textbox只能输入数字

 private void txtJustNumber_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyChar != 8 && !char.IsDigit(e.KeyChar) && e.KeyChar != 13)
            {
                MessageBox.Show("只能输入数字");
                e.Handled = true;
            }
        }