haha

Public Class Form1
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim num1 As Double
        Dim num2 As Double
        Dim result As Double
        Dim op As String

        num1 = TextBox1.Text
        num2 = TextBox2.Text
        op = ComboBox1.Text

        If op = "+" Then
            result = num1 + num2
        ElseIf op = "-" Then
            result = num1 - num2
        ElseIf op = "*" Then
            result = num1 * num2
        ElseIf op = "/" Then
            result = num1 / num2
        End If

        TextBox3.Text = result
    End Sub
End Class