Microsoft introduced Silverlight 4 Tools for Visual Studio 2010. It is an add-on package for the Visual Studio 2010 IDE that enables development with Silverlight 4 rich Internet plug-in platform.
Silverlight 4 Tools for Visual Studio supports capabilities such features such as Silverlight 4's out-of-browser application functions. Silverlight 4 supports other functions such as Style Intellisense for modifying XAML styles, Data Source Selector, for modifying data source information and Go To Value Definition for navigating directly from controls on a page to styles applied to them.
The Visual Studio WPF and Silverlight Designer Team suggested that many of the new designer features work well with WPF (Windows Presentation Foundation) as well as Silverlight projects. So its download is highly recommended for Visual Studio 2010 WPF designer users too.