C# calls the C++ code

 

•     Prepare the C++ code:

    1 create the solution 'TestConsole' by VS.

    2 In this solution, add a new project CppDeno with mode 'Win32 Console Application' and application type 'DLL'

    3 In file CppDemo.cpp add the code as below:

    extern "C" __declspec(dllexport) int Add(int a,int b) {

return a + b; 

    }

    4 compile this simple project.

•     Static call the C++ dll:

    1 Under solution 'TestConsole', add new project 'TestDemo'

    2 In program.cs file, add below code to Main method:

     Console.WriteLine(Add(1, 2)); 

Console.Read();

    3 Copy the CppDemo.lib & CppDemo.dll to debug folder of this project

    4 Press key 'F5' to run

•     Dynamic call C++ code:

    1 Create new class NativeMethod.cs, the code as below:

    using System;

    using System.Runtime.InteropServices;

    namespace TestDemo

   {

    internal class NativeMethod

    {

        [DllImport("kernel32.dll", EntryPoint = "LoadLibrary")]

        public static extern int LoadLibrary([MarshalAs(UnmanagedType.LPStr)] string lpLibFileName);

        [DllImport("kernel32.dll", EntryPoint = "GetProcAddress")]

        public static extern IntPtr GetProcAddress(int hModule, [MarshalAs(UnmanagedType.LPStr)] string lpProcName);

        [DllImport("kernel32.dll", EntryPoint = "FreeLibrary")]

        public static extern bool FreeLibrary(int hModule);

    }

}

    2 add delegate definition to Program.cs:

     delegate int Add(int a, int b);

    3 update method Main as below:

     static void Main(string[] args) {

            //1. 动态加载C++ Dll 　　　　　　　　　　　 

            int hModule = NativeMethod.LoadLibrary(@"c:CppDemo.dll"); 　　　　　　　　　　　 

            if (hModule == 0) return;  　　　　　　　　　　　 

            //2. 读取函数指针 　　　　　　　　　　　 

            IntPtr intPtr = NativeMethod.GetProcAddress(hModule, "Add");  　　　　　　　　　　　 

            //3. 将函数指针封装成委托 　　　　　　　　　　　 

            Add addFunction = (Add)Marshal.GetDelegateForFunctionPointer(intPtr, typeof(Add));  　　　　　　　　　　　 

            //4. 测试 　　　　　　　　　　　 

            Console.WriteLine(addFunction(1, 2)); 　　　　　　　　　　　 

            Console.Read();

}

   4 Press key 'F5' to run