private void usernamTextBox_Leave(object sender, EventArgs e) { usernamTextBox.Enabled = false; if (String.Equals(usernamTextBox.Text, usrname) == false) { datachange = true; if (ValidationCheck.CheckUserName(usernamTextBox.Text)) { usernameExist.Visible = true; button1.Enabled = false; } else { usernameExist.Visible = false; button1.Enabled = true; } } }