I have a solution in .NET v7 with two projects, and I am trying to link to a file from one project to one in the other. Thus, I have added the project and everything compiles and links, until I try to access an overloaded operator in the other project. So, here is some code...trimmed to just show what I am talking about: EditorView Project: #include "..\Math Engine\vector3.h" // Vector3 class definition class Perspective { public: Perspective() : initialEyePos(0.0, 0.0, 20.0), initialLookDir(0.0, 0.0, 0.0), eyePos(), lookDir(), { // initialize camera's initial position eyePos = initialEyePos; lookDir = initialLookDir; } private: const Vector3 initialEyePos; const Vector3 initialLookDir; Vector3 eyePos; Vector3 lookDir; }; Math Engine Project: class Vector3 { public: Vector3& operator=(const Vector3 &); }; // end class Vector3 Now, of course I have all of the needed constructors and other parts needed in each class (like I said, they compile), but my problem arises when I write eyePos = initialEyePos. For instance, I can do: eyePos.set(...) with no problems. But, when I try to use any overloaded operators from the Vector3 class, I get this error: EditorView error LNK2019: unresolved external symbol "public: class Vector3 & __thiscall Vector3::operator=(class Vector3 const &)" (??4Vector3@@QAEAAV0@ABV0@@Z) referenced in function "public: __thiscall Perspective::Perspective(void)" (??0Perspective@@QAE@XZ) Is the fact that my Vector3 object file and Perspective object file are in different folders a problem? I really don't think that is the problem because if it was, I would think that Visual Studio would have taken care of all of that when I added the Math Engine project to the established solution. This problem has been bothering me for some time now and any help, or hint toward a solution would be greatly appreciated. Thanks in advance.

Yeah, of course. Both classes are complete and have been tested (and work fine independently). In fact, I have used the Vector3 class before in different applications. But now, when I try to use it like I have many times in the past, I get this problem. The only thing I can think that I have done different is that I have added Vector3 to a Math Engine project space, and I now just include that entire project in solutions of other applications (so, in the past I just had one project in my solution and I just added all of my files to that one project).

Well, I have finally figured it out! I had alredy set the dependencies for each project (EditorView -> MathEngine) but, I had both projects configured as .exe files when I should have had the MathEngine configured as a .lib file.

So, for any of you reading this and having the same problems, configure one project as a static library (Configuration properties -> General -> Configuration type -> static library) and everything should work fine.

Thank you Fruny for your help.