Read file from FTP to memory in C#

Question

I want to read a file from a FTP server without downloading it to a local file. I wrote a function but it does not work:

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Answer 1

Small binary file

If the file is small, the easiest way is using WebClient.DownloadData:

WebClient client = new WebClient();
string url = "ftp://ftp.example.com/remote/path/file.zip";
client.Credentials = new NetworkCredential("username", "password");
byte[] contents = client.DownloadData(url);

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Small text file

If the small file is a text file, use WebClient.DownloadString:

string contents = client.DownloadString(url);

It assumes that the file contents is in UTF-8 encoding (a plain ASCII file will do too). If you need to use a different encoding, use WebClient.Encoding property.

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Large binary file

If the file is large, so that you need to process it in chunks, instead of loading it to memory whole, use FtpWebRequest:

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 stream = request.GetResponse().GetResponseStream())
{
    byte[] buffer = new byte[10240];
    int read;
    while ((read = stream.Read(buffer, 0, buffer.Length)) > 0)
    {
        // process the chunk in "buffer"
    }
}

---

Large text file

If the large file is a text file and you want to process it by lines, instead of by chunks of a fixed size, use StreamReader:

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

using (Stream stream = request.GetResponse().GetResponseStream())
using (StreamReader reader = new StreamReader(stream))
{
    while (!reader.EndOfStream)
    {
        string line = reader.ReadLine();
        // process the line
        Console.WriteLine(line);
    }
}

Again, this assumes UTF-8 encoding. If you want to use another encoding, use an overload of StreamReader constructor that takes also Encoding.