Private Sub MDIMain_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
If MessageBox.Show("ยืนยันการออกจากโปรแกรม", "Exit Program", MessageBoxButtons.YesNo, MessageBoxIcon.Question) = Windows.Forms.DialogResult.Yes Then
e.Cancel = False
Else
e.Cancel = True
End If
End Sub