We would like to announce that you can now download an Async Targeting Pack for Visual Studio 11 that lets you use Visual Studio 11 Beta to create projects that target .NET 4.0 and Silverlight 5.
The Async Targeting Pack includes DLLs that address an incompatibility between Visual Studio 11 Beta compilers and the DLLs that shipped with the Async CTP for Visual Studio 2010. This issue has been previously discussed on the PFX team blog.
The Async Targeting Pack is available as a NuGet package, with installation details available here.
Read more: BCL Team Blog