修改Model

打開Todo\Models\UserModel.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Todo.Models
{
    public class UserModel
    {
        public string email { get; set; }
        public string password { get; set; }

        public string username { get; set; }
    }
}

修改Service

打開Todo\Services\IAuthService.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Todo.Models;

namespace Todo.Services
{
    public interface IAuthService
    {
        Task<bool> RegisterUserWithEmail(UserModel user);
        Task<bool> LoginUserWithEmail(UserModel user);
        Task LogoutWithEmail();
        UserModel GetUser();
        Task<bool> IsLogin();
    }
}

添加AuthService.cs:

using Firebase.Auth;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Todo.Models;

namespace Todo.Services
{
    public class AuthService : IAuthService
    {
        private readonly String webApikey = "AIzaSyCpllW5JzsuuUkQ0B4cPmZSiTDayle-Gho"; // Type your web api key
        private User _user;
        public bool isLogin = false;

        public UserModel GetUser()
        {
            UserModel model = new UserModel
            {
                username = _user.DisplayName,
                email = _user.Email,
                password = "",
            };
            return model;
        }

        public async Task<bool> IsLogin()
        {
            await Task.Delay(10);
            return isLogin;
        }

        public async Task<bool> LoginUserWithEmail(UserModel user)
        {
            try {
                var authProvider = new FirebaseAuthProvider(new FirebaseConfig(webApikey));
                var auth = await authProvider.SignInWithEmailAndPasswordAsync(user.email, user.password);
                _user = auth.User;
                isLogin = true;
                return true;
            } catch {
                isLogin = false;
                return false;
            }
        }

        public async Task LogoutWithEmail()
        {
            await Task.Delay(10);
            _user = new User();
            isLogin = false;
        }

        public async Task<bool> RegisterUserWithEmail(UserModel user)
        {
            try {
                var authProvider = new FirebaseAuthProvider(new FirebaseConfig(webApikey));
                var auth = await authProvider.CreateUserWithEmailAndPasswordAsync(user.email, user.password);

                return true;
            } catch {
                return false;
            }

        }

    }
}

修改AuthViewModel

打開Todo\ViewModels\AuthViewModel.cs

using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Todo.Models;
using Todo.Services;

namespace Todo.ViewModels
{
    [QueryProperty(nameof(User), "User")]
    public partial class AuthViewModel : ObservableObject
    {
        [ObservableProperty]
        private UserModel _user = new UserModel();
        private readonly IAuthService _authService;
        private bool _isLogin = false;
        public AuthViewModel(IAuthService authService)
        {
            _authService = authService;
        }

        [RelayCommand]
        public async void GetUser()
        {
            if(_isLogin) {
                _user = _authService.GetUser();
            }
            await Shell.Current.DisplayAlert("Please Login", "Login", "Ok");
        }

        [RelayCommand]
        public async void IsLogin()
        {
            _isLogin = await _authService.IsLogin();
        }

        [RelayCommand]
        public async void LogoutUser()
        {
            await _authService.LogoutWithEmail();
            _isLogin = await _authService.IsLogin();
            await Shell.Current.DisplayAlert("Status: Logout Success", "Logout Success", "Ok");
        }

        [RelayCommand]
        public async void LoginUserWithEmailAndPassword()
        {
            var result = await _authService.LoginUserWithEmail(new Models.UserModel
            {
                email=User.email,
                password=User.password,
            });
            if (result) {
                _isLogin = await _authService.IsLogin();
                await Shell.Current.DisplayAlert("Status: Login Success", "Login Success", "Ok");
            } else {
                await Shell.Current.DisplayAlert("Status: Login Failed", "Login failed", "Ok");
            }
        }

        [RelayCommand]
        public async void RegisterUserWithEmailAndPassword()
        {
            var result = await _authService.RegisterUserWithEmail(new Models.UserModel
            {
                email=User.email,
                password=User.password,
            });
            if (result) {
                await Shell.Current.DisplayAlert("Status: Register Success", "User registed", "Ok");
            } else {
                await Shell.Current.DisplayAlert("Status: Register Failed", "Something is failed", "Ok");
            }
        }
    }
}