WorkflowRuntime.ServicesExceptionNotHandled Event

Definition

Namespace:

System.Workflow.Runtime

Assembly:

System.Workflow.Runtime.dll

Occurs when a service that is derived from the WorkflowRuntimeService class calls RaiseServicesExceptionNotHandledEvent(Exception, Guid).

C#

public event EventHandler<System.Workflow.Runtime.ServicesExceptionNotHandledEventArgs> ServicesExceptionNotHandled;

Event Type

EventHandler<ServicesExceptionNotHandledEventArgs>

Examples

The following code example demonstrates how to use WorkflowRuntime functionality from a workflow host. The code associates ServicesExceptionNotHandled with an event handler, a method named OnExceptionNotHandled.

This code example is part of the Custom Persistence Service Sample.

C#

static void Main()
{
    using (WorkflowRuntime workflowRuntime = new WorkflowRuntime())
    {
        try
        {
            // engine will unload workflow instance when it is idle
            workflowRuntime.AddService(new FilePersistenceService(true));

            workflowRuntime.WorkflowCreated += OnWorkflowCreated;
            workflowRuntime.WorkflowCompleted += OnWorkflowCompleted;
            workflowRuntime.WorkflowIdled += OnWorkflowIdle;
            workflowRuntime.WorkflowUnloaded += OnWorkflowUnload;
            workflowRuntime.WorkflowLoaded += OnWorkflowLoad;
            workflowRuntime.WorkflowTerminated += OnWorkflowTerminated;
            workflowRuntime.ServicesExceptionNotHandled += OnExceptionNotHandled;

            workflowRuntime.CreateWorkflow(typeof(PersistenceServiceWorkflow)).Start();

            waitHandle.WaitOne();
        }
        catch (Exception e)
        {
            Console.WriteLine("Exception \n\t Source: {0} \n\t Message: {1}", e.Source, e.Message);
        }
        finally
        {
            workflowRuntime.StopRuntime();
            Console.WriteLine("Workflow runtime stopped, program exiting... \n");
        }
    }
}

Remarks

A service that is derived from the WorkflowRuntimeService class can call the RaiseServicesExceptionNotHandledEvent method to inform subscribers to the ServicesExceptionNotHandled event that an exception that it was unable to handle occurred during its execution. You can subscribe to this event to implement a recovery mechanism.

This event is raised when a workflow instance has not been created yet by the workflow run-time engine and an exception occurs. In this scenario, the only way to inform a host application that an exception occurred is to raise this event. However, the workflow run-time engine does not call this directly. Instead, the workflow run-time engine either delivers an exception to the workflow instance or, if there is no instance, throws back to the caller, which in this case is actually the service that fires this event. If you create your own persistence or scheduler service, you must implement this event yourself through the base RaiseServicesExceptionNotHandledEvent method.

For the ServicesExceptionNotHandled event, the sender contains the WorkflowRuntime and WorkflowEventArgs contains the Guid of the workflow instance that was using the service and the Exception that could not be handled.

For more information about handling events, see Handling and raising events.

Applies to