Question

I have faced with a situation in VB.NET and C# (.NET2) with the visibility of the static/shared members. It seems to me a little strange in VB.NET:

    public class A 
    {
        private static A instance;
        public static A Instance 
        {
            get { return instance; }
        }

        public string Name { get { } }
    }

usage:
A.Instance.Name // ONLY Name is “visible”

---

VB.NET:

Public Class A
  Private Shared _instance As A

  Public Shared ReadOnly Property Instance() As A
    Get
      Return _instance
    End Get
  End Property


  Public ReadOnly Property Name() As String
    Get
      Return ""
    End Get
  End Property

End Class

usage:

A.Instance.Instance.Instance.Instance...

// shared member behaves like a class public one I can repeat it to infinite..

is this a Microsoft oversight or a VB.NET “feature”?

Answer 1

It’s not an oversight but your VB code will trigger a warning, which plainly means: do not use this notation.

In VB, static members can be accessed via an instance, since strictly speaking, VB doesn’t have static: VB has the keyword Shared, meaning that the member is shared between all instances, as opposed to static where a member doesn’t belong to any instance.

Now, this is a semantical distinction between those keywords. It just so happens that these two distinct semantics tend to have the exact same effect.

Of course, static in C# is today identical to Shared in VB.NET but their legacy is different and VB’s Shared simply has a different history and therefore historically a different meaning. With this meaning, it makes absolutely sense to access Shared members via an instance.

It also makes sense when used together with Option Strict Off (loose typing): here, you sometimes don’t know a variable’s type but you still might want to access a Shared member. Now, you’ve got no choice but to use an instance to access it:

Option Strict Off
' … '
Dim o As Object = New A()
' Somewhere else, we want to access a static member of A but we don’t know A: '
Dim instance = o.Instance