Runtime Changes for Migration from .NET Framework 4.6.2 to 4.7

Introduction

Runtime changes affect all apps that are running under a .NET Framework it was not compiled against and that use a particular feature.

In the topics that describe runtime changes, we have classified individual items by their expected impact, as follows:

Major This is a significant change that affects a large number of apps or that requires substantial modification of code.

Minor This is a change that affects a small number of apps or that requires minor modification of code.

Edge case This is a change that affects apps under very specific scenarios that are not common.

Transparent This is a change that has no noticeable effect on the app's developer or user. The app should not require modification because of this change.

If you are migrating from the .NET Framework 4.6.2 to 4.7, review the following topics for application compatibility issues that may affect your app:

JIT

Incorrect code generation when passing and comparing UInt16 values

Details Because of changes introduced in the .NET Framework 4.7, in some cases the code generated by the JIT compiler in applications running on the .NET Framework 4.7 incorrectly compares two T:System.UInt16 values. For more information, see Issue #11508: Silent bad codegen when passing and comparing ushort args on GitHub.com.
Suggestion If you encounter issues in the comparison of 16-bit unsigned values in the .NET Framework 4.7, upgrade to the .NET Framework 4.7.1.
Scope Edge
Version 4.7
Type Runtime

Windows Presentation Foundation (WPF)

Crash in Selector when removing an item from a custom INCC collection

Details An T:System.InvalidOperationException can occur in the following scenario:
  • The ItemsSource for a T:System.Windows.Controls.Primitives.Selector is a collection with a custom implementation of T:System.Collections.Specialized.INotifyCollectionChanged.
  • The selected item is removed from the collection.
  • The T:System.Collections.Specialized.NotifyCollectionChangedEventArgs has P:System.Collections.Specialized.NotifyCollectionChangedEventArgs.OldStartingIndex = -1 (indicating an unknown position).
The exception's callstack begins at System.Windows.Threading.Dispatcher.VerifyAccess() at System.Windows.DependencyObject.GetValue(DependencyProperty dp) at System.Windows.Controls.Primitives.Selector.GetIsSelected(DependencyObject element)This exception can occur in .NET Framework 4.5 if the application has more than one Dispatcher thread. In .NET Framework 4.7 the exception can also occur in applications with a single Dispatcher thread. The issue is fixed in .NET Framework 4.7.1.
Suggestion Upgrade to .NET Framework 4.7.1.
Scope Minor
Version 4.7
Type Runtime

DataGridCellsPanel.BringIndexIntoView throws ArgumentOutOfRangeException

Details ScrollIntoView(Object) will work asynchronously when column virtualization is enabled but the column widths have not yet been determined. If columns are removed before the asynchronous work happens, an ArgumentOutOfRangeException can occur.
Suggestion Any one of the following:
  1. Upgrade to .NET Framework 4.7.
  2. Install the latest servicing patch for .NET Framework 4.6.2.
  3. Avoid removing columns until the asynchronous response to ScrollIntoView(Object) has completed.
Scope Edge
Version 4.6.2
Type Runtime
Affected APIs

ObjectDisposedException thrown by WPF spellchecker

Details WPF applications occasionally crash during application shutdown with an ObjectDisposedException thrown by the spellchecker. This is fixed in .NET Framework 4.7 WPF by handling the exception gracefully, and thus ensuring that applications are no longer adversely affected. It should be noted that occasional first-chance exceptions would continue to be observed in applications running under a debugger.
Suggestion Upgrade to .NET Framework 4.7
Scope Edge
Version 4.6.1
Type Runtime

Resizing a Grid can hang

Details An infinite loop can occur during layout of a T:System.Windows.Controls.Grid under the following circumstances:
  • Row definitions contain two *-rows, both declaring a MinHeight and a MaxHeight.
  • Content of the *-rows doesn't exceed the corresponding MaxHeight
  • The Grid's available height is exceeded by the first MinHeight (plus any other fixed or Auto rows)
  • The app targets .NET Framework 4.7, or opts in to the 4.7 allocation algorithm by setting Switch.System.Windows.Controls.Grid.StarDefinitionsCanExceedAvailableSpace=false
The loop would also happen with more than two rows, or in the analogous case for columns.The issue is fixed in .NET Framework 4.7.1.
Suggestion Upgrade to .NET Framework 4.7.1. Alternatively, if you don't need the 4.7 allocation algorithm you can use the following configuration setting:
<runtime>
<AppContextSwitchOverrides value="Switch.System.Windows.Controls.Grid.StarDefinitionsCanExceedAvailableSpace=true" />
</runtime>
Scope Edge
Version 4.7
Type Runtime

RibbonGroup background is set to transparent in localized builds

Details RibbonGroup background on localized builds was always painted with Transparent brush, resulting in poor UI experience. This is fixed in .NET Framework 4.7 WPF fix by updating the localized resources for RibbonGroup, which in turn ensures that the correct brush is selected.
Suggestion Upgrade to .NET Framework 4.7
Scope Edge
Version 4.6.2
Type Runtime

WPF Printing Stack Update

Details WPF's Printing APIs using PrintQueue now call Window's Print Document Package API in favor of the now deprecated XPS Print API. The change was made with serviceability in mind; neither users nor developers should see any changes in behavior or API usage. The new printing stack is enabled by default when running in Windows 10 Creators Update. The old printing stack will still continue to work just as before in older Windows versions.
Suggestion To use the old stack in Windows 10 Creators Update, set the UseXpsOMPrinting REG_DWORD value of the HKEY_CURRENT_USER\Software\Microsoft.NETFramework\Windows Presentation Foundation\Printing registry key to 1.
Scope Edge
Version 4.7
Type Runtime

Windows Workflow Foundation (WF)

Workflow now throws original exception instead of NullReferenceException in some cases

Details In the .NET Framework 4.6.2 and earlier versions, when the Execute method of a workflow activity throws an exception with a null value for the Message property, the System.Activities Workflow runtime throws a NullReferenceException, masking the original exception.In the .NET Framework 4.7, the previously masked exception is thrown.
Suggestion If your code relies on handling the NullReferenceException, change it to catch the exceptions that could be thrown from your custom activities.
Scope Minor
Version 4.7
Type Runtime
Affected APIs

Workflow SQL persistence adds primary key clusters and disallows null values in some columns

Details Starting with the .NET Framework 4.7, the tables created for the SQL Workflow Instance Store (SWIS) by the SqlWorkflowInstanceStoreSchema.sql script use clustered primary keys. Because of this, identities do not support null values. The operation of SWIS is not impacted by this change. The updates were made to support SQL Server Transactional Replication.
Suggestion The SQL file SqlWorkflowInstanceStoreSchemaUpgrade.sql must be applied to existing installations in order to experience this change. New database installations will automatically have the change.
Scope Edge
Version 4.7
Type Runtime