public class HomeController : Controller
{
    IMondoAuthorizationClient _authClient = new MondoAuthorizationClient(YOUR_CLIENT_ID, YOUR_CLIENT_SECRET);

    [HttpGet]
    public ActionResult Login()
    {
        // an unguessable random string which is used to protect against cross-site request forgery attacks
        string state = ...; 

        // the URL the user should be redirected back to following a successful Mondo login
        string redirectUrl = Url.Action("OAuthCallback", "Home", null, Request.Url.Scheme);

        string mondoLoginPageUrl = _authClient.GetAuthorizeUrl(state, redirectUrl);

        // 1. Send user to Mondo's login page
        return Redirect(mondoLoginPageUrl);
    }

    [HttpGet]
    public async Task<ActionResult> OAuthCallback(string code, string state)
    {
        // confirm the redirect url was valid
        string redirectUrl = Url.Action("OAuthCallback", "Home", null, Request.Url.Scheme);
    
        // 2. Exchange authorization code for access token
        AccessToken accessToken = await _authClient.GetAccessTokenAsync(code, redirectUrl);
            
        // 3. Begin fetching accounts, transactions etc
        using (var client = new MondoClient(accessToken.Value))
        {
            IList<Account> accounts = await client.GetAccountsAsync();

            // ... etc
        }
    }
} 

// create feed item
var parameters = new Dictionary<string, string>
{
    {"title", "My custom item"},
    {"image_url", "www.example.com/image.png"},
    {"background_color", "#FCF1EE"},
    {"body_color", "#FCF1EE"},
    {"title_color", "#333"},
    {"body", "Some body text to display"},
};

await client.CreateFeedItemAsync("myaccountid", "basic", parameters, "https://www.example.com/a_page_to_open_on_tap.html");

// list webhooks
IList<Transaction> webhooks = await client.ListTransactionsAsync("myaccountid");

// register new webhook
Webhook webhook = await client.RegisterWebhookAsync("myaccountid", "http://example.com/webhook");

// delete webhook
await client.DeleteWebhookAsync(webhook.Id);

// upload and register an attachment
using (var stream = File.OpenRead(@"C:\example.png"))
{
    Attachment attachment = await client.UploadAttachmentAsync("example.png", "image/png", transaction.Id, stream);
}

// register an attachment that is already hosted somewhere
Attachment attachment = await client.RegisterAttachmentAsync(transaction.Id, "http://example.com/pic.png", "image/png");

// remove attachment
await client.DeregisterAttachmentAsync(attachment.Id);

private _refreshDisposable = new SerialDisposable();

// schedule automatic token refresh
private void EnqueueRefresh()
{
     DateTimeOffset refreshTime = DateTimeOffset.UtcNow.AddSeconds(_accessToken.ExpiresIn);

    _refreshDisposable.Disposable = Scheduler.Default.Schedule(refreshTime, async () =>
    {
        await _authClient.RefreshAccessTokenAsync(_accessToken.RefreshToken);
        EnqueueRefresh();
    });
}