Updating confirmation box by commandfield.

[C# Programming]

I need to add a confirmation box while updating modifications in the Edit part via GridView_RowUpdate.

MessageBox only works as server-side, but not client-side.

I made some search and found that I can extend the properties of commandfield.

But the problem is how can I call the new extended namespace/class from my current page in website?

Thanks a lot for your response.