How to: Pass a Delegate^ to a Native Function Expecting a Function Pointer
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How to: Pass a Delegate^ to a Native Function Expecting a Function Pointer

From a managed component you can call a native function with function pointer parameters where the native function then can call the member function of the managed component's delegate.

This sample created the .dll that exports the native function.

// delegate_to_native_function.cpp
// compile with: /LD
#include < windows.h >
extern "C" {
   __declspec(dllexport)
   void nativeFunction(void (CALLBACK *mgdFunc)(const char* str)) {
      mgdFunc("Call to Managed Function");
   }
}

This sample consumes the .dll and passes a delegate handle to the native function expecting a function pointer.

// delegate_to_native_function_2.cpp
// compile with: /clr
using namespace System;
using namespace System::Runtime::InteropServices;

delegate void Del(String ^s);
public ref class A {
public:
   void delMember(String ^s) {
      Console::WriteLine(s);
   }
};

[DllImportAttribute("delegate_to_native_function", CharSet=CharSet::Ansi)]
extern "C" void nativeFunction(Del ^d);

int main() {
   A ^a = gcnew A;
   Del ^d = gcnew Del(a, &A::delMember);
   nativeFunction(d);   // Call to native function
}
Call to Managed Function
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