Goal: Simple blazor app in which, after the user has logged in and their authentication state is confirmed, I call the backend to load some user data.

Process: I launch the app locally from Visual Studio and call an [Authorized] Blazor server endpoint.

Problem: Whatever [Authorized] endpoint I call first, no matter what it is, throws an error with "{"'<' is an invalid start of a value. Path: $ | LineNumber: 0 | BytePositionInLine: 0."}" because instead of returning a JSON payload, it's returning a log in page.

The funny bit is that if I refresh the page, every endpoint returns the data it's supposed to just fine.

Code

The first endpoint it calls is immediately in the MainLayout.razor page, UserService.LoadCurrentUserAsync:

    @inject AuthenticationStateProvider AuthenticationStateProvider    @inject IUserService UserService    // ...    protected override async Task OnInitializedAsync()    {        var authState = await AuthenticationStateProvider.GetAuthenticationStateAsync();        var user = authState.User;        if (user.Identity is not null && user.Identity.IsAuthenticated)        {            try            {                await UserService.LoadCurrentUserAsync();            }            catch (Exception ex)            {                await Console.Error.WriteLineAsync("Error with LoadCurrentUserAsync: " + ex.Message);            }        }    }

UserService.LoadCurrentUserAsync could only be called if the user was already authenticated. Here is LoadCurrentUserAsync:

    public async Task LoadCurrentUserAsync()    {        CurrentUser = await apiService.GetAsync<DtoCurrentUser>("api/users/me");        if (CurrentUser is not null)        {            CurrentUser.Initials = GetInitials(CurrentUser?.FullName);            Company = CurrentUser?.Companies.FirstOrDefault();        }    }