Object variable assignment

Question

In my VB application I need to remember object reference and then reassign it back to the variable.

Here is my approach:

Dim v1 as MyObject, v2 as MyObject

v1 = new MyObject()

v2 = new MyObject()

' now do some manipulation on v1 that changes its data

' now I want ot get back my data

v1 = v2

I hoped that now v1 points to the same memory as v2

but when I inspect the code it seems that new memory is used and data copied into that memory.

Is that what is happening, or where is the mistake

Answer 1

Please examine these tests. Reply if you still have questions -

Public Class MyObject
    Public Property SomeString As String
End Class
<TestClass()> _
Public Class UnitTest
    <TestMethod()> _
    Public Sub TestReference1()
        Dim expected = "some string"
        Dim notExpected = "some other string"
        Dim v1 = New MyObject() With {.SomeString = expected}
        Dim v2 = New MyObject() With {.SomeString = expected}
        Assert.AreEqual(expected, v1.SomeString)
        Assert.AreEqual(expected, v2.SomeString)
        v1.SomeString = notExpected
        Assert.AreEqual(notExpected, v1.SomeString)
        Assert.AreEqual(expected, v2.SomeString)
        v1 = v2
        Assert.AreEqual(expected, v1.SomeString)
        Assert.AreEqual(expected, v2.SomeString)
    End Sub
    <TestMethod()> _
    Public Sub TestReference2()
        Dim expected = "some string"
        Dim notExpected = "some other string"
        Dim v1 = New MyObject() With {.SomeString = expected}
        Dim v2 = v1
        Assert.AreEqual(expected, v1.SomeString)
        Assert.AreEqual(expected, v2.SomeString)
        v1.SomeString = notExpected
        Assert.AreNotEqual(expected, v1.SomeString)
        Assert.AreNotEqual(expected, v1.SomeString)
        Assert.AreEqual(notExpected, v1.SomeString)
        Assert.AreEqual(notExpected, v2.SomeString)
    End Sub
End Class

---

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Answer 2

Dim v1 as MyObject
Dim v2 as MyObject

v1 = new MyObject()
' now do some manipulation on v1 that changes its data
...
'Now save a copy of v1
v2 = Ctype(v1.Clone, MyObject) 'v1 and v2 refer to different objects
' now do some more manipulation on v1 that changes its data
...
' now I want to get back my data from the saved copy
v1 = v2  'v1 and v2 now refer to the same object

'now I want to restore the object to its initial default values
v1 = New MyObject()