When going from WIF 3.5 to 4.5 a lot of (breaking) changes were introduced. To help you walk through the migration process, Microsoft created 2 useful articles on MSDN:
- Guidelines for Migrating an Application Built Using WIF 3.5 to WIF 4.5
- Namespace Mapping between WIF 3.5 and WIF 4.5
From the article:
Windows Identity Foundation (WIF) was originally released in the .NET 3.5 SP1 timeframe. That version of WIF is referred to as WIF 3.5. It was released as a separate runtime and SDK, which meant that every computer on which a WIF-enabled application ran had to have the WIF runtime installed and developers had to download and install the WIF SDK to get the Visual Studio templates and tooling that enabled development of WIF-enabled applications. Beginning with .NET 4.5, WIF has been fully integrated into the .NET Framework. A separate runtime is no longer needed and the WIF tooling can be installed in Visual Studio 2012 by using the Visual Studio Extensions Manager. This version of WIF is referred to as WIF 4.5.
The integration of WIF into .NET necessitated several changes in the WIF API surface. WIF 4.5 includes new namespaces, some changes to configuration elements, and new tooling for Visual Studio. This topic provides guidance that you can use to help you migrate applications built using WIF 3.5 to WIF 4.5. There may be scenarios in which you need to run legacy applications built using WIF 3.5 on computers that are running Windows 8 or Windows Server 2012. This topic also provides guidance about how to enable WIF 3.5 for these operating systems.