Q:

How to marshall c++ char* to C# string using P/INVOKE

I'm new to C++. I'm calling a C++ function from C# using a PINVOKE and wanting to get a string back as an out parameter. However I just get an empty string back. The int out parameter works fine. 
Importing:
[DllImport ( @"UnamanagedAssembly.dll", CharSet = CharSet.Ansi)] 
public static extern int Activate(ref int numActivated,  StringBuilder eventsActivated);

extern "C" __declspec(dllexport) int Activate(int *p_NumActivated, char *p_EventsActivated) {return Activation::GetInstance()->Activate(p_NumActivated, p_EventsActivated);}

Calling my C++ function from C#:
int numActivated = 0;
StringBuilder eventsActivated = new StringBuilder();
int status = Activate(ref numActivated, eventsActivated);  

The C++ function:
int Activation::Activate(int *p_NumActivated, char *&p_EventsActivated)
{
    char *pTemp = "Hello";
    p_EventsActivated = pTemp;

    *p_NumActivated = 1;

    return 0;
}

A:

StringBuilder eventsActivated = new StringBuilder(5);

instead of
StringBuilder eventsActivated = new StringBuilder();

A:

[DllImport ( @"UnamanagedAssembly.dll", CharSet = CharSet.Ansi)]
public static extern int Activate(
    ref int numActivated, 
    [MarshalAs(UnmanagedType.LPStr)]StringBuilder eventsActivated);

