Runtime Changes for Migration from .NET Framework 4.5 to 4.5.2

If you are migrating from the .NET Framework 4.5 to 4.5.2, review the following topics for application compatibility issues that may affect your app:

ADO.NET

ADO.NET now attempts to automatically reconnect broken SQL connections

Details

Beginning in the .NET Framework 4.5.1, the .NET Framework will attempt to automatically reconnect broken SQL connections. Although this will typically make apps more reliable, there are edge cases in which an app needs to know that the connection was lost so that it can take some action upon reconnection.

Suggestion

If this feature is undesirable due to compatibility concerns, it can be disabled by setting the System.Data.SqlClient.SqlConnectionStringBuilder.ConnectRetryCount property of a connection string (or System.Data.SqlClient.SqlConnectionStringBuilder) to 0.

Name Value
Scope Edge
Version 4.5.1
Type Runtime

Affected APIs

-IDbConnection.ConnectionString

  • SqlConnection.ConnectionString
  • ConnectionStringSettings.ConnectionString
  • DbConnection.ConnectionString
  • DbConnectionStringBuilder.ConnectionString
  • SqlConnectionStringBuilder()
  • SqlConnectionStringBuilder(String)
  • DbConnectionStringBuilder()
  • DbConnectionStringBuilder(Boolean)
  • |

    ASP.NET

    ASP.NET MVC now escapes spaces in strings passed in via route parameters

    Details

    In order to conform to RFC 2396, spaces in route paths are now escaped when populating action parameters from a route. So, whereas /controller/action/some data would previously match the route /controller/action/{data} and provide some data as the data parameter, it will now provide some%20data instead.

    Suggestion

    Code should be updated to unescape string parameters from a route. If the original URI is needed, it can be accessed with the RequestUri.OriginalString API.

    Name Value
    Scope Minor
    Version 4.5.2
    Type Runtime

    Affected APIs

    -RouteAttribute(String)|

    No longer able to set EnableViewStateMac to false

    Details

    ASP.NET no longer allows developers to specify <pages enableViewStateMac="false"/> or <@Page EnableViewStateMac="false" %>. The view state message authentication code (MAC) is now enforced for all requests with embedded view state. Only apps that explicitly set the EnableViewStateMac property to false are affected.

    Suggestion

    EnableViewStateMac must be assumed to be true, and any resulting MAC errors must be resolved (as explained in this guidance, which contains multiple resolutions depending on the specifics of what is causing MAC errors).

    Name Value
    Scope Major
    Version 4.5.2
    Type Runtime

    Profiling ASP.Net MVC4 apps can lead to Fatal Execution Engine Error

    Details

    Profilers using NGEN /Profile assemblies may crash profiled ASP.NET MVC4 applications on startup with a 'Fatal Execution Engine Exception'

    Suggestion

    This issue is fixed in the .NET Framework 4.5.2. Alternatively, the profiler may avoid this issue by specifying COR_PRF_DISABLE_ALL_NGEN_IMAGES in its event mask.

    Name Value
    Scope Edge
    Version 4.5
    Type Runtime

    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

    ConcurrentQueue<T>.TryPeek can return an erroneous null via its out parameter

    Details

    In some multi-threaded scenarios, System.Collections.Concurrent.ConcurrentQueue<T>.TryPeek(T) can return true, but populate the out parameter with a null value (instead of the correct, peeked value).

    Suggestion

    This issue is fixed in the .NET Framework 4.5.1. Upgrading to that Framework will solve the issue.

    Name Value
    Scope Major
    Version 4.5
    Type Runtime

    Affected APIs

    -ConcurrentQueue<T>.TryPeek(T)|

    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

    Deserialization of objects across appdomains can fail

    Details

    In some cases, when an app uses two or more app domains with different application bases, trying to deserialize objects in the logical call context across app domains throws an exception.

    Suggestion

    See Mitigation: Deserialization of Objects Across App Domains

    Name Value
    Scope Edge
    Version 4.5.1
    Type Runtime

    EventListener truncates strings with embedded nulls

    Details

    System.Diagnostics.Tracing.EventListener truncates strings with embedded nulls. Null characters are not supported by the System.Diagnostics.Tracing.EventSource class. The change only affects apps that use System.Diagnostics.Tracing.EventListener to read System.Diagnostics.Tracing.EventSource data in process and that use null characters as delimiters.

    Suggestion

    System.Diagnostics.Tracing.EventSource data should be updated, if possible, to not use embedded null characters.

    Name Value
    Scope Edge
    Version 4.5.1
    Type Runtime

    Affected APIs

    -EventListener()

  • EventListener.EnableEvents(EventSource, EventLevel)
  • EventListener.EnableEvents(EventSource, EventLevel, EventKeywords)
  • EventListener.EnableEvents(EventSource, EventLevel, EventKeywords, IDictionary<String,String>)
  • |

    EventSource.WriteEvent impls must pass WriteEvent the same parameters that it received (plus ID)

    Details

    The runtime now enforces the contract that specifies the following: A class derived from System.Diagnostics.Tracing.EventSource that defines an ETW event method must call the base class EventSource.WriteEvent method with the event ID followed by the same arguments that the ETW event method was passed.

    Suggestion

    An System.IndexOutOfRangeException exception is thrown if an System.Diagnostics.Tracing.EventListener reads System.Diagnostics.Tracing.EventSource data in process for an event source that violates this contract.

    Name Value
    Scope Minor
    Version 4.5.1
    Type Runtime

    Marshal.SizeOf and Marshal.PtrToStructure overloads break dynamic code

    Details

    Beginning in the .NET Framework 4.5.1, dynamically binding to the methods SizeOf<T>(), SizeOf<T>(T), PtrToStructure(IntPtr, Object), PtrToStructure(IntPtr, Type), PtrToStructure<T>(IntPtr), or PtrToStructure<T>(IntPtr, T), (via Windows PowerShell, IronPython, or the C# dynamic keyword, for example) can result in MethodInvocationExceptions because new overloads of these methods have been added that may be ambiguous to the scripting engines.

    Suggestion

    Update scripts to clearly indicate which overload should be used. This can typically done by explicitly casting the methods' type parameters as Type. See this link for more detail and examples of how to workaround the issue.

    Name Value
    Scope Minor
    Version 4.5.1
    Type Runtime

    Some .NET APIs cause first chance (handled) EntryPointNotFoundExceptions

    Details

    In the .NET Framework 4.5, a small number of .NET methods began throwing first chance System.EntryPointNotFoundExceptions. These exceptions were handled within the .NET Framework, but could break test automation that did not expect the first chance exceptions. These same APIs break some ApiVerifier scenarios when HighVersionLie is enabled.

    Suggestion

    This bug can be avoided by upgrading to .NET Framework 4.5.1. Alternatively, test automation can be updated to not break on first-chance System.EntryPointNotFoundExceptions.

    Name Value
    Scope Edge
    Version 4.5
    Type Runtime

    Affected APIs

    -Debug.Assert(Boolean)

  • Debug.Assert(Boolean, String)
  • Debug.Assert(Boolean, String, String)
  • Debug.Assert(Boolean, String, String, Object[])
  • XmlSerializer(Type)
  • |

    WinRT stream adapters no long call FlushAsync automatically on close

    Details

    In Windows Store apps, Windows Runtime stream adapters no longer call the FlushAsync method from the Dispose method.

    Suggestion

    This change should be transparent. Developers can restore the previous behavior by writing code like this:

    using (var stream = GetWindowsRuntimeStream() as Stream)
    {
    // do something
    await stream.FlushAsync();
    }
    

    Name Value
    Scope Transparent
    Version 4.5.1
    Type Runtime

    Data

    ADO.NET now attempts to automatically reconnect broken SQL connections

    Details

    Beginning in the .NET Framework 4.5.1, the .NET Framework will attempt to automatically reconnect broken SQL connections. Although this will typically make apps more reliable, there are edge cases in which an app needs to know that the connection was lost so that it can take some action upon reconnection.

    Suggestion

    If this feature is undesirable due to compatibility concerns, it can be disabled by setting the System.Data.SqlClient.SqlConnectionStringBuilder.ConnectRetryCount property of a connection string (or System.Data.SqlClient.SqlConnectionStringBuilder) to 0.

    Name Value
    Scope Edge
    Version 4.5.1
    Type Runtime

    Affected APIs

    -IDbConnection.ConnectionString

  • SqlConnection.ConnectionString
  • ConnectionStringSettings.ConnectionString
  • DbConnection.ConnectionString
  • DbConnectionStringBuilder.ConnectionString
  • SqlConnectionStringBuilder()
  • SqlConnectionStringBuilder(String)
  • DbConnectionStringBuilder()
  • DbConnectionStringBuilder(Boolean)
  • |

    SqlConnection.Open fails on Windows 7 with non-IFS Winsock BSP or LSP present

    Details

    Open() and OpenAsync(CancellationToken) fail in the .NET Framework 4.5 if running on a Windows 7 machine with a non-IFS Winsock BSP or LSP are present on the computer.To determine whether a non-IFS BSP or LSP is installed, use the netsh WinSock Show Catalog command, and examine every Winsock Catalog Provider Entry item that is returned. If the Service Flags value has the 0x20000 bit set, the provider uses IFS handles and will work correctly. If the 0x20000 bit is clear (not set), it is a non-IFS BSP or LSP.

    Suggestion

    This bug has been fixed in the .NET Framework 4.5.2, so it can be avoided by upgrading the .NET Framework. Alternatively, it can be avoided by removing any installed non-IFS Winsock LSPs.

    Name Value
    Scope Minor
    Version 4.5
    Type Runtime

    Affected APIs

    -SqlConnection.Open()

  • SqlConnection.OpenAsync(CancellationToken)
  • |

    Entity Framework

    EF no longer throws for QueryViews with specific characteristics

    Details

    Entity Framework no longer throws a System.StackOverflowException exception when an app executes a query that involves a QueryView with a 0..1 navigation property that attempts to include the related entities as part of the query. For example, by calling .Include(e => e.RelatedNavProp).

    Suggestion

    This change only affects code that uses QueryViews with 1-0..1 relationships when running queries that call .Include. It improves reliability and should be transparent to almost all apps. However, if it causes unexpected behavior, you can disable it by adding the following entry to the <appSettings> section of the app's configuration file:

    <add key="EntityFramework_SimplifyUserSpecifiedViews" value="false" />
    

    Name Value
    Scope Edge
    Version 4.5.2
    Type Runtime

    Opt-in break to revert from different 4.5 SQL generation to simpler 4.0 SQL generation

    Details

    Queries that produce JOIN statements and contain a call to a limiting operation without first using OrderBy now produce simpler SQL. After upgrading to .NET Framework 4.5, these queries produced more complicated SQL than previous versions.

    Suggestion

    This feature is disabled by default. If Entity Framework generates extra JOIN statements that cause performance degradation, you can enable this feature by adding the following entry to the <appSettings> section of the application configuration (app.config) file:

    <add key="EntityFramework_SimplifyLimitOperations" value="true" />
    

    Name Value
    Scope Transparent
    Version 4.5.2
    Type Runtime

    Serialization

    NetDataContractSerializer fails to deserialize a ConcurrentDictionary serialized with a different .NET version

    Details

    By design, the System.Runtime.Serialization.NetDataContractSerializer can be used only if both the serializing and deserializing ends share the same CLR types. Therefore, it is not guaranteed that an object serialized with one version of the .NET Framework can be deserialized by a different version.System.Collections.Concurrent.ConcurrentDictionary<TKey,TValue> is a type that is known to not to deserialize correctly if serialized with the .NET Framework 4.5 or earlier and deserialized with the .NET Framework 4.5.1 or later.

    Suggestion

    There are a number of possible work-arounds for this issue:

    Name Value
    Scope Minor
    Version 4.5.1
    Type Runtime

    Affected APIs

    -NetDataContractSerializer.Deserialize(Stream)|

    Windows Communication Foundation (WCF)

    MinFreeMemoryPercentageToActiveService is now respected

    Details

    This setting establishes the minimum memory that must be available on the server before a WCF service can be activated. It is designed to prevent System.OutOfMemoryException exceptions. In the .NET Framework 4.5, this setting had no effect. In the .NET Framework 4.5.1, the setting is observed.

    Suggestion

    An exception occurs if the free memory available on the web server is less than the percentage defined by the configuration setting. Some WCF services that successfully started and ran in a constrained memory environment may now fail.

    Name Value
    Scope Minor
    Version 4.5.1
    Type Runtime

    Windows Presentation Foundation (WPF)

    Calling DataGrid.CommitEdit from a CellEditEnding handler drops focus

    Details

    Calling CommitEdit() from one of the System.Windows.Controls.DataGrid's System.Windows.Controls.DataGrid.CellEditEnding event handlers causes the System.Windows.Controls.DataGrid to lose focus.

    Suggestion

    This bug has been fixed in the .NET Framework 4.5.2, so it can be avoided by upgrading the .NET Framework. Alternatively, it can be avoided by explicitly re-selecting the System.Windows.Controls.DataGrid after calling System.Windows.Controls.DataGrid.CommitEdit().

    Name Value
    Scope Edge
    Version 4.5
    Type Runtime

    Affected APIs

    -DataGrid.CommitEdit()

  • DataGrid.CommitEdit(DataGridEditingUnit, Boolean)
  • |

    Intermittently unable to scroll to bottom item in ItemsControls (like ListBox and DataGrid) when using custom DataTemplates

    Details

    In some instances, a bug in the .NET Framework 4.5 is causing ItemsControls (like System.Windows.Controls.ListBox, System.Windows.Controls.ComboBox, System.Windows.Controls.DataGrid, etc.) to not scroll to their bottom item when using custom DataTemplates. If the scrolling is attempted a second time (after scrolling back up), it will work then.

    Suggestion

    This issue has been fixed in the .NET Framework 4.5.2 and may be addressed by upgrading to that version (or a later version) of the .NET Framework. Alternatively, users can still drag scroll bars to the final items in these collections, but may need to try twice to do so successfully.

    Name Value
    Scope Minor
    Version 4.5
    Type Runtime

    Scrolling a WPF TreeView or grouped ListBox in a VirtualizingStackPanel can cause a hang

    Details

    In the .NET Framework v4.5, scrolling a WPF System.Windows.Controls.TreeView in a virtualized stack panel can cause hangs if there are margins in the viewport (between the items in the System.Windows.Controls.TreeView, for example, or on an ItemsPresenter element). Additionally, in some cases, different sized items in the view can cause instability even if there are no margins.

    Suggestion

    This bug can be avoided by upgrading to .NET Framework 4.5.1. Alternatively, margins can be removed from view collections (like System.Windows.Controls.TreeViews) within virtualized stack panels if all contained items are the same size.

    Name Value
    Scope Major
    Version 4.5
    Type Runtime

    Affected APIs

    -VirtualizingStackPanel.SetIsVirtualizing(DependencyObject, Boolean)|

    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