Question

To try to get a mental grasp on threading, I tried monkey-see-monkey-do, and copied (like read and type, not cut and paste) from THIS_PAGE on MSDN.

When I did that, I got the following errors

Error 2 The type or namespace name ‘SetTextCallback’ could not be found (are you missing a using directive or an assembly reference?) Form1.cs 385 17 ZYX987

Error 3 The type or namespace name ‘SetTextCallback’ could not be found (are you missing a using directive or an assembly reference?) Form1.cs 385 41 ZYX987

I scrolled down aways on the web page and found a lot of community comments indicating that everyone has the exact same problem because the example is misleading. i.e., SetTextCallback is never declared.

This is the copycat version I typed while staring at the MSDN page…

private void SetText(string text)
{
    // InvokeRequired required compares the thread ID of
    // the calling thread to the thread ID of the 
    // creating thread.  If these threads are different, 
    // it returns true
    if (this.label1.InvokeRequired)                    
    {
        SetTextCallback d = new SetTextCallback(SetText);
        this.Invoke(d, new object[] { text });
    }
    else
    {
        this.label1.Text = text;
    }
}

Would someone here please suggest where I should place SetTextCallback in my CopyCatCode ?

Second question: what does the syntax for declaring it look like ?

Third question: if SetTextCallback is a method, then what should be in it ?

I searched for "…SetTextCallback …" (no quotes) here on Stack Overflow and found a few references, but not this exact problem. Hope this is the kind of question that belongs here. Thanks for reading.

Answer 1

Scroll down in the msdn page you linked to (“How to: Make Thread-Safe Calls to Windows Forms Controls“), the full source is listed at the bottom. You’ll find there the definition:

    // This delegate enables asynchronous calls for setting
    // the text property on a TextBox control.
    delegate void SetTextCallback(string text);