Public Class frmMain
 
    Public Sub New()
        InitializeComponent()
    End Sub
 
    Private Sub frmMain_Closing(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles Me.Closing
        Try
            If MsgBox("Are you sure you want to exit?", MsgBoxStyle.Question + MsgBoxStyle.YesNo, "Exit?") = MsgBoxResult.No Then
                e.Cancel = True