.Net how to refresh token for DropBox?

Question

I making .Net MVC application that use DropBox as file storage. I successfuly made uploading files to DropBox from my application but I get short time life token that expires evry 4 hour. I need some code examples how to refresh token.

 OAuth2Response CodeResponse = await DropboxOAuth2Helper.ProcessCodeFlowAsync(result.Data.Code, AppKey, AppSecret, RedirectUri);


                Settings.AccessToken = CodeResponse.AccessToken;
                Settings.RefreshToken = CodeResponse.RefreshToken;

Answer 1

The First-step is open this url on your browser:

https://www.dropbox.com/oauth2/authorize?client_id=<APP_KEY>&token_access_type=offline&response_type=code

Save this string code.

Next-step: You will create a simple project console to read the refresh token:

    using System;
    using System.Collections.Generic;
    using System.Net.Http;
    using System.Threading.Tasks;
    using Newtonsoft.Json;
    
    class Program
    {
        private const string AppKey = "YOUR APP KEY"; 
        private const string AppSecret = "APP SECRET"; 
        private const string AccessCode = "CODE WHATYOU RECEIVED"; 
        private static string RefreshToken = "REPEATE-EXPIRED-TOKEN"; 
        private static string AccessToken = "YOUR-EXPIRED-TOKEN"; 
        static async Task Main(string[] args)
        {
            await GetRefreshToken();
            await RefreshAccessToken();
        }
    
        private static async Task GetRefreshToken()
        {
            try
            {
                var base64Authorization = Convert.ToBase64String(System.Text.Encoding.UTF8.GetBytes($"{AppKey}:{AppSecret}"));
                using (var client = new HttpClient())
                {
                    var requestBody = new FormUrlEncodedContent(new[]
                    {
                        new KeyValuePair<string, string>("code", AccessCode),
                        new KeyValuePair<string, string>("grant_type", "authorization_code"),
                    });
    
                    client.DefaultRequestHeaders.Add("Authorization", $"Basic {base64Authorization}");
    
                    var response = await client.PostAsync("https://api.dropbox.com/oauth2/token", requestBody);
                    var responseString = await response.Content.ReadAsStringAsync();
    
                    Console.WriteLine("Refresh Token Response: " + responseString);
                    if (response.IsSuccessStatusCode)
                    {
                        var tokenResponse = JsonConvert.DeserializeObject<DropboxTokenResponse>(responseString);
                        RefreshToken = tokenResponse.RefreshToken; // Atualize o refresh token
                        Console.WriteLine("🚀 ~ getRefreshToken ~ REFRESH_TOKEN: " + RefreshToken);
                    }
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine("Error getting refresh token: " + ex.Message);
            }
        }
    
        private static async Task RefreshAccessToken()
        {
            try
            {
                var base64Authorization = Convert.ToBase64String(System.Text.Encoding.UTF8.GetBytes($"{AppKey}:{AppSecret}"));
                using (var client = new HttpClient())
                {
                    var requestBody = new FormUrlEncodedContent(new[]
                    {
                        new KeyValuePair<string, string>("refresh_token", RefreshToken),
                        new KeyValuePair<string, string>("grant_type", "refresh_token"),
                    });
    
                    client.DefaultRequestHeaders.Add("Authorization", $"Basic {base64Authorization}");
    
                    var response = await client.PostAsync("https://api.dropbox.com/oauth2/token", requestBody);
                    var responseString = await response.Content.ReadAsStringAsync();
    
                    Console.WriteLine("Access Token Response: " + responseString);
                    if (response.IsSuccessStatusCode)
                    {
                        var tokenResponse = JsonConvert.DeserializeObject<DropboxTokenResponse>(responseString);
                        AccessToken = tokenResponse.AccessToken; // Atualize o access token
                        Console.WriteLine("🚀 ~ refreshAccessToken ~ ACCESS_TOKEN: " + AccessToken);
                    }
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine("Error refreshing access token: " + ex.Message);
            }
        }
    
        private class DropboxTokenResponse
        {
            [JsonProperty("access_token")]
            public string AccessToken { get; set; }
    
            [JsonProperty("refresh_token")]
            public string RefreshToken { get; set; }
    
            [JsonProperty("expires_in")]
            public int ExpiresIn { get; set; }
        }
    }

The last step, you have to create a HTTP Client Dropbox with that configuration:

public async Task<IActionResult> Index()
{
    try
    {
        DropboxClientConfig config = new();
        
        List<Metadata> Pdfs = new List<Metadata>();

        using (var _client = new DropboxClient(_configuration["DropboxToken"], _configuration["DropboxRefreshToken"], _configuration["DropboxAppKey"], _configuration["DropboxAppSecret"], config))
        {
            var isRefresh = await _client.RefreshAccessToken(null);

            var listItems = await _client.Files.ListFolderAsync(_configuration["DropboxFolder"]);
            foreach (var item in listItems.Entries)
            {
                if (item.IsFile)
                {
                    Pdfs.Add(item);
                }
            }
        }
        return View(Pdfs);
    }
    catch(Exception e)
    {
        return View("Erro", "");
    }
   
}