Class1 = Class2 I want an actual copy

[kevinheeney]

VB.NET

Hello,
I am having a problem with copying one class into another. In the following example (a much more detailed example is attached) I have declared to instances of the same class.
When I Make one = another they become linked. So if I change TopClass at all BottomClass changes as well. I don't want BottomClass to be a reference to TopClass, I just want to copy the data as it is at that instant.



Dim TopClass As New Class1
Dim BottomClass As New Class1


BottomClass = TopClass


But I don't want to go through and do...

BottomClass.First = TopClass.First
BottomClass.Last= TopClass.Last

which would keep that from happening.

Kevin

 

[dynamic_sysop]

here's a sample class i knocked up ...

Public Class Class1
    Public intValue As Integer = 0

    Public Sub setValue(ByVal x As Integer)
        intValue = x
    End Sub

    Public Sub CheckValue()
        MessageBox.Show(intValue.ToString())
    End Sub

End Class

then in your form....

    Private cls1 As New Class1() '/// make this one new.
    Private cls2 As Class1 '/// but not this one.

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        cls1.setValue(1500)
        cls2 = DirectCast(cls1, Class1) '/// cls2 is now a copy of cls1
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        If Not cls2 Is Nothing Then
            cls2.CheckValue()
        End If
    End Sub

 

[koschins]

Clone

I think you are looking for the MemberwiseClone() function that creates a shallow copy of the current object. See MSDN for the method System.Object.MemberwiseClone()

 

[Kurt]

You could overload the constructor of your class to create a copy-constructor. It would take an object of the same type as parameter and then copy the state of the object passed to the newly created object.

Public Class cl1

    Public Sub New()
    End Sub

    Public Sub New(ByVal first As Integer, ByVal second As Integer)
        Me.someValue1 = first
        Me.someValue2 = second
    End Sub

    'The Copy-constructor
    Public Sub New(ByVal toCopy As cl1)
        Me.someValue1 = toCopy.someValue1
        Me.someValue2 = toCopy.someValue2
    End Sub

    Public Overrides Function ToString() As String
        Return "(" + Me.someValue1.ToString() + "," + Me.someValue2.ToString() + ")"
    End Function

    Private someValue1 As Integer
    Private someValue2 As Integer

End Class

Public Class Tester

    Public Shared Sub Main()
        Dim obj1 = New cl1(2, 3)
        Dim obj2
        obj2 = New cl1(obj1)

        Console.WriteLine(obj1.ToString())
        Console.WriteLine(obj2.ToString())

    End Sub

End Class