Public Class frmAddition
    Inherits System.Windows.Forms.Form
 
    Dim WithEvents tbo1 As New TextBox _
         With {.Parent = Me, .Width = 150}
 
    Dim WithEvents tbo2 As New TextBox _
         With {.Parent = Me, .Width = 150, .Left = 200}
 
    Dim tbosumme As New TextBox _
         With {.Parent = Me, .Width = 150, .Left = 400, .ReadOnly = True}
 
 
    Private Sub Compute()
 
        'Eingaben prüfen und ggf. Ergebnis berechnen
 
        Dim v1, v2 As Integer
        If Not Integer.TryParse(tbo1.Text, v1) Then
            MsgBox("Ungeeigneter Wert in TBO1")
            Exit sub 
        End If
 
        If Not Integer.TryParse(tbo2.Text, v2) Then
            MsgBox("Ungeeigneter Wert in TBO2")
            Exit Sub 
        End If
 
        tbosumme.Text = (v1 + v2).ToString
    End Sub
 
 
    Private Sub tbo2_KeyDown(sender As Object, _
        e As System.Windows.Forms.KeyEventArgs) Handles tbo2.KeyDown
 
        'Return-Taste in 2. Textbox: Ergebnis wird berechnet 
        If e.KeyCode = Keys.Return Then Compute()
    End Sub
 
 
    Private Sub tbo_TextChanged(sender As Object, e As System.EventArgs) _
        Handles tbo1.TextChanged, tbo2.TextChanged
 
        'Jede Änderung in einer Textbox löscht ggf. das Ergebnis 
        tbosumme.Text = ""
    End Sub
 
 
    Private Sub InitializeComponent()
 
        'Initialisierung der Form (autom. erstellt)
        Me.SuspendLayout()
        Me.ClientSize = New System.Drawing.Size(292, 273)
        Me.Name = "frmAddition"
        Me.ResumeLayout(False)
 
    End Sub
 
 
    Private Sub frmAddition_Load(sender As Object, _
        e As System.EventArgs) Handles Me.Load
 
        Me.Width = 600
    End Sub
End Class