C#截取指定長度漢字超出部分以用指定的字符代替

 ///   <summary> 
    ///   將指定字符串按指定長度進行剪切， 
    ///   </summary> 
    ///   <param   name= "oldStr "> 需要截斷的字符串 </param> 
    ///   <param   name= "maxLength "> 字符串的最大長度 </param> 
    ///   <param   name= "endWith "> 超過長度的後綴 </param> 
    ///   <returns> 如果超過長度，返回截斷後的新字符串加上後綴，否則，返回原字符串 </returns> 
    public static string StringTruncat(string oldStr, int maxLength, string endWith)
    {
        if (string.IsNullOrEmpty(oldStr))
            //   throw   new   NullReferenceException( "原字符串不能爲空 "); 
            return oldStr + endWith;
        if (maxLength < 1)
            throw new Exception("返回的字符串長度必須大於[0] ");
        if (oldStr.Length > maxLength)
        {
            string strTmp = oldStr.Substring(0, maxLength);
            if (string.IsNullOrEmpty(endWith))
                return strTmp;
            else
                return strTmp + endWith;
        }
        return oldStr;
    }