githubdownload.cs

using System.Net;
using Octokit;

var client = new GitHubClient(new ProductHeaderValue("xxx"));
var releases = client.Repository.Release.GetAll("chuongmep", "revitaddinmanager");
var latest = releases.Result.First();
Console.WriteLine(
    "The latest release is tagged at {0} and is named {1}", 
    latest.TagName, 
    latest.Name);
var webClient = new WebClient();
//webClient.Headers.Add("user-agent", "Anything");
// webClient.Headers.Add("authorization", "token " + GitHubToken);
string browserDownloadUrl = latest.Assets[0].BrowserDownloadUrl;
string name = latest.Assets[0].Name;
Console.WriteLine("What is new:");
Console.WriteLine(latest.Body);
webClient.DownloadFileAsync(new Uri(browserDownloadUrl), name);
Console.WriteLine("Downloaded {0} to {1}", browserDownloadUrl, name);
Console.ReadKey();