public class StringHelper     {         public static string GetSubString(string str, int len)         {             string result = string.Empty;// 最终返回的结果             int byteLen = System.Text.Encoding.Default.GetByteCount(str);// 单字节字符长度             int charLen = str.Length;// 把字符平等对待时的字符串长度             int byteCount = 0;// 记录读取进度             int pos = 0;// 记录截取位置             if (byteLen > len)             {                 for (int i = 0; i < charLen; i++)                 {                     if (Convert.ToInt32(str.ToCharArray()[i]) > 255)// 按中文字符计算加2                         byteCount += 2;                     else// 按英文字符计算加1                         byteCount += 1;

if (byteCount > len)// 超出时只记下上一个有效位置                     {                         pos = i;                         break;                     }                     else if (byteCount == len)// 记下当前位置                     {                         pos = i + 1;                         break;                     }                 }

if (pos >= 0)                     result = str.Substring(0, pos);             }             else                 result = str;

return result;         }

/// <summary>         /// c#的中英文混合字符串截取         /// </summary>         /// <param name="inputString"></param>         /// <param name="length">显示的字符长度*2</param>         /// <returns></returns>         public static string SubString(string inputString, int length)         {             byte[] ping = Encoding.UTF8.GetBytes(inputString);             int count=Encoding.UTF8.GetByteCount(inputString);             if (count <= length * 2)             {                 return inputString;             }             ASCIIEncoding ascii = new ASCIIEncoding();             int tempLen = 0;             string tempString = "";             byte[] s = ascii.GetBytes(inputString);             for (int i = 0; i < s.Length; i++)             {                 ////判断是否为汉字或全脚符号                 if ((int)s[i] == 63)                 {                     tempLen += 2;                 }                 else                 {                     tempLen += 1;                 }                 tempString += inputString.Substring(i, 1);                 if (tempLen >= length * 2)                     break;             }             return tempString;         }

public static string GetSub(string sub, int length)         {             //byte[] bytStr = System.Text.Encoding.Default.GetBytes(sub);                if (sub == null) return string.Empty;             int len = length * 2;             //aequilateLength为中英文等宽长度,cutLength为要截取的字符串长度             int aequilateLength = 0, cutLength = 0;             Encoding encoding = Encoding.GetEncoding("gb2312");

string cutStr = sub.ToString();             int strLength = cutStr.Length;             byte[] bytes;             for (int i = 0; i < strLength; i++)             {                 bytes = encoding.GetBytes(cutStr.Substring(i, 1));                 if (bytes.Length == 2)//不是英文                     aequilateLength += 2;                 else                     aequilateLength++;

if (aequilateLength <= len) cutLength += 1;

if (aequilateLength > len)                     return cutStr.Substring(0, cutLength);//+ "..."             }             return cutStr;         }

}