一個(gè)link 2019的錯(cuò)誤，一直沒有解決思路，最后解決掉，把思路記錄下
error msg:

UpDlgView.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) public: __thiscall CMarkup::~CMarkup(void)" (__imp_??1CMarkup@@QAE@XZ) referenced in function "public: void __thiscall CUpDlgView::OnButtonadd(void)" (?OnButtonadd@CUpDlgView@@QAEXXZ)

UpDlgView.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) public: bool __thiscall CMarkup::AddElem(char const *,char const *,int)" (__imp_?AddElem@CMarkup@@QAE_NPBD0H@Z) referenced in function "public: void __thiscall CUpDlgView::OnButtonadd(void)" (?OnButtonadd@CUpDlgView@@QAEXXZ)

UpDlgView.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) public: __thiscall CMarkup::CMarkup(void)" (__imp_??0CMarkup@@QAE@XZ) referenced in function "public: void __thiscall CUpDlgView::OnButtonadd(void)" (?OnButtonadd@CUpDlgView@@QAEXXZ)

分析：
錯(cuò)誤的類別是:unresolved external symbol ,是一個(gè)沒有解決的外部變量，因?yàn)橐恢闭J(rèn)為第三方類不可能有錯(cuò)誤所以一直在自己編寫的代碼中尋找錯(cuò)誤，其實(shí)錯(cuò)誤的關(guān)鍵在這里："__declspec(dllimport)" 這說明這是一個(gè)外部導(dǎo)出類，所以需要?將class? AFX_EXT_CLASS CMarkup?改為 class CMarkUp .