c# 去除文本的html标签

public static string ContentReplace(string input)
        {
            input = Regex.Replace(input, @"<(.[^>]*)>", "", RegexOptions.IgnoreCase);
            input = Regex.Replace(input, @"([
])[s]+", "", RegexOptions.IgnoreCase);
            input = Regex.Replace(input, @"-->", "", RegexOptions.IgnoreCase);
            input = Regex.Replace(input, @"<!--.*", "", RegexOptions.IgnoreCase);

            input = Regex.Replace(input, @"&(quot|#34);", """, RegexOptions.IgnoreCase);
            input = Regex.Replace(input, @"&(amp|#38);", "&", RegexOptions.IgnoreCase);
            input = Regex.Replace(input, @"&(lt|#60);", "<", RegexOptions.IgnoreCase);
            input = Regex.Replace(input, @"&(gt|#62);", ">", RegexOptions.IgnoreCase);
            input = Regex.Replace(input, @"&(nbsp|#160);", " ", RegexOptions.IgnoreCase);
            input = Regex.Replace(input, @"&(iexcl|#161);", "xa1", RegexOptions.IgnoreCase);
            input = Regex.Replace(input, @"&(cent|#162);", "xa2", RegexOptions.IgnoreCase);
            input = Regex.Replace(input, @"&(pound|#163);", "xa3", RegexOptions.IgnoreCase);
            input = Regex.Replace(input, @"&(copy|#169);", "xa9", RegexOptions.IgnoreCase);
            input = Regex.Replace(input, @"&#(d+);", "", RegexOptions.IgnoreCase);

            input.Replace("<", "");
            input.Replace(">", "");
            input.Replace("
", "");
            //去两端空格，中间多余空格
            input = Regex.Replace(input.Trim(), "\s+", " ");
            return input;
        }