<DllImport("user32.dll", SetLastError:=True)> _
    Private Shared Function GetForegroundWindow() As IntPtr
    End Function
 
    <DllImport("user32.dll", SetLastError:=True, CharSet:=CharSet.Auto)> _
    Private Shared Function GetWindowTextLength(ByVal hwnd As IntPtr) As Integer
    End Function
 
    <DllImport("user32.dll", SetLastError:=True, CharSet:=CharSet.Auto)> _
    Private Shared Function GetWindowText(ByVal hwnd As IntPtr, _
                       ByVal lpString As StringBuilder, _
                       ByVal cch As Integer) As Integer
    End Function
 
    Public Sub DisplayCurrentWindowTextIfAny()
 
        Dim awh As IntPtr = GetForegroundWindow()
        If awh = IntPtr.Zero Then
            Label1.Text = "Kein Forgroundwindow!"
            Return
        End If
 
        Dim wtl As Integer = GetWindowTextLength(awh)
        If wtl = 0 Then
            Label1.Text = "Kein Windowtext!"
            Return
        End If
 
        Dim sb As New System.Text.StringBuilder("", wtl + 1)
        GetWindowText(awh, sb, sb.Capacity)
        Label1.Text = "Windowtext = """ & sb.ToString() & """"
 
    End Sub
 
    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Timer1.Tick
        DisplayCurrentWindowTextIfAny()
    End Sub

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Alle Angaben ohne Gewähr. Keine Haftung für Vorschläge, Tipps oder sonstige Hilfe, falls es schiefgeht, nur Zeit verschwendet oder man sonst nicht zufrieden ist