我在用MFC做个小程序，调试时没错，编译时出现如下错误：
Linking...
youxi_1View.obj : error LNK2001: unresolved external symbol "protected: virtual void __thiscall CYouxi_1View::OnEndPrinting(class CDC *,struct CPrintInfo *)" (?OnEndPrinting@CYouxi_1View@@MAEXPAVCDC@@PAUCPrintInfo@@@Z)
youxi_1View.obj : error LNK2001: unresolved external symbol "protected: virtual void __thiscall CYouxi_1View::OnBeginPrinting(class CDC *,struct CPrintInfo *)" (?OnBeginPrinting@CYouxi_1View@@MAEXPAVCDC@@PAUCPrintInfo@@@Z)
youxi_1View.obj : error LNK2001: unresolved external symbol "protected: virtual int __thiscall CYouxi_1View::OnPreparePrinting(struct CPrintInfo *)" (?OnPreparePrinting@CYouxi_1View@@MAEHPAUCPrintInfo@@@Z)
youxi_1View.obj : error LNK2001: unresolved external symbol "public: class CYouxi_1Doc * __thiscall CYouxi_1View::GetDocument(void)" (?GetDocument@CYouxi_1View@@QAEPAVCYouxi_1Doc@@XZ)
Debug/youxi_1.exe : fatal error LNK1120: 4 unresolved externals
好像是一类错误，求帮忙啊！很是着急啊。。。