获取当前时间戳

/// <summary>
       /// 获取当前时间戳
       /// </summary>
       /// <returns></returns>
       public static string GetTimeStamp()
       {
           DateTime date = DateTime.Now;
           TimeSpan span = date - new DateTime(1970,1,1,0,0,0,0);
           return Convert.ToString(Convert.ToUInt64( span.TotalSeconds));
       }