如何使FtpWebResponse异步

FtpWebRequest request = (FtpWebRequest)WebRequest.Create("ftp://example.com/file.txt");
request.Method = WebRequestMethods.Ftp.DownloadFile;

// 使用APM模型
IAsyncResult result = request.BeginGetResponse(new AsyncCallback(FtpResponseCallback), request);

// 异步回调函数
void FtpResponseCallback(IAsyncResult ar)
{
    FtpWebRequest request = (FtpWebRequest)ar.AsyncState;
    FtpWebResponse response = (FtpWebResponse)request.EndGetResponse(ar);

    // 处理FtpWebResponse对象
    // ...

    response.Close();
}

async Task FtpResponseAsync()
{
    FtpWebRequest request = (FtpWebRequest)WebRequest.Create("ftp://example.com/file.txt");
    request.Method = WebRequestMethods.Ftp.DownloadFile;

    // 使用TAP模型
    FtpWebResponse response = (FtpWebResponse)await request.GetResponseAsync();

    // 处理FtpWebResponse对象
    // ...

    response.Close();
}