Beginning Web Development, Silverlight, and ASP.NET AJAX

CHAPTER 9 ■ .NET 3.0: WINDOWS WORKFLOW FOUNDATION 217
AutoResetEvent waitHandle = new AutoResetEvent(false);
workflowRuntime.WorkflowCompleted +=
delegate(object sender, WorkflowCompletedEventArgs e)
{waitHandle.Set();};
workflowRuntime.WorkflowTerminated +=
delegate(object sender, WorkflowTerminatedEventArgs e)
{
Console.WriteLine(e.Exception.Message);
waitHandle.Set();
};
WorkflowInstance instance =
workflowRuntime.CreateWorkflow(typeof
(FirstWorkflowApp.Workflow1));
instance.Start();
}
}
}
}
waitHandle.WaitOne();
This code creates the new instance of the WorkflowRuntime called workflowRuntime.
With this, it creates a waitHandle that exits the workflow when set. It adds a couple of
event handlers to execute when the workflow completes or is terminated. When the
workflow completes, you simply set the waitHandle. When it terminates, you dump out
the error message and then set the waitHandle.
Next, it uses the workflowRuntime to create a WorkflowInstance. This instance is initialized
with the workflow that you want to run, which in this case is called Workflow1 and is
in the FirstWorkflowApp namespace.
It will then start the instance, calling the waitOne method on the waitHandle. This
locks activity until the waitHandle is set.
Thus, when your application is run, the line instance.Start() kicks off the workflow
sequence. This hits the CodeActivity node, which causes its ExecuteCode function to run.
This function writes the text out to the console window and waits for a key to be pressed.
When the key is pressed, the sequence moves to the next node, which is the end of the
workflow. This causes the WorkflowCompleted event to fire, which sets the waitHandle,
which in turn completes the waitOne method on the instance. At this point, the flow
passes to the next line, which is the end of the application, so the application terminates.