So what’s New in WPF Version 4.5 Developer Preview ? Here is a list of the new features and their regarding post :

1. Synchronously and Asynchronously validating data
2. Improved Support for Establishing a Weak Reference to an Event
3. New methods and features for the Dispatcher class
4. Automatically updating the source of a data binding
5. Retrieving data binding information from a binding expression
6. Markup Extensions for Events (advanced example)
7. Accessing collections on non-UI Threads
8. Integrating WPF with win32 Graphical User Interfaces
9. Binding to static properties
10. Repositioning data as the data’s values change (Live shaping)
11. New features for the VirtualizingPanel
12. Improved performance when displaying large sets of grouped data (same post)
13. Binding to types that Implement ICustomTypeProvider
14. Ribbon control
15. Checking for a valid DataContext object

You can also read this MSDN page : “New and enhanced features in Windows Presentation Foundation (WPF) version 4.5″.