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TaskScheduler.UnobservedTaskException Event

Occurs when a faulted task's unobserved exception is about to trigger exception escalation policy, which, by default, would terminate the process.

Namespace:  System.Threading.Tasks
Assembly:  mscorlib (in mscorlib.dll)

public static event EventHandler<UnobservedTaskExceptionEventArgs> UnobservedTaskException

This application domain-wide event provides a mechanism to prevent exception escalation policy (which, by default, terminates the process) from triggering.

To make it easier for developers to write asynchronous code based on tasks, the .NET Framework 4.5 changes the default exception behavior for unobserved exceptions. Although unobserved exceptions still raise the UnobservedTaskException exception, the process does not terminate by default. Instead, the exception is handled by the runtime after the event is raised, regardless of whether an event handler observes the exception. This behavior can be configured. Starting with the .NET Framework 4.5, you can use the <ThrowUnobservedTaskExceptions> configuration element to revert to the behavior of the .NET Framework 4 and terminate the process:

<configuration> 
   <runtime> 
      <ThrowUnobservedTaskExceptions enabled="true"/> 
   </runtime> 
</configuration>

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4

.NET Framework Client Profile

Supported in: 4

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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