All project references have yellow triangles every time solution is loaded

Question

All my project (from the same solution) references are marked with a yellow triangle. The projects are all set to the same .NET version (4.5.1). The error log says:

Answer 1

I had similar issues and it usually comes down to the Target Framework (Project>Properties>Application). I was working on a solution using .NET 4.6 and for some reason the default framework for new projects have a different target (in my case it was 4.5.2). So make sure you check all your project at the very least have the same target framework.