代码求解释,该如何解决

typedef struct tagWNDINFO
...{
DWORD dwProcessId;
HWND hWnd;
} WNDINFO, *LPWNDINFO;

BOOL　CALLBACK YourEnumProc(HWND hWnd,LPARAM lParam)
...{
DWORD dwProcessId;
GetWindowThreadProcessId(hWnd, &dwProcessId);
LPWNDINFO pInfo = (LPWNDINFO)lParam;
if(dwProcessId == pInfo->dwProcessId)
...{
pInfo->hWnd = hWnd;
return FALSE;
}
return TRUE;
}
HWND GetProcessMainWnd(DWORD dwProcessId)
...{
WNDINFO wi;
wi.dwProcessId = dwProcessId;
wi.hWnd = NULL;
EnumWindows(YourEnumProc,(LPARAM)&wi);
return wi.hWnd;
}