C++ dll function using std:string [duplicate]

Possible Duplicate:
std::string in C#?
How can I call a function of a C++ DLL that accepts a parameter of type stringstream from C#?

Is there a way to convert from a c++ std:string to C# System.String? I'm calling a function from a C++ dll that takes a std:string as input. Is there a simple way to do this?

C#:

[DllImport(@"MyDLL.dll")]
[return:MarshalAs(UnmanagedType.I1)]
public static extern bool myFunction([In, Out]string input);

C++:

extern "C" __declspec(dllexport) BOOL __stdcall myFunction(const std::string& input)
{
  //Code is here
}