防止AutoPost

public string CheckUrl()
        {
            Uri ComeUrl = HttpContext.Current.Request.UrlReferrer;
            string cUrl = string.Empty;
            HttpContext context = HttpContext.Current;

            if (context.Request.Browser.Browser.ToLower() == "unknown")
            {
                return "浏览器未知!";
            }

            if (context.Request.Browser.Platform.ToLower() == "unknown")
            {
                return "操作系统未知!";
            }

            if (context.Request.HttpMethod.ToUpper() != "POST")
            {
                return "提交错误!";
            }

            if (ComeUrl == null)
            {
                return "请从UrL访问!";
            }
            else
            {
                string reffer = ComeUrl.ToString();
                cUrl = "http://" + HttpContext.Current.Request.ServerVariables["SERVER_NAME"];

                if (reffer.Substring(cUrl.Length, 1) == ":")
                {
                    cUrl += ":" + HttpContext.Current.Request.ServerVariables["SERVER_PORT"].ToString();
                }
                int lenth;
                lenth = cUrl.Length;
                cUrl += HttpContext.Current.Request.ServerVariables["SCRIPT_NAME"];
                int result;
                result = String.Compare(reffer, 1, cUrl, 1, lenth, true);

                if (result != 0)
                {
                    return "请从请从正确UrL访问!";
                }
            }

            return "";
        }