How to download a file from Google Drive in c#

using Google.Apis.Authentication;
using Google.Apis.Drive.v2;
using Google.Apis.Drive.v2.Data;

using System.Net;

public class MyClass {

  // ...

  /// <summary>
  /// Download a file and return a string with its content.
  /// </summary>
  /// <param name="authenticator">
  /// Authenticator responsible for creating authorized web requests.
  /// </param>
  /// <param name="file">Drive File instance.</param>
  /// <returns>File's content if successful, null otherwise.</returns>
  public static System.IO.Stream DownloadFile(
      IAuthenticator authenticator, File file) {
    if (!String.IsNullOrEmpty(file.DownloadUrl)) {
      try {
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(
            new Uri(file.DownloadUrl));
        authenticator.ApplyAuthenticationToRequest(request);
        HttpWebResponse response = (HttpWebResponse) request.GetResponse();
        if (response.StatusCode == HttpStatusCode.OK) {
          return response.GetResponseStream();
        } else {
          Console.WriteLine(
              "An error occurred: " + response.StatusDescription);
          return null;
        }
      } catch (Exception e) {
        Console.WriteLine("An error occurred: " + e.Message);
        return null;
      }
    } else {
      // The file doesn't have any content stored on Drive.
      return null;
    }
  }
}