我正在尝试将 ViewModel (ComboBox) 中的 SelectedItems
(ListView) 和 SelectedItem
或 SelectedCategory 多重绑定(bind)到只读 TextBox
。 OutputConverter 仅在为 TextBox
创建文本之前检查是否至少选择了一项 (ListView) 和 TypeData (ComboBox)。
但是,如果我仅尝试这样做,则 TextBox
仅在 ComboBox.SelectedItem
更改时更新,而不是在 ListView 内的 SelectedItems
更改时更新。
因此,我还从我的 ViewModel SelectedEntry
(ListView)(与 SelectedItem
相同)中包含了作为 MultiBinding 的绑定(bind)。
现在我得到以下信息:
说明:
Selection 始终落后一步,并使用 ListView 中的前一个 SelectedItems
绑定(bind)到 TextBox.Text
。即使我通过 CTRL 或 Shift + Click 选择多个条目。但是,如果 ComboBox.SelectedItem
发生更改,它会按预期更新 TextBox
。
如果 ListView 中的选择发生变化,TextBox
会立即相应地更新其内容(最好我想使用 ViewModel 的 SelectedEntries
和不是 ListView 的 SelectedItems
(如果可能的话,以符合 MVVM 的方式)?
编辑:
- 我注意到转换器被称为 SelectedEntry (实现 INotifyPropertyChanged) 已更新,但 SelectedEntries (ObservableCollection 并实现 INotifyPropertyChanged)不是。
- 我还添加了一个调用命令的 SelectionChanged 事件 并将 SelectedItems 作为参数传递给命令。如果说 可能有帮助,但我宁愿有一个适当的绑定(bind) 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(ListView):
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));
}
}
}
View 模型:
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();
}
}
最佳答案
我建议为您的 Entry Class 提供一个 IsSelected 属性(绑定(bind)到 ListViewItem 的 IsSelectedProperty)。当选择更改时,您只需迭代集合(绑定(bind)到 ListView)并检查它们是否被选中。像这样(请原谅 MvvmLight、RelayCommand = ICommand、ViewModelBase 扩展 ObservableObject):
View 模型:
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(bind)到文本框或将项目添加到集合(可能绑定(bind)到显示所选条目的 ListBox 或 ItemsControl)。
测试项目:
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>
关于c# - MVVM ListView 多重绑定(bind) SelectedItems + SelectedItem (ListView) + SelectedItem (ComboBox) 到 TextBox.Text。无法正确更新,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/49467551/