Cant get value from VB class - vb.net

Question

I am trying to make a simple, class based calculator in Visual Basic, but when I press the buttons (Add) (Multiply) it shows 0 as the value in the textbox.
Here is my code:
FORM 2:
Public Class Form2
Dim Class2 As part2Class = New part2Class()
Dim Class2b As part2ClassB = New part2ClassB()
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim Num1 As Integer = CType(TextBox1.Text, Integer)
Dim Num2 As Integer = CType(TextBox2.Text, Integer)
MessageBox.Show(Class2.Calculate().ToString())
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Dim Num1 As Integer = CType(TextBox1.Text, Integer)
Dim Num2 As Integer = CType(TextBox2.Text, Integer)
MessageBox.Show(Class2b.Calculate())
End Sub
End Class
part2Class CLASS
Public Class part2Class
Public Property Num1
Public Property Num2
Public Overridable Function Calculate() As Integer
Return Num1 + Num2
End Function
End Class
Part2ClassB
Public Class part2ClassB
Inherits part2Class
Public Overrides Function Calculate() As Integer
Return Num1 * Num2
End Function
End Class
When I put values in the textbox and press ADD/MULIPLY it shows 0 as the value.

Answer 1

You are not assigning the values to the properties of your classes. Try this:
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Dim Num1 As Integer = CType(TextBox1.Text, Integer)
Dim Num2 As Integer = CType(TextBox2.Text, Integer)
Class2b.Num1=Num1
Class2b.Num2=Num2
MessageBox.Show(Class2b.Calculate())
End Sub

Answer 2

If CType fails you will crash your program. I changed it to TryParse which sets the variable in the second parameter (in this case a property of the class) and returns True or False. The AndAlso stops as soon as it reaches a False and proceeds to the Else part of the If
You need to declare your properties with a datatype in your class. See my comment about Option Strict.
Public Class part2Class
Public Property Num1 As Integer
Public Property Num2 As Integer
Public Overridable Function Calculate() As Integer
Return Num1 + Num2
End Function
End Class
Public Class part2ClassB
Inherits part2Class
Public Overrides Function Calculate() As Integer
Return Num1 * Num2
End Function
End Class
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim Class2 As part2Class = New part2Class()
Dim message As String
If Integer.TryParse(TextBox1.Text, Class2.Num1) AndAlso Integer.TryParse(TextBox2.Text, Class2.Num2) Then
message = Class2.Calculate().ToString
Else
message = "Please enter a number in both text boxes."
End If
MessageBox.Show(message)
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Dim Class2b As part2ClassB = New part2ClassB()
Dim message As String
If Integer.TryParse(TextBox1.Text, Class2b.Num1) AndAlso Integer.TryParse(TextBox2.Text, Class2b.Num2) Then
message = Class2b.Calculate().ToString
Else
message = "Please enter a number in both text boxes."
End If
MessageBox.Show(message)
End Sub