Como hacer una calculadora en visual basic

Hola amig@s para los que estén usando el lenguje de programacion de visual basic en su versión 2010 0 2012 aquí les traigo este ejemplo de como hacer una calculadora.

Crean una ventana así o como quieran decorar la, siempre y cuando mantenga la escencia de la calculadora.



Public Class Form1
.....creamos dos variables llamadas r y c.
    Dim r As Double
    Dim c As Integer
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

    End Sub
A los textbox le ponemos esta propiedad para que solo acepte numero y no letras.
    Private Sub TxtCal_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TxtCal.KeyPress
        If Char.IsDigit(e.KeyChar) Then
            e.Handled = False
        ElseIf Char.IsControl(e.KeyChar) Then
            e.Handled = False
        Else
            e.Handled = True


        End If
    End Sub

    Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TxtCal.TextChanged

    End Sub
En cada boton le agreamos esa liena de codigo ---- txtCal es el nombre que le puse al textbox
 Private Sub Boton1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Boton1.Click
        If TxtCal.Text > "0" Then
            TxtCal.Text = TxtCal.Text + Boton1.Text
        Else
            TxtCal.Text = Boton1.Text
        End If

 Private Sub Boton2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Boton2.Click
        If TxtCal.Text > "0" Then
            TxtCal.Text = TxtCal.Text + Boton2.Text
        Else
            TxtCal.Text = Boton2.Text
     
        End If
End Sub

    Private Sub Boton3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Boton3.Click
        If TxtCal.Text > "0" Then
            TxtCal.Text = TxtCal.Text + Boton3.Text
        Else
            TxtCal.Text = Boton3.Text
        End If
    End Sub

    Private Sub Boton4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Boton4.Click
        If TxtCal.Text > "0" Then
            TxtCal.Text = TxtCal.Text + Boton4.Text
        Else
            TxtCal.Text = Boton4.Text
        End If
    End Sub

    Private Sub Boton5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Boton5.Click
        If TxtCal.Text > "0" Then
            TxtCal.Text = TxtCal.Text + Boton5.Text
        Else
            TxtCal.Text = Boton5.Text
        End If
    End Sub

    Private Sub Boton6_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Boton6.Click
        If TxtCal.Text > "0" Then
            TxtCal.Text = TxtCal.Text + Boton6.Text
        Else
            TxtCal.Text = Boton6.Text
        End If
    End Sub

    Private Sub Boton7_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Boton7.Click
        If TxtCal.Text > "0" Then
            TxtCal.Text = TxtCal.Text + Boton7.Text
        Else
            TxtCal.Text = Boton7.Text
        End If
    End Sub

    Private Sub Boton8_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Boton8.Click
        If TxtCal.Text > "0" Then
            TxtCal.Text = TxtCal.Text + Boton8.Text
        Else
            TxtCal.Text = Boton8.Text
        End If
    End Sub

    Private Sub Boton9_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Boton9.Click
        If TxtCal.Text > "0" Then
            TxtCal.Text = TxtCal.Text + Boton9.Text
        Else
            TxtCal.Text = Boton9.Text
        End If
    End Sub
En este boton solo se le añadio 0 para al momento de compilar siempre aparesca 0 en el textbox
    Private Sub Boton0_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Boton0.Click
        TxtCal.Text = Boton0.Text
    End Sub
Este es el boton para borrar
    Private Sub borrado_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles borrado.Click
        TxtCal.Text = 0
        igual.Visible = True


    End Sub
Boton de igual
    Private Sub igual_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles igual.Click
        If c = 1 Then
            r = r + TxtCal.Text
            TxtCal.Text = r
        Else
            If c = 2 Then
                r = r - TxtCal.Text
                TxtCal.Text = r
            Else
                If c = 3 Then
                    r = r * TxtCal.Text
                    TxtCal.Text = r
                Else
                        r = r / TxtCal.Text
                        TxtCal.Text = r
                End If
            End If
        End If

    End Sub

    Private Sub Button16_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnSuma.Click

        r = Val(TxtCal.Text)
        TxtCal.Text = BtnSuma.Text
        c = 1
    End Sub

    Private Sub Boton17_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Boton17.Click
        r = Val(TxtCal.Text)
        TxtCal.Text = Boton17.Text
        c = 2
    End Sub

    Private Sub Boton18_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Boton18.Click
        r = Val(TxtCal.Text)
        TxtCal.Text = Boton18.Text
        c = 3
    End Sub

    Private Sub Boton19_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Boton19.Click
        r = Val(TxtCal.Text)
        TxtCal.Text = Boton19.Text
        c = 4
    End Sub
End Class

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