C# Interop - passing structure from UNmanaged to managed code

[ElysianEagle]

Hi,

I have a DLL written in C that creates a structure as a local variable, populates it, and then calls a function in managed c#. here is what im talking about:

//-----unmanged code's header file

typedef struct M
{
int a;
int b;
int c;
} MO;

typedef void (*MyCallBack)(MO m)
void register_callback(MyCallBack);

//------unmanged code's .c file

void register_callback(MyCallBack mcb)
{
MO co;
co.a = 67;

mcb(co);

}


-------------managed code (in rough, for brevity)

//struct MO
{
int a;
int b;
int c;
}


delegate void MyDelegate(MO m);

MyDelegate mdg;

mdg += delegate (MO m) {
MessageBox.Show(m.a.ToString());
}

register_callback(mdg);
---------------------------------------------

when I run this code, the managed function does get called by the unmanaged dll code, and the message box pops up showing '67', however after that my program crashes. does anyone know why??

thanks!!