c# - 多个 ItemsSource 集合绑定(bind)

Question

如何将多个不同类型的集合绑定(bind)到 ItemsControl 的 ItemsSource？

使用单一绑定(bind)效果很好:

<ItemsControl ItemsSource="{Binding Foo}" />

但是当我尝试 CompositeCollection 时，Foo 中的项目没有显示:

    <ItemsControl>
        <ItemsControl.ItemsSource>
            <CompositeCollection>
                <CollectionContainer Collection="{Binding Foo}" />
            </CompositeCollection>
        </ItemsControl.ItemsSource>
    </ItemsControl>

Answer 1

我建议将 ListBox 绑定(bind)到您在代码中构建的 CompositeCollection。在此示例中，我使用的是 ViewModel，但您也可以在代码隐藏中执行相同的操作。您可以通过谷歌找到许多关于如何为 ViewModel 实现 ViewModelBase 和 DelegateCommand 的示例。

下面是这个例子的分解:

• 此示例将 Customer 和 Person 对象加载到两个 ObservableCollection 容器中以支持修改集合。
• ListBox 将其 ItemsSource 绑定(bind)到包含两个 ObservableCollection 的 CompositeCollection (ObjectCollection)。
• ListBox 还将其 SelectedItem 绑定(bind)到一个对象 (SelectedObject) 以支持两种基本类型。
• Button 添加了一个新的 Person 以表明您可以修改 CompositeCollection。
• 为了完整性，我在最后添加了 Customer 和 Person 定义。

这是 View :

<Window x:Class="StackOverflow.Views.MainView"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  Title="Main Window" Height="400" Width="800">
  <Grid>
    <Grid.RowDefinitions>
        <RowDefinition/>
        <RowDefinition Height="Auto"/>
    </Grid.RowDefinitions>
    <ListBox Grid.Row="0" 
             SelectedItem="{Binding Path=SelectedObject}"
             ItemsSource="{Binding Path=ObjectCollection}">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <Label Content="{Binding FirstName}" />
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>
    <Button Grid.Row="1" Content="Add Person" Command="{Binding Path=AddPerson}"/>
  </Grid>
</Window>

这是 View 模型:

using System.Collections.Generic;
using System.Windows.Data;
using System.Windows.Input;
using ContextMenuNotFiring.Commands;
using ContextMenuNotFiring.Models;

namespace StackOverflow.ViewModels
{
  public class MainViewModel : ViewModelBase
  {
    public MainViewModel()
    {
      AddPerson = new DelegateCommand<object>(OnAddPerson, CanAddPerson);

      CollectionContainer customers = new CollectionContainer();
      customers.Collection = Customer.GetSampleCustomerList();

      CollectionContainer persons = new CollectionContainer();
      persons.Collection = Person.GetSamplePersonList();

      _oc.Add(customers);
      _oc.Add(persons);
    }

    private CompositeCollection _oc = new CompositeCollection();
    public CompositeCollection ObjectCollection
    {
      get { return _oc; }
    }

    private object _so = null;
    public object SelectedObject
    {
      get { return _so; }
      set
      {
       _so = value;
      }
    }

    public ICommand AddPerson { get; set; }
    private void OnAddPerson(object obj)
    {
      CollectionContainer ccItems = _oc[1] as CollectionContainer;
      if ( ccItems != null )
      {
        ObservableCollection<Person> items = ccItems.Collection as ObservableCollection<Person>;
        if (items != null)
        {
          Person p = new Person("AAAA", "BBBB");
          items.Add(p);
        }
      }
    }

    private bool CanAddPerson(object obj)
    {
      return true;
    }
  }
}

模型如下:

public class Customer
{
  public String FirstName { get; set; }
  public String LastName { get; set; }

  public Customer(String firstName, String lastName)
  {
     this.FirstName = firstName;
     this.LastName = lastName;
  }

  public static ObservableCollection<Customer> GetSampleCustomerList()
  {
    return new ObservableCollection<Customer>(new Customer[4] {
            new Customer("Charlie", "Zero"), 
            new Customer("Cathrine", "One"),
            new Customer("Candy", "Two"),
            new Customer("Cammy", "Three")
        });
  }
}


public class Person
{
  public String FirstName { get; set; }
  public String LastName { get; set; }

  public Person(String firstName, String lastName)
  {
     this.FirstName = firstName;
     this.LastName = lastName;
  }

  public static ObservableCollection<Person> GetSamplePersonList()
  {
    return new ObservableCollection<Person>(new Person[4] {
            new Person("Bob", "Smith"), 
            new Person("Barry", "Jones"),
            new Person("Belinda", "Red"),
            new Person("Benny", "Hope")
        });
  }
}