Blazor WASM - AzureAD Auth - HttpContext.User.Claims are Empty? - azure-active-directory

Question

I am trying to switchover to Azure AD for my identity platform on a Blazor WASM app I am building. I have followed this documentation from Microsoft incredibly closely.
When I log in to the app, the client app is able to display the logged in user's name, which comes from the AuthenticationState object.
However, on the server side, when I sent a an HTTP request (POSTing a comment for example), the HttpContext.User.Claims are empty, and the following line I was using previously to get the userId returns null:
comment.UserId = HttpContext.User.FindFirstValue(ClaimTypes.NameIdentifier);
I plead some ignorance on Claims/Identitys/Microsoft Graph etc., but I still don't know understand why the user / claims would be unknown given this information was accessible at least at one point since the Client App was able to display the user's name...
I've also looked at the following StackOverflow/GitHub posts, but have not found anything that has solved this issue:
Blazor with AzureAD Auth, Context.Identity.User.Name is null
Out of box AAD B2C not grabbing user.identity.name
User.Identity.Name empty when implementing Azure B2C in Blazor WebAssembly
What am I missing here to be able to identify the user on the incoming HTTP requests?
FWIW, here is my Startup.cs class (with some irrelevant code emitted):
public void ConfigureServices(IServiceCollection services)
{
#region Azure Active Directory
services.AddAuthentication(AzureADDefaults.BearerAuthenticationScheme)
.AddAzureADBearer(options => {
Configuration.Bind("AzureAd", options);
}
);
#endregion
services.Configure<JwtBearerOptions>(
AzureADDefaults.JwtBearerAuthenticationScheme, options =>
{
options.TokenValidationParameters.NameClaimType = "name";
//options.TokenValidationParameters.NameClaimType = "preferred_username";
});
services.AddHttpContextAccessor();
services.AddControllersWithViews().AddNewtonsoftJson(x => x.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore);
services.AddRazorPages();
}
And Configure():
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
app.UseHttpsRedirection();
app.UseBlazorFrameworkFiles();
app.UseStaticFiles();
app.UseRouting();
app.UseAuthentication();
app.UseAuthorization();
app.UseEndpoints(endpoints =>
{
endpoints.MapRazorPages();
endpoints.MapControllers();
endpoints.MapFallbackToFile("index.html");
});
}

Answer 1

The issue was that removing/not having the "api://" scheme prepended to the client ID caused this to not populate the claims for some reason. Very odd. .