Public Class Calculadora

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim StrOper As String
        Dim LngValor As Long


    End Sub

    Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged

    End Sub

    Private Sub Cmd0_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Cmd0.Click
        TextBox1.Text() = TextBox1.Text & "0"
    End Sub

    Private Sub Cmd1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Cmd1.Click
        TextBox1.Text() = TextBox1.Text & "1"
    End Sub

    Private Sub Cmd2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Cmd2.Click
        TextBox1.Text = TextBox1.Text & "2"
    End Sub

    Private Sub Cmd3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Cmd3.Click
        TextBox1.Text = TextBox1.Text & "3"
    End Sub

    Private Sub Cmd4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Cmd4.Click
        TextBox1.Text = TextBox1.Text & "4"
    End Sub

    Private Sub Cmd5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Cmd5.Click
        TextBox1.Text = TextBox1.Text & "5"
    End Sub

    Private Sub Cmd6_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Cmd6.Click
        TextBox1.Text = TextBox1.Text & "6"
    End Sub

    Private Sub Cmd7_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Cmd7.Click
        TextBox1.Text = TextBox1.Text & "7"
    End Sub

    Private Sub Cmd8_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Cmd8.Click
        TextBox1.Text = TextBox1.Text & "8"
    End Sub

    Private Sub Cmd9_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Cmd9.Click
        TextBox1.Text = TextBox1.Text & "9"
    End Sub

    Private Sub Cmdmas_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Cmdmas.Click
        StrOper = "+"
        LngValor = TextBox1.Text
        TextBox1.Text = ""
    End Sub

    Private Sub Cmdmenos_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Cmdmenos.Click
        StrOper = "-"
        LngValor = TextBox1.Text
        TextBox1.Text = ""
    End Sub

    Private Sub Cmdpor_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Cmdpor.Click
        StrOper = "*"
        LngValor = TextBox1.Text
        TextBox1.Text = ""
    End Sub

    Private Sub Cmdentre_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Cmdentre.Click
        StrOper = "/"
        LngValor = TextBox1.Text
        TextBox1.Text = ""
    End Sub

    Private Sub CmdIgual_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CmdIgual.Click
        If StrOper = "+" Then
            TextBox1 = LngValor + TextBox1.Text
        End If
        If StrOper = "-" Then
            TextBox1 = LngValor - TextBox1.Text
        End If
        If StrOper = "*" Then
            TextBox1 = LngValor * TextBox1.Text
        End If
        If StrOper = "/" Then
            TextBox1 = LngValor / TextBox1.Text
        End If
    End Sub
End Class

Variable local sin utilizar: 'StrOper'.	
Variable local sin utilizar: 'LangValor'.	

No se ha declarado el nombre 'StrOper'.	
No se ha declarado el nombre 'LangValor'.