SharePoint 2010 ISAPI WCF Service for Search using KeywordQuery not working

Below is my Applied code for Search in ISAPI WCF service, here when I debug DataTable count gives me zero. It works fine in SharePoint 2010 OOTB Search and have also configured Crawl settings. Can you please help me out guys.

try
        {                
            SearchServiceApplicationProxy proxy = (SearchServiceApplicationProxy)SearchServiceApplicationProxy.GetProxy(SPServiceContext.GetContext(SPContext.Current.Site));

            KeywordQuery keywordQuery = new KeywordQuery(proxy);
            keywordQuery.ResultsProvider = SearchProvider.Default;
            keywordQuery.ResultTypes = ResultType.RelevantResults;
            keywordQuery.TrimDuplicates = true;
            keywordQuery.RowLimit = 10;
            keywordQuery.QueryText = queryText;
            keywordQuery.SortList.Add("LastModifiedTime", Microsoft.Office.Server.Search.Query.SortDirection.Descending);
            keywordQuery.HiddenConstraints = string.Concat("scope:\"", "All Sites", "\"");

            ResultTableCollection results = keywordQuery.Execute();
            ResultTable result = results[ResultType.RelevantResults];
            DataTable dt = new DataTable();
            dt.Load(result, LoadOption.OverwriteChanges);

            DataTable dtFinal = dt.Copy();
        }
        catch (Exception ex)
        {
        }

Here is the image of DataTable count