how to show confirm box in ASP .Net

Question

Dear All,

I have webform with textfields & with submit button.

My requirement is after clicking submit button it should show as follows

If fields are empty it should show alertbox with certain message &

if fields contains data the if should show confirm box with yes & cancel

If ther user select yes it will redirect to another page or If the user select cancel the operation will cancel & the cursor will focus to first textbox.

How to do this?

Thanks