在 WPF 中绑定到由属性指定的数组元素 [英] Binding in WPF to element of array specified by property

问题描述

假设我的 UI 上有一些 TextBlock，如下所示:

Say I've got some TextBlocks on my UI, something like so:

<StackPanel Orientation="Vertical">
    <TextBlock Text="{Binding DessertIndex}" />
    <TextBlock Text="{Binding Food[2]}" />
    <TextBlock Text="{Binding Food[{Binding DessertIndex}]}" />
</StackPanel>

在我后面的代码中，我有这样的东西:

and in my code behind I've got something like this:

public partial class MainWindow : Window
{
    public int DessertIndex
    {
        get { return 2; }
    }

    public object[] Food
    {
        get
        {
            return new object[]{"liver", "spam", "cake", "garlic" };
        }
    }

    public MainWindow()
    {
        InitializeComponent();
        DataContext = this;
    }
}

前两个 TextBlock 对我来说显示良好，分别显示 2 和 'cake'.第三个没有完成我想要的，即使用 DessertIndex 属性索引到该数组并显示蛋糕".我在 SO 上做了一些类似的问题的搜索，但没有找到.最终，我不想在我的 .xaml 文件中指定像 2 这样的值，而是想依赖一个属性而不是索引到该数组中.这可能吗?如果是这样，我在这里做错了什么?

The first two TextBlocks display fine for me, displaying 2 and 'cake' respectively. The third one doesn't accomplish what I'd like, namely use the DessertIndex property to index into that array and also display 'cake'. I did a little searching here on SO for a similar question but didn't find one. Ultimately, I don't want to specify values like 2 in my .xaml file and would like to rely upon a property instead for indexing into that array. Is this possible? If so, what am I doing wrong here?

所以我更接近的是一种情况，其中数据是这些对象的列表[]，并且我使用上面的 StackPanel 作为 ListBox 的 DataTemplate 的一部分.因此，正如马克·希思 (Mark Heath) 在下面所建议的那样，使用取消引用数组的属性的想法似乎并不像我想要的那样工作.想法?

So what I more closely have is a situation where the data is a List of these object[] and I'm using the above StackPanel as part of a DataTemplate for a ListBox. So the idea, as Mark Heath suggests below, of using a property that dereferences the array doesn't seem to work as I'd want. Ideas?

推荐答案

另一种选择是将 MultiBinding 与转换器一起使用:

Another alternative is to use MultiBinding with a converter:

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:WpfApplication1"
        Title="MainWindow" Height="350" Width="525">
    <StackPanel Orientation="Vertical">
        <StackPanel.Resources>
            <local:FoodIndexConverter x:Key="foodIndexConverter" />
        </StackPanel.Resources>
        <TextBlock Text="{Binding DessertIndex}" />
        <TextBlock Text="{Binding Food[2]}" />
        <TextBlock>
                <TextBlock.Text>
                    <MultiBinding Converter="{StaticResource foodIndexConverter}">
                        <Binding Path="DessertIndex" />
                        <Binding Path="Food"/>
                    </MultiBinding>
                </TextBlock.Text>
        </TextBlock>
    </StackPanel>
</Window>

然后在代码隐藏中，转换器定义如下:

Then in the code-behind, the converter is defined something like this:

namespace WpfApplication1
{
    public class FoodIndexConverter : IMultiValueConverter
    {
        public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            if (values == null || values.Length != 2)
                return null;

            int? idx = values[0] as int?;
            object[] food = values[1] as object[];

            if (!idx.HasValue || food == null)
                return null;

            return food[idx.Value];
        }

        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }
}

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