My MZ-Tools add-in was experiencing a random “System.Runtime.InteropServices.COMException (0x80004005): Error HRESULT E_FAIL has been returned from a call to a COM component.” when using the EnvDTE.DTE.ActiveSolutionProjects property that I knew that other developer reported in the MSDN VSX Forum in January. Today I tested a guess of Ryan Molden (from Microsoft) in his answer about a dependency on the visibility of the Solution Explorer and he was right.

But when I was writing the corresponding MZ-Tools Series article as I always do to document all the issues and bugs of the Visual Studio automation model (EnvDTE), I noticed that the problem didn’t happen in Visual Studio 2005 or 2008, only in VS 2010, so rather than considering it a “by design” issue, I opened a bug at Microsoft Connect:

BUG: DTE.ActiveSolutionProjects property causes COMException if Solution Explorer is not shown
https://connect.microsoft.com/VisualStudio/feedback/details/735830/bug-dte-activesolutionprojects-property-causes-comexception-if-solution-explorer-is-not-shown#details

So, in VS 2010 the problem happens when one condition is met: The Solution Explorer is not shown.

Then, I tried in VS 11 Beta, which is more annoying because the Macros IDE is gone and you have to use an add-in to reproduce bugs, and I noticed that the problem doesn’t happen when a solution is loaded, but still happens when two conditions are met: The Solution Explorer is not shown and there is no solution loaded. So, I opened a separate bug against VS 11 Beta:

BUG: DTE.ActiveSolutionProjects property causes COMException if Solution Explorer is not shown and no solution loaded
https://connect.microsoft.com/VisualStudio/feedback/details/735835/bug-dte-activesolutionprojects-property-causes-comexception-if-solution-explorer-is-not-shown-and-no-solution-loaded#details