For our new friends

Every app needs authentication and authorization. Logto is an Auth0 alternative designed for modern apps and SaaS products.

In this article, we will go through the steps to quickly build the GitHub sign-in experience (user authentication) with .NET Core (Blazor Server) and  Logto.

Prerequisites

• A running Logto instance. Check out the get started page if you don't have one.
• Basic knowledge of .NET Core (Blazor Server).
• A usable GitHub account.

Create an application in Logto

In you browser, open a new tab and enter the link of Logto Admin Console.

Once the page is loaded, in the "Get Started" section click the View all link to open the application framework list page.

Choose your application type

In the opening modal, scroll to the "Traditional web" section or filter all the available " Traditional web" frameworks using the quick filter checkboxes on the left.

Click the ".NET Core (Blazor Server)" framework card to start creating your application.

Enter application name

Enter the application name, e.g., "Bookstore," and click "Create Application."

🎉 Ta-da! You just created your first application in Logto. You'll see a congrats page which includes a detailed integration guide. Follow the guide to see what the experience will be in your application.

Integrate Logto SDK

tip

• The following demonstration is built on .NET Core 8.0. The SDK is compatible with .NET 6.0 or higher.
• The .NET Core sample projects are available in the GitHub repository.

Installation

Add the NuGet package to your project:

dotnet add package Logto.AspNetCore.Authentication

Add Logto authentication

Open Startup.cs (or Program.cs) and add the following code to register Logto authentication services:

using Logto.AspNetCore.Authentication;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddLogtoAuthentication(options =>
{
  options.Endpoint = builder.Configuration["Logto:Endpoint"]!;
  options.AppId = builder.Configuration["Logto:AppId"]!;
  options.AppSecret = builder.Configuration["Logto:AppSecret"];
});

The AddLogtoAuthentication method will do the following things:

• Set the default authentication scheme to LogtoDefaults.CookieScheme.
• Set the default challenge scheme to LogtoDefaults.AuthenticationScheme.
• Set the default sign-out scheme to LogtoDefaults.AuthenticationScheme.
• Add cookie and OpenID Connect authentication handlers to the authentication scheme.

Add sign-in redirect URI

Add the following URI to the Redirect URIs list in the Logto application details page:

http://<your-web-app-uri>/Callback

Note this is different from the redirect URI we'll use later in AuthenticationProperties:

// Just for reference, we will demonstrate how to use it later
new AuthenticationProperties
{
  RedirectUri = "/"
};

The RedirectUri property is used to redirect the user back to your web application after authentication. Note it is different from the redirect URI you configured in the Logto application details page:

1. The redirect URI in the Logto application details page is the URI that Logto will redirect the user back to after the user has signed in.
2. The RedirectUri property is the URI that will be redirected to after necessary actions have been taken in the Logto authentication middleware.

The order of the actions is 1 -> 2. For clarity, let's call the redirect URI in the Logto application details page the Logto redirect URI and the RedirectUri property the application redirect URI.

The Logto redirect URI has a default value of /Callback, which you can leave it as is if there's no special requirement. If you want to change it, you can set the CallbackPath property for LogtoOptions:

builder.Services.AddLogtoAuthentication(options =>
{
  // Other configurations...
  options.CallbackPath = "/SomeOtherCallbackPath";
});

Remember to update the value in the Logto application details page accordingly.

note

No need to set the application redirect URI in the Logto application details page.

Add sign-out redirect URI

Add the following URI to the Post sign-out redirect URIs list in the Logto application details page:

http://<your-web-app-uri>/SignedOutCallback

Note this is different from the redirect URI we'll use later in AuthenticationProperties:

// Just for reference, we will demonstrate how to use it later
new AuthenticationProperties
{
  RedirectUri = "/"
};

The RedirectUri property is used to redirect the user back to your web application after sign-out. Note it is different from the post sign-out redirect URI you configured in the Logto application details page:

1. The post sign-out redirect URI in the Logto application details page is the URI that Logto will redirect the user back to after the user has signed out.
2. The RedirectUri property is the URI that will be redirected to after necessary actions have been taken in the Logto authentication middleware.

The order of the actions is 1 -> 2. For clarity, let's call the post sign-out redirect URI in the Logto application details page the Logto post sign-out redirect URI and the RedirectUri property the application post sign-out redirect URI.

The Logto post sign-out redirect URI has a default value of /SignedOutCallback, which you can leave it as is if there's no special requirement. If you want to change it, you can set the SignedOutCallbackPath property for LogtoOptions:

builder.Services.AddLogtoAuthentication(options =>
{
  // Other configurations...
  options.SignedOutCallbackPath = "/SomeOtherSignedOutCallbackPath";
});

Remember to update the value in the Logto application details page accordingly.

note

No need to set the application post sign-out redirect URI in the Logto application details page.

Add routes

Since Blazor Server uses SignalR to communicate between the server and the client, this means methods that directly manipulate the HTTP context (like issuing challenges or redirects) don't work as expected when called from a Blazor component.

To make it right, we need to explicitly add two endpoints for sign-in and sign-out redirects:

app.MapGet("/SignIn", async context =>
{
    if (!(context.User?.Identity?.IsAuthenticated ?? false))
    {
        await context.ChallengeAsync(new AuthenticationProperties { RedirectUri = "/" });
    } else {
        context.Response.Redirect("/");
    }
});

app.MapGet("/SignOut", async context =>
{
    if (context.User?.Identity?.IsAuthenticated ?? false)
    {
        await context.SignOutAsync(new AuthenticationProperties { RedirectUri = "/" });
    } else {
        context.Response.Redirect("/");
    }
});

Now we can redirect to these endpoints to trigger sign-in and sign-out.

Implement sign-in/sign-out buttons

In the Razor component, add the following code:

@using Microsoft.AspNetCore.Components.Authorization
@using System.Security.Claims
@inject AuthenticationStateProvider AuthenticationStateProvider
@inject NavigationManager NavigationManager

@* ... *@

<p>Is authenticated: @User.Identity?.IsAuthenticated</p>
@if (User.Identity?.IsAuthenticated == true)
{
    <button @onclick="SignOut">Sign out</button>
}
else
{
    <button @onclick="SignIn">Sign in</button>
}

@* ... *@

@code {
    private ClaimsPrincipal? User { get; set; }

    protected override async Task OnInitializedAsync()
    {
        var authState = await AuthenticationStateProvider.GetAuthenticationStateAsync();
        User = authState.User;
    }

    private void SignIn()
    {
        NavigationManager.NavigateTo("/SignIn", forceLoad: true);
    }

    private void SignOut()
    {
        NavigationManager.NavigateTo("/SignOut", forceLoad: true);
    }
}

Explanation:

• The injected AuthenticationStateProvider is used to get the current user's authentication state, and populate the User property.
• The SignIn and SignOut methods are used to redirect the user to the sign-in and sign-out endpoints respectively. Since the nature of Blazor Server, we need to use NavigationManager with force load to trigger the redirection.

The page will show the "Sign in" button if the user is not authenticated, and show the "Sign out" button if the user is authenticated.

The <AuthorizeView /> component

Alternatively, you can use the AuthorizeView component to conditionally render content based on the user's authentication state. This component is useful when you want to show different content to authenticated and unauthenticated users.

In your Razor component, add the following code:

@using Microsoft.AspNetCore.Components.Authorization

@* ... *@

<AuthorizeView>
    <Authorized>
        <p>Name: @User?.Identity?.Name</p>
        @* Content for authenticated users *@
    </Authorized>
    <NotAuthorized>
        @* Content for unauthenticated users *@
    </NotAuthorized>
</AuthorizeView>

@* ... *@

The AuthorizeView component requires a cascading parameter of type Task<AuthenticationState>. A direct way to get this parameter is to add the <CascadingAuthenticationState> component. However, due to the nature of Blazor Server, we cannot simply add the component to the layout or the root component (it may not work as expected). Instead, we can add the following code to the builder (Program.cs or Startup.cs) to provide the cascading parameter:

builder.Services.AddCascadingAuthenticationState();

Then you can use the AuthorizeView component in every component that needs it.

Test your integration

Open your .NET Core (Blazor Server) app to test if the integration works. When you click the "Sign In" button, the page should be redirected to a Logto sign-in page, and you should be able to create a new account by entering username and password and complete the sign-in process.

Add GitHub connector

To add a social connector, go to the "Connector" tab in the Admin Console, then click on "Social Connectors". From there, click "Add Social Connector".

In the openning modal, select "GitHub" and click "Next".

On the next page, you will see a two-column layout with the README content on the left and configuration on the right.

Feel free to follow the README file in place or read the following section to complete the configuration process. If you follow the in-place guide, you can skip the next section.

Set up GitHub OAuth app

Sign in with GitHub account

Go to the GitHub website and sign in with your GitHub account. You may register a new account if you don't have one.

Create and configure OAuth app

Follow the creating an OAuth App guide, and register a new application.

Name your new OAuth application in Application name and fill up Homepage URL of the app. You can leave Application description field blank and customize Authorization callback URL as ${your_logto_origin}/callback/${connector_id}. The connector_id can be found on the top bar of the Logto Admin Console connector details page.

Note: If you encounter the error message "The redirect_uri MUST match the registered callback URL for this application." when logging in, try aligning the Authorization Callback URL of your GitHub OAuth App and your Logto App's redirect URL (of course, including the protocol) to resolve the issue.

We suggest not to check the box before Enable Device Flow, or users who sign in with GitHub on mobile devices must confirm the initial sign-in action in the GitHub app. Many GitHub users do not install the GitHub mobile app on their phones, which could block the sign-in flow. Please ignore our suggestion if you are expecting end-users to confirm their sign-in flow. See details of device flow.

Managing OAuth apps

Go to the OAuth Apps page and you can add, edit or delete existing OAuth apps. You can also find Client ID and generate Client secrets in OAuth app detail pages.

Compose the connector JSON

Let's go back to Logto. Fill out the clientId and clientSecret field with Client ID and Client Secret you've got from OAuth app detail pages mentioned in the previous section.

Here is an example of GitHub connector config JSON.

{
  "clientID": "<your-client-id>",
  "clientSecret": "<your-client-secret>"
}

Config types

Name	Type
clientId	string
clientSecret	string

Save your configuration

Double check you have filled out necessary values in the Logto connector configuration area. Click "Save and Done" (or "Save Changes") and the GitHub connector should be available now.

Enable GitHub connector in Sign-in Experience

Switch to the "Sign-in Experience" tab, then click the "Sign-up and Sign-in" tab.

note

If it's the first time you enter the tab, you will see a quick introduction about Sign-in Experience and its basic configuration.

Select "None" for the "Sign-up identifier" to provide minimum sign-up effort for GitHub sign-in, which may increase your conversion rate.

In the "Social sign-in" section, add "Add Social Connector" and choose "GitHub". Then you should be able to see a button with text "Continue with GitHub" in the preview section.

Finally, click "Save Changes" on the bottom right corner.

Testing and Validation

Return to your .NET Core (Blazor Server) app. You should now be able to sign in with GitHub. Enjoy!

Further readings

⚔️ Protect your API For native and single page apps, you'll need to call one or more API endpoints to retrieve and update data.
Learn more about identifying who's who and keeping your API secure.

🧑‍🚀 Manage users We know you care about user management and activities, as we also do.
Learn more about how to know your users and see the figures like DAU and MAU graphically.

🌐 Localization From one regional business to a global corporate, the willingness to offer the best user experience won't change.
You can change current language phrases or add a new language without friction.

🧑‍🎓 Customer IAM series Our serial blog posts about Customer (or Consumer) Identity and Access Management, from 101 to advanced topics and beyond.