Question

See the following code:

Private Function EqualsNothing(ByVal item As Object) As Boolean
  Return item.Equals(Nothing)
End Function

Console.WriteLine(0.Equals(Nothing)) ' True
Console.WriteLine(EqualsNothing(0)) ' False

How do I avoid Equals from returning something different after boxing structures? Is there some way to call the original Equals implementation?

I know I can use the = operator in this case, but EqualsNothing is supposed to work with both classes and structures. The = operator will not work with classes in VB.NET, and it will also not work with structures that not have implemented this operator. Equals does work with everything, but as I demonstrated above, Equals doesn’t return the same thing after boxing.

So, how should I rewrite EqualsNothing so that it works with classes and structures?

Edit: I tried making EqualsNothing generic, but that did not help.

Answer 1

I’m not sure this will work in all cases, but you might try this generic method:

Sub Main
    Console.WriteLine(0.Equals(Nothing)) ' True
    Console.WriteLine(EqualsNothing(0)) 'True
End Sub

Private Function EqualsNothing(Of T)(ByVal item As T) As Boolean
  Dim i As T = Nothing
  Return (item.Equals(i))
End Function