OAuthController.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using BoxOAuth.Models;
using Microsoft.Extensions.Options;
using Box.V2.Config;
using Box.V2;
using Box.V2.Auth;

namespace BoxOAuth.Controllers
{
    public class OAuthController : Controller
    {
        const string BOX_AUTH_URL = "https://account.box.com/api/oauth2/authorize";
        private BoxAppSettings _boxSettings { get; set; }
        private BoxClient _boxClient { get; set; }
        private BoxConfig _boxConfig { get; set; }
        public OAuthSession BoxAuthenicatedSession { get; set; }
        public OAuthController(IOptions<BoxAppSettings> settings)
        {
            this._boxSettings = settings.Value;
            this._boxConfig = new BoxConfig(this._boxSettings.ClientId,
                this._boxSettings.ClientSecret, 
                new Uri(this._boxSettings.RedirectUrl));
            this._boxClient = new BoxClient(this._boxConfig);
        }

        [Route("start")]
        public IActionResult Start()
        {
            var clientIdParam = $"client_id={this._boxSettings.ClientId}";
            var redirectUrlParam = $"redirect_uri={this._boxSettings.RedirectUrl}";
            return Redirect(
                $"{BOX_AUTH_URL}?response_type=code&{clientIdParam}&{redirectUrlParam}");
        }

        [Route("return")]
        public async Task<IActionResult> Return()
        {
            var code = Request.Query["code"];
            this.BoxAuthenicatedSession = await this._boxClient.Auth.AuthenticateAsync(code);
            var client = new BoxClient(this._boxConfig, this.BoxAuthenicatedSession);
            var user = await client.UsersManager.GetCurrentUserInformationAsync();
            System.Console.WriteLine(user.Name);
            return Content($"Hello, {user.Name}");
        }
    }
}