C# 截取指定长度字符串

        /// <summary>
        /// 截取指定长度字符串
        /// </summary>
        /// <param name="inputString">要处理的字符串</param>
        /// <param name="len">指定长度</param>
        /// <returns>返回处理后的字符串</returns>
        public static string ClipString(string inputString, int len)
        {
            bool isShowFix = false;
            if (len % 2 == 1)
            {
                isShowFix = true;
                len--;
            }
            System.Text.ASCIIEncoding ascii = new System.Text.ASCIIEncoding();
            int tempLen = 0;
            string tempString = "";
            byte[] s = ascii.GetBytes(inputString);
            for (int i = 0; i < s.Length; i++)
            {
                if ((int)s[i] == 63)
                    tempLen += 2;
                else
                    tempLen += 1;

                try
                {
                    tempString += inputString.Substring(i, 1);
                }
                catch
                {
                    break;
                }

                if (tempLen > len)
                    break;
            }

            byte[] mybyte = System.Text.Encoding.Default.GetBytes(inputString);
            if (isShowFix && mybyte.Length > len)
                tempString += "";
            return tempString;
        }