截取制定长度字符串

一、

#region 根据字节数长度来截取字符串。加省略号。
        /// <summary>
        /// 根据字节数长度来截取字符串。加省略号。
        /// </summary>
        /// <param name="value">字符串</param>
        /// <param name="length">字节数</param>
        /// <returns></returns>
        public static String SubByte(object value, int length)
        {
            if (length < 1)
            {
                return value.ToString();
            }
            byte[] bytes = Encoding.Unicode.GetBytes(value.ToString());
            int len = bytes.GetLength(0);
            if (len > length)
            {
                int n = 0;
                int i = 0;
                for (; i < len && n < length; i++)
                {
                    if (i % 2 == 0)
                    {
                        n++;
                    }
                    else
                    {
                        if (bytes[i] > 0)
                        {
                            n++;
                        }
                    }

                }
                if (i % 2 == 1)
                {
                    if (bytes[i] > 0)
                        i = i - 1;
                    else
                        i = i + 1;
                }
                return Encoding.Unicode.GetString(bytes, 0, i) + (bytes.Length > length ? "..." : string.Empty);
            }
            return value.ToString();
        }
        #endregion

二、

//文章显示内容和截取的长度设置
        public static string StringTruncat(string oldStr, int maxLength, string endWith)
        {
            if (string.IsNullOrEmpty(oldStr))
                //   throw   new   NullReferenceException( "原字符串不能为空 ");  
                return oldStr + endWith;
            if (maxLength < 1)
                throw new Exception("返回的字符串长度必须大于[0] ");
            if (oldStr.Length > maxLength)
            {
                string strTmp = oldStr.Substring(0, maxLength);
                if (string.IsNullOrEmpty(endWith))
                    return strTmp;
                else
                    return strTmp + endWith;
            }
            return oldStr;
        }