Cross thread operation not valid : C# threading

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hello friends, once again i triggered this message,
can anyone of u teach me how to settle down this problem..

i try to start a thread to get the information from task manager
so i can get the information of which process is currently activate, suspended or close

previously i triggered the same error message by try to create new usercontrol with thread which are wrong

in this case how do i change my label's text ??
cause when i try to change my text of label inside the thread it will trigger this.

What I have tried:

<pre>private void detector() {
            while (true) {
                var mycafeclientPro = Process.GetProcessesByName("notepad");
                if (mycafeclientPro.Length > 0) {
                    foreach (Process p in mycafeclientPro) {
                        if (p.Responding) {
                            //statusPanel.BackColor = Color.FromArgb(190, 197, 209);
                            statusLabel.Text = "Application activated";
                            //statusLabel.ForeColor = Color.FromArgb(255, 255, 255);
                            //statusLabel.Location = new Point((statusPanel.Width - statusLabel.Width) / 2, (statusPanel.Height - statusLabel.Height) / 2);
                        }
                        else {

                        }
                    }
                }
                else {
                    
                }
            }
        }

Posted 12-Dec-17 19:23pm

newbie1992

Updated 12-Dec-17 20:11pm

v2

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OriginalGriff · Accepted Answer · 2017-12-12T19:51:00

You cannot access UI elements (controls, forms) at all, except on the thread on which they were created: the UI thread. If you try, you will get a cross thread exception.
So this code:

statusLabel.Text = "Application activated";

cannot be executed on your "new" thread.

To solve this, either
1) Invoke your control: Control.Invoke Method (Delegate) (System.Windows.Forms)[^]
Or
2) Use the BackgroundWorker class (BackgroundWorker Class (System.ComponentModel)[^] and do the control updates in the ProgressChanged event handler.

________________ · Accepted Answer · 2017-12-12T20:07:00

delegate void  SetTextOnControl (Control controlToChange, string message);


			public void SetText(Control controlToChange, string message)
			{
				if (controlToChange.InvokeRequired)
				{
					SetTextOnControl DDD = new SetTextOnControl(SetText);
					controlToChange.Invoke(DDD, controlToChange, message);
				}
				else
				{
					controlToChange.Text = message;
				}
			}

Than call this SetTexst from any thread.

Cross thread operation not valid : C# threading

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