请教个关于DLL问题
我建立MFC extension DLL
<<<<<<CmControl.H>>>>>>>>
#pragma once
class AFX_EXT_CLASS rxgas
{
public:
rxgas();
};

<<<<<<CmControl.Cpp>>>>>>>>
#include "stdafx.h"
#include "CmControl.h"
rxgas::rxgas()
{
AfxMessageBox(_T("qwe"));
}

在一个应用程序是这样写的
#include "CmControl.h"
.....................
void CTestDlg::OnBnClickedOk()
{
rxgas dd;
}
报错如下:
TestDlg.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) public: __thiscall rxgas::rxgas(void)" (__imp_??0rxgas@@QAE@XZ) referenced in function "public: void __thiscall CTestDlg::OnBnClickedOk(void)" (?OnBnClickedOk@CTestDlg@@QAEXXZ)