C# 全选中数字文本框内容

/// <summary>
        /// 全选中数字文本框内容
        /// </summary>
        /// <param name="o"></param>
        public static void numericSelectAll(this object o)
        {
            System.Windows.Forms.NumericUpDown upDown = (System.Windows.Forms.NumericUpDown)o;
            upDown.Focus();
            System.Windows.Forms.UpDownBase up = upDown;
            upDown.Select(0, up.Text.Length);
        }