Getting Cross-thread operation not valid

Question

Possible Duplicate:
Cross-thread operation not valid: Control accessed from a thread other than the thread it was created on

public void CheckUnusedTabs(string strTabToRemove)
{ 
    TabPage tp = TaskBarRef.tabControl1.TabPages[strTabToRemove];
    tp.Controls.Remove(this);
    TaskBarRef.tabControl1.TabPages.Remove(tp);
}

I am trying to close a tab in the tabcontrol of windows application using the above code and i encountered the error:

Cross-thread operation not valid.

How to solve this ?

even a search on "cross thread" in SO gives lots of results... — Stormenet, Oct 06 '09 at 06:25

score 25 · Accepted Answer · answered Oct 06 '09 at 06:24

You can only make changes to WinForm controls from the master thread. You need to check whether InvokeRequired is true on the control and then Invoke the method as needed.

You can do something like this to make it work:

public void CheckUnusedTabs(string strTabToRemove)
{ 
    if (TaskBarRef.tabControl1.InvokeRequired)
    {
        TaskBarRef.tabControl1.Invoke(new Action<string>(CheckUnusedTabs), strTabToRemove);
        return;
    }      

    TabPage tp = TaskBarRef.tabControl1.TabPages[strTabToRemove];
    tp.Controls.Remove(this);
    TaskBarRef.tabControl1.TabPages.Remove(tp);
}

FYI, your clear update of the original code was the only way I was able to figure out how to properly implement this in mine. Thanks. — Jason, Dec 18 '12 at 16:29

score 20 · Answer 2 · answered Oct 06 '09 at 06:24

20

call using invoke, because you're accessing the GUI thread using another thread

 this.Invoke((MethodInvoker)delegate() {CheckUnusedTabs(""); });

answered Oct 06 '09 at 06:24

mustafabar

2,317
6
31
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This worked for me with a similar case: updating GUI from external event. – Ryan R Apr 19 '11 at 20:23

Adriaan Stander · Answer 3 · 2009-10-06T07:03:43.233

When using threads and UI controls, in winforms, you need to use InvokeRequired to make changes to the controls.

EDIT.

added an example.

Form, with button and label.

try

private void button2_Click(object sender, EventArgs e)
        {
            Thread thread = new Thread(UpdateProcess);
            thread.Start();
        }

        private void SetLabelText(string val)
        {
            label1.Text = val;
        }
        delegate void m_SetLabel(string val);

        private void UpdateProcess()
        {
            int i = 0;

            while (true)
            {
                if (label1.InvokeRequired)
                {
                    m_SetLabel setLabel = SetLabelText;
                    Invoke(setLabel, i.ToString());
                }
                else
                    label1.Text = i.ToString();
                i++;
                Thread.Sleep(500);
            }
        }

@astander i tried adding ... if(TaskBarRef.tabControl1.incokerequired) — Anuya, Oct 06 '09 at 06:26

score 1 · Answer 4 · answered Oct 29 '11 at 02:35

1

Cross thread not valid exception is due to the UI controls being accessed from other threads than main thread.see this http://helpprogramming.blogspot.com/2011/10/invalid-cross-thread-operation.html

answered Oct 29 '11 at 02:35

art

11
1

score -3 · Answer 5 · edited Aug 28 '12 at 02:41

-3

Set the following variable:

CheckIllegalCrossThreadValidation = false

edited Aug 28 '12 at 02:41

Steve Guidi

19,700
9
74
90

answered Oct 06 '09 at 07:17

maxy

438
3
10
20

7

CheckIllegalCrossThreadValidation is a safety check to prevent some versions of Windows from crashing when you try to do cross-thread UI updates. It's madness to turn it off. – Christian Hayter Oct 06 '09 at 07:42
For some reason Microsoft has added that option. – Tanner Ornelas Sep 27 '19 at 20:55

Getting Cross-thread operation not valid

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