How can I get file from FTP (using C#)?

Take a look at How to: Download Files with FTP or downloading all files in directory ftp and c#

 // Get the object used to communicate with the server.
            FtpWebRequest request = (FtpWebRequest)WebRequest.Create("ftp://www.contoso.com/test.htm");
            request.Method = WebRequestMethods.Ftp.DownloadFile;

            // This example assumes the FTP site uses anonymous logon.
            request.Credentials = new NetworkCredential ("anonymous","[email protected]");

            FtpWebResponse response = (FtpWebResponse)request.GetResponse();

            Stream responseStream = response.GetResponseStream();
            StreamReader reader = new StreamReader(responseStream);
            Console.WriteLine(reader.ReadToEnd());

            Console.WriteLine("Download Complete, status {0}", response.StatusDescription);

            reader.Close();
            reader.Dispose();
            response.Close();  

Edit If you want to rename file on FTP Server take a look at this Stackoverflow question

Easiest way

The most trivial way to download a binary file from an FTP server using .NET framework is using WebClient.DownloadFile.

It takes an URL to the source remote file and a path to the target local file. So you can use a different name for the local file, if you need that.

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");

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Advanced options

If you need greater control, that WebClient does not offer (like TLS/SSL encryption, ASCII mode, active mode, etc), use FtpWebRequest. Easy way is to just copy an FTP response stream to FileStream using Stream.CopyTo:

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);
}

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Progress monitoring

If you need to monitor a download progress, you have to copy the contents by chunks yourself:

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);
    }
}

For GUI progress (WinForms ProgressBar), see:
FtpWebRequest FTP download with ProgressBar

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Downloading folder

If you want to download all files from a remote folder, see
C# Download all files and subdirectories through FTP.