Sure you can. You can do PInvoke in two ways, explicit PInvoke and C++
interop.
You would use the explicit PInvoke when you have the source code for the
assembly available. The C++ interop or the implicit PInvoke will have to be
used if you dont have the source code available.

For documentation, please look into
http://msdn2.microsoft.com/library/2x8kf7zx(en-us,vs.80).aspx

I have added an example of explicit Pinvoke,

//native.cpp
#include <stdio.h>
class __declspec(dllexport) Native
{
    public:
        void foo()
        {
            printf("Native foo called");
        }
};

//managed.cpp

using namespace System;

class __declspec(dllimport) Native
{
    public:
    void foo();
};

int main()
{
    Native obj;
    obj.foo();
}

cl /LD native.cpp
cl /clr managedcpp.cpp /link native.lib

Foo called.

Thanks,
Kapil