Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        MsgBox([Enum].GetName(GetType(CloseReason), e.CloseReason))
 
    End Sub
 
    Private Const WM_SYSCOMMAND As Integer = &H112
    Private Const SC_CLOSE As Integer = &HF060
 
    Protected Overrides Sub WndProc(ByRef m As Message)
        If m.Msg = WM_SYSCOMMAND And m.WParam.ToInt32 = SC_CLOSE Then
            ' Form wird per Systemmenü bzw. Klick auf X geschlossen
            MsgBox("Form wird per X geschlossen!")
            ' ...
        End If
        MyBase.WndProc(m)
    End Sub

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Betriebssystem: Schrott (Vista)
Entwicklungsumgebung: VS 2008