WorkflowRuntime Execution

Question

I designed a Workflow in WF4 in visual studio . It is so simple and I only want to execute this in this way.

 using (WorkflowRuntime workflowRuntime = new WorkflowRuntime())
 {
     System.Workflow.Runtime.WorkflowInstance instance =  workflowRuntime.CreateWorkflow(typeof(Workflow1));//My workflow
     instance.Start();     
 }

But when i execute this i get the following error.

The input workflow type must be an Activity.Parameter name: workflowType

Answer 1

There is a similar discussion in Technet. The WorkflowRuntime class is part of Workflow Foundation 3 and doesn't work with WF4 types. It is included only for backwards compatibility. In fact, in 4.5 WorkflowRuntime is marked obsolete.

You are probably trying to use a System.Activities.Activity based workflow to WorkflowRuntime, which will raise the ArgumentException error you describe.

To host/run a WF4 workflow you should use one of the following classes: WorkflowInvoker, WorkflowApplication and WorkflowServiceHost. This is described in the documentation, in Using WorkflowInvoker and WorkflowApplication.

The simplest way is to use WorkflowInvoker to run a workflow as a method, eg:

Activity wf = new WriteLine
{
    Text = "Hello World."
};

WorkflowInvoker.Invoke(wf);

although this doesn't give you much control over the workflow's lifecycle.

WorkflowApplication gives you full control and WorkflowServiceHost allows you to host the workflow as a WCF service.

In fact, you can host a WF4 workflow using Windows Server AppFabric without creating your own host and let AppFabric manage instances, security and recovery.