截取字符串，中文安两个字符处理

        /// <summary>
        /// 截取字符串，中文安两个字符处理
        /// </summary>
        /// <param name="stringToSub"></param>
        /// <param name="length"></param>
        /// <returns></returns>
        public static string GetFirstString(object stringToSub, int length)
        {
            Regex regex = new Regex("[u4e00-u9fa5]+", RegexOptions.Compiled);
            char[] stringChar = stringToSub.ToString().ToCharArray();
            StringBuilder sb = new StringBuilder();
            int nLength = 0;
            for (int i = 0; i < stringChar.Length; i++)
            {
                if (regex.IsMatch((stringChar[i]).ToString()))
                {
                    sb.Append(stringChar[i]);
                    nLength += 2;
                }
                else
                {
                    sb.Append(stringChar[i]);
                    nLength = nLength + 1;
                }

                if (nLength > length)
                {
                    break;
                }
            }
            return sb.ToString();
        }