在ItemsControl Tap事件上绑定CommandParameter [英] Binding CommandParameter on ItemsControl Tap event

问题描述

我正在使用ItemsControl，并且我想确定在Tap命令上选择了哪个项目.我的xaml在这里定义:

I'm using an ItemsControl, and I want to identify which item was selected on the Tap command. My xaml is defined here:

<ItemsControl ItemsSource="{Binding AllMyItems}">
    <i:Interaction.Triggers>
        <i:EventTrigger EventName="Tap">
              <cmd:EventToCommand Command="{Binding ItemSelectedCommand}" CommandParameter="{Binding}"/>
         </i:EventTrigger>
    </i:Interaction.Triggers>
    .... item template ....

这是我的视图模型:

public RelayCommand<MyItem> ItemSelectedCommand { get; private set; }
public MainViewModel()
    {
        ItemSelectedCommand = new RelayCommand<MyItem>(ItemSelected);
    }

private void ItemSelected(MyItem myItem)
    {
        throw new NotImplementedException();
    }

命令事件有效，但是当我进入ItemSelected方法时，myItem要么为Null，要么会抛出异常(取决于我在xaml中定义CommandParameter的方式).

The event to command works, but when I get to the ItemSelected method, myItem is either Null, or I get an exception casting it (depending on how I define the CommandParameter in the xaml).

如果我使用ListBox并设置CommandParameter="{Binding SelectedItem, ElementName=MyItemsList"}

I can do this if I use a ListBox and set CommandParameter="{Binding SelectedItem, ElementName=MyItemsList"}

关于如何使用ItemsControl做到这一点的任何想法?还是在芒果方面两者之间的性能差异没有太大差别?

Any ideas on how to do this with ItemsControl? Or does the perf difference not make much of a difference between the two in Mango?

推荐答案

您的Tap事件发生在ItemsControl上，您应该将EventToCommand放在ItemTemplate中，并使用一些XAML来为您清除内容

Your Tap Event is occuring on the ItemsControl , you should place your EventToCommand inside the ItemTemplate , some XAML to clear the things for you

<ItemsControl ItemsSource="{Binding AllMyItems}">
<ItemsControl.ItemTemplate>
<...>
<i:Interaction.Triggers>
    <i:EventTrigger EventName="Tap">
          <cmd:EventToCommand Command="{Binding ItemSelectedCommand}" CommandParameter="{Binding}"/>
     </i:EventTrigger>
</i:Interaction.Triggers>
</...>                                    
</ItemsControl.ItemTemplate>
...

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