C#过滤所有HTML代码的函数

public string checkStr(string html)
     {
         System.Text.RegularExpressions.Regex regex1 = new System.Text.RegularExpressions.Regex(@"<script[\s\S]+</script *>", System.Text.RegularExpressions.RegexOptions.IgnoreCase);
         System.Text.RegularExpressions.Regex regex2 = new System.Text.RegularExpressions.Regex(@" href *= *[\s\S]*script *:", System.Text.RegularExpressions.RegexOptions.IgnoreCase);
         System.Text.RegularExpressions.Regex regex3 = new System.Text.RegularExpressions.Regex(@" on[\s\S]*=", System.Text.RegularExpressions.RegexOptions.IgnoreCase);
         System.Text.RegularExpressions.Regex regex4 = new System.Text.RegularExpressions.Regex(@"<iframe[\s\S]+</iframe *>", System.Text.RegularExpressions.RegexOptions.IgnoreCase);
         System.Text.RegularExpressions.Regex regex5 = new System.Text.RegularExpressions.Regex(@"<frameset[\s\S]+</frameset *>", System.Text.RegularExpressions.RegexOptions.IgnoreCase);
         System.Text.RegularExpressions.Regex regex6 = new System.Text.RegularExpressions.Regex(@"\<img[^\>]+\>", System.Text.RegularExpressions.RegexOptions.IgnoreCase);

         System.Text.RegularExpressions.Regex regex7 = new System.Text.RegularExpressions.Regex(@"</p>", System.Text.RegularExpressions.RegexOptions.IgnoreCase);
         System.Text.RegularExpressions.Regex regex8 = new System.Text.RegularExpressions.Regex(@"<p>", System.Text.RegularExpressions.RegexOptions.IgnoreCase);
         System.Text.RegularExpressions.Regex regex9 = new System.Text.RegularExpressions.Regex(@"<[^>]*>", System.Text.RegularExpressions.RegexOptions.IgnoreCase);
         html = regex1.Replace(html, ""); //过滤<script></script>标记
         html = regex2.Replace(html, ""); //过滤href=javascript: (<A>) 属性
         html = regex3.Replace(html, " _disibledevent="); //过滤其它控件的on...事件
         html = regex4.Replace(html, ""); //过滤iframe
         html = regex5.Replace(html, ""); //过滤frameset
         html = regex6.Replace(html, ""); //过滤frameset
         html = regex7.Replace(html, ""); //过滤frameset
         html = regex8.Replace(html, ""); //过滤frameset
         html = regex9.Replace(html, "");
         html = html.Replace(" ", "");
         html = html.Replace("</strong>", "");
         html = html.Replace("<strong>", "");
         return html;
     }