Windows Workflow: Getting variable from WorkflowApplication

Question

I'm using the Windows Workflow Foundation (WWF). I made an Activity (XAML) with one Sequence in which I defined a variable.

I run the activity in the console application by creating an instance of WorkflowApplication. How can I get the value of a variable in my console application?

I persist an instance of WorkflowApplication in XML and in it I saw my variable and its value. Is there any correct way to get the value of a variable from XML?

Answer 1

So in your last comment you stated you want to get the state in the console application before the workflow is completed. Unfortunately In/Out and Out arguments are only available upon completion of the workflow. But there are ways to communicate with the host process using other constructs than workflow variables and arguments.

One of the ways to do that is to use a custom extension that can be used to interact with the host process. An extensions can be of any type and is available to the workflow and the host process. A complete example:

using System;
using System.Activities;

namespace WorkflowDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            var app = new WorkflowApplication(new MyCustomActivity());
            var myExtension = new MyCommunicationExtension();
            myExtension.MyValueChanged += (s, e) => Console.WriteLine(myExtension.MyValue);

            app.Extensions.Add(myExtension);
            app.Run();

            Console.ReadKey();
        }
    }

    public class MyCommunicationExtension
    {
        public string MyValue { get; private set; }

        public event EventHandler<EventArgs> MyValueChanged;

        public void OnMyValueChanged(string value)
        {
            MyValue = value;
            MyValueChanged?.Invoke(this, EventArgs.Empty);
        }
    }

    public class MyCustomActivity : CodeActivity
    {
        protected override void Execute(CodeActivityContext context)
        {
            var extensionObj = context.GetExtension<MyCommunicationExtension>();
            if (extensionObj != null)
            {
                extensionObj.OnMyValueChanged("Hello World");
            }
        }
    }
}