在 C#/.NET 中上传和下载文件到/从 FTP 服务器

Question

我正在使用 .NET 4 C#。我正在尝试将 ZIP 文件上传然后下载到（我的）服务器。

为了上传我有

using (WebClient client = new WebClient())
{
    FtpWebRequest request = (FtpWebRequest)WebRequest.Create(MyUrl);
    request.Method = WebRequestMethods.Ftp.UploadFile;
    request.EnableSsl = false;
    request.Credentials = new NetworkCredential(MyLogin, MyPassword);
    byte[] fileContents = null;
    using (StreamReader sourceStream = new StreamReader(LocalFilePath))
    {
        fileContents = Encoding.UTF8.GetBytes(sourceStream.ReadToEnd());
    }
    request.ContentLength = fileContents.Length;
    using (Stream requestStream = request.GetRequestStream())
    {
        requestStream.Write(fileContents, 0, fileContents.Length);
    }
    FtpWebResponse response = null;
    response = (FtpWebResponse)request.GetResponse();
    response.Close();
}

这似乎可行，因为我在服务器上获得了一个大小合适的文件。

1) 我如何流式传输它，而不是先将其加载到内存中？我将上传非常大的文件。

为了下载我有

using (WebClient client = new WebClient())
{
    string HtmlResult = String.Empty;
    FtpWebRequest request = (FtpWebRequest)WebRequest.Create(remoteFile);
    request.Method = WebRequestMethods.Ftp.DownloadFile;
    request.EnableSsl = false;
    request.Credentials = new NetworkCredential(MyLogin, MyPassword);
    using (FtpWebResponse response = (FtpWebResponse)request.GetResponse())
    using (Stream responseStream = response.GetResponseStream())
    using (StreamReader reader = new StreamReader(responseStream))
    using (FileStream writer = new FileStream(localFilename, FileMode.Create))
    {
        long length = response.ContentLength;
        int bufferSize = 2048;
        int readCount;
        byte[] buffer = new byte[2048];
        readCount = responseStream.Read(buffer, 0, bufferSize);
        while (readCount > 0)
        {
            writer.Write(buffer, 0, readCount);
            readCount = responseStream.Read(buffer, 0, bufferSize);
        }
    }
}

2) 一切似乎都正常...除了当我尝试解压缩下载的 ZIP 文件时，我得到一个无效的 ZIP 文件。

Answer 1

上传

使用 .NET 框架将二进制文件上传到 FTP 服务器最简单的方法是使用WebClient.UploadFile：

WebClient client = new WebClient();
client.Credentials = new NetworkCredential("username", "password");
client.UploadFile(
    "ftp://ftp.example.com/remote/path/file.zip", @"C:\local\path\file.zip");

如果您需要更大的控制，WebClient 不提供（如TLS/SSL encryption、ascii/文本传输模式、传输恢复等），请使用FtpWebRequest。简单的方法是使用Stream.CopyTo 将FileStream 复制到FTP 流：

FtpWebRequest request =
    (FtpWebRequest)WebRequest.Create("ftp://ftp.example.com/remote/path/file.zip");
request.Credentials = new NetworkCredential("username", "password");
request.Method = WebRequestMethods.Ftp.UploadFile;  

using (Stream fileStream = File.OpenRead(@"C:\local\path\file.zip"))
using (Stream ftpStream = request.GetRequestStream())
{
    fileStream.CopyTo(ftpStream);
}

如果你需要监控一个上传进度，你必须自己分块复制内容：

FtpWebRequest request =
    (FtpWebRequest)WebRequest.Create("ftp://ftp.example.com/remote/path/file.zip");
request.Credentials = new NetworkCredential("username", "password");
request.Method = WebRequestMethods.Ftp.UploadFile;  

using (Stream fileStream = File.OpenRead(@"C:\local\path\file.zip"))
using (Stream ftpStream = request.GetRequestStream())
{
    byte[] buffer = new byte[10240];
    int read;
    while ((read = fileStream.Read(buffer, 0, buffer.Length)) > 0)
    {
        ftpStream.Write(buffer, 0, read);
        Console.WriteLine("Uploaded {0} bytes", fileStream.Position);
    } 
}

有关 GUI 进度 (WinForms ProgressBar)，请参阅：
How can we show progress bar for upload with FtpWebRequest

如果您想上传文件夹中的所有文件，请参阅
Recursive upload to FTP server in C#。

---

下载

使用 .NET 框架从 FTP 服务器下载二进制文件最简单的方法是使用 WebClient.DownloadFile：

WebClient client = new WebClient();
client.Credentials = new NetworkCredential("username", "password");
client.DownloadFile(
    "ftp://ftp.example.com/remote/path/file.zip", @"C:\local\path\file.zip");

如果您需要更大的控制，WebClient 不提供（如TLS/SSL encryption、ascii/文本传输模式、resuming transfers 等），请使用FtpWebRequest。简单的方法是使用 Stream.CopyTo 将 FTP 响应流复制到 FileStream：

FtpWebRequest request =
    (FtpWebRequest)WebRequest.Create("ftp://ftp.example.com/remote/path/file.zip");
request.Credentials = new NetworkCredential("username", "password");
request.Method = WebRequestMethods.Ftp.DownloadFile;

using (Stream ftpStream = request.GetResponse().GetResponseStream())
using (Stream fileStream = File.Create(@"C:\local\path\file.zip"))
{
    ftpStream.CopyTo(fileStream);
}

如果你需要监控下载进度，你必须自己分块复制内容：

FtpWebRequest request =
    (FtpWebRequest)WebRequest.Create("ftp://ftp.example.com/remote/path/file.zip");
request.Credentials = new NetworkCredential("username", "password");
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);
        Console.WriteLine("Downloaded {0} bytes", fileStream.Position);
    }
}

有关 GUI 进度 (WinForms ProgressBar)，请参阅：
FtpWebRequest FTP download with ProgressBar

如果您想从远程文件夹下载所有文件，请参阅
C# Download all files and subdirectories through FTP。