Import a C++ .lib and .h file into a C# project?

What you could do, is creating a C++/CLI wrapper and expose the functionality of the lib you want to use via your wrapper. The created wrapper dll you can easily reference in your C# project. This of course takes a little bit of work to create the managed/unmanaged wrapper, but will pay off in the long run.

To create a managed C++ project select under the C++ project templates CLR and Class Library. Here you can link to your lib, use the header file the way you are used to.

Next create a new class (ref class) and wrap your library in it. An example might look something like this:

LibHeader.h

int foo(...);

You write a wrapper class like this: Header:

Wrapper.h

public ref class MyWrapper
{
    public:
        int fooWrapped();
};

Your Implementation:

Wrapper.cpp

#include Libheader.h

int MyWrapper::fooWrapped()
{
     return foo();
}

Namespaces and all the good stuff omitted for simplicity. Now you can use MyWrapper in your C# code just as easy as any other managed class. Of course when the interface of the lib gets more complicated you have to think about it a bit more, but it might help to separate the lib-code from your application. Hope to have shed some light on it.