VS2012 $(exists) only accepts scalar values

Question

Okay, this is more of a build error than a programming error. I have never had much reason to get my hands dirty with builds, so this error is baffling me.

I have tried

Answer 1

Had the same issue in VS 2012 -

Error   48  04115: The "exists" function only accepts a scalar value, but its argument "@(_UnmanagedRegistrationCache)" evaluates to "obj\TheQueueData.sqlproj.UnmanagedRegistration.cache;obj\TheQueueData.sqlproj.UnmanagedRegistration.cache" which is not a scalar value.   C:\Windows\Microsoft.NET\Framework\v4.0.30319\Microsoft.Common.targets  1091    7   TheQueueData

Closing and re-opening the solution did the trick for me.