MVVM ListView MultiBinding SelectedItems + SelectedItem (ListView) + SelectedItem (ComboBox) 到 TextBox.Text。没有正确更新

Question

我正在尝试将我的 ViewModel (ComboBox) 中的 SelectedItems (ListView) 和 SelectedItem 或 SelectedCategory 多重绑定到只读 TextBox。 OutputConverter 仅检查在为 TextBox.

创建文本之前是否至少选择了一项 (ListView) 和 TypeData (ComboBox)

但是，如果我只尝试这样做，TextBox 只会在 ComboBox.SelectedItem 发生变化时更新，而不会在 ListView 内部的 SelectedItems 发生变化时更新。
因此，我还从我的 ViewModel SelectedEntry (ListView)（与 SelectedItem 相同）中包含作为 MultiBinding 的绑定。

现在我得到以下信息：

解释：
Selection 始终落后一步，并使用 ListView 中的前一个 SelectedItems 绑定到 TextBox.Text。即使我通过 CTRL 或 Shift + Click 选择多个条目。但是，如果 ComboBox.SelectedItem 更改，它会按预期更新 TextBox。

如果 ListView 中的选择发生变化，我如何获得行为 TextBox 立即相应地更新其内容（最好我想使用我的 ViewModel 的 SelectedEntries 而不是 [= ListView 的 16=]，如果可能的话，以符合 MVVM 的方式）？

编辑：

我注意到转换器何时被称为 SelectedEntry（实现 INotifyPropertyChanged) 已更新，但 SelectedEntries （ObservableCollection 和实现 INotifyPropertyChanged）不是。
我还包含了调用命令的 SelectionChanged 事件并将 SelectedItems 作为参数传递给命令。如果说可能会有所帮助，但我宁愿有一个适当的绑定相应更新。

代码：

模型类型数据（组合框）：

public class TypeData : INotifyPropertyChanged
{
    public enum Type
    {
        NotSet = '0',
        A = 'A',
        B = 'B',
        C = 'C'
    }

    private string name;

    public string Name
    {
        get { return name; }
        set
        {
            name = value;
            //OnPropertyChanged("Name");
            OnPropertyChanged(nameof(Name));
        }
    }
    private Type category;

    public Type Category
    {
        get { return category; }
        set { category = value; }
    }


    public TypeData(string name)
    {
        Name = name;
    }

    public event PropertyChangedEventHandler PropertyChanged;

    private void OnPropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;

        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    public override string ToString()
    {
        return Name;
    }
}

模型条目（列表视图）：

public class Entry : INotifyPropertyChanged
{
    private string title;
    public string Title
    {
        get { return title; }
        set
        {
            title = value;
            OnPropertyChanged(nameof(Title));
        }
    }

    private string author;

    public string Author
    {
        get { return author; }
        set
        {
            author = value;
            OnPropertyChanged(nameof(Author));
        }
    }

    private string year;

    public string Year
    {
        get { return year; }
        set
        {
            year = value;
            OnPropertyChanged(nameof(Year));
        }
    }


    public Entry(string title, string author, string year)
    {
        Title = title;
        Author = author;
        Year = year;
    }

    public event PropertyChangedEventHandler PropertyChanged;

    private void OnPropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;

        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

ViewModel:

public class MainViewModel
{
    public ObservableCollection<Entry> Entries { get; set; }

    public Entry SelectedEntry { get; set; }

    public ObservableCollection<Entry> SelectedEntries { get; set; }

    public ObservableCollection<TypeData> Types { get; set; }

    private TypeData selectedCategory;

    public TypeData SelectedCategory { get; set; }

    public RelayCommand<object> SelectionChangedCommand { get; set; }

    public MainViewModel()
    {
        Entries = new ObservableCollection<Entry>
        {
            new Entry("Title1", "Author1", "Year1"),
            new Entry("Title2", "Author2", "Year2"),
            new Entry("Title3", "Author3", "Year3"),
            new Entry("Title4", "Author4", "Year4"),
        };

        Types = new ObservableCollection<TypeData>
        {
            new TypeData("A"),
            new TypeData("B"),
            new TypeData("C"),
        };

        SelectionChangedCommand = new RelayCommand<object>(items =>
        {
            var selectedEntries = (items as ObservableCollection<object>).Cast<Entry>();
            SelectedEntries = new ObservableCollection<Entry>(selectedEntries);
        });
    }
}

XAML:

<Window x:Class="MvvmMultiBinding.View.MainWindow"
    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:MvvmMultiBinding"
    xmlns:m="clr-namespace:MvvmMultiBinding.Model"
    xmlns:vm="clr-namespace:MvvmMultiBinding.ViewModel"
    xmlns:conv="clr-namespace:MvvmMultiBinding.View.Converter"
    xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
    xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions"
    xmlns:sys="clr-namespace:System;assembly=mscorlib"
    mc:Ignorable="d"
    Title="MainWindow" Height="350" Width="525">
<Window.DataContext>
    <vm:MainViewModel></vm:MainViewModel>
</Window.DataContext>
<Window.Resources>
    <conv:OutputConverter x:Key="OutputConverter"/>
</Window.Resources>
<Grid>
    <DockPanel>
        <ListView Name="ListViewEntries" ItemsSource="{Binding Entries}" SelectedItem="{Binding SelectedEntry}" DockPanel.Dock="Top">
            <ListView.View>
                <GridView>
                    <GridViewColumn Header="Title" Width="250" DisplayMemberBinding="{Binding Title}" />
                    <GridViewColumn Header="Author" Width="150" DisplayMemberBinding="{Binding Author}" />
                    <GridViewColumn Header="Year" Width="50" DisplayMemberBinding="{Binding Year}" />
                </GridView>
            </ListView.View>
            <i:Interaction.Triggers>
                <i:EventTrigger EventName="SelectionChanged">
                    <i:InvokeCommandAction Command="{Binding DataContext.SelectionChangedCommand, ElementName=ListViewEntries}"
                                       CommandParameter="{Binding SelectedItems, ElementName=ListViewEntries}"/>
                </i:EventTrigger>
            </i:Interaction.Triggers>
        </ListView>
        <ComboBox ItemsSource="{Binding Types}" SelectedItem="{Binding SelectedCategory}" MinWidth="200" DockPanel.Dock="Right"/>
        <TextBox IsReadOnly="True" DockPanel.Dock="Left">
            <TextBox.Text>
                <MultiBinding Converter="{StaticResource OutputConverter}">
                    <Binding ElementName="ListViewEntries" Path="SelectedItems" Mode="OneWay"/>
                    <!--<Binding Path="SelectedEntries" Mode="OneWay"/>-->
                    <Binding Path="SelectedCategory" Mode="OneWay"/>
                    <!-- Without it converter is not called after selection changes -->
                    <Binding Path="SelectedEntry" Mode="OneWay"/>
                </MultiBinding>
            </TextBox.Text>
        </TextBox>
    </DockPanel> 
</Grid>

输出转换器:

public class OutputConverter : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        System.Collections.IList items = (System.Collections.IList)values[0];
        var entries = items.Cast<Entry>();
        TypeData type = values[1] as TypeData;
        List<Entry> selectedEntries = new List<Entry>();

        foreach (var entry in entries)
        {
            selectedEntries.Add(entry);
        }
        StringBuilder sb = new StringBuilder();

        // ComboBox and Selection must not be empty
        if (type != null && selectedEntries.Count > 0)
        {
            foreach (var selectedEntry in selectedEntries)
            {
                sb.AppendFormat("{0} {1}\n\n", selectedEntry.Author, type);
            }
        }

        return sb.ToString();
    }

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

Answer 1

我建议给您的条目 Class 一个 IsSelected 属性（绑定到 ListViewItem 的 IsSelectedProperty）。 When the selection changes you can just iterate through your collection (bound to the ListView) and check if they are selected or not.像这样（请原谅 MvvmLight，RelayCommand = ICommand，ViewModelBase extends ObservableObject）：

ViewModel:

public class MainViewModel : ViewModelBase
{
    public MainViewModel()
    {
        TestItemCollection = new ObservableCollection<TestItem>
        {
            new TestItem("Test1"),
             new TestItem("Test2"),
              new TestItem("Test3")
            };
    }

    private TestItem m_selectedItemProperty;
    public TestItem SelectedItemProperty
    {
        get
        {
            return m_selectedItemProperty;
        }
        set
        {
            m_selectedItemProperty = value;
            RaisePropertyChanged("SelectedItemProperty");
        }
    }

    public ObservableCollection<TestItem> TestItemCollection
    {
        get;
        set;
    }

    public RelayCommand SelectionChanged
    {
        get { return new RelayCommand(OnSelectionChanged); }
    }

    private void OnSelectionChanged()
    {
        foreach (var item in TestItemCollection)
        {
            if (item.IsSelected)
                Console.WriteLine("Name: " + item.Name);
        }
    }
}

我在这里打印了名称，但您也可以将它们添加到字符串属性并将其绑定到您的文本框或将项目添加到集合（可能绑定到 ListBox 或 ItemsControl 显示所选条目）。

测试项：

public class TestItem : ObservableObject
{
    public TestItem(string a_name)
    {
        m_name = a_name;
    }

    private string m_name;
    public string Name
    {
        get
        {
            return m_name;
        }
        set
        {
            m_name = value;
            RaisePropertyChanged("Name");
        }
    }

    private bool m_isSelected;
    public bool IsSelected
    {
        get
        {
            return m_isSelected;
        }
        set
        {
            m_isSelected = value;
            RaisePropertyChanged("IsSelected");
        }
    }
}

查看：

<Window x:Class="WpfAppTests.MainWindow"
    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:WpfAppTests"
    xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
    xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions"
    mc:Ignorable="d"
    xmlns:modelNoMvvmLight="clr-namespace:WpfAppTests"
    xmlns:modelMvvmLight="clr-namespace:WpfAppTests.ViewModel"
    Title="MainWindow" Height="350" Width="525" >
<Window.DataContext>
    <modelMvvmLight:MainViewModel/>
</Window.DataContext>

<StackPanel>
    <ListView Name="ListView" ItemsSource="{Binding TestItemCollection}" SelectedItem="{Binding SelectedItemProperty}">
        <i:Interaction.Triggers>
            <i:EventTrigger EventName="SelectionChanged">
                <i:InvokeCommandAction Command="{Binding SelectionChanged}"/>
            </i:EventTrigger>
        </i:Interaction.Triggers>

        <ListView.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding Name}"/>
            </DataTemplate>
        </ListView.ItemTemplate>

        <ListView.ItemContainerStyle>
            <Style TargetType="ListViewItem" >
                <Setter Property="IsSelected" Value="{Binding IsSelected}"/>
            </Style>
        </ListView.ItemContainerStyle>
    </ListView>
</StackPanel>
</Window>

MVVM ListView MultiBinding SelectedItems + SelectedItem (ListView) + SelectedItem (ComboBox) 到 TextBox.Text。没有正确更新

MVVM ListView MultiBinding SelectedItems + SelectedItem (ListView) + SelectedItem (ComboBox) to TextBox.Text. Does not update properly

c#

wpf

listview

mvvm

multibinding

代码：