对话框窗口过程与普通窗口过程的区别

对话框窗口是指通过CreateDialog，DialogBox 这些API创建的窗口，其中DLGPROC与普通窗口有一些区别。

HWND WINAPI CreateDialog(
  _In_opt_  HINSTANCE hInstance,
  _In_      LPCTSTR lpTemplate,
  _In_opt_  HWND hWndParent,
  _In_opt_  DLGPROC lpDialogFunc
);

MSDN对这种区别有如下解释，消息处理方面流程有所不同，我们创建对话框时传入的窗口过程，不是最终的消息处理函数，而且是供系统的DialogProc调用，切忌在自已的DialogProc中写出 return ::DefWindowProc()这样的代码。

The dialog box procedure is very similar to a window procedure except for the type of return value which is TRUE/FALSE instead of LRESULT. The internal dialog box manager inside Windows IS the true window procedure for the dialog box. It calls our dialog box procedure with some messages that it received. So the general rule of thumb is that: if our dialog box procedure processes a message,it MUST return TRUE in eax and if it does not process the message, it must return FALSE in eax. Note that a dialog box procedure doesn't pass the messages it does not process to the DefWindowProc call since it's not a real window procedure.