using a pointer to a value type in a Dictionary value

This small snippet of code is to increment a count value (integer) which is stored in a dictionary using my referenced object as a key. When the dictionary is small, multiple lookups aren't a big deal but this particular dictionary can get quite large.

Private RefCount As IDictionary(Of ILifeTimeManaged, Integer)
......... CODE HERE.....

Private Sub IncrementRefCount(ByVal entity As ILifeTimeManaged)

    Dim prevCount As Integer

    ''# if we have no reference entry, add one and set its count to 1

    If Not RefCount.TryGetValue(entit开发者_开发技巧y, prevCount) Then
        RefCount.Add(entity, 1)
    Else
        ''# otherwise increment its count by 1

        RefCount.Item(entity) = prevCount + 1
    End If

End Sub

I find a corresponding dictionary entry then increment the int stored in the value, or add a new dictionary entry.

Is it a bad idea to use a pointer to the dictionary value? Then I can avoid the second key lookup when I already have gotten the value. How would you implement it? Is this even possible in .NET4?

Can I do it using IntPtr do you think? http://msdn.microsoft.com/en-us/library/system.intptr.aspx

RefCount.Item(entity) = prevCount + 1

That does not look like a bad idea.

If you want to improve performance, you may want to add a property RefCount to the ILifeTimeManaged interface and use it instead of using the dictionary. But I don't know your design and goal, so can't say is this apropriate to you.

You cannot make a pointer to any given type in VB like you could in C++. However, you can wrap a value type in a reference type to get the semantics you want.

Public Class Ref(Of T As Structure)

    Public Sub New()
    End Sub
    Public Sub New(ByVal value As T)
        Me.Value = value
    End Sub

    Public Property Value As T

End Class

This lets you return a "pointer" to an integer (more correctly, a reference to something containing an integer). You could then write something like this:

Private RefCount As IDictionary(Of ILifeTimeManaged, Ref(Of Integer))
......... CODE HERE.....

Private Sub IncrementRefCount(ByVal entity As ILifeTimeManaged)
    Dim count As Integer

    ''# if we have no reference entry, add one and set its count to 1
    If Not RefCount.TryGetValue(entity, count) Then
        RefCount.Add(entity, New Ref(Of Integer)(1))
    Else
        ''# otherwise increment its count by 1
        count.Value += 1
    End If
End Sub

You could add some conversion methods between T and Ref(Of T) to the Ref class to possibly simplify the syntax (like in the Add call). In my opinion, doing so would give you something closer to C++ references than C++ pointers. Whether that's what you want or not is up to you.

Edit RE your Edit: IntPtr is designed to represent any pointer type in interop code calls. Perhaps a better name would have been NativePtr. There is no way to use an IntPtr in managed code the way I think you want, as you would a pointer in C++.