if you want to add Product Grid inside Category Grid, what you can do is you can add Product Grid inside Category Grid in _ItemDataBound event, where you can add product grid inside that.
eg:-
e.Item.Cells(1).Controls.Add(grdProduct)
where cell 1 is link button on Onclick event of this you have to pass its id and fill the product grid.
eg :- Cell 1 is
<asp:TemplateColumn>
<ItemTemplate>
<asp:LinkButton ID="btnChild" Text="ProductID" runat="server" OnClick="ShowProduct" Width="15px"></asp:LinkButton>
</ItemTemplate>
</asp:TemplateColumn>
onclick event have ShowProduct where you pass productid and get you details in child grid depend on what you click in parent grid.
hope this will help you
Manoj Karkera
Zenith Software LTD

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