学习网络编程，一个项目里建有两工程，出现无解的问题，求大神指导，

[_COUT]

error LNK2005: "public: __thiscall CAboutDlg::CAboutDlg(void)" (??0CAboutDlg@@QAE@XZ) already defined in chat1Dlg.obj
hostDlg.obj : error LNK2005: "protected: virtual void __thiscall CAboutDlg::DoDataExchange(class CDataExchange *)" (?DoDataExchange@CAboutDlg@@MAEXPAVCDataExchange@@@Z) already defined in chat1Dlg.obj
hostDlg.obj : error LNK2005: "protected: static struct AFX_MSGMAP const * __stdcall CAboutDlg::_GetBaseMessageMap(void)" (?_GetBaseMessageMap@CAboutDlg@@KGPBUAFX_MSGMAP@@XZ) already defined in chat1Dlg.obj
hostDlg.obj : error LNK2005: "protected: virtual struct AFX_MSGMAP const * __thiscall CAboutDlg::GetMessageMap(void)const " (?GetMessageMap@CAboutDlg@@MBEPBUAFX_MSGMAP@@XZ) already defined in chat1Dlg.obj
hostDlg.obj : error LNK2005: "unsigned int __cdecl ThreadProc(void *)" (?ThreadProc@@YAIPAX@Z) already defined in chat1Dlg.obj
hostDlg.obj : error LNK2005: "protected: static struct AFX_MSGMAP const CAboutDlg::messageMap" (?messageMap@CAboutDlg@@1UAFX_MSGMAP@@B) already defined in chat1Dlg.obj
hostDlg.obj : error LNK2005: "private: static struct AFX_MSGMAP_ENTRY const * const CAboutDlg::_messageEntries" (?_messageEntries@CAboutDlg@@0QBUAFX_MSGMAP_ENTRY@@B) already defined in chat1Dlg.obj
Debug/chat1.exe : fatal error LNK1169: one or more multiply defined symbols found
Error executing link.exe.
Creating browse info file...

chat1.exe - 8 error(s), 0 warning(s)


还出现了2个CAboutDlg,,

[zyjj_99]

看编译错误是链接错误，是不是工程之间相互调用了，你路径没配置

[jianghandaxue]

看看你自己生成的头文件是否重复include了 在头文件中这么搞一下可以避免重复include： #ifndef __YOURHEADFILE_H__ //自己起个名字 #define __YOURHEADFILE_H__ ...//头文件内容 #endif

[ouyh12345]

为什么chat1有2个CAboutDlg？