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);
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.
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"
}
}
You can also simplify the code by using WebClient.OpenRead.
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.
As previously, you can simplify the code by using WebClient.OpenRead.
Stream interface
Though, in many cases, you will want to use the downloaded data in some API that uses the Stream interface. In that case, instead of using any of the solutions above, directly use the stream returned by request.GetResponse().GetResponseStream() or WebClient.OpenRead in the API.
For an example, see Transferring files from FTP directly to Azure Blob storage in C#.
