Why won't C++ project automatically rebuild when C# project on which it depends is modified?

I have a Visual Studio 2012 solution which includes a C# project Addin and a C++ projectShim. If I make a change to Addin (C#), I want Shim (C++) to rebuild, but I can't seem to achieve it. When I press F5,Addin is rebuilt but Shim is not. If I Rebuild Solution then it's fine, but there are many other projects in the solution and it takes too long to do this every time.

I'm running Visual Studio 2012 Update 4 on 64-bit Windows Pro 8.0 with a 64-bit processor.

This is what I've tried so far:

• Making Shim depend on Addin via 'Project Dependencies...'

• Setting Shim to reference Addin

• (Having added the reference) Setting 'Reference Assembly Output' and 'Link Library Dependencies' to True

• Adding both the project folder and the output folder of Addin to 'Additional Include Directories' underShim's properties => Config => C/C++

• Changing the intermediate folder for Shim to a new folder didn't work)

• Checking that Addin is being rebuilt properly by checking the obj and bin folders (it is)

• Checking whether there are any changes to the obj and bin folders ofShim (there are not)

• Checking the build output log. The only warning is that Project file contains ToolsVersion="12.0". This toolset is unknown or missing., which I believe is an unrelated NuGet (package manager) error because I'm running VS2012 rather than VS2013.

• Reading the MSDN articles on Project Dependencies, Build Order etc which seem to suggest I've done the necessary things.

Plus googling extensively and looking through as many VS settings as I can think of.

I know that I can force the rebuild by right-clicking and selecting 'Project only' => Rebuild, but it's easy to forget so I'd really like to solve this. Can anyone help?