Running Workflows in .NET 4.0

An article by Ogi Ivanov No Comments

Workflows can be run synchronously and asynchronously. Below is an example how you run a workflow instance synchronously:

Dictionary<string, object> inputs = new Dictionary();
inputs.Add("InArgument", "SomeValue");
inputs.Add("InOutArgument", "SomeOtherValue");
WorkflowElement activity = workflow;
IDictionary<string, object> outputs = WorkflowInvoker.Invoke(new MyWorkflow(), inputs);
MyObject obj = (MyObject)outputs["OutArgument"];
MyOtherObject obj = (MyOtherObject)outputs["InOutArgument"];

Note that now workflows have arguments as well as parameters. Arguments are for passing data to and from the Workflow where parameters are for internal use. Remember: Workflow is an activity so the same goes for any custom activity you create. Any In or In/Out arguments have to be passed to the workflow for it to execute.

Now here is a very simplified example of how to run a workflow instance asynchronously. The OnCompleted event is raised when the workflow has finished running and the IDictionary<string, object> outputs can be read off of the WorkflowCompletedEventArgs.

ManualResetEvent resetEvent = new ManualResetEvent(false);
WorkflowInstance instance = new WorkflowInstance(new MyWorkflow());

instance.OnCompleted = delegate(WorkflowCompletedEventArgs e)
{
    Console.WriteLine("workflow instance completed, Id = " + instance.Id);
    resetEvent.Set();
};
instance.Run();
resetEvent.WaitOne();

I haven't done it yet but I presume running a workflow in IIS and interacting with it before it finishes would not be as staighforward as the examples above.