Workflow 4.0 custom activity to start external process

I am trying out Workflow 4.0 and hoping to write a custom activity to start an external executable, wait for that process to complete and then resume subsequent steps in the workflow.

I found the following example that shows (towards the bottom of the page) how to write an activity to waiting for a file to arrive in a specific directory:

Creating Custom Activities with Workflow 4.0

I have a couple of problems wi开发者_JS百科th the example. Firstly, when I add the following code:

void FileCreated(object sender, FileSystemEventArgs e)
{
    instance.ResumeBookmark(bookmarkName, e.FullPath);
    fsw.Dispose();
}

instance.Resumebookmark(...) does not seem to be available but instance.BeginResumeBookmark and instance.EndResumeBookmark are.

I am also unsure of how to change this around to deal with external processes, rather than just watching the contents of a directory.

Is this even the best approach for this kind of thing?

I would suggest writing an AyncCodeActivity and avoid bookmarks altogether. Here is an example of a custom activity that returns the process exit code as the result:

    public sealed class RunProcess : AsyncCodeActivity<int>
    {
        public InArgument<string> FileName { get; set; }
        public InArgument<string> Arguments { get; set; }

        private Func<string, string, int> runProcessAsyncCall;

        protected override IAsyncResult BeginExecute(AsyncCodeActivityContext context, AsyncCallback callback, object state)
        {
            this.runProcessAsyncCall = this.RunProcessImpl;
            return runProcessAsyncCall.BeginInvoke(FileName.Get(context), Arguments.Get(context), callback, state);
        }

        protected override int EndExecute(AsyncCodeActivityContext context, IAsyncResult result)
        {
            return this.runProcessAsyncCall.EndInvoke(result);
        }

        private int RunProcessImpl(string fileName, string arguments)
        {
            Process p = Process.Start(fileName, arguments);
            p.WaitForExit();
            return p.ExitCode;
        }
    }

In general, bookmarks are great if the external event will not come for a potentially long time. If the process you're invoking is short-lived, an AsyncCodeActivity might be a better choice (it's certainly an easier one to manage).

This approach works perfectly well for running other processes. Use the Process.WaitForExit to check when the process is done, optionally checking the ExitCode, and resume the bookmark.