Xamarin 表单数据绑定“."分隔器 [英] Xamarin Forms Databinding "." separator

问题描述

我在 Xamarin Forms 中挣扎于数据绑定.这就是为什么我希望从以下 XAML 语句中发生的事情:

I'm struggling with databinding in Xamarin Forms. Here's why, what I expect to happen from the following XAML statement:

IsVisible="{Binding Path=UserContext.IsLoggedOut}"

Is - 该属性绑定到视图模型的子对象.现在，要么 Xamarin Forms 不支持此功能，要么我错过了一个技巧.

Is - That the property is bound to a child object of the View Model. Now either this isn't supported in Xamarin Forms or I am missing a trick.

如果 Xamarin 不支持它，而 WPF 支持它，那么我们应该怎么做才能传播嵌套对象?扁平化视图模型让我写了一大堆不优雅的代码.

If this is not supported in Xamarin, where it is supported in WPF, then what are we supposed to do in order to propagate nested objects? Flattening the View Model is making me write reams and reams of inelegant code.

推荐答案

支持嵌套属性，就像其他非常复杂的表达式一样:

Nested properties are supported, like other pretty complex expression as well:

你可以测试一下:

Xaml

<StackLayout Spacing="20">
  <StackLayout Orientation="Horizontal">
    <Label Text="Subproperties: " HorizontalOptions="FillAndExpand" FontSize="15"></Label>
    <Label Text="{Binding Item.SubItem.Text}" HorizontalOptions="FillAndExpand" FontSize="15"></Label>
  </StackLayout>
  <StackLayout Orientation="Horizontal">
    <Label Text="Indexer: " HorizontalOptions="FillAndExpand" FontSize="15"></Label>
    <Label Text="{Binding Item.Dictionary[key].Text}" HorizontalOptions="FillAndExpand" FontSize="15"></Label>
  </StackLayout>
  <StackLayout Orientation="Horizontal">
    <Label Text="Array Indexer: " HorizontalOptions="FillAndExpand" FontSize="15"></Label>
    <Label Text="{Binding Item.Array[1].Text}" HorizontalOptions="FillAndExpand" FontSize="15"></Label>
  </StackLayout>
</StackLayout>

页面

public partial class Page2 : ContentPage
{
    public ItemModel Item { get; }

    public Page2()
    {
        InitializeComponent();
        Item = new ItemModel();
        BindingContext = this;

    }
}

public class ItemModel
{
    public ItemSubModel SubItem { get; set; }
    public Dictionary<string, ItemSubModel>  Dictionary { get; set; }
    public ItemSubModel[] Array { get; set; }

    public ItemModel()
    {
        SubItem = new ItemSubModel();
        Dictionary = new Dictionary<string, ItemSubModel>
        {
            {"key", new ItemSubModel()}
        };
        Array = new [] {new ItemSubModel(), new ItemSubModel() };
    }
}

public class ItemSubModel
{
    public string Text { get; set; } = "Supported";
}

结果

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