检验请求的参数名称（对象）是否存在

  public static string GetQueryString(string QueryStringName)
        {
            if (System.Web.HttpContext.Current.Request.QueryString[QueryStringName] != null)
            {
                return System.Web.HttpContext.Current.Server.HtmlEncode(System.Web.HttpContext.Current.Request.QueryString[QueryStringName].ToString().Replace("'", "").Replace(";", "").Replace("--", "")).Trim();
            }
            else
            {
                return "";
            }
        }