45 lines
2.0 KiB
Markdown
45 lines
2.0 KiB
Markdown
## New (ambiguous) Dispatcher.Invoke overloads could result in different behavior
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### Scope
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Minor
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### Version Introduced
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4.5
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### Source Analyzer Status
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Available
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### Change Description
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The .NET Framework 4.5 adds new overloads to Dispatcher.Invoke that include a
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parameter of type @System.Action. When existing code is recompiled, compilers
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may resolve calls to Dispatcher.Invoke methods that have a @System.Delegate
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parameter as calls to Dispatcher.Invoke methods with an @System.Action
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parameter. If a call to a Dispatcher.Invoke overload with a @System.Delegate
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parameter is resolved as a call to a Dispatcher.Invoke overload with an
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@System.Action parameter, the following differences in behavior may occur:
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- If an exception occurs, the <xref:System.Windows.Threading.Dispatcher.UnhandledExceptionFilter> and <xref:System.Windows.Threading.Dispatcher.UnhandledException> events are not raised. Instead, exceptions are handled by the <xref:System.Threading.Tasks.TaskScheduler.UnobservedTaskException?displayProperty=name> event.
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- Calls to some members, such as <xref:System.Windows.Threading.DispatcherOperation.Result>, block until the operation has completed.
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- [ ] Quirked
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- [x] Build-time break
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### Recommended Action
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To avoid ambiguity (and potential differences in exception handling or blocking
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behaviors), code calling Dispatcher.Invoke can pass an empty object[] as a
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second parameter to the Invoke call to be sure of resolving to the .NET 4.0
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method overload.
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### Affected APIs
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* `M:System.Windows.Threading.Dispatcher.Invoke(System.Delegate,System.Object[])`
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* `M:System.Windows.Threading.Dispatcher.Invoke(System.Delegate,System.TimeSpan,System.Object[])`
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* `M:System.Windows.Threading.Dispatcher.Invoke(System.Delegate,System.TimeSpan,System.Windows.Threading.DispatcherPriority,System.Object[])`
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* `M:System.Windows.Threading.Dispatcher.Invoke(System.Delegate,System.Windows.Threading.DispatcherPriority,System.Object[])`
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### Category
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Windows Workflow Foundation (WF)
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<!-- breaking change id: 23 -->
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