Kenny Hsu's Blog: Download a single file from the remote FTP site (Updated)

Three approaches to download a file from FTP server: WebRequest, FtpWebRequest, and WebClient. Here are the examples:
url = "ftp://xxx.xxx.xxx.xxx/test.txt"

WebRequest

using System.Net;  //don't forget this

public string DownloadFile(string url, string username, string pw)
{
    string strResult = "";
    try
    {
        //According to the rule below, we should pass Uri object instead of string.
        //http://msdn.microsoft.com/en-us/library/ms182360.aspx
        WebRequest oRequest = HttpWebRequest.Create(new Uri(url));
        oRequest.Credentials = new NetworkCredential(username, pw);
        WebResponse oResponse = oRequest.GetResponse();

        using (StreamReader sr = new StreamReader(oResponse.GetResponseStream()))
        {
            strResult = sr.ReadToEnd();
            sr.Close();
        }

        oRequest = null;
        oResponse = null;
    }
    catch (WebException wex)
    {
        //your error handling here
    }
    return strResult;
}

MS recommend us to use the FtpWebRequest class if the file is on a FTP server.

public string DownloadFile(string url, string username, string pw)
{
    string strResult = "";
    try
    {
        FtpWebRequest oFtpReq = (FtpWebRequest)WebRequest.Create(new Uri(url));
        oFtpReq.Method = WebRequestMethods.Ftp.DownloadFile;

        //set the username & password
        oFtpReq.Credentials = new NetworkCredential(username, pw);

        //There is no need to use the binary mode for a simple and small text file
        oFtpReq.UseBinary = false;

        //Add this if you get an error like this:
        //The remote server returned an error: 227 Entering Passive Mode
        oFtpReq.UsePassive = false;
        FtpWebResponse oFtpResp = (FtpWebResponse)oFtpReq.GetResponse();

        using (StreamReader sr = new StreamReader(oFtpResp.GetResponseStream()))
        {
            strResult = sr.ReadToEnd();
            sr.Close();
        }

        oFtpResp.Close();
        oFtpReq = null;
        oFtpResp = null;
    }
    catch (WebException wex)
    {
        //your error handling here
    }
    return strResult;
}

Basically, using WebClient is the same with using WebRequest.

public string DownloadFile3(string url, string username, string pw)
{
    string strResult = "";
    try
    {
        using (WebClient oWebClient = new WebClient())
        {
            oWebClient.Credentials = new NetworkCredential(username, pw);
            strResult = oWebClient.DownloadString(new Uri(url));
        }
    }
    catch (WebException wex)
    {
        //your error handling here
    }
    return strResult;
}