C / C++ / MFC

// something like that : ( not tested )
void MyWnd::OnSetFocus( CWnd* pOldWnd )
{
  (void)pOldWnd->SetFocus( );
}

try
{
	CFileDialog fd(true,_T("txt"), _T("*.txt"));
	if(fd.DoModal() == IDOK)
	{
		CString buff = "";
		int i=0;
		int max_size = 256;
		ifstream inFile;
		inFile.open(fd.GetPathName());
		
		do
		{
			inFile.getline(buff.GetBuffer(max_size),max_size);
			this->m_ListCtrl.InsertItem(i, buff);
			i++;
		}while(!inFile.eof());
		
		inFile.close();
	}

	return true;
}

catch(...)
{
	// Handle Error
	return false;
}