i want to use a cofirm box in asp.net grid view

Just add onClientClick attribute to the control if inside TemplateField.

How to add a “confirm delete” option in ASP.Net Gridview?[^].

XML

<asp:TemplateField ShowHeader="False">
    <ItemTemplate>
         <asp:ImageButton ID="DeleteButton" 
                          runat="server" 
                          ImageUrl="~/site/img/icons/cross.png" 
                          CommandName="Delete" 
                          OnClientClick="return confirm('Are you sure you want to delete this event?');" 
                          AlternateText="Delete" />
    </ItemTemplate>
</asp:TemplateField>

And also check DISPLAY CONFIRMATION MESSAGE ON GRIDVIEW DELETING[^] for detailed and clear implementation techniques using "Option A: Using the ShowDeleteButton CommandField" and "Option B: Using TemplateField with LinkButton".

Thanks...