error LNK2019: unresolved external symbol

I created a "Win 32 Project" with these three simple files, but when I
try to link, I get a LNK2019 error, I think it is a project setting,
but canone throw some light on this?

Thanks,
Bob

// FooBase.h

#ifndef _FooBase_h
#define _FooBase_h

class FooBase
{
    public:
        virtual ~FooBase();
        virtual int GetNumber() = 0;

    protected:
        FooBase();
};

#endif _FooBase_h

// Foo.h

#ifndef _Foo_h
#define _Foo_h

#include "FooBase.h"

class Foo : virtual public FooBase
{
    public:
        Foo();
        ~Foo();
        int GetNumber();
};

#endif _Foo_h

// Foo.cpp

#include "Foo.h"

Foo::Foo() : FooBase() {}

Foo::~Foo() {}

int Foo::GetNumber()
{
    return 5;
}

Error 1 error LNK2019: unresolved external symbol "protected:
__thiscall FooBase::FooBase(void)" (??0FooBase@@IAE@XZ) referenced in
function "public: __thiscall Foo::Foo(void)" (??0Foo@@QAE@XZ) Foo.obj
Error 2 error LNK2019: unresolved external symbol "public: virtual
__thiscall FooBase::~FooBase(void)" (??1FooBase@@UAE@XZ) referenced in
function "public: void __thiscall Foo::`vbase destructor'(void)" (??
_DFoo@@QAEXXZ) Foo.obj
Error 3 fatal error LNK1120: 2 unresolved externals C:\scratch\Scratch
\Debug\CPP.dll