, reflection should now be used to explicitly look for multiple indexers, instead.

Name Value
Scope Edge
Version 4.6
Type Runtime

Affected APIs

-Attribute.GetCustomAttribute(MemberInfo, Type)

  • Attribute.GetCustomAttribute(MemberInfo, Type, Boolean)
  • Attribute.GetCustomAttributes(MemberInfo)
  • Attribute.GetCustomAttributes(MemberInfo, Boolean)
  • Attribute.GetCustomAttributes(MemberInfo, Type)
  • Attribute.GetCustomAttributes(MemberInfo, Type, Boolean)
  • CustomAttributeExtensions.GetCustomAttribute(MemberInfo, Type)
  • CustomAttributeExtensions.GetCustomAttribute(MemberInfo, Type, Boolean)
  • CustomAttributeExtensions.GetCustomAttribute<T>(MemberInfo)
  • CustomAttributeExtensions.GetCustomAttribute<T>(MemberInfo, Boolean)
  • CustomAttributeExtensions.GetCustomAttributes(MemberInfo)
  • CustomAttributeExtensions.GetCustomAttributes(MemberInfo, Boolean)
  • CustomAttributeExtensions.GetCustomAttributes(MemberInfo, Type)
  • CustomAttributeExtensions.GetCustomAttributes(MemberInfo, Type, Boolean)
  • CustomAttributeExtensions.GetCustomAttributes<T>(MemberInfo)
  • CustomAttributeExtensions.GetCustomAttributes<T>(MemberInfo, Boolean)
  • |

    COR_PRF_GC_ROOT_HANDLEs are not being enumerated by profilers

    Details

    In the .NET Framework v4.5.1, the profiling API RootReferences2() is incorrectly never returning COR_PRF_GC_ROOT_HANDLE (they are returned as COR_PRF_GC_ROOT_OTHER instead). This issue is fixed beginning in the .NET Framework 4.6.

    Suggestion

    This issue has been fixed in the .NET Framework 4.6 and may be addressed by upgrading to that version of the .NET Framework.

    Name Value
    Scope Minor
    Version 4.5.1
    Type Runtime

    ETW EventListeners do not capture events from providers with explicit keywords (like the TPL provider)

    Details

    ETW EventListeners with a blank keyword mask do not properly capture events from providers with explicit keywords. In the .NET Framework 4.5, the TPL provider began providing explicit keywords and triggered this issue. In the .NET Framework 4.6, EventListeners have been updated to no longer have this issue.

    Suggestion

    To work around this problem, replace calls to EnableEvents(EventSource, EventLevel) with calls to the EnableEvents overload that explicitly specifies the "any keywords" mask to use: EnableEvents(eventSource, level, unchecked((EventKeywords)0xFFFFffffFFFFffff)).Alternatively, this issue has been fixed in the .NET Framework 4.6 and may be addressed by upgrading to that version of the .NET Framework.

    Name Value
    Scope Edge
    Version 4.5
    Type Runtime

    Affected APIs

    -EventListener.EnableEvents(EventSource, EventLevel)|

    Persian calendar now uses the Hijri solar algorithm

    Details

    Starting with the .NET Framework 4.6, the System.Globalization.PersianCalendar class uses the Hijri solar algorithm. Converting dates between the System.Globalization.PersianCalendar and other calendars may produce a slightly different result beginning with the .NET Framework 4.6 for dates earlier than 1800 or later than 2023 (Gregorian).Also, PersianCalendar.MinSupportedDateTime is now March 22, 0622 instead of March 21, 0622.

    Suggestion

    Be aware that some early or late dates may be slightly different when using the PersianCalendar in .NET Framework 4.6. Also, when serializing dates between processes which may run on different .NET Framework versions, do not store them as PersianCalendar date strings (since those values may be different).

    Name Value
    Scope Minor
    Version 4.6
    Type Runtime

    Affected APIs

    -System.Globalization.PersianCalendar|

    Reflection objects can no longer be passed from managed code to out-of-process DCOM clients

    Details

    Reflection objects can no longer be passed from managed code to out-of-process DCOM clients. The following types are affected:

    Calls to IMarshal for the object return E_NOINTERFACE.

    Suggestion

    Update marshaling code to work with non-reflection objects

    Name Value
    Scope Minor
    Version 4.6
    Type Runtime

    TargetFrameworkName for default app domain no longer defaults to null if not set

    Details

    The System.AppDomainSetup.TargetFrameworkName was previously null in the default app domain, unless it was explicitly set. Beginning in 4.6, the System.AppDomainSetup.TargetFrameworkName property for the default app domain will have a default value derived from the TargetFrameworkAttribute (if one is present). Non-default app domains will continue to inherit their System.AppDomainSetup.TargetFrameworkName from the default app domain (which will not default to null in 4.6) unless it is explicitly overridden.

    Suggestion

    Code should be updated to not depend on TargetFrameworkName defaulting to null. If it is required that this property continue to evaluate to null, it can be explicitly set to that value.

    Name Value
    Scope Edge
    Version 4.6
    Type Runtime

    Affected APIs

    -AppDomainSetup.TargetFrameworkName|

    X509Certificate2.ToString(Boolean) does not throw now when .NET cannot handle the certificate

    Details

    In .NET Framework 4.5.2 and earlier versions, this method would throw if true was passed for the verbose parameter and there were certificates installed that weren't supported by the .NET Framework. Now, the method will succeed and return a valid string that omits the inaccessible portions of the certificate.

    Suggestion

    Any code depending on X509Certificate2.ToString(Boolean) should be updated to expect that the returned string may exclude some certificate data (such as public key, private key, and extensions) in some cases in which the API would have previously thrown.

    Name Value
    Scope Edge
    Version 4.6
    Type Runtime

    Affected APIs

    -X509Certificate2.ToString(Boolean)|

    Data

    Attempting a TCP/IP connection to a SQL Server database that resolves to localhost fails

    Details

    In the .NET Framework 4.6 and 4.6.1, attempting a TCP/IP connection to a SQL Server database that resolves to localhost fails with the error, "A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)"

    Suggestion

    This issue has been addressed and the previous behavior restored in the .NET Framework 4.6.2. To connect to a SQL Server database that resolves to localhost, upgrade to the .NET Framework 4.6.2.

    Name Value
    Scope Minor
    Version 4.6
    Type Runtime

    Debugger

    Null coalescer values are not visible in debugger until one step later

    Details

    A bug in the .NET Framework 4.5 causes values set via a null coalescing operation to not be visible in the debugger immediately after the assignment operation is executed when running on the 64-bit version of the Framework.

    Suggestion

    Stepping one additional time in the debugger will cause the local/field's value to be correctly updated. Also, this issue has been fixed in the .NET Framework 4.6; upgrading to that version of the Framework should solve the issue.

    Name Value
    Scope Edge
    Version 4.5
    Type Runtime

    Networking

    ContentDisposition DateTimes returns slightly different string

    Details

    String representations of System.Net.Mime.ContentDisposition's have been updated, beginning in 4.6, to always represent the hour component of a System.DateTime with two digits. This is to comply with RFC822 and RFC2822. This causes ToString() to return a slightly different string in 4.6 in scenarios where one of the disposition's time elements was before 10:00 AM. Note that ContentDispositions are sometimes serialized via converting them to strings, so any ToString() operations, serialization, or GetHashCode calls should be reviewed.

    Suggestion

    Do not expect that string representations of ContentDispositions from different .NET Framework versions will correctly compare to one another. Convert the strings back to ContentDispositions, if possible, before conducting a comparison.

    Name Value
    Scope Minor
    Version 4.6
    Type Runtime

    Affected APIs

    -ContentDisposition.ToString()

  • ContentDisposition.GetHashCode()
  • |

    Serialization

    Exception message has changed for failed DataContract serialization in case of an unknown type

    Details

    Beginning in the .NET Framework 4.6, the exception message given if a System.Runtime.Serialization.DataContractSerializer or System.Runtime.Serialization.Json.DataContractJsonSerializer fails to serialize or deserialize due to missing 'known types' has been clarified.

    Suggestion

    Apps should not depend on specific exception messages. If an app depends on this message, either update it to expect the new message or (preferably) change it to depend only on the exception type.

    Name Value
    Scope Edge
    Version 4.6
    Type Runtime

    Affected APIs

    -DataContractJsonSerializer(Type)

  • DataContractJsonSerializer(Type, IEnumerable<Type>)
  • DataContractJsonSerializer(Type, DataContractJsonSerializerSettings)
  • DataContractJsonSerializer(Type, String)
  • DataContractJsonSerializer(Type, String, IEnumerable<Type>)
  • DataContractJsonSerializer(Type, XmlDictionaryString)
  • DataContractJsonSerializer(Type, XmlDictionaryString, IEnumerable<Type>)
  • DataContractJsonSerializer(Type, IEnumerable<Type>, Int32, Boolean, IDataContractSurrogate, Boolean)
  • DataContractJsonSerializer(Type, String, IEnumerable<Type>, Int32, Boolean, IDataContractSurrogate, Boolean)
  • DataContractJsonSerializer(Type, XmlDictionaryString, IEnumerable<Type>, Int32, Boolean, IDataContractSurrogate, Boolean)
  • DataContractSerializer(Type)
  • DataContractSerializer(Type, DataContractSerializerSettings)
  • DataContractSerializer(Type, IEnumerable<Type>)
  • DataContractSerializer(Type, String, String)
  • DataContractSerializer(Type, String, String, IEnumerable<Type>)
  • DataContractSerializer(Type, XmlDictionaryString, XmlDictionaryString)
  • DataContractSerializer(Type, XmlDictionaryString, XmlDictionaryString, IEnumerable<Type>)
  • DataContractSerializer(Type, IEnumerable<Type>, Int32, Boolean, Boolean, IDataContractSurrogate)
  • DataContractSerializer(Type, IEnumerable<Type>, Int32, Boolean, Boolean, IDataContractSurrogate, DataContractResolver)
  • DataContractSerializer(Type, String, String, IEnumerable<Type>, Int32, Boolean, Boolean, IDataContractSurrogate)
  • DataContractSerializer(Type, String, String, IEnumerable<Type>, Int32, Boolean, Boolean, IDataContractSurrogate, DataContractResolver)
  • DataContractSerializer(Type, XmlDictionaryString, XmlDictionaryString, IEnumerable<Type>, Int32, Boolean, Boolean, IDataContractSurrogate)
  • DataContractSerializer(Type, XmlDictionaryString, XmlDictionaryString, IEnumerable<Type>, Int32, Boolean, Boolean, IDataContractSurrogate, DataContractResolver)
  • |

    Setup and Deployment

    Product versioning changes in the .NET Framework 4.6 and later versions

    Details

    Product versioning has changed from the previous releases of the .NET Framework, and particularly from the .NET Framework 4, 4.5, 4.5.1, and 4.5.2. The following are the detailed changes:

    • The value of the Version entry in the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full key has changed to 4.6.xxxxx for the .NET Framework 4.6 and its point releases, and to 4.7.xxxxx for the .NET Framework 4.7 and 4.7.1. In the .NET Framework 4.5, 4.5.1, and 4.5.2, it had the format 4.5.xxxxx.
    • The file and product versioning for .NET Framework files has changed from the earlier versioning scheme of 4.0.30319.x to 4.6.X.0 for the .NET Framework 4.6 and its point releases, and to 4.7.X.0 for the .NET Framework 4.7 and 4.7.1. You can see these new values when you view the file's Properties after right-clicking on a file.
    • The AssemblyFileVersionAttribute and AssemblyInformationalVersionAttribute attributes for managed assemblies have Version values in the form 4.6.X.0 for the .NET Framework 4.6 and its point releases, and 4.7.X.0 for the .NET Framework 4.7 and 4.7.1.
    • In the .NET Framework 4.6, 4.6.1, 4.6.2, 4.7, and 4.7.1, the Environment.Version property returns the fixed version string 4.0.30319.42000. In the .NET Framework 4, 4.5, 4.5.1, and 4.5.2, it returns version strings in the format 4.0.30319.xxxxx (for example, "4.0.30319.18010"). Note that we do not recommend application code taking any new dependency on the Environment.Version property.
    For more information, see How to: Determine which .NET Framework Versions Are Installed.

    Suggestion

    In general, applications should depend on the recommended techniques for detecting such things as the runtime version of the .NET Framework and the installation directory:

    [!IMPORTANT] The subkey name is NET Framework Setup, not .NET Framework Setup.
    • To determine the directory path to the .NET Framework common language runtime, call the RuntimeEnvironment.GetRuntimeDirectory() method.
    • To get the CLR version, call the RuntimeEnvironment.GetSystemVersion() method. For the .NET Framework 4 and its point releases (the .NET Framework 4.5, 4.5.1, 4.5.2, and .NET Framework 4.6, 4.6.1, 4.6.2, 4.7, and 4.7.1), it returns the string v4.0.30319.

    Name Value
    Scope Minor
    Version 4.6
    Type Runtime

    The .NET Framework 4.6 does not use a 4.5.x.x version when registering itself in the registry

    Details

    As one might expect, the version key set in the registry (at HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\NET Framework Setup\NDP\v4\Full) for the .NET Framework 4.6 begins with '4.6', not '4.5'. Apps that depend on these registry keys to know which .NET Framework versions are installed on a machine should be updated to understand that 4.6 is a new possible version, and one that is compatible with previous 4.5.x releases.

    Suggestion

    Update apps probing for a .NET Framework 4.5 install by looking for 4.5 registry keys to also accept 4.6.

    Name Value
    Scope Edge
    Version 4.6
    Type Runtime

    Windows Communication Foundation (WCF)

    WCF services that use NETTCP with SSL security and MD5 certificate authentication

    Details

    The .NET Framework 4.6 adds TLS 1.1 and TLS 1.2 to the WCF SSL default protocol list. When both client and server machines have the .NET Framework 4.6 or later installed, TLS 1.2 is used for negotiation.TLS 1.2 does not support MD5 certificate authentication. As a result, if a customer uses an MD5 certificate, the WCF client will fail to connect to the WCF service.

    Suggestion

    You can work around this issue so that a WCF client can connect to a WCF server by doing any of the following:

    • Update the certificate to not use the MD5 algorithm. This is the recommended solution.
    • If the binding is not dynamically configured in source code, update the application's configuration file to use TLS 1.1 or an earlier version of the protocol. This allows you to continue to use a certificate with the MD5 hash algorithm.

    Warning

    This workaround is not recommended, since a certificate with the MD5 hash algorithm is considered insecure.

    The following configuration file does this:

    <configuration>
      <system.serviceModel>
        <bindings>
          <netTcpBinding>
            <binding>
              <security mode= "None/Transport/Message/TransportWithMessageCredential" >
                <transport clientCredentialType="None/Windows/Certificate"
                           protectionLevel="None/Sign/EncryptAndSign"
                           sslProtocols="Ssl3/Tls1/Tls11">
                </transport>
              </security>
            </binding>
          </netTcpBinding>
        </bindings>
      </system.ServiceModel>
    </configuration>
    

    Warning

    This workaround is not recommended, since a certificate with the MD5 hash algorithm is considered insecure.

    Name Value
    Scope Minor
    Version 4.6
    Type Runtime

    Windows Presentation Foundation (WPF)

    Accessing a WPF DataGrid's selected items from a handler of the DataGrid's UnloadingRow event can cause a NullReferenceException

    Details

    Due to a bug in the .NET Framework 4.5, event handlers for DataGrid events involving the removal of a row can cause a System.NullReferenceException to be thrown if they access the DataGrid's System.Windows.Controls.Primitives.Selector.SelectedItem or System.Windows.Controls.Primitives.MultiSelector.SelectedItems properties.

    Suggestion

    This issue has been fixed in the .NET Framework 4.6 and may be addressed by upgrading to that version of the .NET Framework.

    Name Value
    Scope Minor
    Version 4.5
    Type Runtime

    Affected APIs

    -DataGrid.UnloadingRow

  • DataGrid.UnloadingRowDetails
  • |

    Calling Items.Refresh on a WPF ListBox, ListView, or DataGrid with items selected can cause duplicate items to appear in the element

    Details

    In the .NET Framework 4.5, calling ListBox.Items.Refresh from code while items are selected in a System.Windows.Controls.ListBox can cause the selected items to be duplicated in the list. A similar issue occurs with System.Windows.Controls.ListView and System.Windows.Controls.DataGrid. This is fixed in the .NET Framework 4.6.

    Suggestion

    This issue may be worked around by programmatically unselecting items before System.Windows.Data.CollectionView.Refresh() is called and then re-selecting them after the call is completed. Alternatively, this issue has been fixed in the .NET Framework 4.6 and may be addressed by upgrading to that version of the .NET Framework.

    Name Value
    Scope Minor
    Version 4.5
    Type Runtime

    Affected APIs

    -CollectionView.Refresh()|

    CoerceIsSelectionBoxHighlighted

    Details

    Certain sequences of actions involving a System.Windows.Controls.ComboBox and its data source can result in a System.NullReferenceException.

    Suggestion

    If possible, upgrade to .NET Framework 4.6.2.

    Name Value
    Scope Minor
    Version 4.6
    Type Runtime

    Affected APIs

    -ComboBox.IsSelectionBoxHighlighted|

    ListBoxItem IsSelected binding issue with ObservableCollection<T>.Move

    Details

    Calling Move(Int32, Int32) or MoveItem(Int32, Int32) on a collection bound to a System.Windows.Controls.ListBox with items selected can lead to erratic behavior with future selection or unselection of System.Windows.Controls.ListBox items.

    Suggestion

    Calling System.Collections.ObjectModel.Collection<T>.Remove(T) and System.Collections.ObjectModel.Collection<T>.Insert(Int32, T) instead of Move(Int32, Int32) will work around this issue. Alternatively, this issue has been fixed in the .NET Framework 4.6 and may be addressed by upgrading to that version of the .NET Framework.

    Name Value
    Scope Minor
    Version 4.5
    Type Runtime

    Affected APIs

    -ObservableCollection<T>.Move(Int32, Int32)

  • ObservableCollection<T>.MoveItem(Int32, Int32)
  • |

    Right clicking on a WPF DataGrid row header changes the DataGrid selection

    Details

    Right-clicking a selected System.Windows.Controls.DataGrid row header while multiple rows are selected results in the System.Windows.Controls.DataGrid's selection changing to only that row.

    Suggestion

    This issue has been fixed in the .NET Framework 4.6 and may be addressed by upgrading to that version of the .NET Framework.

    Name Value
    Scope Edge
    Version 4.5
    Type Runtime

    Affected APIs

    -DataGrid()|

    WPF spawns a wisptis.exe process which can freeze the mouse

    Details

    An issue was introduced in 4.5.2 that causes wisptis.exe to be spawned that can freeze mouse input.

    Suggestion

    A fix for this issue is available in a servicing release of the .NET Framework 4.5.2 (hotfix rollup 3026376), or by upgrading to the .NET Framework 4.6

    Name Value
    Scope Major
    Version 4.5.2
    Type Runtime

    WPF spell checking in text-enabled controls will not work in Windows 10 for languages not in the OS's input language list

    Details

    When running on Windows 10, the spell checker may not work for WPF text-enabled controls because platform spell-checking capabilities are available only for languages present in the input languages list.In Windows 10, when a language is added to the list of available keyboards, Windows automatically downloads and installs a corresponding Feature on Demand (FOD) package that provides spell-checking capabilities. By adding the language to the input languages list, the spell checker will be supported.

    Suggestion

    Be aware that the language or text to be spell-checked must be added as an input language for spell-checking to work in Windows 10.

    Name Value
    Scope Edge
    Version 4.6
    Type Runtime

    WPF windows are rendered without clipping when extending outside a single monitor

    Details

    In the .NET Framework 4.6 running on Windows 8 and above, the entire window is rendered without clipping when it extends outside of single display in a multi-monitor scenario. This is different from previous versions of the .NET Framework which would clip WPF windows that extended beyond a single display.

    Suggestion

    This behavior (whether to clip or not) can be explicitly set using the <EnableMultiMonitorDisplayClipping> element in <appSettings> in an application's configuration file, or by setting the EnableMultiMonitorDisplayClipping property at app startup.

    Name Value
    Scope Minor
    Version 4.6
    Type Runtime