MAUI使用MVVM代码步骤

 public class UserViewModel : ObservableObject
    {
        private UserModel _userModel;
        private string _username;
        private string _password;
        private ICommand _btnLogin;
        private ICommand _btnAdd;
        private ICommand _btnResetPwd;

        public string UserName { get => _username; set => SetProperty(ref _username, value); }
        public string Password { get => _password; set => SetProperty(ref _password, value); }
        public ICommand BtnLogin { get => _btnLogin ?? (_btnLogin = new RelayCommand(BtnLoginCallback)); }
        public ICommand BtnAdd { get => _btnAdd ?? (_btnAdd = new RelayCommand(BtnAddCallback)); }
        public ICommand BtnResetPwd { get => _btnResetPwd ?? (_btnResetPwd = new RelayCommand(BtnResetPwdCallback)); }
        private void BtnLoginCallback()
        {
            Console.WriteLine("Login");
            Shell.Current.GoToAsync("//SecretManager");
        }
        private void BtnAddCallback()
        {
            Console.WriteLine("add");
        }
        private void BtnResetPwdCallback()
        {
            Console.WriteLine("reset");
        }

        public void ApplyQueryAttributes(IDictionary<string, object> query)
        {
            if (query.ContainsKey(""))
            {
                RefreshProperties();
            }
        }

        private void RefreshProperties()
        {
            OnPropertyChanged(nameof(UserModel));
        }
    }

    public class ServiceLocator
    {
        private IServiceProvider _serviceProvider;
        public UserViewModel UserViewModel=>_serviceProvider.GetService<UserViewModel>();

        public ServiceLocator()
        {
            var serviceCollection=new ServiceCollection();
            serviceCollection.AddSingleton<UserViewModel>();//视图注册到容器内，就不用new对象
            
            _serviceProvider= serviceCollection.BuildServiceProvider();
        }
    }

                <ResourceDictionary>
                    <local:ServiceLocator x:Key="ServiceLocator"/>
                </ResourceDictionary>

   BindingContext="{Binding UserViewModel, Source={StaticResource ServiceLocator}}"

Text="{Binding UserName}"/>