You can supply a username and password to an HTTP or FTP site by creating a NetworkCredential object and assigning it to the Credentials property of WebClient or WebRequest:
using System;
using System.Net;
using System.IO;
using System.Linq;
using System.Text;
class Program
{
static void Main()
{
WebClient wc = new WebClient();
wc.Proxy = null;
wc.BaseAddress = "ftp://ftp.abc.com";
// Authenticate, then upload and download a file to the FTP server.
// The same approach also works for HTTP and HTTPS.
string username = "nutshell";
string password = "yourValue";
wc.Credentials = new NetworkCredential(username, password);
wc.DownloadFile("guestbook.txt", "guestbook.txt");
string data = "Hello from " + Environment.UserName + "!\r\n";
File.AppendAllText("guestbook.txt", data);
wc.UploadFile("guestbook.txt", "guestbook.txt");
}
}