Deeply understand the conversion between char* wchar_t* string and wstring in c++

    #ifndef USE_H_  
    #define USE_H_  

    #include <iostream>  
    #include <windows.h>  
    #include <string>  
    using namespace std;  
    class CUser  
    {  
    public:  
        CUser();  
        virtual~ CUser();  
        char* WcharToChar(const wchar_t* wp);  
        char* StringToChar(const string& s);  
        char* WstringToChar(const wstring& ws);  
        wchar_t* CharToWchar(const char* c);  
        wchar_t* WstringToWchar(const wstring& ws);  
        wchar_t* StringToWchar(const string& s);  
        wstring StringToWstring(const string& s);  
        string WstringToString(const wstring& ws);  
        void Release();  
    private:  
        char* m_char;  
        wchar_t* m_wchar;  
    };  
    #endif;  

    #include "stdafx.h"  
    #include "use.h"  
    CUser::CUser()  
    :m_char(NULL)  
    ,m_wchar(NULL)  
    {  
    }  
    CUser::~CUser()  
    {  
        Release();  
    }  
    char* CUser::WcharToChar(const wchar_t* wp)  
    {  
        Release();  
        int len= WideCharToMultiByte(CP_ACP,0,wp,wcslen(wp),NULL,0,NULL,NULL);  
        m_char=new char[len+1];  
        WideCharToMultiByte(CP_ACP,0,wp,wcslen(wp),m_char,len,NULL,NULL);  
        m_char[len]='0';  
        return m_char;  
    }  
    wchar_t* CUser::CharToWchar(const char* c)  
    {  
        Release();  
        int len = MultiByteToWideChar(CP_ACP,0,c,strlen(c),NULL,0);  
        m_wchar=new wchar_t[len+1];  
        MultiByteToWideChar(CP_ACP,0,c,strlen(c),m_wchar,len);  
        m_wchar[len]='0';  
        return m_wchar;  
    }  
    void CUser::Release()  
    {  
        if(m_char)  
        {  
            delete m_char;  
            m_char=NULL;  
        }  
        if(m_wchar)  
        {  
            delete m_wchar;  
            m_wchar=NULL;  
        }  
    }  
    char* CUser::StringToChar(const string& s)  
    {  
        return const_cast<char*>(s.c_str());  
    }  
    char* CUser::WstringToChar(const std::wstring &ws)  
    {  
        const wchar_t* wp=ws.c_str();  
        return WcharToChar(wp);  
    }  
    wchar_t* CUser::WstringToWchar(const std::wstring &ws)  
    {  
        return const_cast<wchar_t*>(ws.c_str());  
    }  
    wchar_t* CUser::StringToWchar(const string& s)  
    {  
        const char* p=s.c_str();  
        return CharToWchar(p);  
    }  
    string CUser::WstringToString(const std::wstring &ws)  
    {  
        string s;  
        char* p=WstringToChar(ws);  
        s.append(p);  
        return s;  
    }  
    wstring CUser::StringToWstring(const std::string &s)  
    {  
        wstring ws;  
        wchar_t* wp=StringToWchar(s);  
        ws.append(wp);  
        return ws;  
    }  

If CString is involved, you can use the CString::GetBuffer() function to do the conversion, just the same.