将参数扩展为指定长度的字符串，不足位数的在前方加0

/// <summary>
        /// 将参数扩展为指定长度的字符串，不足位数的在前方加0
        /// </summary>
        /// <param name="origin"></param>
        /// <param name="length"></param>
        /// <returns></returns>
        public static string GetLengthString(string origin, int length)
        {
            int l = origin.Length;

            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < length - l; i++)
                sb.Append("0");
            sb.Append(origin);
            return sb.ToString();
        }