不能用的SelectedItem = NULL明确列表框选择 - MVVM [英] Can't clear ListBox selection using SelectedItem = null - MVVM

问题描述

我有以下的数据模板（以及相应的视图模型，未显示）：

I have the following data template (and a corresponding view model, not shown):

<DataTemplate DataType="{x:Type logic:SnapshotListViewModel}">
    <ListBox ItemsSource="{Binding Snapshots}" />
</DataTemplate>

的ItemsSource绑定到快照列表，在视图模型发现里面。我的目标是明确的SelectedItem，因此列表框回到其初始，未选中状态。该视图模型实现IPropertyNotified

ItemsSource is bound to a list of Snapshots, found inside the viewmodel. My goal is to clear the SelectedItem, so the listbox goes back to its initial, unselected state. The view model implements IPropertyNotified.

我说像这样的XAML绑定：

I added a binding in the XAML like so:

<ListBox SelectedItem={Binding SelectedSnapshot} .... />

在视图模型，我设置SelectedSnapshot = null，但什么也没有发生，即使RaisePropertyChanged被称为上属性。

In the view model, I set SelectedSnapshot = null, but nothing happens, even though RaisePropertyChanged was called on the property.

我再次SelectedIndex的，而不是尝试过的SelectedItem。仍然没有运气。

I tried again with SelectedIndex instead of SelectedItem. Still no luck.

我终于找到了解决方案，我将在下面详细信息。

I finally found the solution, which I will detail below.

推荐答案

忘记的SelectedItem和SelectedIndex的。答案就是的SelectedValue ，随着 IsSynchronizedWithCurrentItem =真。

Forget SelectedItem and SelectedIndex. The answer is SelectedValue, along with IsSynchronizedWithCurrentItem="True".

<ListBox IsSynchronizedWithCurrentItem="True" 
         SelectedValue="{Binding SelectedSnapshotValue}" .../>

然后，当我在视图模型调用ResetSelection（），SelectedSnapshotValue被设置为null，

Then, when I call ResetSelection() in the view model, SelectedSnapshotValue is set to null,

void ResetSelection()
{
    SelectedSnapshotValue = null;
}

这将更新数据模板的绑定，使用绑定属性：

which updates the binding in the data template, using the bound property:

    private SnapshotViewModel selectedSnapshotValue;
    public SnapshotViewModel SelectedSnapshotValue
    {
        get { return selectedSnapshotValue; }
        set
        {
            if (selectedSnapshotValue != value)
            {
                selectedSnapshotValue = value;
                RaisePropertyChanged("SelectedSnapshotValue");
            }
        }
    }

这是我唯一的出路能得到我的列表框中重新选择。

This is the only way I was able to get my listbox to reset the selection.

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