How to build Azure AD sign-in with .NET Core (Blazor Server)

For our new friends:

Logto is an Auth0 alternative designed for modern apps and SaaS products. It offers both Cloud and Open-source services to help you quickly launch your identity and management (IAM) system. Enjoy authentication, authorization, and multi-tenant management all in one.

We recommend starting with a free development tenant on Logto Cloud. This allows you to explore all the features easily.

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

Prerequisites

A running Logto instance. Check out the introduction page to get started.
Basic knowledge of .NET Core (Blazor Server).
A usable Azure AD account.

Create an application in Logto

Logto is based on OpenID Connect (OIDC) authentication and OAuth 2.0 authorization. It supports federated identity management across multiple applications, commonly called Single Sign-On (SSO).

To create your Traditional web application, simply follow these steps:

Open the Logto Console. In the "Get started" section, click the "View all" link to open the application frameworks list. Alternatively, you can navigate to Logto Console > Applications, and click the "Create application" button.
In the opening modal, click 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 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 .Net Core (Blazor Server) 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:

Program.cs
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.

Before we proceed, there are two confusing terms in the .NET Core authentication middleware that we need to clarify:

CallbackPath: The URI that Logto will redirect the user back to after the user has signed in (the "redirect URI" in Logto)
RedirectUri: The URI that will be redirected to after necessary actions have been taken in the Logto authentication middleware.

The sign-in process can be illustrated as follows:

Similarly, .NET Core also has SignedOutCallbackPath and RedirectUri for the sign-out flow.

For the sack of clarity, we'll refer them as follows:

Term we use	.NET Core term
Logto redirect URI	CallbackPath
Logto post sign-out redirect URI	SignedOutCallbackPath
Application redirect URI	RedirectUri

This authentication process follows the OpenID Connect (OIDC) protocol, and Logto enforces strict security measures to protect user sign-in.
If you have multiple apps, you can use the same identity provider (Logto). Once the user signs in to one app, Logto will automatically complete the sign-in process when the user accesses another app.

To learn more about the rationale and benefits of redirect-based sign-in, see Logto sign-in experience explained.

Configure redirect URIs

note:

In the following code snippets, we assume your app is running on http://localhost:3000/.

First, let's configure the Logto redirect URI. Add the following URI to the "Redirect URIs" list in the Logto application details page:

http://localhost:3000/Callback

To configure the Logto post sign-out redirect URI, add the following URI to the "Post sign-out redirect URIs" list in the Logto application details page:

http://localhost:3000/SignedOutCallback

Change the default paths

The Logto redirect URI has a default path of /Callback, and the Logto post sign-out redirect URI has a default path of /SignedOutCallback.

You can leave them as are if there's no special requirement. If you want to change it, you can set the CallbackPath and SignedOutCallbackPath property for LogtoOptions:

Program.cs
builder.Services.AddLogtoAuthentication(options =>
{
  // Other configurations...
  options.CallbackPath = "/Foo";
  options.SignedOutCallbackPath = "/Bar";
});

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

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:

Program.cs
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:

Components/Pages/Index.razor
@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:

Components/Pages/Index.razor
@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:

Program.cs
builder.Services.AddCascadingAuthenticationState();

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

Checkpoint: Test your application

Now, you can test your application:

Run your application, you will see the sign-in button.
Click the sign-in button, the SDK will init the sign-in process and redirect you to the Logto sign-in page.
After you signed in, you will be redirected back to your application and see the sign-out button.
Click the sign-out button to clear token storage and sign out.

Add Azure AD connector

To enable quick sign-in and improve user conversion, connect with .Net Core (Blazor Server) as an identity provider. The Logto social connector helps you establish this connection in minutes by allowing several parameter inputs.

To add a social connector, simply follow these steps:

Navigate to Console > Connectors > Social Connectors.
Click "Add social connector" and select "Azure AD".
Follow the README guide and complete required fields and customize settings.

note:

If you are following the in-place Connector guide, you can skip the next section.

Set up Azure AD

Set up Microsoft Azure AD in the Azure Portal

Visit the Azure Portal and sign in with your Azure account. You need to have an active subscription to access Microsoft Azure AD.
Click the Azure Active Directory from the services they offer, and click the App Registrations from the left menu.
Click New Registration at the top, enter a description, select your access type and add your Redirect URI, which will redirect the user to the application after logging in. In our case, this will be ${your_logto_endpoint}/callback/${connector_id}. e.g. https://foo.logto.app/callback/${connector_id}. The connector_id can be also found on the top bar of the Logto Admin Console connector details page. You can copy the Callback URI in the configuration section.
Select Web as Platform.

Fill in the configuration in Logto

Name	Type
clientId	string
clientSecret	string
tenantId	string
cloudInstance	string

Client ID

You may find the Application (client) ID in the Overview section of your newly created application in the Azure Portal.

Client Secret

In your newly created application, click the Certificates & Secrets to get a client secret, and click the New client secret from the top.
Enter a description and an expiration.
This will only show your client secret once. Fill the value to the Logto connector configuration and save it to a secure location.

Cloud Instance

Usually, it is https://login.microsoftonline.com/. See Azure AD authentication endpoints for more information.

Tenant ID

Logto will use this field to construct the authorization endpoints. This value is dependent on the access type you selected when creating the application in the Azure Portal.

If you select Accounts in this organizational directory only for access type then you need to enter your {TenantID}. You can find the tenant ID in the Overview section of your Azure Active Directory.
If you select Accounts in any organizational directory for access type then you need to enter organizations.
If you select Accounts in any organizational directory or personal Microsoft accounts for access type then you need to enter common.
If you select Personal Microsoft accounts only for access type then you need to enter consumers.

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 Azure AD connector should be available now.

Once you create a social connector successfully, you can enable it as a "Continue with Azure AD" button in Sign-in Experience.

Navigate to Console > Sign-in experience > Sign-up and sign-in.
(Optional) Choose "Not applicable" for sign-up identifier if you need social login only.
Add configured Azure AD connector to the "Social sign-in" section.

Sign-in Experience tab

Testing and Validation

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

Create an application in Logto​

Integrate .Net Core (Blazor Server) SDK​

Installation​

Add Logto authentication​

Sign-in and sign-out flows​

Regarding redirect-based sign-in​

Configure redirect URIs​

Change the default paths​

Add routes​

Implement sign-in/sign-out buttons​

The <AuthorizeView /> component​

Checkpoint: Test your application​

Add Azure AD connector​

Set up Azure AD​

Set up Microsoft Azure AD in the Azure Portal​

Fill in the configuration in Logto​

Client ID​

Client Secret​

Cloud Instance​

Tenant ID​

Save your configuration​

Enable Azure AD connector in Sign-in Experience​

Testing and Validation​

Further readings​