Need a help for cross thread operation in C# Threads

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4.00/5 (3 votes)

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Hello!

I got an exception called cross thread operation invalid in ma test programme.I knw the error.But I dnt knw how to fix it.Please comment on this matter.Thank you all.

Here is my simple code:

private void button1_Click(object sender, EventArgs e)
       {
           Thread thr1 = new Thread(adddata);
           thr1.Start();
           //if (thr1.IsAlive)
             //  addvalue();
       }
       private void adddata() {
           for (int i = 0; i < 20;i++) {
               listBox1.Items.Add(i);
           }
       }
       private void addvalue() {
           int a = 0;
           for (int j = 0; j < 20;j++ ) {
              listBox2.Items.Add(listBox1.Items[0].ToString());
           }
       }

[edit]Code block added - OriginalGriff[/edit]

Posted 22-Apr-11 19:52pm

Sameera Fonseka

Updated 22-Apr-11 20:31pm

OriginalGriff

v4

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Patrick Kalkman · Accepted Answer · 2011-04-22T20:20:00

Most controls dont allow to be accessed from a thread other than the UI thread. Therefore, these controls have an invoke method which can be called from a different thread.

Your AddData could be written like this so that it will also function from a different thread.

C#

public void AddData()
{
  if (this.InvokeRequired)
  {
    // call method on the ui thread...
    this.Invoke(new MethodInvoker(AddData));
  }
  else
  {
    // In the ui thread
    for (int i = 0; i < 20; i++)
    {
      listBox1.Items.Add(i);
    }
  }
}

Hope this helps.