BindableProperty的Setter仅在XAML引用时触发？技术求助

我尝试创建一个ContentView来封装逻辑实现代码复用（DRY原则），但遇到了两个核心问题：

• 只有当TotalItems属性在XAML中直接引用时，它的Setter才会被调用（已断点验证）；
• 无法将父页面ViewModel里的TotalItems值成功传递给ContentView的BindableProperty（期望实现类似Vue/Angular的组件传值效果）。

以下是相关代码：

ContentView.xaml.cs #

public static readonly BindableProperty TotalItemsProperty = BindableProperty.Create(nameof(TotalItems), typeof(int), typeof(SortingPageView),
    defaultBindingMode: BindingMode.TwoWay);

public int TotalItems
{
    get => (int)GetValue(TotalItemsProperty);
    set
    {
        SetValue(TotalItemsProperty, value);
        OnPropertyChanged(nameof(CurrentPageText));
    }
}

public string CurrentPageText { get => $" / {TotalPages}"; }

ContentView.xaml #

<Grid ColumnDefinitions="50, auto, 50" Grid.Column="1" HorizontalOptions="End">
    <Image Grid.Column="0" IsVisible="{Binding CanGoBack}" Source="left_arrow.png" HeightRequest="30">
        <Image.GestureRecognizers>
            <TapGestureRecognizer Tapped="GoBack"/>
        </Image.GestureRecognizers>
    </Image>
    <HorizontalStackLayout Margin="10, 0" Grid.Column="1">
        <Entry FontSize="20" Text="{Binding CurrentPage}"/>
        <Label FontSize="20" Text="{Binding CurrentPageText}" VerticalOptions="Center"/>
    </HorizontalStackLayout>
    <Image Grid.Column="2" Source="right_arrow.png" HeightRequest="30">
        <Image.GestureRecognizers>
            <TapGestureRecognizer Tapped="GoNext"/>
        </Image.GestureRecognizers>
    </Image>
</Grid>

ViewModel.cs #

public async Task LoadJobs(bool resetCurrentPage = false)
{
    this.IsLoading = true;

    try
    {
        if(resetCurrentPage)
        {
            this.CurrentPage = 1;
        }

        var jobs = await this.jobsService.GetJobs(Filter, Pagination);

        this.InitialJobs = jobs.Items.Select(x => new JobDto(x)).ToList();
        this.TotalItems = jobs.TotalItems;   // 关键代码行

        MainThread.BeginInvokeOnMainThread(() =>
        {
            this.Jobs.Clear();
            this.Jobs.AddRange(jobs.Items);
        });
    }
    catch(Exception ex)
    {

    }
    finally 
    { 
        this.IsLoading = false;
    }
}

ContentView构造函数 #

public SortingPageView()
{
    InitializeComponent();
    Content.BindingContext = this;
}

1. TotalItems的Setter不触发的原因 #

这是MAUI BindableProperty的核心机制：当通过绑定更新BindableProperty时，不会执行你手动编写的CLR属性Setter，而是直接调用SetValue方法。只有在代码中直接给CLR属性赋值（比如myPageView.TotalItems = 200）时，Setter才会被执行。

你在Setter中写的OnPropertyChanged(nameof(CurrentPageText))只会在手动赋值时触发，但绑定更新时不会走这个逻辑，导致CurrentPageText的变更通知无法触发，UI也就不会更新。

2. 正确的BindableProperty实现方式 #

不要依赖CLR属性的Setter处理变更逻辑，而是在注册BindableProperty时指定propertyChanged回调：

public static readonly BindableProperty TotalItemsProperty = BindableProperty.Create(
    nameof(TotalItems), 
    typeof(int), 
    typeof(SortingPageView),
    defaultBindingMode: BindingMode.TwoWay,
    // 绑定属性变更时自动触发回调
    propertyChanged: (bindable, oldValue, newValue) =>
    {
        var view = (SortingPageView)bindable;
        // 触发CurrentPageText的变更通知
        view.OnPropertyChanged(nameof(view.CurrentPageText));
        // 如果TotalPages也依赖TotalItems，这里也可以触发它的变更通知
        view.OnPropertyChanged(nameof(view.TotalPages));
    });

// CLR属性保持极简，不要添加额外逻辑
public int TotalItems
{
    get => (int)GetValue(TotalItemsProperty);
    set => SetValue(TotalItemsProperty, value);
}

public string CurrentPageText { get => $" / {TotalPages}"; }

3. 父ViewModel向ContentView传值的正确方式 #

因为你把ContentView的BindingContext设为了自身，所以父页面绑定ContentView的属性时，需要明确指定绑定源：

假设父页面的BindingContext就是目标ViewModel，在父页面XAML中引用ContentView时，直接绑定对应属性即可：

<local:SortingPageView 
    TotalItems="{Binding TotalItems}"
    CurrentPage="{Binding CurrentPage}"
    CanGoBack="{Binding CanGoBack}" />

注意：ContentView中需要同步更新的属性（比如CurrentPage、CanGoBack）也需要定义成BindableProperty，才能实现和父ViewModel的双向同步：

public static readonly BindableProperty CurrentPageProperty = BindableProperty.Create(
    nameof(CurrentPage), 
    typeof(int), 
    typeof(SortingPageView),
    defaultValue: 1,
    propertyChanged: (bindable, oldValue, newValue) =>
    {
        var view = (SortingPageView)bindable;
        view.OnPropertyChanged(nameof(view.CurrentPageText));
        view.OnPropertyChanged(nameof(view.CanGoBack));
    });

public int CurrentPage
{
    get => (int)GetValue(CurrentPageProperty);
    set => SetValue(CurrentPageProperty, value);
}

public bool CanGoBack => CurrentPage > 1;

内容的提问来源于stack exchange，提问作者Nicoara