C# Download all files and subdirectories through FTP

The FtpWebRequest does not have any explicit support for recursive file operations (including downloads). You have to implement the recursion yourself:

List the remote directory
Iterate the entries, downloading files and recursing into subdirectories (listing them again, etc.)

Tricky part is to identify files from subdirectories. There's no way to do that in a portable way with the FtpWebRequest. The FtpWebRequest unfortunately does not support the MLSD command, which is the only portable way to retrieve directory listing with file attributes in FTP protocol. See also Checking if object on FTP server is file or directory.

Your options are:

Do an operation on a file name that is certain to fail for file and succeeds for directories (or vice versa). I.e. you can try to download the "name". If that succeeds, it's a file, if that fails, it's a directory.
You may be lucky and in your specific case, you can tell a file from a directory by a file name (i.e. all your files have an extension, while subdirectories do not)
You use a long directory listing (LIST command = ListDirectoryDetails method) and try to parse a server-specific listing. Many FTP servers use *nix-style listing, where you identify a directory by the d at the very beginning of the entry. But many servers use a different format. The following example uses this approach (assuming the *nix format)

void DownloadFtpDirectory(
    string url, NetworkCredential credentials, string localPath)
{
    FtpWebRequest listRequest = (FtpWebRequest)WebRequest.Create(url);
    listRequest.Method = WebRequestMethods.Ftp.ListDirectoryDetails;
    listRequest.Credentials = credentials;

    List<string> lines = new List<string>();

    using (var listResponse = (FtpWebResponse)listRequest.GetResponse())
    using (Stream listStream = listResponse.GetResponseStream())
    using (var listReader = new StreamReader(listStream))
    {
        while (!listReader.EndOfStream)
        {
            lines.Add(listReader.ReadLine());
        }
    }

    foreach (string line in lines)
    {
        string[] tokens =
            line.Split(new[] { ' ' }, 9, StringSplitOptions.RemoveEmptyEntries);
        string name = tokens[8];
        string permissions = tokens[0];

        string localFilePath = Path.Combine(localPath, name);
        string fileUrl = url + name;

        if (permissions[0] == 'd')
        {
            if (!Directory.Exists(localFilePath))
            {
                Directory.CreateDirectory(localFilePath);
            }

            DownloadFtpDirectory(fileUrl + "/", credentials, localFilePath);
        }
        else
        {
            FtpWebRequest downloadRequest =
                (FtpWebRequest)WebRequest.Create(fileUrl);
            downloadRequest.Method = WebRequestMethods.Ftp.DownloadFile;
            downloadRequest.Credentials = credentials;

            using (FtpWebResponse downloadResponse =
                      (FtpWebResponse)downloadRequest.GetResponse())
            using (Stream sourceStream = downloadResponse.GetResponseStream())
            using (Stream targetStream = File.Create(localFilePath))
            {
                byte[] buffer = new byte[10240];
                int read;
                while ((read = sourceStream.Read(buffer, 0, buffer.Length)) > 0)
                {
                    targetStream.Write(buffer, 0, read);
                }
            }
        }
    }
}

Use the function like:

NetworkCredential credentials = new NetworkCredential("user", "mypassword");
string url = "ftp://ftp.example.com/directory/to/download/";
DownloadFtpDirectory(url, credentials, @"C:\target\directory");

If you want to avoid troubles with parsing the server-specific directory listing formats, use a 3rd party library that supports the MLSD command and/or parsing various LIST listing formats; and recursive downloads.

For example with WinSCP .NET assembly you can download whole directory with a single call to the Session.GetFiles:

// Setup session options
SessionOptions sessionOptions = new SessionOptions
{
    Protocol = Protocol.Ftp,
    HostName = "ftp.example.com",
    UserName = "user",
    Password = "mypassword",
};

using (Session session = new Session())
{
    // Connect
    session.Open(sessionOptions);

    // Download files
    session.GetFiles("/directory/to/download/*", @"C:\target\directory\*").Check();
}

Internally, WinSCP uses the MLSD command, if supported by the server. If not, it uses the LIST command and supports dozens of different listing formats.

The Session.GetFiles method is recursive by default.

(I'm the author of WinSCP)

C# Download all files and subdirectories through FTP

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