C#截取字符串

    public class SubStrHelper

    {

        /// <summary>

        /// 截取字符串长度，中文二字节

        /// </summary>

        /// <param name="str"></param>

        /// <param name="length">字节长度</param>

        /// <returns></returns>

        public static string GetSubString(string str, int byteLength, string moreTag = "...")

        {

            string temp = str;

            int j = 0;

            int k = 0;

            for (int i = 0; i < temp.Length; i++)

            {

                // if (Regex.IsMatch(temp.Substring(i, 1), @"[\u4e00-\u9fa5]+"))            //匹配中文

                if (Regex.IsMatch(temp.Substring(i, 1), @"[^\x00-\xff]+"))                  //匹配双字节字符（包括中文）

                {

                    j += 2;

                }

                else

                {

                    j += 1;

                }

                if (j <= byteLength)

                {

                    k += 1;

                }

                if (j > byteLength)

                {

                    return string.Format("{0}{1}", temp.Substring(0, k), moreTag);

                }

            }

            return temp;

        }

    }

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