Read file from FTP to memory in C#

Solution 1:

Here's a simple working example using your code to grab a file from the Microsoft public FTP servers:

WebClient request = new WebClient();
string url = "ftp://ftp.microsoft.com/developr/fortran/" +"README.TXT";
request.Credentials = new NetworkCredential("anonymous", "[email protected]");

try
{
  byte[] newFileData = request.DownloadData(url);
  string fileString = System.Text.Encoding.UTF8.GetString(newFileData);
  Console.WriteLine(fileString);
}
catch (WebException e)
{
  // Do something such as log error, but this is based on OP's original code
  // so for now we do nothing.
}

I reckon you're missing a slash on this line here in your code:

string url = FtpPath + FileName;

Perhaps between FtpPath and FileName ?

Solution 2:

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#.

Solution 3:

The code you have above is very simillar to another Stackoverlow example I found and used myself 2 days ago. Provided you set the URI, User and Password correctly, it will download the file and set the contents to FileString. I'm not sure what you mean by wanting to read the file without downloading it. This is not really an option.

If you want to look at file attributes (I see you mention "version"), you could use the code below to get all the file Name, Data, and Size from the FTP server without downloading the file.

Call GetFileInfo and pass in the file name (make sure you follow through the code to set the full FTP path, User and Password). This will give you back a FTPFileInfo object with a Name, Date and Size.

  public static FTPFileInfo GetFileInfo(string fileName)
        {
            var dirInfo = WordstockExport.GetFTPDirectoryDetails();
            var list = FTPFileInfo.Load(dirInfo);
            try
            {
                FTPFileInfo ftpFile = list.SingleOrDefault(f => f.FileName == fileName);
                return ftpFile;
            }
            catch { }
            return null;
        }
     class FTPFileInfo
        {
            private DateTime _FileDate;
            private long _FileSize;
            private string _FileName;

            public DateTime FileDate
            {
                get { return _FileDate; }
                set { _FileDate = value; }
            }
            public long FileSize
            {
                get { return _FileSize; }
                set { _FileSize = value; }
            }
            public string FileName
            {
                get { return _FileName; }
                set { _FileName = value; }
            }

            public FTPFileInfo() { }
            public static FTPFileInfo LoadFromLine(string line)
            {
                FTPFileInfo file = new FTPFileInfo();

                string[] ftpFileInfo = line.Split(" ".ToCharArray(), StringSplitOptions.RemoveEmptyEntries);
                file._FileDate = DateTime.Parse(ftpFileInfo[0] + " " + ftpFileInfo[1]);
                file._FileSize = long.Parse(ftpFileInfo[2]);
                file._FileName = ftpFileInfo[3];

                return file;

            }
            public static List<FTPFileInfo> Load(string listDirectoryDetails)
            {
                List<FTPFileInfo> files = new List<FTPFileInfo>();

                string[] lines = listDirectoryDetails.Split("\r\n".ToCharArray(), StringSplitOptions.RemoveEmptyEntries);
                foreach(var line in lines)
                    files.Add(LoadFromLine(line));

                return files;
            }

        }
       private static string GetFTPDirectoryDetails()
            {
                FtpWebRequest request = (FtpWebRequest)WebRequest.Create(App.Export_FTPPath);
                request.Method = WebRequestMethods.Ftp.ListDirectoryDetails;
                request.Credentials = new NetworkCredential(App.FTP_User, App.FTP_Password);
                FtpWebResponse response = (FtpWebResponse)request.GetResponse();

                Stream responseStream = response.GetResponseStream();
                StreamReader reader = new StreamReader(responseStream);
                string fileLines = reader.ReadToEnd();
                reader.Close();
                response.Close();

                return fileLines;
            }