.NET MAUI绑定值变更后Entry控件值不更新问题求助

1. Patient类无属性变更通知：Patient的Id、Lastname是普通自动属性，修改时不会触发PropertyChanged事件，UI绑定无法感知数据变化。
2. ViewModel属性未实现可观察：HomePageViewModel中的MyPatient是普通属性，即使替换对象也无法通知UI；同时修改对象内部属性时，因Patient无通知机制，UI也不会更新。
3. ImportPage导航逻辑混乱：btnCancel_Clicked中先跳转HomePage再执行返回操作，导致导航栈异常，参数传递失效。

1. 改造Patient类实现属性变更通知 #

借助CommunityToolkit.Mvvm的ObservableObject和[ObservableProperty]特性，自动生成带变更通知的属性：

using CommunityToolkit.Mvvm.ComponentModel;

namespace Aequus.CoreBusiness
{
    public partial class Patient : ObservableObject
    {
        [ObservableProperty]
        private int id;

        [ObservableProperty]
        private string lastname = string.Empty;

        [ObservableProperty]
        private string firstname = string.Empty;

        public override string ToString()
        {
            return Lastname + ", " + Firstname;
        }
    }
}

2. 修正ViewModel的MyPatient属性 #

将MyPatient改为可观察属性，确保对象替换或内部属性修改时能通知UI：

using Aequus.CoreBusiness;
using Aequus.UseCases.Interfaces;
using CommunityToolkit.Mvvm.ComponentModel;
using DicomObjects;
using DicomObjects.Enums;

namespace Aequus.Maui.ViewModels
{
    public partial class HomePageViewModel : ObservableObject, IQueryAttributable
    {
        [ObservableProperty]
        private Patient? myPatient;

        public ILoadPatientUseCase LoadPatientUseCase { get; }
        private DicomImage? currentDicomImage = null;

        public HomePageViewModel(ILoadPatientUseCase loadPatientUseCase)
        {
            LoadPatientUseCase = loadPatientUseCase;
            LoadPatientAsync();
        }

        public async Task LoadPatientAsync()
        {
            MyPatient = await LoadPatientUseCase.ExecuteAsync();  
        }

        public void ApplyQueryAttributes(IDictionary<string, object> query)
        {
            if (query.TryGetValue("ReturnedObject", out var obj))
            {
                MyPatient.Lastname = "Peters";
                MyPatient.Id = 2;
                Application.Current.MainPage.DisplayAlert("MESSAGE", MyPatient.Lastname, "OK");
            }
        }
    }
}

3. 修复ImportPage导航逻辑 #

删除重复导航操作，直接返回上一页并传递参数：

namespace Aequus.Maui.Views;

using DicomObjects;

public partial class ImportPage : ContentPage
{
    public DicomImage? currentDicomImage;

    public ImportPage()
    {
        InitializeComponent();
    }

    private async void btnImport_Clicked(object sender, EventArgs e)
    {
    }

    private async void btnCancel_Clicked(object sender, EventArgs e)
    {
        var navigationParameter = new Dictionary<string, object>
        {
            { "ReturnedObject", currentDicomImage }
        };
        await Shell.Current.GoToAsync("..", navigationParameter);
    }
}

4. 验证绑定逻辑 #

XAML中的绑定无需修改，因[ObservableProperty]生成的属性名与原MyPatient、Id、Lastname一致，修改后UI会自动同步数据变化。

内容的提问来源于stack exchange，提问作者Sabre