-------------------Configuration: Tree - Win32 Debug--------------------
Compiling...
Tree.cpp
Generating Code...
Compiling...
TreeDlg.cpp
myTreeCtrl.cpp
Generating Code...
Linking...
myTreeCtrl.obj : error LNK2001: unresolved external symbol "protected: void __thiscall CmyTreeCtrl::OnItemxpanding(struct tagNMHDR *,long *)" (?OnItemxpanding@CmyTreeCtrl@@IAEXPAUtagNMHDR@@PAJ@Z)
myTreeCtrl.obj : error LNK2001: unresolved external symbol "protected: void __thiscall CmyTreeCtrl::OnItemxpanded(struct tagNMHDR *,long *)" (?OnItemxpanded@CmyTreeCtrl@@IAEXPAUtagNMHDR@@PAJ@Z)
Debug/Tree.exe : fatal error LNK1120: 2 unresolved externals
Error executing link.exe.
Creating browse info file...

Tree.exe - 3 error(s), 0 warning(s)
请问这是说些什么？

你的函数实现没有被包含到工程中.
如果CmyTreeCtrl::OnItemxpanding与CmyTreeCtrl::OnItemxpanded是在Dll中实现, 请保证Dll文件被正确的link.
如果是在Cpp文件中实现, 请确保h, cpp被添加到工程中, 而非只是include.

对于lnk2001我一般就遇到这两种情况.

谢谢poppylx