OAuth2 1.0.0

OAuth2

OAuth2 is a library for user authentication using third-party services (OAuth/OAuth2 protocol) such as Google, Facebook and so on.

Standard Flow

1. Generate a login URL and render a page with it
2. Define a callback endpoint that the third-party service redirects to after successful authentication
3. Retrieve user info on callback from the third-party service

Installation

Install the OAuth2 NuGet package:

dotnet add package OAuth2

Usage Example (ASP.NET Core Minimal API)

using System.Collections.Specialized;
using OAuth2.Client.Impl;
using OAuth2.Configuration;
using OAuth2.Infrastructure;

var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();

// Helper to create a GoogleClient instance
GoogleClient CreateGoogleClient()
{
    return new GoogleClient(new RequestFactory(), new ClientConfiguration
    {
        ClientId = app.Configuration["Google:ClientId"]!,
        ClientSecret = app.Configuration["Google:ClientSecret"]!,
        RedirectUri = "https://localhost:5001/auth/google/callback",
        Scope = "profile email"
    });
}

// Step 1: Redirect the user to Google's login page
app.MapGet("/auth/google", async () =>
{
    var client = CreateGoogleClient();
    var loginUri = await client.GetLoginLinkUriAsync();
    return Results.Redirect(loginUri);
});

// Step 2: Handle the callback after authentication
app.MapGet("/auth/google/callback", async (HttpContext context) =>
{
    var code = context.Request.Query["code"].ToString();
    if (string.IsNullOrEmpty(code))
        return Results.BadRequest("Missing authorization code.");

    var client = CreateGoogleClient();
    var userInfo = await client.GetUserInfoAsync(new NameValueCollection { { "code", code } });

    return Results.Ok(new
    {
        userInfo.Id,
        userInfo.FirstName,
        userInfo.LastName,
        userInfo.Email,
        AvatarUri = userInfo.AvatarUri?.ToString()
    });
});

app.Run();

Supported Services

Removed providers (Instagram, Xing): These providers' APIs have been retired or shut down. The client classes have been removed.

• Instagram: Basic Display API shut down Dec 4, 2024. There is no consumer OAuth replacement — the remaining Instagram APIs are business/creator-only. Announcement
• Xing: OAuth 1.0a REST API discontinued. dev.xing.com only hosts plugins.

Renamed providers: TwitterClient → XClient (Twitter rebranded to X). The old class name is preserved as an obsolete derived class that produces a compiler error directing users to the new name.

Legacy (Working): WindowsLiveClient — Microsoft officially retired the Live SDK in Nov 2018 but the endpoints continue to function in production. Confirmed working in Exceptionless. For new integrations, use MicrosoftClient (Microsoft Identity Platform v2.0 + Graph). User IDs differ between the two platforms.

Deprecated providers:

• Foursquare: v2 consumer OAuth API deprecated. The replacement Places API v3 uses API keys, not OAuth.
• VSTS (Azure DevOps): Azure DevOps OAuth stopped accepting new app registrations in April 2025 and is scheduled for full retirement in 2026. Use MicrosoftClient with Microsoft Entra ID OAuth instead

Goals

• Simplicity in usage — even a newcomer can call a couple of methods and receive the expected result
• Well-documented, testable, and tested code
• Flexible, transparent, and easily understandable design
• Support for both fine-grained control and simple plug-and-play usage

Dependencies

• RestSharp

Contributors

• Constantin Titarenko (started development, defined library structure, released initial version)
• Blake Niemyjski (helped a lot to maintain the project, currently (since 2015) — top maintainer)
• Andriy Somak (helped with improvements on configuration and extending the list of supported services)
• Sascha Kiefer (simplified extending the library with own provider implementations, added GitHub client)
• Krisztián Pócza (added LinkedIn (OAuth 2) client)
• Jamie Houston (added a Todoist client)
• Sasidhar Kasturi (added Uber, Spotify, Yahoo)
• Jamie Dalton (added Visual Studio Team Services)

Acknowledgements

Many thanks to JetBrains company for providing free OSS licenses for ReSharper and dotCover - these tools allow us to work on this project with pleasure!

Also we glad to have opportunity to use free Teamcity CI server provided by Codebetter.com and JetBrains - many thanks for supporting OSS!

OAuth2 optimization would never be so simple without YourKit .NET profiler! We appreciate kind support of open source projects by YourKit LLC - the creator of innovative and intelligent tools for profiling .NET YourKit .NET Profiler and Java applications YourKit Java Profiler.

License

The MIT License (MIT) Copyright (c) 2012-2013 Constantin Titarenko, Andrew Semack and others

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.