HttpWebRequest返回空而不是json

Question

我有以下url在浏览器中返回JSON但在使用httpwebrequest时返回空。我需要得到json

https://www.dell.com/support/orders/us/en/04/order/GetMultipleOrderList?Period=180&PageSize=1000&PageNumber=1&SortBy=Date&SortDirection=DESC&SearchType=PoNumber&SearchValue=PO0008362&ActionItem=Select&VerifyType=PostalCode&VerifyValue=30082

我的代码是

PONumber = "PO0008362";
            ZipCode = "30082";

            String URL = String.Format("https://www.dell.com/support/orders/us/en/19/order/GetMultipleOrderList?Period=180&PageSize=1000&PageNumber=1&SortBy=Date&SortDirection=DESC&SearchType=PoNumber&SearchValue={0}&ActionItem=Select&VerifyType=PostalCode&VerifyValue={1}", PONumber, ZipCode);

            HttpWebRequest Request = WebRequest.Create(URL) as HttpWebRequest;

            Request.Method = "GET";
            Request.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";
            Request.Headers.Add("Accept-Language: en-US,en;q=0.5");
            Request.UserAgent = "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET CLR 1.1.4322; InfoPath.2; .NET4.0C; .NET4.0E)";

            Request.UserAgent = "User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:16.0) Gecko/20100101 Firefox/16.0";

            Request.CookieContainer = new CookieContainer();


            HttpWebResponse Response = Request.GetResponse() as HttpWebResponse;

            StreamReader sr = new StreamReader(Response.GetResponseStream());

            StringBuilder HTMLResponse = new StringBuilder("");
            HTMLResponse.Append(sr.ReadToEnd());
            sr.Close();
            return HTMLResponse;

使用上面的代码我总是得到一个空结果而不是json，但是当我在浏览器中使用相同的URL时，我收到了json。