FtpWebRequest 使用进度条进行 FTP 下载

我的代码有效，但是ProgressBar直接跳到100%，然后继续下载。当它完成后，就会出现一个消息框来获取信息。

我已经改变了缓冲区大小，但这并不重要。

我在这里做错了什么？

这是我的代码：

void workerDOWN_DoWork(object sender, DoWorkEventArgs e)
{
    string fileFullPath = e.Argument as String;
    string fileName = Path.GetFileName(fileFullPath);
    string fileExtension = Path.GetExtension(fileName);

    label4.Invoke((MethodInvoker)delegate { label4.Text = "Downloading File.."; });

    string ftpServerIP = "XXX";
    string ftpUserName = "XXX";
    string ftpPassword = "XXX";

    try
    {
        //Datei vom FTP Server downloaden
        FtpWebRequest request = (FtpWebRequest)WebRequest.Create("ftp://" + ftpServerIP + "/" + fileName);
        request.Credentials = new NetworkCredential(ftpUserName, ftpPassword);
        request.Method = WebRequestMethods.Ftp.DownloadFile;
        using (Stream ftpStream = request.GetResponse().GetResponseStream())
        using (Stream fileStream = File.Create(fileFullPath))
        {
            var buffer = new byte[32 * 1024];
            int totalReadBytesCount = 0;
            int readBytesCount;
            while ((readBytesCount = ftpStream.Read(buffer, 0, buffer.Length)) > 0)
            {
                fileStream.Write(buffer, 0, readBytesCount);
                totalReadBytesCount += readBytesCount;
                var progress = (int)((float)totalReadBytesCount / (float)fileStream.Length * 100);
                workerDOWN.ReportProgress((int)progress);
                label3.Invoke((MethodInvoker)delegate { label3.Text = progress + " %"; });
            }
        }
    }
    catch (WebException ex)
    {
        FtpWebResponse response = (FtpWebResponse)ex.Response;

        if (response.StatusCode == FtpStatusCode.ActionNotTakenFileUnavailable)
        {
            MessageBox.Show("Datei nicht gefunden!", "Error");
        }
    }
    e.Result = fileFullPath;
}


void workerDOWN_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
     string fileFullPath = e.Result as String;
     string fileName = Path.GetFileName(fileFullPath);

     MessageBox.Show("Download erfolgreich!","Information");

     progressBar1.Value = 0;
     label3.Invoke((MethodInvoker)delegate { label3.Text = " "; });
     label4.Invoke((MethodInvoker)delegate { label4.Text = " "; });      
}

使用 FTP 下载的简单示例FtpWebRequest使用 WinForms 进度条：

private void button1_Click(object sender, EventArgs e)
{
    // Run Download on background thread
    Task.Run(() => Download());
}

private void Download()
{
    try
    {
        const string url = "ftp://ftp.example.com/remote/path/file.zip";
        var credentials = new NetworkCredential("username", "password");

        // Query size of the file to be downloaded
        WebRequest sizeRequest = WebRequest.Create(url);
        sizeRequest.Credentials = credentials;
        sizeRequest.Method = WebRequestMethods.Ftp.GetFileSize;
        int size = (int)sizeRequest.GetResponse().ContentLength;

        progressBar1.Invoke(
            (MethodInvoker)(() => progressBar1.Maximum = size));
        
        // Download the file
        WebRequest request = WebRequest.Create(url);
        request.Credentials = credentials;
        request.Method = WebRequestMethods.Ftp.DownloadFile;

        using (Stream ftpStream = request.GetResponse().GetResponseStream())
        using (Stream fileStream = File.Create(@"C:\local\path\file.zip"))
        {
            byte[] buffer = new byte[10240];
            int read;
            while ((read = ftpStream.Read(buffer, 0, buffer.Length)) > 0)
            {
                fileStream.Write(buffer, 0, read);
                int position = (int)fileStream.Position;
                progressBar1.Invoke(
                    (MethodInvoker)(() => progressBar1.Value = position));
            }
        }
    }
    catch (Exception e)
    {
        MessageBox.Show(e.Message);
    }
}

核心下载代码基于：
在 C#/.NET 中向 FTP 服务器上传和下载文件

解释一下为什么你的代码不起作用：

• 您正在使用目标文件的大小进行计算：fileStream.Length– 它总是等于totalReadBytesCount，因此progress永远是 100。
• 你可能想使用ftpStream.Length，但无法读取。
• 基本上使用 FTP 协议，您不知道正在下载的文件的大小。如果您需要知道它，则必须在下载之前明确查询。这里我使用的是WebRequestMethods.Ftp.GetFileSize为了那个原因。