我有绑定的问题DataTemplate基础上定义DataType的ItemsControl,当我想结合我的 自定义用户控件 。
DataTemplate
DataType
ItemsControl
出于演示目的,我创建了一个简单的 Item类 示例,其中收集了以下项目:
public class Item { public string ItemNameToBeSureWhatPropertyIsBound { get; set; } }
在我的 ViewModel中, 我创建了这样的集合,并公开了它(其中一个用于单独比较):
public class MainWindowViewModel : INotifyPropertyChanged { private ObservableCollection<Item> _items; private Item _exampleItem; public MainWindowViewModel() { Items = new ObservableCollection<Item>(new[] { new Item { ItemNameToBeSureWhatPropertyIsBound = "Me" }, new Item { ItemNameToBeSureWhatPropertyIsBound = "MySelf" }, new Item { ItemNameToBeSureWhatPropertyIsBound = "Ich" }, }); ExampleItem = Items.LastOrDefault(); } public ObservableCollection<Item> Items { get { return _items; } set { _items = value; OnPropertyChanged(); } } public Item ExampleItem { get { return _exampleItem; } set { _exampleItem = value; OnPropertyChanged();} } public event PropertyChangedEventHandler PropertyChanged; protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null) { PropertyChangedEventHandler handler = PropertyChanged; if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName)); } }
我的 自定义用户控件 的定义如下:
<UserControl x:Class="WpfDataTemplate.ItemRowUserControl" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" mc:Ignorable="d" d:DesignHeight="40" d:DesignWidth="300" x:Name="ItemRowControl" DataContext="{Binding Mode=OneWay, RelativeSource={RelativeSource Self}}"> <Grid Background="Yellow" Height="40"> <TextBlock Text="{Binding ItemName}" Foreground="Black"/> </Grid> </UserControl>
......它有一个DependencyProperty在 后面的代码 :
DependencyProperty
public partial class ItemRowUserControl : UserControl { public ItemRowUserControl() { InitializeComponent(); } public static readonly DependencyProperty ItemNameProperty = DependencyProperty.Register( "ItemName", typeof (string), typeof (ItemRowUserControl), new PropertyMetadata(default(string))); public string ItemName { get { return (string) GetValue(ItemNameProperty); } set { SetValue(ItemNameProperty, value); } } }
问题是,当我尝试绑定到ItemsControl的DataTemplate中的Item的属性时,我正在 MainWindow中 这样进行操作(注意:我只有虚拟转换器用于调试目的,返回值,仅此而已):
<Window.DataContext> <my:MainWindowViewModel /> </Window.DataContext> <Window.Resources> <my:MyDummyConverter x:Key="MyDummyConverter" /> </Window.Resources> <Grid> <Grid.RowDefinitions> <RowDefinition /> <RowDefinition Height="50" /> </Grid.RowDefinitions> <ItemsControl Name="ItemsControl" ItemsSource="{Binding Items}" Grid.Row="0" Background="Red"> <ItemsControl.ItemsPanel> <ItemsPanelTemplate> <StackPanel /> </ItemsPanelTemplate> </ItemsControl.ItemsPanel> <ItemsControl.ItemTemplate> <DataTemplate DataType="{x:Type my:Item}"> <my:ItemRowUserControl ItemName="{Binding ItemNameToBeSureWhatPropertyIsBound, Converter={StaticResource MyDummyConverter}}" /> <!--<Grid Background="Pink"> <TextBlock Text="{Binding ItemNameToBeSureWhatPropertyIsBound, Converter={StaticResource MyDummyConverter}}" Foreground="Black" Height="30" /> </Grid>--> </DataTemplate> </ItemsControl.ItemTemplate> </ItemsControl> <Grid Grid.Row="1"> <my:ItemRowUserControl ItemName="{Binding DataContext.ExampleItem.ItemNameToBeSureWhatPropertyIsBound, ElementName=MyWindow, Converter={StaticResource MyDummyConverter}}" /> </Grid> </Grid>
现在,如果我绑定到自定义的ItemRowUserControl,则进入转换器(在“调试输出”中看到的值)的值就是ItemRowUserControl本身。但是,如果我绑定注释掉的代码,一切都会很好。为什么会这样,如何对DataTemplate进行自定义控件,以使绑定(由Intellisense提供)可以正常工作?在侧面说明:绑定到网格第1行(位于底部)中的ItemRowUserControl可以正常工作,因此我猜想控件是否设置为可以正常工作?
问题是您DataContext将UserControl的显式设置为其自身:
DataContext
DataContext="{Binding Mode=OneWay, RelativeSource={RelativeSource Self}}
删除该分配并编写如下ItemName绑定:
ItemName
<TextBlock Text="{Binding ItemName, RelativeSource={RelativeSource AncestorType=UserControl}}"/>
或像这样
<TextBlock Text="{Binding ItemName, ElementName=ItemRowControl}"/>