Why Does my Paging and sorting not working correctl

[Perry]

I have a radgrid with these propertie

AutoGenerateColumns="false"
               AllowAutomaticDeletes="true"
               AllowSorting="True"
               AllowPaging="true"
               AllowFilteringByColumn="true"
               OnInsertCommand="rgData_InsertCommand"
               OnUpdateCommand="rgData_UpdateCommand"
               OnItemDataBound="rgData_ItemDataBound"
               OnDeleteCommand="rgData_DeleteCommand"
               EnableViewState="true"
               OnItemCommand="rgData_ItemCommand"
               ShowStatusBar="true"
               OnInit="RgHomicideData_Init"
               OnNeedDataSource="rgData_NeedDataSource"
               CommandItemStyle-HorizontalAlign="Left">

 

The radgrid works as expected.  I use this code in my needdatasource

string strYear = DateTime.Now.Year.ToString();
            DateTime StartDate = Convert.ToDateTime("1/1/" + strYear);
            DateTime EndDate = Convert.ToDateTime("12/31/" + strYear);
            rgData.DataSource = DbContext.tblData
                .Where(d => d.deleted == false).ToList();

 

sort and paging is working properly

Now I want to filter the data by a date range so I use this code

Boolean DateChk1 = dpStartDate.SelectedDate.HasValue;
            Boolean DateChk2 = dpStartDate.SelectedDate.HasValue;
            string comboSearch = cboxSearch.Text;
            int intComboSearch = comboSearch.Length;

            if (comboSearch.Length > 0 && DateChk1 == true && DateChk2 == true)
            {

                DateTime Date1 = dpStartDate.SelectedDate.Value;
                DateTime Date2 = dpEndDate.SelectedDate.Value;
                rgData.DataSource = DbContext.AAADataSearchByDateRange(comboSearch, Date1, Date2).ToList();

The data refreshes and shows the filtered data.  Now if I click the column header to sort or I chnage to another page the radgrid looses all data and all I see is a line on the screen.  Can someone please explain the problem and how to fix it

 

Thanks