C#的拓展方法

必須是靜態類的靜態方法 參數必須使用this指定是哪種類型的拓展方法
public static class Common
    {
        /// <summary>
        /// 轉換Object類型為string,null為空值
        /// </summary>
        /// <param name="val"></param>
        /// <returns></returns>
        public static string Conversion(object val)
        {
            if (val == DBNull.Value)
                return "";
            else if (val == null)
                return "";
            else
                return val.ToString();
        }

        public static int ToInt(this object val)
        {
            int i = 0;
            try
            {
                i = Convert.ToInt32(val);
            }
            catch{}
            return i;
        }
}