String^ declaration in C++

Question

As far as I am aware C++ string declaration follows the form:

std::string param;

I was walking through a code and realised the declaration of string is done this way:

System::String^ param;

Can anyone share light on this declaration?! Is this Microsoft Visual C++ string declaration or a special library which provides another alternative to using C++ string.

Answer 1

It's Microsoft-specific, and is part of a language they call C++/CLI. This syntax declares a Common Language Runtime (CLR) String variable (the same kind you get when you declare a string in C#). These are not directly interchangeable with the several C/C++ string types, but Microsoft provides marshalling facilities to convert CLR String objects to unmanaged strings and vice versa.

C++/CLI enables developers to create programs that bridge regular C++ classes/functions (otherwise called "unmanaged code") with CLR classes/functions (otherwise called "managed code"). Microsoft also exposes lower-level features of the CLR to C++/CLI, some that are exposed to C# too (like pointers), and some that aren't (like finer granularity over member access levels).

It's useful if you want to use an existing C or C++ library in a language like C# (by making the bindings in C++/CLI then exposing them to the CLR without going through P/Invokes), or if you want to port an existing unmanaged C/C++ library or application to a managed environment.

Answer 2

This is C++/CLI syntax for a handle to an object on the managed heap.