非托管代码中调用托管代码

托管类库(CSharp):

using System;

namespace ManagedPerson
{
    public class Person
    {
        private string _name;
        private DateTime _birthday;

        public Person(string name, DateTime birthday)
        {
            _name = name;
            _birthday = birthday;
        }

        public uint Age
        {
            get
            {
                DateTime now = DateTime.Now;
                int age = now.Year - _birthday.Year;
                if (_birthday.Month > now.Month ||
                    (_birthday.Month == now.Month && _birthday.Day > now.Day))
                {
                    --age;
                }

                return (uint) age;
            }
        }

        public string Birthdaystr => _birthday.ToShortDateString();

        public DateTime Birthday => _birthday;
    }
}

C++/CLI包装类库(Managed C++):

#pragma once

#ifdef CLIPERSON_EXPORTS
#define CLIPERSON_API __declspec(dllexport)
#else
#define CLIPERSON_API __declspec(dllimport)
#endif

#include <string>
#include <Windows.h>

using namespace std;

class CLIPERSON_API CPerson
{
public:
    CPerson(string name, const SYSTEMTIME *birthday);
    virtual ~CPerson();

    unsigned int getAge() const;
    string getBirthdaystr() const;
    SYSTEMTIME getBirthday() const;

private:
    void *clrPerson;
};

// CLIPerson.cpp: 定义 DLL 应用程序的导出函数。
//

#include "stdafx.h"
#include "CLIPerson.h"
#include <vcclr.h>

using namespace System;
using namespace Runtime::InteropServices;
using namespace ManagedPerson;

CPerson::CPerson(string name, const SYSTEMTIME * birthday)
{
    DateTime ^datetime = gcnew DateTime(birthday->wYear, birthday->wMonth, birthday->wDay);

    //int nu = strlen(name.c_str());
    //int n = (size_t)MultiByteToWideChar(CP_ACP, 0, (const char *)name.c_str(), (int)nu, NULL, 0);
    //wchar_t *pwstr = new wchar_t[n];
    //MultiByteToWideChar(CP_ACP, 0, (const char *)name.c_str(), (int)nu, pwstr, (int)n);
    //String ^str = gcnew String(pwstr);
    //delete []pwstr;

    String ^str = gcnew String(name.c_str());

    Person ^person = gcnew Person(str, *datetime);
    // managed type conversion into unmanaged pointer is not allowed.
    // we can use gcroot<> wrapper.
    gcroot<Person ^> *pp = new gcroot<Person ^>(person);
    clrPerson = static_cast<void *>(pp);
}

CPerson::~CPerson()
{
    if (clrPerson)
    {
        gcroot<Person ^> *pp = static_cast<gcroot<Person ^> *>(clrPerson);
        delete pp;

        clrPerson = 0;
    }
}

unsigned int CPerson::getAge() const
{
    if (clrPerson != 0)
    {
        gcroot<Person ^> *pp = static_cast<gcroot<Person ^> *>(clrPerson);
        return ((Person ^)*pp)->Age;
    }

    return 0;
}

string CPerson::getBirthdaystr() const
{
    string strage;
    if (clrPerson != 0)
    {
        gcroot<Person ^> *pp = static_cast<gcroot<Person ^> *>(clrPerson);
        strage = (const char *)Marshal::StringToHGlobalAnsi(((Person ^)*pp)->Birthdaystr).ToPointer();
    }

    return strage;
}

SYSTEMTIME CPerson::getBirthday() const
{
    SYSTEMTIME st;
    if (clrPerson != 0)
    {
        gcroot<Person ^> *pp = static_cast<gcroot<Person ^> *>(clrPerson);
        DateTime dt = ((Person ^)*pp)->Birthday;
        st.wYear = dt.Year;
        st.wMonth = dt.Month;
        st.wDay = dt.Day;
    }

    return st;
}

此处需要特别注意的地方是Dll入口点不可以编译为MSIL,详细信息:https://msdn.microsoft.com/zh-cn/library/ccthbfk8(v=vs.100).aspx

// dllmain.cpp : 定义 DLL 应用程序的入口点。
#include "stdafx.h"

#pragma unmanaged
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;
}

传统C++引入Library并测试:

// main.cpp: 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include "CLIPerson.h"
#include <iostream>

using namespace std;

int main()
{
    SYSTEMTIME st = { 0 };
    const char *name = "native call managed code";

    st.wYear = 1975;
    st.wMonth = 8;
    st.wDay = 15;

    CPerson person(name, &st);

    cout << name << ":" << endl;
    cout << "age:" << person.getAge() << endl;
    cout << "birthday:" << person.getBirthdaystr().c_str() << endl;

    system("pause");

    return 0;
}

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