我有一个绑定到动物集合的ComboBox。我从中选择我的最爱动物。我需要在绑定的项上方添加一个静态的null项。我使用CompositeCollection声明它。当ComboBox绑定时,它不能选择我的初始最爱动物。如何解决这个问题?类似的问题可以在这里找到,但仍未解决。
观察结果:
观察结果:
- 绑定到静态项是有效的,即如果我没有最喜欢的动物,静态项将被选中。
- 如果删除静态项,则该问题消失。当然,这将使CompositeCollection和整个问题都变得无用。
using System;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Controls;
namespace WpfApplication1
{
public class Animal
{
public int Id { get; set; }
public string Name { get; set; }
}
public class Zoo
{
private IEnumerable<Animal> _animals = new Animal[]
{
new Animal() { Id = 1, Name = "Tom" },
new Animal() { Id = 2, Name = "Jerry" }
};
public Zoo(int initialId)
{
FavouriteId = initialId;
}
public int FavouriteId { get; set; }
public IEnumerable<Animal> Animals { get { return _animals; } }
}
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private void BindComboBox(object sender, RoutedEventArgs e)
{
// Selecting the static item by default works.
//DataContext = new Zoo(-1);
// Selecting "Jerry" by default does not work.
DataContext = new Zoo(2);
}
}
}
XAML
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WpfApplication1">
<Window.Resources>
<CollectionViewSource x:Key="AnimalsBridge" Source="{Binding Path=Animals}" />
<CompositeCollection x:Key="AnimalsWithNullItem">
<local:Animal Id="-1" Name="Pick someone..."/>
<CollectionContainer Collection="{Binding Source={StaticResource AnimalsBridge}}" />
</CompositeCollection>
</Window.Resources>
<StackPanel>
<Button Content="Bind" Click="BindComboBox"/>
<ComboBox x:Name="cmbFavourite"
SelectedValue="{Binding Path=FavouriteId}"
SelectedValuePath="Id" DisplayMemberPath="Name"
ItemsSource="{StaticResource AnimalsWithNullItem}"/>
</StackPanel>
</Window>
new[] { new Animal() { ... } }.Concat(_animals)
。 - idilov