Problem during filtering rad grid template columns

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C#

hello all
I am using rad grid having template columns for "Date" field and and column containing
double type values but when i am trying to filter using in built filters of grid its not working.
any help regarding this issue will be appreciated.

grid template column for date-

< telerik:GridTemplateColumn HeaderText="Date" UniqueName="ChangedOn" AutoPostBackOnFilter="true" DataType="System.DateTime" CurrentFilterFunction="Contains" DataField="ChangedOn" 
     <ItemTemplate>
                                  <%#DataBinder.Eval(Container,"DataItem.ChangedOn")%>;
                              </ItemTemplate>
                                
                               
                 </telerik:GridTemplateColumn>

and for this column problem is when i am trying to filter the values which are less than 0 i am not able to get required results

<telerik:gridtemplatecolumn uniquename="ForeignExchangeRateTypeName" headertext="Exchange Rate Type" datafield="ForeignExchangeRateTypeName" autopostbackonfilter="true"
                                           SortExpression ="ForeignExchangeRateTypeName" currentfilterfunction="Contains" FilterControlWidth="50%">
                               <ItemTemplate>
                                   <asp:Label ID="Lbl_ForeignExchangeRateTypeName" runat="server" Text='<%# DataBinder.Eval(Container,"DataItem.ForeignExchangeRateTypeName")%>' ></asp:Label>
                               </ItemTemplate>
                               <EditItemTemplate >
                                     <telerik:RadComboBox ID="rcb_ForeignExchangeRateTypeName"  runat="server"
                                                             DataTextField="ForeignExchangeRateTypeName" DataValueField="ForeignExchangeRateTypeID"AutoPostBack="true"
  MarkFirstMatch="True"  OnSelectedIndexChanged="rcb_ForeignExchangeRateTypeName_OnSelectedIndexChanged"Height="100px">     </telerik:RadComboBox>
                               </EditItemTemplate>
                               <ItemStyle Width="10%" 
                                                                                                                    
                                                             
                                                            
                                   HorizontalAlign="Left" />
                               <HeaderStyle   />
            </telerik:gridtemplatecolumn>