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WorkflowApplication.OnUnhandledException Property

.NET Framework 4.6 and 4.5

Gets or sets the Func<T, TResult> that is invoked when the current workflow instance encounters an unhandled exception.

Namespace:  System.Activities
Assembly:  System.Activities (in System.Activities.dll)

public Func<WorkflowApplicationUnhandledExceptionEventArgs, UnhandledExceptionAction> OnUnhandledException { get; set; }

Property Value

Type: System.Func<WorkflowApplicationUnhandledExceptionEventArgs, UnhandledExceptionAction>
The delegate that is invoked when a workflow instance encounters an unhandled exception.

Both OnUnhandledException and WorkflowUnhandledExceptionBehavior dictate the behavior of the runtime when an exception is not handled in the workflow; however, WorkflowUnhandledExceptionBehavior has the option of leaving a suspended workflow in the persistence store, while OnUnhandledException does not. The reason for this is that what happens to a suspended workflow is host-specific, and WorkflowApplication is not. To implement this functionality using WorkflowApplication, create a custom PersistenceParticipant that has this behavior.

The following example invokes a workflow that throws an exception. The exception is unhandled by the workflow and the OnUnhandledException handler is invoked. The WorkflowApplicationUnhandledExceptionEventArgs are inspected to provide information about the exception, and the workflow is terminated.

Activity wf = new Sequence
{
    Activities =
     {
         new WriteLine
         {
             Text = "Starting the workflow."
         },
         new Throw
        {
            Exception = new InArgument<Exception>((env) => 
                new ApplicationException("Something unexpected happened."))
        },
        new WriteLine
         {
             Text = "Ending the workflow."
         }
     }
};

WorkflowApplication wfApp = new WorkflowApplication(wf);

wfApp.OnUnhandledException = delegate(WorkflowApplicationUnhandledExceptionEventArgs e)
{
    // Display the unhandled exception.
    Console.WriteLine("OnUnhandledException in Workflow {0}\n{1}",
        e.InstanceId, e.UnhandledException.Message);

    Console.WriteLine("ExceptionSource: {0} - {1}",
        e.ExceptionSource.DisplayName, e.ExceptionSourceInstanceId);

    // Instruct the runtime to terminate the workflow. 
    return UnhandledExceptionAction.Terminate;

    // Other choices are UnhandledExceptionAction.Abort and  
    // UnhandledExceptionAction.Cancel
};

wfApp.Run();

.NET Framework

Supported in: 4.6, 4.5, 4

.NET Framework Client Profile

Supported in: 4
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