.NET截取指定长度汉字超出部分以"..."代替

/// <summary>
/// 将指定字符串按指定长度进行剪切，
/// </summary>
/// <param name= "oldStr "> 需要截断的字符串 </param>
/// <param name= "maxLength "> 字符串的最大长度 </param>
/// <param name= "endWith "> 超过长度的后缀 </param>
/// <returns> 如果超过长度，返回截断后的新字符串加上后缀，否则，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;
}