NetworkCredential

using System;//from  ja v a 2s.  co  m
using System.Net;
using System.Text;

class MainClass
{
   public static void Main()
   {
      WebClient wc = new WebClient();

      NetworkCredential nc = new NetworkCredential("usr", "mypassword");

      wc.Credentials = nc;

      byte[] response = wc.DownloadData("http://localhost/testlogin");
      Console.WriteLine(Encoding.ASCII.GetString(response));
   }
}

using System;//from ja v  a 2  s.c  o  m
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");
    }
}