Confirm box for popup button

<asp:ConfirmButtonExtender ID="CBE" runat="server" TargetControlID="btnDelete" ConfirmText="Are you sure you want to delete?"></asp:ConfirmButtonExtender>

//In this button we can define functions for confirm OK button click. Cancel will done automatically.
<asp:Button ID="btnDelete" Text="Delete" runat="server" Width="70px" OnClick="btnDelete_Click" />