Hi, I want to remove checked items from checklistbox (winform control) in class file method which i am calling asynchronously using deletegate. but it showing me this error message:- Cross-thread operation not valid: Control 'checkedListBox1' accessed from a thread other than the thread it was created on. i have tried invoke required but again got the same error. Sample code is below: private void button1_Click(object sender, EventArgs e) { // Create an instance of the test class. Class1 ad = new Class1(); // Create the delegate. AsyncMethodCaller1 caller = new AsyncMethodCaller1(ad.TestMethod1); //callback delegate IAsyncResult result = caller.BeginInvoke(checkedListBox1, new AsyncCallback(CallbackMethod)," "); } In class file code for TestMethod1 is : - private delegate void dlgInvoke(CheckedListBox c, Int32 str); private void Invoke(CheckedListBox c, Int32 str) { if (c.InvokeRequired) { c.Invoke(new dlgInvoke(Invoke), c, str); c.Items.RemoveAt(str); } else { c.Text = ""; } } // The method to be executed asynchronously. public string TestMethod1(CheckedListBox chklist) { for (int i = 0; i < 10; i++) { string chkValue = chklist.CheckedItems[i].ToString(); //do some other database operation based on checked items. Int32 index = chklist.FindString(chkValue); Invoke(chklist, index); } return ""; }