C#-防止用户输入具有风险的敏感字符

　　最近有涉及到要防止用户在网页文本框中输入具有风险的敏感字符所以特地编写了一套针对用户输入的字符进行安全过滤的一个方法，在后台接收到用户输入的字符后调用执行该方法即可完成过滤操作，主要使用正则来匹配并替换掉敏感字符!

    /// <summary>
    /// obj向string转换,替换具有风险的敏感字符并去除多余的空格;
    /// </summary>
    /// <param name="o"></param>
    /// <returns></returns>
    public static string RequestFilter(this object o)
    {
        if (o == DBNull.Value || o == null)
        {
            return "";
        }
        else
        {
            string str = o.ToString().Trim();
            //删除脚本
            str = Regex.Replace(str, @"<script[^>]*?>.*?</script>", "", RegexOptions.IgnoreCase);
            //删除HTML
            str = Regex.Replace(str, @"<(.[^>]*)>", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, @"([\r\n])[\s]+", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, @"-->", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, @"<!--.*", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, @"&(quot|#34);", "\"", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, @"&(amp|#38);", "&", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, @"&(lt|#60);", "<", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, @"&(gt|#62);", ">", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, @"&(nbsp|#160);", " ", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, @"&(iexcl|#161);", "\xa1", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, @"&(cent|#162);", "\xa2", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, @"&(pound|#163);", "\xa3", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, @"&(copy|#169);", "\xa9", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, @"&#(\d+);", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, "xp_cmdshell", "", RegexOptions.IgnoreCase);

            //删除与数据库相关的词
            str = Regex.Replace(str, "select", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, "insert", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, "delete from", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, "count''", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, "drop table", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, "truncate", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, "asc", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, "mid", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, "char", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, "xp_cmdshell", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, "exec master", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, "net localgroup administrators", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, "and", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, "net user", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, "or", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, "net", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, "delete", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, "drop", "", RegexOptions.IgnoreCase);
            str = Regex.Replace(str, "script", "", RegexOptions.IgnoreCase);

            str = str.Replace("<", "");
            str = str.Replace(">", "");
            str = str.Replace("*", "");
            str = str.Replace("--", "");
            str = str.Replace("?", "");
            str = str.Replace(",", "");
            str = str.Replace("/", "");
            str = str.Replace(";", "");
            str = str.Replace("*/", "");
            str = str.Replace("\r\n", "");
            return str;
        }
    }