On Android, you have to specify the current Activity from which the browser pop-up will be displayed using the WithParentActivityOrWindow method

I'm implementing Azure AD B2C authentication in my .NET MAUI app using MSAL.NET. My .NET MAUI app targets .NET 8 and I'm using Microsoft.Identity.Client.Extensions.Msal version 4.66.0.

My app uses the AppShell and upon start, it hits the InitializeAsync() method of my StartupPage.cs. The first thing I do in InitializeAsync() is to make the following call:

var authenticatedUser = await _authService.IsAuthenticated();. This method looks like this:

public async Task<User> IsAuthenticated()
{
   await PublicClientSingleton.Instance.AcquireTokenSilentAsync();
   var claims = PublicClientSingleton.Instance.MSALClientHelper.AuthResult.ClaimsPrincipal.Claims; // This throws that error!

   ...
}

And this is where the System.InvalidOperation exception is thrown with the message:

System.InvalidOperationException: On Android, you have to specify the current Activity from which the browser pop-up will be displayed using the WithParentActivityOrWindow method.

BTW, this is what my MainActivity.cs file looks like under Android in Platforms folder:

protected override void OnCreate(Bundle savedInstanceState)
{
    base.OnCreate(savedInstanceState);
    // configure platform specific params
    PlatformConfig.Instance.RedirectUri = $"msal{PublicClientSingleton.Instance.MSALClientHelper.AzureADB2CConfig.ClientId}://auth";
    PlatformConfig.Instance.ParentWindow = this;

    // Initialize MSAL and platformConfig is set
    _ = Task.Run(async () => await PublicClientSingleton.Instance.MSALClientHelper.InitializePublicClientAppAsync()).Result;
}

Any suggestions on how I can address this issue?

Solution

The code I used to implement MSAL.NET in my .NET MAUI app came from this Microsoft repo: https://github.com/Azure-Samples/ms-identity-dotnetcore-maui

Someone had already posted the answer to this issue here: https://github.com/SyncfusionExamples/Authenticate-.NET-MAUI-App-with-Azure-AD/issues/1#issuecomment-1576183450

I think Microsoft team needs to update their code in the Azure Samples GitHub repo in the first link I provided.

Here's the solution: it looks like a small modification is necessary for it to work on Android. I added the following conditional method call in InitializePublicClientAppAsync() method in MSALClientHelper. Please notice that the added line is for Android only, hence the condition:

public async Task<IAccount> InitializePublicClientAppAsync()
{
   // Initialize the MSAL library by building a public client application
   this.PublicClientApplication = this.PublicClientApplicationBuilder
      .WithRedirectUri($"msal{PublicClientSingleton.Instance.MSALClientHelper.AzureADB2CConfig.ClientId}://auth")
#if ANDROID
      .WithParentActivityOrWindow(() => Platform.CurrentActivity) // This is needed for Android
#endif
      .Build();

      await AttachTokenCache();
      return await FetchSignedInUserFromCache().ConfigureAwait(false);
}