Visual Studio 2015 has been RTM for one month. However, it blows up very often, such as Razor editor. When I try to open any .cshtml file, it blows up with this error, then the syntax highlight is gone. I tried to uninstall all add-on, even repair install VS2015 can't get it working.
The detailed error message is:
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.ArgumentException: Item has already been added. Key in dictionary: 'RazorSupportedRuntimeVersion'
Someone has already filed a bug on "connect", and it is active:
The solution is：
1. Close all instance of VS2015
2. Run cmd as administrator, go to VS2015 setup directory, and run:
3. Go to your project folder, delete a hidden folder named ".VS"
4. Restart VS2015, it will work fine!