Raise Events to the UI thread from a Task

Question

I have been trying to determine the proper approach to manipulate the UI from an asynchronous task. My application has become cluttered with threaded Invokes and BeginInvokes. I am trying to alleviate this clutter as well as provide a bit more responsiveness on the UI by taking advantage of C# async and await .

Somewhere on the UI thread I initialize IProgress event handler and pass it to an asynchronous function called DoInfiniteWorkAsync . This function runs infinitely in a background task but often has the need to update portions of the UI.

   private void Form1_Load(object sender, EventArgs e)
   {
       // Create a UIEventHandler on our UI thread.
       Progress<string> UIEventHandler = new Progress<string>();
       UIEventHandler.ProgressChanged += UIEventHandler_CommandRaised;
       // Pass the UIEventHandler to our Asyncronous task.
       DoInfiniteWorkAsync(UIEventHandler);

   }
   void UIEventHandler_EventRaised(object sender, string e)
   {
       string eventMessage = e;
       // Update UI based on the event message.
   }

My DoInfiniteWorkAsync function uses the passed in UIEventHandler to report UIEventMessages while running its task.

    private async Task DoInfiniteWorkAsync(IProgress<string> UIEventHandler)
    {
        await Task.Run(() =>
        {
            // 24/7 running tasks. 
            // Sets a UIEventMessage to signal UI thread to do something.
            UIEventHandler.Report(UIEventMessage);
        });
    }

Is this the proper way to be updating the UI thread from a long running background thread? The fact that my event handler datatype (IProgress) is specifically directed at progress reporting is making me feel like I'm missing the point.

Answer 1

To bring in data from one asynchronous thread to another you have to invoke it.

Define in your class a field of property:

    string _readData = null;

Then fill the string with the eventMessage and call a method to invoke the data.

string eventMessage = e;
_readData = eventMessage;
Msg();

This is the method Msg():

    private void Msg()
    {
        if (this.InvokeRequired)
        {
            this.Invoke(new MethodInvoker(Msg));
        }
        else
        {
            textBox2.Text = textBox2.Text + Environment.NewLine + " >> " + _readData;
        }
    }