C# – Update GUI from Another Thread and Class in Windows Forms Application

.netc++multithreadingwinforms

I've searched a ton, but I can't seem find anything relating to my specific problem.

I want to be able to update my MainUI form from another class (SocketListener) and within that I have a thread that handles the networking (clientThread). Right now I can run simple outputs from the networking thread such as writing to the debugger output and creating a MessageBox.

But what I really want to do is be able to invoke code from the clientThread that will do things on my MainUI instance. How can I do this?

Also, if anyone wants specific portions of the code then I can post it to help give you a better understanding of what I'm asking.

Best regards!

Best Answer

Check the InvokeRequired of the Control class, and if it's true, then call the Invoke and pass in a delegate (usually an anonymous method) that does what you want to do on the client's thread.

Example:

public void DoWork(Form form)
{
    if (form.InvokeRequired)
    {
        // We're on a thread other than the GUI thread
        form.Invoke(new MethodInvoker(() => DoWork(form)));
        return;
    }

    // Do what you need to do to the form here
    form.Text = "Foo";
}

Related Solutions

C# – How to Update the GUI from Another Thread

The simplest way is an anonymous method passed into Label.Invoke:

// Running on the worker thread
string newText = "abc";
form.Label.Invoke((MethodInvoker)delegate {
    // Running on the UI thread
    form.Label.Text = newText;
});
// Back on the worker thread

Notice that Invoke blocks execution until it completes--this is synchronous code. The question doesn't ask about asynchronous code, but there is lots of content on Stack Overflow about writing asynchronous code when you want to learn about it.

C# WinForms – How to Force GUI Update from UI Thread

At first I wondered why the OP hadn't already marked one of the responses as the answer, but after trying it myself and still have it not work, I dug a little deeper and found there's much more to this issue then I'd first supposed.

A better understanding can be gained by reading from a similar question: Why won't control update/refresh mid-process

Lastly, for the record, I was able to get my label to update by doing the following:

private void SetStatus(string status) 
{
    lblStatus.Text = status;
    lblStatus.Invalidate();
    lblStatus.Update();
    lblStatus.Refresh();
    Application.DoEvents();
}

Though from what I understand this is far from an elegant and correct approach to doing it. It's a hack that may or may not work depending upon how busy the thread is.

Best Answer

Related Solutions

C# – How to Update the GUI from Another Thread

C# WinForms – How to Force GUI Update from UI Thread

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