C++ 调用C#类库

#include <msclr\marshal_cppstd.h>
using namespace System;
using namespace msclr::interop;
using namespace std;
#include <string>
#using "..\\Debug\\ClassLibrary1.dll"
using namespace ClassLibrary1;


void CCPlusTestProjectDlg::OnBnClickedOk()
{
    ClassLibrary1::WebHttp ^ http = gcnew ClassLibrary1::WebHttp();
    ClassLibrary1::ReturnMsg ^ ret = http->Test();
    int code = ret->code;
    CString strMsg = ClrStringToCString(ret->msg);
}

CString CCPlusTestProjectDlg::ClrStringToCString(String^clrString)
{
    CString strRet = "";
    string sMsg;
    sMsg = marshal_as<std::string>(clrString);
    CA2T szr((sMsg).c_str());
    strRet = (LPCTSTR)szr;

    return strRet;
}