NemAn/NemAnCore/AuthProvider.cs

using Blazored.SessionStorage;
using System.Security.Claims;

namespace NemAnBlazor
{
    public class AuthProvider : AuthenticationStateProvider
    {
        private readonly ISessionStorageService _sessionStorage;
        public AuthProvider(ISessionStorageService sessionStorage)
        {
            _sessionStorage = sessionStorage;
        }
        public override async Task<AuthenticationState> GetAuthenticationStateAsync()
        {
            string token = await _sessionStorage.GetItemAsync<string>("token");

            ClaimsIdentity identity = new ();
            ClaimsPrincipal user = new (identity);
            AuthenticationState state = new(user);

            NotifyAuthenticationStateChanged(Task.FromResult(state));

            return state;
        }
    }
}