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page_type languages products name urlFragment description
sample
csharp
aspnet-core
dotnet-core
azure-active-directory-b2c
msal-dotnet
Enable your Blazor Server to sign-in users and call web API with the Microsoft identity platform in Azure AD B2C
ms-identity-blazor-server
This sample demonstrates an ASP.NET Core Blazor Server application calling an ASP.NET Core web API that is secured using Azure AD B2C

Enable your Blazor Server to sign-in users and call web API with the Microsoft identity platform in Azure AD B2C

  1. Overview
  2. Scenario
  3. Contents
  4. Prerequisites
  5. Setup
  6. Registration
  7. Running the sample
  8. Explore the sample
  9. About the code
  10. More information
  11. Community Help and Support
  12. Contributing
  13. Code of Conduct

.NET Core

Overview

In the second chapter, we extend our ASP.NET Core Blazor Server application to call a downstream ASP.NET Core web API that is secured using Azure AD B2C.

Scenario

Continuing from the previous chapter of the tutorial, this chapter adds the following steps:

  1. The client application acquires an Access Token for the Web API.
  2. The Access Token is used as a bearer token to authorize the user to call secure ASP.NET Core web API.

Overview

How to run this sample

In the downloaded folder

From your shell or command line:

cd ms-identity-blazor-server\WebApp-your-API\B2C

Register the service app (ToDoListService-aspnetcore)

  1. Navigate to the Azure portal and select the Azure AD B2C service.
  2. Select the App Registrations blade on the left, then select New registration.
  3. In the Register an application page that appears, enter your application's registration information:
    • In the Name section, enter a meaningful application name that will be displayed to users of the app, for example ToDoListService-aspnetcore.
    • Under Supported account types, select Accounts in any identity provider or organizational directory (for authenticating users with user flows).
  4. Select Register to create the application.
  5. In the app's registration screen, find and note the Application (client) ID. You use this value in your app's configuration file(s) later in your code.
  6. Select Save to save your changes.
  7. In the app's registration screen, select the Expose an API blade to the left to open the page where you can declare the parameters to expose this app as an Api for which client applications can obtain access tokens for. The first thing that we need to do is to declare the unique resource URI that the clients will be using to obtain access tokens for this Api. To declare an resource URI, follow the following steps:
    • Select Set next to the Application ID URI to generate a URI that is unique for this app.
    • For this sample, accept the proposed Application ID URI (https://{tenantName}.onmicrosoft.com/{clientId}) by selecting Save.
  8. All Apis have to publish a minimum of one scope for the client's to obtain an access token successfully. To publish a scope, follow the following steps:
    • Select Add a scope button open the Add a scope screen and Enter the values as indicated below:
      • For Scope name, use access_as_user.
      • For Admin consent display name type Access TodoListService-aspnetcore-webapi.
      • For Admin consent description type Allows the app to access TodoListService-aspnetcore-webapi as the signed-in user.
      • Keep State as Enabled.
      • Select the Add scope button on the bottom to save this scope.

Configure the service app (ToDoListService-aspnetcore) to use your app registration

Open the project in your IDE (like Visual Studio or Visual Studio Code) to configure the code.

In the steps below, "ClientID" is the same as "Application ID" or "AppId".

  1. Open the Service\appsettings.json file.
  2. Find the key Instance and replace the value with your tenant name. For example, https://fabrikam.b2clogin.com
  3. Find the key ClientId and replace the existing value with the application ID (clientId) of the ToDoListService-aspnetcore application copied from the Azure portal.
  4. Find the key Domain and replace the existing value with your Azure AD tenant name.
  5. Find the key SignedOutCallbackPath and add the name of the Sign up and sign in policy you created.
  6. Find the key SignUpSignInPolicyId and replace with the name of the Sign up and sign in policy you created.

Update the registration for the web app (WebApp-calls-API-blazor-server)

  1. In App registrations page, find the WebApp-calls-API-blazor-server app.
  2. In the app's registration screen, select the Certificates & secrets blade in the left to open the page where we can generate secrets and upload certificates.
  3. In the Client secrets section, select New client secret:
    • Type a key description (for instance app secret),
    • Select one of the available key durations (In 1 year, In 2 years, or Never Expires) as per your security posture.
    • The generated key value will be displayed when you select the Add button. Copy the generated value for use in the steps later.
    • You'll need this key later in your code's configuration files. This key value will not be displayed again, and is not retrievable by any other means, so make sure to note it from the Azure portal before navigating to any other screen or blade.
  4. In the app's registration screen, select the API permissions blade in the left to open the page where we add access to the APIs that your application needs.
    • Select the Add a permission button and then,
    • Ensure that the My APIs tab is selected.
    • In the list of APIs, select the API ToDoListService-aspnetcore.
    • In the Delegated permissions section, select the Access 'ToDoListService-aspnetcore' in the list. Use the search box if necessary.
    • Select the Add permissions button at the bottom.
    • Select Grant admin consent.

Configure the web app (WebApp-calls-API-blazor-server) to use your app registration

Open the project in your IDE (like Visual Studio or Visual Studio Code) to configure the code.

In the steps below, "ClientID" is the same as "Application ID" or "AppId".

  1. Open WebApp-your-API\B2C\Client\appsettings.json file and copy the keys from "AzureAd" section of previous chapter's WebApp-OIDC\B2C\blazorserver-B2C\appsettings.json file.
  2. Find the key ClientSecret and replace the existing value with the key you saved during the creation of the WebApp-calls-API-blazor-server app, in the Azure portal.
  3. Find the key TodoListScope and replace the value with API Scope defined in the Azure portal.
  4. Find the key TodoListBaseAddress and replace the existing value with the base address of the ToDoListService-aspnetcore project (by default https://localhost:44332).

Running the sample

You can run the sample by using either Visual Studio or command line interface as shown below:

Run the sample using Visual Studio

Clean the solution, rebuild the solution, and run it. You might want to go into the solution properties and set both projects as startup projects, with the service project starting first.

When you start the web API from Visual Studio, depending on the browser you use, you'll get:

  • an empty web page (with Microsoft Edge)
  • or an error HTTP 401 (with Chrome)

This behavior is expected as the browser is not authenticated. The Web application will be authenticated, so it will be able to access the web API.

Run the sample using a command line interface such as VS Code integrated terminal

Step 1. Install .NET Core dependencies

cd Client
dotnet restore

Then:
In a separate console window, execute the following commands

cd Service
dotnet restore

Step 2. Trust development certificates

dotnet dev-certs https --clean
dotnet dev-certs https --trust

Learn more about HTTPS in .NET Core.

Step 3. Run the applications

In both the console windows execute the below command:

dotnet run

Explore the sample

If you are using incognito mode of browser to run this sample then allow third party cookies.

  1. Open your browser and navigate to https://localhost:44365.

  2. Select the Sign in button on the top right corner. You will see claims from the signed-in user's token.

    UserClaims

  3. Select ToDoList from navigation bar and you can create, edit or delete the todo list items.

    ToDoList

ℹ️ Did the sample not work for you as expected? Then please reach out to us using the GitHub Issues page.

We'd love your feedback!

Were we successful in addressing your learning objective? Do consider taking a moment to share your experience with us.

About the code

  1. In Startup.cs, add below lines of code in ConfigureServices method:

    services.AddMicrosoftIdentityWebAppAuthentication(Configuration, "AzureAdB2C")
        .EnableTokenAcquisitionToCallDownstreamApi(new string[] { Configuration["TodoList:TodoListScope"] })
        .AddInMemoryTokenCaches();

    This enables your application to use the Microsoft identity platform endpoint to sign-in users and to call the protected web API.

    The following code registers client service to use the HttpClient by dependency injection.

    services.AddToDoListService(Configuration);

    Below code adds the incremental consent and conditional access handler for Blazor server side pages.

    services.AddServerSideBlazor()
            .AddMicrosoftIdentityConsentHandler();

  2. ToDoList.razor component displays list of items created by signed-in user. List can be updated and deleted.

    ToDoListBase.cs calls GetToDoListService method to retrieve the todo list.

    public class ToDoListBase : ComponentBase
{
    [Inject]
    ToDoListService ToDoListService { get; set; }
    [Inject]
    MicrosoftIdentityConsentAndConditionalAccessHandler ConsentHandler { get; set; }
    [Inject]
    NavigationManager Navigation { get; set; }
    protected IEnumerable<ToDo> toDoList = new List<ToDo>();
    protected ToDo toDo = new ToDo();
    protected override async Task OnInitializedAsync()
    {
        await GetToDoListService();
    }
    [AuthorizeForScopes(ScopeKeySection = "TodoList:TodoListScope")]
    private async Task GetToDoListService()
    {
        try
        {
            toDoList = await ToDoListService.GetAsync();
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);
            ConsentHandler.HandleException(ex);
        }
    }
    protected async Task DeleteItem(int Id)
    {
        await ToDoListService.DeleteAsync(Id);
        await GetToDoListService();
    }
}

  3. ToDoListService.cs class in client project defines method to call protected API. PrepareAuthenticatedClient method retrieves the Access Token for the web API and sets authorization and accept headers for the request.

    private async Task PrepareAuthenticatedClient()
{
    var accessToken = await _tokenAcquisition.GetAccessTokenForUserAsync(new[] { _TodoListScope });
    Debug.WriteLine($"access token-{accessToken}");
    _httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", accessToken);
    _httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
}

More information

For more information about how OAuth 2.0 protocols work in this scenario and other scenarios, see Authentication Scenarios for Azure AD.

Community Help and Support

Use Stack Overflow to get support from the community. Ask your questions on Stack Overflow first and browse existing issues to see if someone has asked your question before. Make sure that your questions or comments are tagged with [azure-active-directory azure-ad-b2c ms-identity msal].

If you find a bug in the sample, raise the issue on GitHub Issues.

To provide feedback on or suggest features for Azure Active Directory, visit User Voice page.

Contributing

If you'd like to contribute to this sample, see CONTRIBUTING.MD.

This project has adopted the Microsoft Open Source Code of Conduct. For more information, see the Code of Conduct FAQ or contact [email protected] with any additional questions or comments.