Custom DropDown in RadFilter

[Chamara]

i'm trying to add a RadFilter to filter my RadGrid which has several coulmns.it works fine. now i need to add a dropdown only for a one column filter.i have a column named  Revision in my RadGrid.i'm trying the following but it doesn't work

   <telerik:RadFilter runat="server" ID="RadFilter1" 
                FilterContainerID="gridSearchL3" ShowApplyButton="true" Height="100px" >
                <FieldEditors>
                <custom:RadFilterDropDownEditor DataValueField="Revision" DataTextField="Revision" DataType="System.String" FieldName="Revision" />
       
                </FieldEditors>
                </telerik:RadFilter>

i'm getting the error " Object reference not set to an instance of an object"
for creating custom dropdown i've used following class

http://www.telerik.com/help/aspnet-ajax/filter-custom-editors.html  

[Tsvetina]

Hi Chamara,

It seems that you have opened identical tickets for the RadFilter control. Please check the reply in the other thread:
http://www.telerik.com/community/forums/aspnet-ajax/filter/add-custom-dropdown-to-radfilter.aspx

If it does not help, post only there, so that we avoid duplicate posts.

Greetings,
Tsvetina
the Telerik team