Question

我将此代码放在按钮附加的TargetedTriggerAction＆lt; DataGrid＆gt;

我要做的是找到我喜欢的项目并将它们放入列表中。完成后，我想将DataGrid的SelectedItems设置为列表。

我想这样做，因为我有成千上万的项目要迭代，在后台线程上占多数并在最后设置SelectedItems，避免使用对SelectedItems.Add（）的单独调用的UI线程会更有效率。无论如何，这是我的逻辑。

我意识到SelecteedItems是readonly所以我的问题是我真的可以这样做吗？如何通过列表设置SelectedItems？另一方面，如果SelectAll按钮可以在短时间内选择所有内容，那么必须有一种方法可以实现我想要的......不应该在那里吗？

IList<Object> tempItems = new List<Object>();
var itemsSource = this.Target.Items as IEnumerable;
Task.Factory.StartNew(() =>
{
    FullTextSearch<UserViewModel>.FullTextSearchInit();

    if (itemsSource != null)
    {
        foreach (var item in itemsSource)
        {
            if (FullTextSearch<UserViewModel>.Match((UserViewModel)item, sv))
            {
                tempItems.Add(item);
            }
        }
        if (tempItems.Count > 0)
        {
            Application.Current.Dispatcher.Invoke(new Action(() =>
                /**** How to set? ****/
                this.Target.SelectedItems = tempList
                ));
        }
    }
});

[编辑] 但是，尝试执行以下操作时，IsUpdatingSelectedItems，BeginUpdateSelectedItems和EndUpdateSelectedItems都返回了类似的错误：

System.Windows.Controls.Primitives.MultiSelector.BeginUpdateSelectedItems（）＆＃39;由于其保护级别而无法访问

if (!this.Target.IsUpdatingSelectedItems)
{
    this.Target.BeginUpdateSelectedItems();
    foreach (object item in this.Target.Items)
    {
        if (FullTextSearch<UserViewModel>.Match((UserViewModel)item, sv))
        {
            this.Target.SelectedItems.Add(item);
        }
    }
    this.Target.EndUpdateSelectedItems();
}

Answer 1

在评论和编辑过的问题中，有人询问如何调用DataGrid的受保护BeginUpdateSelectedItems和EndUpdateSelectedItems方法。

最简单的方法是继承DataGrid并实现一个可以调用这些受保护方法的方法：

    public class MyDataGrid : DataGrid
    {
        public void SelectManyItems(IEnumerable itemsToBeSelected)
        {
            if (!IsUpdatingSelectedItems)
            {
                BeginUpdateSelectedItems();
                foreach (object item in itemsToBeSelected)
                    SelectedItems.Add(item);
                EndUpdateSelectedItems.Invoke();
            }
        }
    }

虽然这看起来很简单，但它的缺点是需要您在需要此功能的地方用 MyDataGrid 替换 DataGrid 。在处理现有或第三方代码库时，这种方法很快变得不可行。

另一种更通用的方法是利用反射从外部调用受保护的方法＆＃34; DataGrid对象实例。这不需要对 DataGrid 进行子类化。

public static class MultiSelectorHelper
{
    private static readonly PropertyInfo _piIsUpdatingSelectedItems;
    private static readonly MethodInfo _miBeginUpdateSelectedItems;
    private static readonly MethodInfo _miEndUpdateSelectedItems;

    static MultiSelectorHelper()
    {
        _piIsUpdatingSelectedItems = typeof(MultiSelector).GetProperty("IsUpdatingSelectedItems", BindingFlags.NonPublic | BindingFlags.Instance);
        _miBeginUpdateSelectedItems = typeof(MultiSelector).GetMethod("BeginUpdateSelectedItems", BindingFlags.NonPublic | BindingFlags.Instance);
        _miEndUpdateSelectedItems = typeof(MultiSelector).GetMethod("EndUpdateSelectedItems", BindingFlags.NonPublic | BindingFlags.Instance);
    }


    public static void SelectManyItems(this MultiSelector control, IEnumerable itemsToBeSelected)
    {
        control.Dispatcher.Invoke(
            (Action) (() =>
            {
                if (!(bool) _piIsUpdatingSelectedItems.GetValue(control, null))
                {
                    _miBeginUpdateSelectedItems.Invoke(control, null);
                    try
                    {
                        foreach (object item in itemsToBeSelected)
                            control.SelectedItems.Add(item);
                    }
                    finally
                    {
                        _miEndUpdateSelectedItems.Invoke(control, null);
                    }
                }
            })
        );
    }
}

请注意， SelectManyItems 是作为扩展方法实现的，适用于从 MultiSelector （包括DataGrid）派生的任何控件。

另请注意尝试 - 最终块，即使在添加所选项目时发生异常，也会确保调用 EndUpdateSelectedItems 方法

这种扩展方法的用法很简单：

IEnumerable collectionWithItemsToSelect = ...
dataGridInstance.SelectManyItems(collectionWithItemsToSelect);

Answer 2

您可以在SelectionChanged()

中获取选定项目

XAML：

    <Window x:Class="ListViewSelectedItemsBinding.Window1"

xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

xmlns:local="clr-namespace:ListViewSelectedItemsBinding"

xmlns:w="clr-namespace:System.Windows.Workarounds"

x:Name="root" Width="500" Height="700">

<Window.Resources>

<local:MyConverter x:Key="myConverter"/>

</Window.Resources>

<StackPanel>

<ListView x:Name="listView" ItemsSource="{Binding}" SelectionMode="Extended"

SelectionChanged="listView_SelectionChanged"

w:ListView.HasBindableSelectedItems="True">

<ListView.View>

<GridView>

<GridViewColumn Header="Artist" DisplayMemberBinding="{Binding Path=Artist}" />

<GridViewColumn Header="Title" DisplayMemberBinding="{Binding Path=Title}" />

<GridViewColumn Header="Genre" DisplayMemberBinding="{Binding Path=Genre}" />

</GridView>

</ListView.View>

</ListView>

<StackPanel Background="LightGreen">

<DockPanel>

<Label DockPanel.Dock="Left" Content="SelectedItems.Count = " />

<TextBox Text="{Binding ElementName=listView, Path=SelectedItems.Count, Mode=OneWay}" IsReadOnly="True" />

</DockPanel>

<DockPanel>

<Label DockPanel.Dock="Left" Content="SelectedItems = " />

<TextBox Text="{Binding ElementName=listView, Path=SelectedItems, Mode=OneWay,

Converter={StaticResource myConverter}, ConverterParameter='Artist'}" IsReadOnly="True" />

</DockPanel>

</StackPanel>

<StackPanel Background="LightBlue">

<DockPanel>

<Label DockPanel.Dock="Left" Content="Selection.Count = " />

<TextBox Text="{Binding ElementName=root, Path=Selection.Count, Mode=OneWay}" IsReadOnly="True" />

</DockPanel>

<DockPanel>

<Label DockPanel.Dock="Left" Content="Selection = " />

<TextBox Text="{Binding ElementName=root, Path=Selection, Mode=OneWay,

Converter={StaticResource myConverter}, ConverterParameter='Artist'}" IsReadOnly="True" />

</DockPanel>

</StackPanel>

<local:PropertiesPanel x:Name="propertiesPanel1" Background="LightGreen"

Subjects="{Binding ElementName=listView, Path=SelectedItems, Mode=OneWay}" />

<local:PropertiesPanel x:Name="propertiesPanel2" Background="LightBlue"

Subjects="{Binding ElementName=root, Path=Selection, Mode=OneWay}" />

<local:PropertiesPanel x:Name="propertiesPanel3" Background="LightPink"

Subjects="{Binding ElementName=listView, Path=BindableSelectedItems}" />

</StackPanel>

</Window>

背景：

    using System;

using System.Collections;

using System.Windows.Data;

using System.Windows.Controls;



namespace System.Windows.Workarounds

{

public static class ListView

{

    public static readonly DependencyProperty HasBindableSelectedItemsProperty;

    public static readonly DependencyProperty BindableSelectedItemsProperty;

    static DependencyProperty SelectionChangedHandlerProperty;



    static ListView()

    {

    BindableSelectedItemsProperty = DependencyProperty.Register("BindableSelectedItems", typeof(IList),typeof(System.Windows.Controls.ListView));

    HasBindableSelectedItemsProperty = DependencyProperty.RegisterAttached("HasBindableSelectedItems", typeof(bool),typeof(System.Windows.Controls.ListView), new PropertyMetadata(false));

    SelectionChangedHandlerProperty = DependencyProperty.RegisterAttached("SelectionChangedHandler", typeof(SelectionChangedHandler),typeof(System.Windows.Controls.ListView));

    }



    public static void SetHasBindableSelectedItems(System.Windows.Controls.ListView source, bool value)
    {
    SelectionChangedHandler Handler = (SelectionChangedHandler)source.GetValue(SelectionChangedHandlerProperty);

    if (value && Handler == null)
    {
        Handler = new SelectionChangedHandler(source);
        source.SetValue(SelectionChangedHandlerProperty, Handler);
    } 
    else if (!value && Handler != null)
    {
        source.ClearValue(SelectionChangedHandlerProperty);
    }
}

}



internal class SelectionChangedHandler
{

    Binding Binding;
    internal SelectionChangedHandler(System.Windows.Controls.ListView owner)
    {
        Binding = new Binding("SelectedItems");
        Binding.Source = owner;
        owner.SetBinding(ListView.BindableSelectedItemsProperty, Binding);
        owner.SelectionChanged +=new SelectionChangedEventHandler(Owner_SelectionChanged);
    }

    void Owner_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        System.Windows.Controls.ListView Owner =(System.Windows.Controls.ListView)sender;
        BindingOperations.ClearBinding(Owner, ListView.BindableSelectedItemsProperty);
        Owner.SetBinding(ListView.BindableSelectedItemsProperty, Binding);
    }
}
}

您还可以创建依赖属性来替换“选择项目”

http://blog.functionalfun.net/2009/02/how-to-databind-to-selecteditems.html

您可以通过列表在DataGrid上设置SelectedItems

2 个答案: