New features in WPF 4.0 are as following

More controls.

The family of WPF elements keeps growing. It now includes a professional DataGrid, a standard DatePicker and Calendar,and a native WebBrowser for HTML viewing and web surfing. A
separate download also adds the useful Ribbon control, which can give any application a slick, modern look.

2-D drawing improvements.

Now the visual appearance of any element can be radically altered with PhotoShop-style effects through pixel shaders (using up to version 3 of the pixel-shader standard). Developers who want to manipulate individual pixels by hand can also generate and modify images with the WriteableBitmap class.

Animation easing.

These functions allow you to create more lifelike animations

that bounce, accelerate, and oscillate naturally.

Visual state manager.

First introduced in Silverlight, the visual state manager

gives you an easier way to reskin controls without needing to

understand the intricate details of their inner workings.

Windows 7.

Microsoft’s newest operating system adds a slew of new features. WPF

includes native support for the revamped taskbar, allowing you to use jump lists,

icon overlays, progress notifications, and thumbnail toolbars.

And if you have the right hardware, you can use WPF’s

support for Windows 7 multitouch, which is the ability to gesture on a

touchscreen to manipulate visual objects.

Better rendering.

WPF continues to improve display quality and deal with the

idiosyncrasies and scaling artifacts that can occur because of its resolution

independent drawing model. In WPF 4, you can use layout rounding to make sure

layout containers line up with real pixel positions, guaranteeing a clear display.

You can also do the same for rendered text, making sure it stays

sharp even at vanishingly small sizes.

Bitmap caching.

In the right scenario, you can spare the CPU’s workload by

caching complex vector art in video card memory. This technique is particularly

handy when using animation,

XAML 2009.

WPF introduces a new version of the XAML markup standard that’s

used to declare the user interface in a window or page. It introduces a number of

small refinements, but you probably won’t use them just yet, because the standard

isn’t built into the WPF XAML compiler.