char szFileName[MAX_PATH]={0};  OPENFILENAME openFileName = {0};  openFileName.lStructSize = sizeof(OPENFILENAME);  openFileName.nMaxFile = MAX_PATH;  //这个必须设置，不设置的话不会出现打开文件对话框  openFileName.lpstrFilter = "文本文件(*.txt)\0*.txt\0所有文件(*.*)\0*.*\0\0";  openFileName.lpstrFile = szFileName;  openFileName.nFilterIndex = 1;  openFileName.Flags = OFN_PATHMUSTEXIST | OFN_FILEMUSTEXIST;    if (::GetOpenFileName(&openFileName))  {      ::MessageBoxA(hwndDlg, openFileName.lpstrFile, "", MB_OK);  }