Question

So I am looking at some sample code, and I am not sure what to make of this:

    Private Shared _instance As PollsProvider = Nothing      Public Shared ReadOnly Property Instance() As PollsProvider         Get             If IsNothing(_instance) Then                 _instance = CType(Activator.CreateInstance( _                     Type.GetType(Globals.Settings.Polls.ProviderType)), PollsProvider)             End If             Return _instance         End Get     End Property 

What is the difference between the above and how I would normally make a singleton:

    Private Shared _instance As PollsProvider = Nothing      Public Shared ReadOnly Property Instance() As PollsProvider         Get             If IsNothing(_instance) Then                 _instance = New PollsProvider             End If             Return _instance         End Get     End Property 

Answer 1

The first code fragment reads the type of PollsProvider to create from config, whereas the second has the type of PollsProvider compiled in. The first fragment therefore allows you to switch in configuration (without a recompile/redeploy) between RealPollsProvider, TestPollsProvider, FiddledByOurEvilPaymastersPollsProvider, etc.