Exposing unmanaged const static std::string in a managed C++ class - c++-cli

Question

I have a non-.NET C++ class as follows:
Foo.h:
namespace foo {
const static std::string FOO;
...
}
Foo.cc:
using namespace foo;
const std::string FOO = "foo";
I want to expose this for use in a C# application, but I keep getting errors about mixed types when I try the following:
FooManaged.h:
namespace foo {
namespace NET {
public ref class Foo {
public:
const static std::string FOO;
}
}
}
FooManaged.cc:
using namespace foo::NET;
const std::string Foo::FOO = foo::FOO;
What's the right way to translate an unmanaged string constant to a managed string constant?

Answer 1

In C++/CLI, the literal keyword is used in place of static const where you want the constant definition to be included in the interface exposed to fully managed applications.
public:
literal String^ Foo = "foo";
Unfortunately, literal requires an immediate value, so using the std::string value is not possible. As an alternative, you can create a static read-only property that returns the string.
public:
static property String^ Foo
{
String^ get()
{
return gcnew String(Foo::FOO.c_str());
}
}
Personally, I believe rewriting the string again and using literal is the better option. However, if you are highly concerned about the constant changing (in a newer version, for example), the property will use the version of FOO in the native library.