Visual studio本地拷贝参考不工作

I have two Unmanaged C++ DLLs in a solution, called A and B, and A has a reference to B. I want to copy B.dll to the application directory for A. When I click "Copy Local" on the reference in A's "Framework and References" tab in its project properties, it looks like it is set to true, but clicking apply reverts the value back to false. Any idea whats up here?I have two Unmanaged C++ DLLs in a solution, ca