eBay Finding API .NET SDK 'findItemsAdvanced' returns null response – Ebay API

I’m trying to use the eBay Finding API to send an advanced search request and return the results. I have included my code below.

For some reason when I get to the following line:

FindItemsAdvancedResponse response = service.findItemsAdvanced(request);

the object called “response” is coming back as null.

I’m not sure where I’m going wrong and no exception is being thrown from the call to service.findItemsAdvanced()

If you could take a look and offer any advice at all I would be most grateful.

Here is my program.cs up until the problem

Progam.cs

using System;
using System.ServiceModel;
using System.ServiceModel.Channels;
using EbayParser.com.ebay.developer;
using System.Net;
namespace EbayParser
{

    class Program
    {
        static void Main(string[] args)
        {
            try
            {

                // Creating an object to the BestMatchService class

                CustomFindingService service = new CustomFindingService();
                service.Url = "http://svcs.sandbox.ebay.com/services/search/FindingService/v1";

                com.ebay.developer.FindItemsAdvancedRequest request = new EbayParser.com.ebay.developer.FindItemsAdvancedRequest();

                //Create Filter Objects
                com.ebay.developer.ItemFilter filterEndTimeFrom = new EbayParser.com.ebay.developer.ItemFilter();
                com.ebay.developer.ItemFilter filterEndTimeTo = new EbayParser.com.ebay.developer.ItemFilter();
                com.ebay.developer.ItemFilter filterCatID = new EbayParser.com.ebay.developer.ItemFilter();

                //Set Values for each filter
                filterEndTimeFrom.name = EbayParser.com.ebay.developer.ItemFilterType.EndTimeFrom;
                filterEndTimeFrom.value = new string[] { "" };

                filterEndTimeTo.name = EbayParser.com.ebay.developer.ItemFilterType.EndTimeTo;
                filterEndTimeTo.value = new string[] { "" };

                filterCatID.name = EbayParser.com.ebay.developer.ItemFilterType.EndTimeFrom;
                filterCatID.value = new string[] { "" };

                //Create the filter array
                com.ebay.developer.ItemFilter[] itemFilters = new EbayParser.com.ebay.developer.ItemFilter[3];

                //Add Filters to the array
                itemFilters[0] = filterCatID;
                itemFilters[1] = filterEndTimeFrom;
                itemFilters[2] = filterEndTimeTo;

                request.itemFilter = itemFilters;
                request.keywords = "ipod";

                // Creating response object

                FindItemsAdvancedResponse response = service.findItemsAdvanced(request);

and here is the code for the class called “CustomFindingService.cs”

CustomFindingService.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.Net;
using EbayParser.com.ebay.developer;

namespace EbayParser
{
    class CustomFindingService : FindingService
    {
        protected override System.Net.WebRequest GetWebRequest(Uri uri)
        {

            try
            {

                HttpWebRequest request = (HttpWebRequest)base.GetWebRequest(uri);

                request.Headers.Add("X-EBAY-SOA-SECURITY-APPNAME", "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx");

                request.Headers.Add("X-EBAY-SOA-OPERATION-NAME", "findItemsByKeywords");

                request.Headers.Add("X-EBAY-SOA-SERVICE-NAME", "FindingService");

                request.Headers.Add("X-EBAY-SOA-MESSAGE-PROTOCOL", "SOAP11");

                request.Headers.Add("X-EBAY-SOA-SERVICE-VERSION", "1.0.0");

                request.Headers.Add("X-EBAY-SOA-GLOBAL-ID", "EBAY-US");

                return request;

            }

            catch (Exception ex)
            {

                throw ex;

            }

        }
    }
}