ListView SelectedItems DataBinding在MVVM中的实现
ListView SelectedItems DataBinding在MVVM中的实现
提问于 2016-12-28 13:06:31
我有一个问题要绑定SelectedItems of ListView控件，为了解决这个问题，我扩展了ListView控件，ListViewExtended使用这个post的引用来公开SelectedItemsList，但是双向绑定并不能在模型中获得SelectedItems。
请帮助指出这个演示源代码中的问题。
自定义控件：
public sealed class ListViewExtended : ListView
{
public ListViewExtended()
{
this.SelectionChanged += ListViewExtended_SelectionChanged;
}
void ListViewExtended_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
this.SelectedItemsList = this.SelectedItems;
}
#region SelectedItemsList
public IEnumerable SelectedItemsList
{
get { return (IEnumerable)GetValue(SelectedItemsListProperty); }
set { SetValue(SelectedItemsListProperty, value); }
}
public static readonly DependencyProperty SelectedItemsListProperty =
DependencyProperty.Register("SelectedItemsList",
typeof(IEnumerable),
typeof(ListViewExtended),
new FrameworkPropertyMetadata(null));
#endregion
}模型：
public class Member
{
public string Name { get; set; }
public int Age { get; set; }
}
public class Family : BindableBase
{
private string _name;
public string Name
{
get { return _name; }
set { _name = value; OnPropertyChanged("Name"); }
}
private IList<Member> _selectedMembers;
public IList<Member> SelectedMembers
{
get { return _selectedMembers; }
set { _selectedMembers = value; OnPropertyChanged("SelectedMembers"); }
}
public override string ToString()
{
return Name;
}
}ViewModel:
public class ListViewSelectedItemsExtendedViewModel : BindableBase
{
Dictionary<string, IEnumerable> _repository = new Dictionary<string, IEnumerable>();
public ListViewSelectedItemsExtendedViewModel()
{
var families = new List<Family>();
families.Add(new Family() { Name = "family 1" });
families.Add(new Family() { Name = "family 2" });
Families = families;
var items = new List<Member>();
items.Add(new Member() { Name = "John", Age = 30 });
items.Add(new Member() { Name = "Chapel", Age = 50 });
items.Add(new Member() { Name = "Max", Age = 46 });
_repository.Add(families[0].Name, items);
items = new List<Member>();
items.Add(new Member() { Name = "Warner", Age = 28 });
items.Add(new Member() { Name = "Peter", Age = 36 });
items.Add(new Member() { Name = "Tom", Age = 5 });
_repository.Add(families[1].Name, items);
}
private IList<Family> _families;
public IList<Family> Families
{
get { return _families; }
set { _families = value; OnPropertyChanged("Families"); }
}
private Family _selectedFamily;
public Family SelectedFamily
{
get { return _selectedFamily; }
set { _selectedFamily = value; OnPropertyChanged("SelectedFamily"); }
}
private ICommand _familySelectionChangedCommand;
public ICommand FamilySelectionChangedCommand
{
get
{
return _familySelectionChangedCommand ?? (_familySelectionChangedCommand = new DelegateCommand(
() =>
{
Members = (IList<Member>)_repository[SelectedFamily.Name];
}
));
}
}
}XAML:
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="1*" />
<ColumnDefinition Width="3*" />
</Grid.ColumnDefinitions>
<ListBox ItemsSource="{Binding Families}" SelectedItem="{Binding SelectedFamily}">
<i:Interaction.Triggers>
<i:EventTrigger EventName="SelectionChanged">
<i:InvokeCommandAction Command="{Binding FamilySelectionChangedCommand}" />
</i:EventTrigger>
</i:Interaction.Triggers>
</ListBox>
<Grid Grid.Column="1">
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<fsx:ListViewExtended Margin="10" Grid.Row="0"
ItemsSource="{Binding Members}"
SelectedItemsList="{Binding SelectedFamily.SelectedMembers, Mode=TwoWay}">
<ListView.View>
<GridView>
<GridViewColumn Header="Include">
<GridViewColumn.CellTemplate>
<DataTemplate>
<CheckBox IsChecked="{Binding Path=IsSelected,
RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type ListViewItem}}}" />
</DataTemplate>
</GridViewColumn.CellTemplate>
</GridViewColumn>
<GridViewColumn Header="Name" Width="120" DisplayMemberBinding="{Binding Name}" />
<GridViewColumn Header="Age" Width="50" DisplayMemberBinding="{Binding Age}" />
</GridView>
</ListView.View>
<!--<i:Interaction.Behaviors>
<fsx:ListViewMultiSelectionBehavior
SelectedItems="{Binding SelectedFamily.SelectedMembers}" />
</i:Interaction.Behaviors>-->
</fsx:ListViewExtended>
<ListView Margin="10" Grid.Row="1"
ItemsSource="{Binding SelectedFamily.SelectedMembers}">
<ListView.View>
<GridView>
<GridViewColumn Header="Name" Width="120" DisplayMemberBinding="{Binding Name}" />
<GridViewColumn Header="Age" Width="50" DisplayMemberBinding="{Binding Age}" />
</GridView>
</ListView.View>
</ListView>
</Grid>
</Grid>除了上面的实现之外，我还尝试了使用这个post中给出的方法，但是没有成功地获得100%的结果。
Stack Overflow用户
回答已采纳
发布于 2016-12-28 16:48:07
这里的问题是，您不能将泛型类型IList的源属性设置为非泛型IList，这是ListView的SelectedItems属性的类型。如果您自己尝试这一点，您会注意到它甚至不会编译：
IList<Member> members = listView1.SelectedItems; //WON'T COMPILE泛型IList接口不扩展IList接口，因此这是两种完全不同的类型。这就像尝试将int属性设置为字符串一样。只是没用了。
如果您将家族类的SelectedMembers属性的类型更改为非泛型IList，它将工作：
public class Family : BindableBase
{
private string _name;
public string Name
{
get { return _name; }
set { _name = value; OnPropertyChanged("Name"); }
}
//change the type here:
private IList _selectedMembers;
public IList SelectedMembers
{
get { return _selectedMembers; }
set { _selectedMembers = value; OnPropertyChanged("SelectedMembers"); }
}
public override string ToString()
{
return Name;
}
}必须有某种方法将其泛化，就像其他内置控件的DependencyProperty工作一样。
如前所述，为了能够将源属性设置为ListView的ListView属性的值，源属性的类型必须与SelectedItems属性的类型相匹配，即源属性应该是非泛型的IList。
您可能还想阅读以下内容：https://blog.magnusmontin.net/2014/01/30/wpf-using-behaviours-to-bind-to-readonly-properties-in-mvvm/。它是关于如何使用行为绑定到只读属性。属性的类型仍然必须匹配，尽管无论您选择采用什么解决方案。
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/41362768
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