Why is my project reference working without issue but as soon as I build the solution the reference fails?
I have multiple projects under one solution. I add a reference to Project A from Project B. Now I can add 'using ProjectA.Models;' (intellisense works!) to classes in Project B because it now has the reference, and the keyword coloring for custom objects works, the autocomplete/intellisense all works fine... 

Right until I build my solution. Suddenly I get a reference failure, the 'using' line that I added becomes underlined with red, and all the object references lose their keyword coloring.

I can repeat the process indefinitely by removing and recreating the reference, which allows the IDE to be fine with 'using ProjectA;' and all intellisense, right up until I hit build again.

What is causing this?
Why is my project reference working without issue but as soon as I build the solution the reference fails?
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I have multiple projects under one solution. I add a reference to Project A from Project B. Now I can add 'using ProjectA.Models;' (intellisense works!) to classes in Project B because it now has the reference, and the keyword coloring for custom objects works, the autocomplete/intellisense all works fine... 

Right until I build my solution. Suddenly I get a reference failure, the 'using' line that I added becomes underlined with red, and all the object references lose their keyword coloring.

I can repeat the process indefinitely by removing and recreating the reference, which allows the IDE to be fine with 'using ProjectA;' and all intellisense, right up until I hit build again.

What is causing this?