CODEWITHSUNDEEP
c#invoke
mohammad Mustafa
mohammad Mustafa

Reputation: 41

cannot invoke a non-delegate type

I am trying to use threading and that includes a GUI controller, so I needed to invoke that controller but I have this problem- I cannot invoke a non-delegate type in this part of the code

if (toolStripTextBox1.Text != "")
{
    if (RT[j].tabvalue.ToString() == tabControl1.Invoke(() =>
                                       { tabControl1.SelectedTab.Name; }))
    {
        RT[j].RitchT.Text = getH.getHtmlCode(toolStripTextBox1.Text);
    }
}

while this is working on the other hand

tabControl1.Invoke(
    () => { tabControl1.TabPages[R.RitchT.Name].Controls.Add(R.RitchT);
});

This is the invoke class 

 public static class ControlExtensions
 {
    public static void Invoke(this Control control, Action action)
    {
        if (control.InvokeRequired)
            control.Invoke(new MethodInvoker(action), null);
        else
            action.Invoke();
    }
 }

How can I solve this?

Upvotes: 3

Views: 15081

Answers (1)

Hans Passant
Hans Passant

Reputation: 942257

  tabControl1.Invoke(() => { tabControl1.SelectedTab.Name; })

Yes, that's not legal syntax. The Control.BeginInvoke() method takes a Delegate as its first argument. A lambda expression doesn't convert implicitly to Delegate, you have to help. Fix:

  tabControl1.Invoke(new Func<string>(() => { return tabControl1.SelectedTab.Name; }))

You'll have more trouble, you cannot assign the Text property of a RichTextBox in a worker thread, you'll have to use BeginInvoke() there as well. You'll get away with reading the Text properties but it is rather a bad idea, they may change while the worker thread is running and the user keeps operating the UI. You really want to favor a BackgroundWorker or Task, collect the data you need for the worker before you start it, update the UI with the results of the worker after it is done.

Upvotes: 3

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