WebClient Download Sample

// Specify the URL of the file to download
const string url = @"http://www.datavoila.com/download/datavoila-setup.exe";

// Specify the path of the file to write to
const string outputFile = @"C:\Downloads\datavoila-setup.exe";

// Create output directory (if necessary)
string outputFolder = Path.GetDirectoryName(outputFile);
if (!Directory.Exists(outputFolder))
    Directory.CreateDirectory(outputFolder);

WebClient webClient = new WebClient();

// Optional: Specify proxy server settings
//webClient.Proxy = new WebProxy("http://proxyserver:80/", true);
//webClient.Proxy.Credentials = new NetworkCredential("user", "password");

// Optional: Add "User-Agent" header
//webClient.Headers["User-Agent"] = "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1)";

// Download the file and write it to disk
using (Stream webStream = webClient.OpenRead(url))
using (FileStream fileStream = new FileStream(outputFile, FileMode.Create))
{
    var buffer = new byte[32768];
    int bytesRead;
    Int64 bytesReadComplete = 0;  // Use Int64 for files larger than 2 gb
   
    // Get the size of the file to download
    Int64 bytesTotal = Convert.ToInt64(webClient.ResponseHeaders["Content-Length"]);
   
    // Start a new StartWatch for measuring download time
    Stopwatch sw = Stopwatch.StartNew();
   
    // Download file in chunks
    while ((bytesRead = webStream.Read(buffer, 0, buffer.Length)) > 0)
    {
        bytesReadComplete += bytesRead;
        fileStream.Write(buffer, 0, bytesRead);
       
        // Output current progress to the "Output" editor
        StringBuilder sb = new StringBuilder();
        sb.AppendLine(String.Format("Progress: {0:0%}", (double)bytesReadComplete / bytesTotal));
        sb.AppendLine(String.Format("Downloaded: {0:0,0} Bytes", bytesReadComplete));
        sb.AppendLine(String.Format("Time Elapsed: {0:0,.00}s", sw.ElapsedMilliseconds));
        sb.AppendLine(String.Format("Average Speed: {0:0,0} KB/s", sw.ElapsedMilliseconds > 0 ? bytesReadComplete / sw.ElapsedMilliseconds / 1.024 : 0));
        Output.Text = sb.ToString();
    }
   
    sw.Stop();
}

출처 : http://www.datavoila.com/projects/internet/download-file-using-webclient-class.html