截取字符串

public string Leftxxx(string strHtml, int L)
    {
        string strOutput = strHtml;
        Regex regex = new Regex(@"<[^>]+>|</[^>]+>");
        strOutput = regex.Replace(strOutput, "");
        string tmpStr;
        tmpStr = strHtml;
        if (strOutput.Length > L)
        {
           tmpStr = strOutput.Substring(0, L) + "...";
        }
        return tmpStr;
    }