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问WPF MVVM ListBox MultiSelect
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Stack Overflow用户

提问于 2022-11-02 09:37:22

回答 2查看 52关注 0票数 -1

我已经创建了一个包含项目列表的列表框，我需要在选择更改(选择和取消选择)时绑定它们。

ABCD.xalm

<ListBox Grid.Column="2" Grid.ColumnSpan="9" Height="30" Margin="0 0 5 0" Foreground="{StaticResource AcresTheme}" SelectedItem="{Binding Path=UpdateSimulationItem,UpdateSourceTrigger=PropertyChanged}"                               
                            ItemsSource="{Binding SmulationTypes, NotifyOnSourceUpdated=True}" 
                            Background="{Binding }"
                            MinHeight="65" SelectionMode="Multiple">
                        <ListBox.ItemTemplate>
                            <DataTemplate>
                                <CheckBox  Foreground="{StaticResource AcresTheme}"
                                           Content="{Binding Item}" 
                                           IsChecked="{Binding Path=IsSelected, Mode=TwoWay}"></CheckBox>
                            </DataTemplate>
                        </ListBox.ItemTemplate>
                        <ListBox.ItemContainerStyle>
                            <Style TargetType="{x:Type ListBoxItem}">
                                <Setter Property="IsSelected" Value="{Binding Mode=TwoWay, Path=IsSelected}"/>
                            </Style>
                        </ListBox.ItemContainerStyle>
                    </ListBox>

ABCD.cs (视图模型)

public List<string> SimulationTypesList { get; set; } = new List<string>();
    private ObservableCollection<SimulationType> _simulationTypes = new ObservableCollection<SimulationType>();

    public ObservableCollection<Items> SimulationTypes
    {
        get
        {
            return _simulationTypes;
        }
        set
        {
            _simulationTypes = value;
            OnPropertyChanged("SimulationTypes");
        }
    }

    private Items _updateSimulationItem;
    public Items UpdateSimulationItem
    {
        get
        {
            return _updateSimulationItem;
        }
        set
        {
          //Logic for getting the selected item
            _updateSimulationItem = value;
            OnPropertyChanged("UpdateSimulationItem");
        }
    }
public ABCD()
{
        SimulationTypes.Add(new SimulationType() { Item = "Simulation 1", IsSelected = false });
        SimulationTypes.Add(new SimulationType() { Item = "Simulation 2", IsSelected = false });
        SimulationTypes.Add(new SimulationType() { Item = "Simulation 3", IsSelected = false });
}

Items.cs

public class Items: ViewModelBase
{
    private string item;
    public string Item
    {
        get { return item; }
        set
        {
            item = value;
            this.OnPropertyChanged("Item");
        }
    } 
    
    private bool isSelected;
    public bool IsSelected
    {
        get { return isSelected; }
        set
        {
            isSelected = value;
            this.OnPropertyChanged("IsSelected");
        }
    }
}

我确实尝试了在https://stackoverflow.com/a/34632944/12020323中给出的解决方案，这对于删除单个项或选择单个项都很有效。

当我们选择第二项时，它不会触发属性更改。

wpf

mvvm

listbox

回答 2

Stack Overflow用户

回答已采纳

发布于 2022-11-10 08:33:27

@EldHasp，谢谢你花时间回答我的问题。对所提供的解决方案非常满意。

目前，我非常热衷于在ViewModel中使用完整的代码，我发现了我在ViewModel中所犯的错误。

旧法典：

private ObservableCollection<SimulationType> _simulationTypes = new ObservableCollection<SimulationType>();

public ObservableCollection<Items> SimulationTypes
{
    get
    {
        return _simulationTypes;
    }
    set
    {
        _simulationTypes = value;
        OnPropertyChanged("SimulationTypes");
    }
}

private Items _updateSimulationItem;
public Items UpdateSimulationItem
{
    get
    {
        return _updateSimulationItem;
    }
    set
    {
        //Logic for getting the selected item
        _updateSimulationItem = value;
        OnPropertyChanged("UpdateSimulationItem");
    }
}

_updateSimulationItem =；将第一个选定的项绑定到UpdateSimulationItem，属性更改仅在更改该perticular项时才会触发。

例如：

SimulationTypes.Add(新项目=“模拟1"，IsSelected =假}；SimulationTypes.Add(新SimulationType() { SimulationType() =”模拟2"，IsSelected =假})；SimulationTypes.Add(新SimulationType() {项目=“模拟3"，IsSelected = false })；

在这三个项目中，如果我选择模拟1，那么UpdateSimulationItem将绑定到模拟1，属性的变化将缩小到一个项目，即模拟1。现在如果我们点击仿真2，那么peopertychange将不会触发，因为UpdateSimulationItem仅绑定到模拟1项更改。

我所做的改变。

更新代码：

private Items _updateSimulationItem;
public Items UpdateSimulationItem
{
    get
    {
        return _updateSimulationItem;
    }
    set
    {
      //Removed unnecessary code and the assignment of value to _updateSimulationItem
      OnPropertyChanged("UpdateSimulationItem");
    }
}

我们已经将SimulationTypes绑定到ABC.XAML中的ItemSource中，如下所示

<ListBox Foreground="{StaticResource AcresTheme}" 
         SelectedItem="{Binding Path=UpdateSimulationItem,UpdateSourceTrigger=PropertyChanged}" 
         ItemsSource="{Binding SimulationTypes, NotifyOnSourceUpdated=True}" 
         MinHeight="65" SelectionMode="Multiple">

当我单击视图中的复选框时，它将自动将SimulationTypes绑定到IsSelected。

<CheckBox  Foreground="{StaticResource AcresTheme}"
           Content="{Binding Item}"
           IsChecked="{Binding Path=IsSelected, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}">

@EldHasp我们在代码中必须做的代码更改是将赋值移除给setter属性中的OnPropertychange(nameOf(SelectedItem)).，只保留

公共物品？SelectedItem { get => _selectedItem；set => Set(ref _selectedItem，value); }粗体文本使=>绑定到一个项，这将在选择其他项时限制触发器。

再次感谢 @EldHasp在这方面花费了你的时间。

票数 0

Stack Overflow用户

发布于 2022-11-02 17:39:53

错误不在此代码中。您可能对VM实例感到困惑。这通常是初学者的情况。SimulationType的实现可能有问题。你没表现出来。

下面是一个完整的代码示例，演示多选择绑定正确工作。

using Simplified;
using System;
using System.Collections.ObjectModel;

namespace Core2022.SO.ChaithanyaS
{
    public class Item : ViewModelBase
    {
        private string _title = string.Empty;
        public string Title
        {
            get => _title;
            set => Set(ref _title, value ?? string.Empty);
        }

        private bool _isSelected;
        public bool IsSelected
        {
            get => _isSelected;
            set => Set(ref _isSelected, value);
        }
    }

    public class SimulationType : Item
    {
        private int _count;
        public int Count { get => _count; set => Set(ref _count, value); }
    }

    public class ItemsViewModel : ViewModelBase
    {
        private static readonly Random random = new Random();
        private Item? _selectedItem;

        public ObservableCollection<Item> Items { get; } =
                    new ObservableCollection<Item>()
                    {
                new Item() {Title = "First" },
                new SimulationType() { Title = "Yield Simulation", Count = random.Next(5, 15) },
                new Item() {Title = "Second" },
                new SimulationType() { Title = "HLR Simulation", Count = random.Next(5, 15) },
                new SimulationType() { Title = "UnCorr HLR Simulation", Count = random.Next(5, 15)},
                new Item() {Title = "Third" }
                    };

        public Item? SelectedItem { get => _selectedItem; set => Set(ref _selectedItem, value); }
    }
}

<Window x:Class="Core2022.SO.ChaithanyaS.ItemsWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:Core2022.SO.ChaithanyaS"
        mc:Ignorable="d"
        Title="ItemsWindow" Height="450" Width="800">
    <Window.DataContext>
        <local:ItemsViewModel/>
    </Window.DataContext>
    <UniformGrid Columns="2">
        <ListBox Margin="10"
                 SelectedItem="{Binding SelectedItem}"
                 ItemsSource="{Binding Items}"
                 SelectionMode="Multiple">
            <FrameworkElement.Resources>
                <DataTemplate DataType="{x:Type local:Item}">
                    <CheckBox  Foreground="Red"
                               Content="{Binding Title}"
                               IsChecked="{Binding Path=IsSelected, Mode=TwoWay}"/>
                </DataTemplate>
                <DataTemplate DataType="{x:Type local:SimulationType}">
                    <CheckBox Foreground="Green"
                               IsChecked="{Binding Path=IsSelected, Mode=TwoWay}">
                        <TextBlock>
                            <TextBlock.Text>
                                <MultiBinding StringFormat="{}{0} ({1})">
                                    <Binding Path="Title"/>
                                    <Binding Path="Count"/>
                                </MultiBinding>
                            </TextBlock.Text>
                        </TextBlock>
                    </CheckBox>
                </DataTemplate>
            </FrameworkElement.Resources>
            <ListBox.ItemContainerStyle>
                <Style TargetType="{x:Type ListBoxItem}">
                    <Setter Property="IsSelected" Value="{Binding Mode=TwoWay, Path=IsSelected}"/>
                </Style>
            </ListBox.ItemContainerStyle>
        </ListBox>

        <ItemsControl ItemsSource="{Binding Items}" Margin="10"
                      BorderBrush="Green" BorderThickness="1"
                      Padding="10">
            <ItemsControl.ItemTemplate>
                <DataTemplate DataType="{x:Type local:Item}">
                    <DataTemplate.Resources>
                        <DataTemplate DataType="{x:Type local:Item}">
                            <TextBlock  Foreground="Red"
                               Text="{Binding Title}"/>
                        </DataTemplate>
                        <DataTemplate DataType="{x:Type local:SimulationType}">
                            <TextBlock Foreground="Green">
                                <TextBlock.Text>
                                    <MultiBinding StringFormat="{}{0} ({1})">
                                        <Binding Path="Title"/>
                                        <Binding Path="Count"/>
                                    </MultiBinding>
                                </TextBlock.Text>
                            </TextBlock>
                        </DataTemplate>
                    </DataTemplate.Resources>
                    <Label x:Name="cc" Content="{Binding}" Margin="1" BorderBrush="Gray" BorderThickness="1"/>
                    <DataTemplate.Triggers>
                        <DataTrigger Binding="{Binding IsSelected}" Value="True">
                            <Setter TargetName="cc" Property="Background" Value="LightPink"/>
                        </DataTrigger>
                    </DataTemplate.Triggers>
                </DataTemplate>
            </ItemsControl.ItemTemplate>
        </ItemsControl>
    </UniformGrid>
</Window>

也许您的意思是，在多选择模式下，SelectedItem属性始终只有首先选定的项，直到取消选中为止？

不幸的是，这样一项任务的执行并不容易。最好是创建一个自定义AP属性，然后在XAML中使用它。

    public static class MuliSelectorHelper
    {
        /// <summary>Returns the value of the IsSelectedItemLast attached property for <paramref name="multiSelector"/>.</summary>
        /// <param name="multiSelector"><see cref="DependencyObject"/> whose property value will be returned.</param>
        /// <returns><see cref="bool"/> property value.</returns>
        public static bool GetIsSelectedItemLast(DependencyObject multiSelector)
        {
            return (bool)multiSelector.GetValue(IsSelectedItemLastProperty);
        }

        /// <summary>Sets the value of the IsSelectedItemLast attached property for <paramref name="multiSelector"/>.</summary>
        /// <param name="multiSelector"><see cref="MultiSelector"/> whose property value will be returned.</param>
        /// <param name="value"><see cref="bool"/> value for property.</param>
        public static void SetIsSelectedItemLast(DependencyObject multiSelector, bool value)
        {
            multiSelector.SetValue(IsSelectedItemLastProperty, value);
        }

        /// <summary><see cref="DependencyProperty"/> for methods <see cref="GetIsSelectedItemLast(MultiSelector)"/>
        /// and <see cref="SetIsSelectedItemLast(MultiSelector, bool)"/>.</summary>
        public static readonly DependencyProperty IsSelectedItemLastProperty =
            DependencyProperty.RegisterAttached(
                nameof(GetIsSelectedItemLast).Substring(3),
                typeof(bool),
                typeof(MuliSelectorHelper),
                new PropertyMetadata(false, OnIsSelectedItemLastChanged));

        private static void OnIsSelectedItemLastChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            if (d is not Selector selector || selector.GetValue(ListBox.SelectedItemsProperty) is not IList list)
            {
                throw new NotImplementedException("Implemented only types that derive from Selector and that use the ListBox.SelectedItems dependency property.");
            }

            if (Equals(e.NewValue, true))
            {
                selector.SelectionChanged += OnSelectionChanged;
            }
            else
            {
                selector.SelectionChanged -= OnSelectionChanged;
            }
        }

        private static async void OnSelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            if (e.AddedItems.Count == 0)
                return;

            Selector selector = (Selector)sender;
            IList selectedItems = (IList)selector.GetValue(ListBox.SelectedItemsProperty);

            if (selectedItems.Count != e.AddedItems.Count && !Equals(selectedItems[0], e.AddedItems[0]))
            {
                selector.SelectionChanged -= OnSelectionChanged;

                int beginIndex = selectedItems.Count - e.AddedItems.Count;
                var selectedItemsArray = new object[selectedItems.Count];
                selectedItems.CopyTo(selectedItemsArray, 0);
                selectedItems.Clear();
                await selector.Dispatcher.BeginInvoke(() =>
                {
                    for (int i = selectedItemsArray.Length-1; i >= beginIndex; i--)
                    {
                        selectedItems.Add(selectedItemsArray[i]);
                    }
                    for (int i = 0; i < beginIndex; i++)
                    {
                        selectedItems.Add(selectedItemsArray[i]);
                    }

                });

                selector.SelectionChanged += OnSelectionChanged;
            }

        }
    }

    <UniformGrid Columns="2">
        <ListBox Margin="10"
                 SelectedItem="{Binding SelectedItem}"
                 ItemsSource="{Binding Items}"
                 SelectionMode="Multiple"
                 local:MuliSelectorHelper.IsSelectedItemLast="true">
            <FrameworkElement.Resources>
                <DataTemplate DataType="{x:Type local:Item}">
                    <CheckBox  Foreground="Red"
                               Content="{Binding Title}"
                               IsChecked="{Binding Path=IsSelected, Mode=TwoWay}"/>
                </DataTemplate>
                <DataTemplate DataType="{x:Type local:SimulationType}">
                    <CheckBox Foreground="Green"
                               IsChecked="{Binding Path=IsSelected, Mode=TwoWay}">
                        <TextBlock>
                            <TextBlock.Text>
                                <MultiBinding StringFormat="{}{0} ({1})">
                                    <Binding Path="Title"/>
                                    <Binding Path="Count"/>
                                </MultiBinding>
                            </TextBlock.Text>
                        </TextBlock>
                    </CheckBox>
                </DataTemplate>
            </FrameworkElement.Resources>
            <ListBox.ItemContainerStyle>
                <Style TargetType="{x:Type ListBoxItem}">
                    <Setter Property="IsSelected" Value="{Binding Mode=TwoWay, Path=IsSelected}"/>
                </Style>
            </ListBox.ItemContainerStyle>
        </ListBox>

        <ContentControl Content="{Binding SelectedItem}">
            <ContentControl.ContentTemplate>
                <DataTemplate DataType="{x:Type local:Item}">
                    <DataTemplate.Resources>
                        <DataTemplate DataType="{x:Type local:Item}">
                            <TextBlock  Foreground="Red"
                               Text="{Binding Title}"/>
                        </DataTemplate>
                        <DataTemplate DataType="{x:Type local:SimulationType}">
                            <TextBlock Foreground="Green">
                                <TextBlock.Text>
                                    <MultiBinding StringFormat="{}{0} ({1})">
                                        <Binding Path="Title"/>
                                        <Binding Path="Count"/>
                                    </MultiBinding>
                                </TextBlock.Text>
                            </TextBlock>
                        </DataTemplate>
                    </DataTemplate.Resources>
                    <Label x:Name="cc" Content="{Binding}" Margin="1" BorderBrush="Gray" BorderThickness="1"/>
                    <DataTemplate.Triggers>
                        <DataTrigger Binding="{Binding IsSelected}" Value="True">
                            <Setter TargetName="cc" Property="Background" Value="LightPink"/>
                        </DataTrigger>
                    </DataTemplate.Triggers>
                </DataTemplate>
            </ContentControl.ContentTemplate>
        </ContentControl>
    </UniformGrid>

票数 0

页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持

原文链接：

https://stackoverflow.com/questions/74287084

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