public void EnablePasswordTextBox(Boolean Enable) { // InvokeRequired required compares the thread ID of the // calling thread to the thread ID of the creating thread. // If these threads are different, it returns true. if (this.textBoxPassword.InvokeRequired) { EnablePasswordTextboxCallback d = new EnablePasswordTextboxCallback(EnablePasswordTextBox); this.Invoke(d, new object[] { Enable }); } else { // enable or disable the login button textBoxPassword.Enabled = Enable; } }