截取指定长度的字符串，超过指定长度的加...

        /**//// <summary>
        /// 按指定汉字的宽度截取字符串
        /// </summary>
        /// <param name="sourceStr">源字符串</param>
        /// <param name="length">要截取汉字的个数</param>
        /// <param name="isRounLastChar">当源串中存在半角和全角交替是，当结尾存在半个汉字时是否保留最后一位汉字</param>
        /// <returns>截取后的字符串</returns>
        /// <summary>
        /// 超过指定汉字长度截取字符串并加上．．．
        /// </summary>
        /// <param name="str">要截取的字符串</param>
        /// <param name="length">截取汉字长度</param>
        /// <param name="isRounLastChar">当结尾存在半个汉字时是否保留</param>
        /// <returns>截取后的结果</returns>
        public string CutString4(string str, int length, bool isRounLastChar)
        ...{
            int n = length * 2;
            string dStr = str;
            string tempStr = string.Empty;
            System.Text.Encoding gbEncoding = System.Text.Encoding.GetEncoding("gb2312");
            if (n < gbEncoding.GetBytes(dStr).Length)
            ...{    
                int i = 0;
                while (n != 0)
                ...{
                    if (n == 1)
                    ...{
                        if (isRounLastChar)
                        ...{
                            tempStr += dStr[i];
                        }
                        break;
                    }
                    if (isCn(dStr[i]))
                    ...{
                        tempStr += dStr[i];
                        n = n - 2;
                    }
                    else
                    ...{
                        tempStr += dStr[i];
                        n--;
                    }
                    i++;
                }
                tempStr=tempStr+"...";
            }
            else
            ...{
                tempStr=dStr;
            }
            tempStr=replace(tempString,"/");
            return(tempStr);
        }
        /**//// <summary>
        /// 是否为汉字
        /// </summary>
        /// <param name="c">字符</param>
        /// <returns>true/false</returns>
        public bool isCn(char c)
        ...{
            byte[] bs = System.Text.Encoding.UTF8.GetBytes(c.ToString());
            if (bs.Length == 3)
            ...{
                return true;
            }
            else
            ...{
                return false;
            }
        }