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

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

No longer able to set EnableViewStateMac to false

Details

ASP.NET no longer allows developers to specify <pages enableViewStateMac=&quot;false&quot;/> or <@Page EnableViewStateMac=&quot;false&quot; %>. 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

Affected APIs

Not detectable via API analysis.

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

Affected APIs

Not detectable via API analysis.

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

Affected APIs

Not detectable via API analysis.

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

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

Affected APIs

Not detectable via API analysis.

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

Affected APIs

Not detectable via API analysis.

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

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

Affected APIs

Not detectable via API analysis.

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

Affected APIs

Not detectable via API analysis.

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

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

Affected APIs

Not detectable via API analysis.

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

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

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 =&gt; 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

Affected APIs

Not detectable via API analysis.

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

Affected APIs

Not detectable via API analysis.

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

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

Affected APIs

Not detectable via API analysis.

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

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

Affected APIs

Not detectable via API analysis.

Scrolling a WPF TreeView or grouped ListBox in a VirtualizingStackPanel can cause the application to stop responding

Details

In the .NET Framework v4.5, scrolling a WPF System.Windows.Controls.TreeView in a virtualized stack panel can cause the application to stop responding 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

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

Affected APIs

Not detectable via API analysis.

XML

XML parsing changes

Name Value
Scope Minor
Version 4.5.2
Type Runtime

Details

For security reasons, the following changes were introduced into XML parsing APIS:

Note

XmlReaderSettings is used by all XML parsers, so while this change helps the XmlReader case, it also affects other scenarios.

Suggestion

To revert to the previous behavior, you can set a value in the registry. Add a DWORD value named EnableLegacyXmlSettings to the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\XML registry key, and set its value to 1. You can also add the registry value in the HKEY_CURRENT_USER hive instead.

Affected APIs

In addition, any XML API that depends on XmlResolver, either directly or indirectly, is affected.