问题
I have installed the latest Visual Studio Async CTP for Visual Studio 2010 (SP1 Refresh) package from here: http://msdn.microsoft.com/en-gb/vstudio/async.aspx
The update shows up in my Windows 7 updates list. I do not see any other traces of it being installed (i.e. program list, registry).
However, when I try to run some Silverlight demo code (SilverlightOccasionallyConnectedDemo) the async and await keywords are not recognized at all. I have references to the AsyncCtpLibrary_Silverlight in my project Silverlight projects. I am using the Silverlight 5 Beta SDK.
I removed all traces of MVC as per other postings here and that does not do the trick.
I am using Visual Studio Premium Version 10.0.40219.1 SP1Rel
The specific error is: The type or namespace name 'async' could not be found.
回答1:
Uninstall KB2615527, KB2635973, KB2549864, see MSDN
回答2:
Update, 2011-11-01: The Async CTP Version 3 is now available, and should solve both of your problems.
The VS Async CTP SP1 Refresh (Version 2) is not compatible with Silverlight 5. This is a known issue.
Also, your Async CTP is probably not installed correctly; you can check for a folder called "Microsoft Visual Studio Async CTP" under "My Documents" - if it's not there, then it wasn't correctly installed. Some of the Windows Updates for Visual Studio prevent the Async CTP installer from working correctly. This is another known issue (independent from the issue causing lack of SL5 support).
As of right now (2011-10-29), the Async team is aware of both these issues and are working on a new installer that will resolve them. There is an announcement at the top of the official forum dated 2011-10-10, stating that they are working on an updated installer.
In the meantime, it is possible to install the Async CTP on a machine with VS2010 SP1 (and no other updates); but it will only work with SL4, not SL5.
来源：https://stackoverflow.com/questions/7934998/install-of-visual-studio-async-ctp-does-not-work