After a few hours of searching the internet on the error "Specified argument was out of the range of valid values", I discovered that the cause was the GridTemplateColumn behaving differently that a GridBoundColumn with regards to filtering. In the code snippet below, you can use the one filter just fine. If you change the telerik:GridTemplateColumn (column 2) to AllowFiltering='true' while having a <FilterTemplate> element, using the filter on column 3 will throw an error. AllowFiltering='true' doesn't cause a problem if there's no <FilterTemplate> element. Note that changing the GridBoundColumn ( column 1) between AllowFiltering= true/false doesn't cause an issue. It's only the GridTemplateColumn type.
The different behavior between the GridBoundColumn and GridTemplateColumn types seems like a bug.
<telerik:RadGridrunat="server"DataSourceID="sql_tables"AllowFilteringByColumn="true"AutoGenerateColumns="false"> <MasterTableView> <Columns> <telerik:GridBoundColumnDataField="name"HeaderText="name"AllowFiltering="true"UniqueName="name1"> <FilterTemplate> custom filter template on GridBoundColumn is OK </FilterTemplate> </telerik:GridBoundColumn> <telerik:GridTemplateColumnDataField="name"HeaderText="name-template"AllowFiltering="false"UniqueName="name2"> <ItemTemplate> <%#Eval("name") %> </ItemTemplate> <FilterTemplate>custom filter on GridTemplateColumn breaks filtering.</FilterTemplate> <HeaderStyleBackColor="Pink"/> </telerik:GridTemplateColumn><telerik:GridBoundColumnDataField="type"HeaderText="type"AllowFiltering="true"UniqueName="type"/> </Columns> </MasterTableView> </telerik:RadGrid> <asp:SqlDataSourcerunat="server"ID="sql_tables"ConnectionString="<%$ ConnectionStrings:MyDB%>" SelectCommand="select top 4 name, object_id, schema_id, type, type_desc from sys.tables" />