NullReference Exception to an objet that I initialized as New List(Of)?

Question

Could someone explain why I obtain a NullReference Exception to an objet that I initialized as New List(Of)??

Module Module1
  ' MAIN =================================    
  Sub Main()
    Console.Clear()
    Console.WriteLine("Creating Bar")
    Dim myBar As New Bar()
    Console.ReadLine()
  End Sub    
End Module

Class Foo
  Public Overridable Property Test As String

  Public Sub New()
    Me.Test = "hello"
  End Sub
End Class

Class Bar
  Inherits Foo
  Private _MyString As New List(Of String)

  Public Sub New()
    MyBase.New()
  End Sub

  Public Overrides Property Test As String
    Get
      Return MyBase.Test
    End Get
    Set(value As String)
      MyBase.Test = value
      ' NULL REFERENCE EXCEPTION ???????!!!!!!!!!!!
      Console.WriteLine("{0}, and _MyString.Count = {1}", MyBase.Test, Me._MyString.Count)
    End Set
  End Property
End Class

http://stackoverflow.com/questions/4602468/can-vb-net-be-forced-to-initialize-instance-variables-before-invoking-the-base-t — SLaks, Sep 25 '12 at 14:54

score 2 · Accepted Answer · answered Sep 25 '12 at 14:54

2

Foo.New() runs before the field initializers in Bar().

The New part of As New List(Of String) is actually part of the Bar.New() constructor, which runs after MyBase.New().

answered Sep 25 '12 at 14:54

SLaks

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3

Don't call virtual members in a constructor. http://msdn.microsoft.com/en-us/library/ms182331.aspx – SLaks Sep 25 '12 at 14:55

NullReference Exception to an objet that I initialized as New List(Of)?

1 Answers1

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