“Cross-thread operation not valid” exception on inner controls

Question

I\'ve been struggling with this for quite a while: I have a function designed to add control to a panel with cross-thread handling, the problem is that though the panel and

Answer 1

Here is a working piece of code :

public delegate void AddControlToPanelDlg(Panel p, Control c);

        private void AddControlToPanel(Panel p, Control c)
        {
            p.Controls.Add(c);
        }

        private void AddNewContol(object state)
        {
            object[] param = (object[])state;
            Panel p = (Panel)param[0];
            Control c = (Control)param[1]
            if (p.InvokeRequired)
            {
                p.Invoke(new AddControlToPanelDlg(AddControlToPanel), p, c);
            }
            else
            {
                AddControlToPanel(p, c);
            }
        }

And here is how I tested it. You need to have a form with 2 buttons and one flowLayoutPanel (I chose this so I didn't have to care about location hwhen dinamically adding controls in the panel)

private void button1_Click(object sender, EventArgs e)
        {
            AddNewContol(new object[]{flowLayoutPanel1, CreateButton(DateTime.Now.Ticks.ToString())});
        }

        private void button2_Click(object sender, EventArgs e)
        {
            ThreadPool.QueueUserWorkItem(new WaitCallback(AddNewContol), new object[] { flowLayoutPanel1, CreateButton(DateTime.Now.Ticks.ToString()) });
        }

I that he probem with your exaple is that when you get in the InvokeRequired branch you invoke the same function wou are in, resulting in a strange case of recurssion.