System.ArgumentException : The input workflow type must be an Activity.

Question

Hi everyone! I’m getting this error when starting up the workflow:

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

The code I’m using is shown below:

using (var wf = new WorkflowRuntime())
{
  wf.WorkflowCompleted += (_, __) => signal.Set();
  wf.WorkflowTerminated += (_, __) => signal.Set();
  var args = new Dictionary<string, object>();
  args.Add("Input", plainText);
  args.Add("Output", string.Empty);
  var inst = wf.CreateWorkflow(typeof (HtmlTypography), args);
  inst.Start();
  signal.WaitOne();
  return (string) args["Output"];
}

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- Dmitri Nesteruk

Answer 1

Do you mean HtmlTypography is indeed a workflow but you are still getting the error? As suggested by the exception, we need the Type of a workflow to be passed to CreateWorkflow(). What is HtmlTypography?

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Cecilia Leung This posting is provided "AS IS" and confers no rights or warranties.

Answer 2

Not sure who decided to mark this as answer since it's clearly isn't.

I'm passing a very valid Activity into the method.

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- Dmitri Nesteruk

Answer 3

Hi Dmitri,

I think the Activity you pass in is an type of  System.Activities.Activity , this type is supported from WF 4.

And the WorkflowRuntime is a type from WF 3.5, WorkflowRuntime.CreateWorkflow needs an activity type from

System.Workflow.ComponentModel.Activity.

If you want to use WF4 feature, please use WorkflowApplication/WorkflowInvoker isntead of WorkflowRuntime.