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This article mainly explains "how c # calls C++ 's DLL". The content of the article is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "c # how to call C++ 's DLL".

C # is a managed code, and the created objects are automatically recycled. C++ is unmanaged code, the created objects need to be manually recycled (sometimes not manually recycled, memory overflow problems may occur).

There are two ways for C # to call C++: (1) managed calls and (2) unmanaged calls.

1. It is called in a managed way, just like the dll that normally calls c#

Create a new C++ project

The code in Function.h, a method that returns the sum of two numbers, a method that returns a string

# pragma once#include public ref class Function {public: Function (void); ~ Function (void); int menber; int menberFuncAdd (int aline int b); System:: string ^ say (System:: string ^ str);}; / .CPP # include "Function.h" Function::Function (void) {} Function::~Function (void) {} int Function::menberFuncAdd (int aline int b) {return astring;} System:: string ^ Function::say (System:: string ^ str) {return str;}

There is no need to write blank space in Function.h.

# include "Function.h"

Note: C++ projects must choose common language runtime support

Reference in the project of c # like the dll of c #

Call in the code

Function fun = new Function (); int a = fun.menberFuncAdd (1,2); string s = fun.say ("Hello World")

Note: x86 must be selected for the c # project, otherwise an error will be reported.

Running effect:

two。 Call in an unmanaged manner

Create a new C++ project

Code in stdafx.h

/ / stdafx.h: the include file of the standard system include file / / or frequently used but infrequently changed / / project-specific include files / / # pragma once # include "targetver.h" # ifdef A_EXPORTS#define DLL_API _ _ declspec (dllexport) # else#define DLL_API _ _ declspec (dllimport) # endif#define WIN32_LEAN_AND_MEAN / / exclude rarely used information from Windows header files / / Windows header files: # include extern "C" DLL_API void MessageBoxShow () / / TODO: refer to other header files required by the program here

Code in dllmain.cpp

# include "stdafx.h" BOOL APIENTRY DllMain (HMODULE hModule, DWORD ul_reason_for_call, LPVOID lpReserved) {switch (ul_reason_for_call) {case DLL_PROCESS_ATTACH: case DLL_THREAD_ATTACH: case DLL_THREAD_DETACH: case DLL_PROCESS_DETACH: break;} return TRUE } # ifdef _ MANAGED#pragma managed (push, off) # endif void MessageBoxShow () {MessageBox (NULL, TEXT ("Hello World"), TEXT ("In a DLL"), MB_OK);} # ifdef _ MANAGED#pragma managed (pop) # endif

Note: C++ projects must choose common language runtime support

Add to the code

[DllImport ("ll.dll")] public extern static void MessageBoxShow ()

Note: x86 must be selected for the c # project, otherwise an error will be reported.

Running result:

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