Exception using VB expressions in Visual Studio 2012 RC

Question

When using VB Workflow projects in Visual Studio 2012 RC, you may receive an InvalidCastException while editing expressions.  After closing the exception, Intellisense will stop working in your VB expressions.  However, you can still successfully author and run your workflows.  Highlighting and expression validation will continue to work.

This situation can also occur with C# projects if you target 4.0.

The Visual Studio team is currently working on a fix for this issue.

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Answer 1

The following KB article addresses the problem  (includes Hotfix information):

http://support.microsoft.com/KB/2718685

Alternatively, you can download and install the "July 2012 Update for Microsoft Visual Studio 2012 RC" which includes a number of fixes besides the above fix:

http://www.microsoft.com/en-us/download/details.aspx?id=30178

Answer 2

If you are hitting this issue, you might find the following blog post helpful:

http://blogs.msdn.com/b/workflowteam/archive/2012/06/19/exception-using-vb-expressions-in-visual-studio-2012-rc.aspx