使用分组绑定WPF中的列表框 [英] Bind listbox in WPF with grouping

问题描述

我有一个ViewModels集合，想要将一个ListBox绑定到它们.经过调查，我发现了这.

I've got a collection of ViewModels and want to bind a ListBox to them. Doing some investigation I found this.

所以我的ViewModel看起来像这样(伪代码)

So my ViewModel look like this (Pseudo Code)

interface IItemViewModel 
{
 string DisplayName { get; }
}

class AViewModel : IItemViewModel 
{
 string DisplayName { return "foo"; }
}

class BViewModel : IItemViewModel 
{
 string DisplayName { return "foo"; } 
}

class ParentViewModel 
{
 IEnumerable<IItemViewModel> Items 
 {
  get
  {
   return new IItemViewModel[] {
    new AItemViewModel(),
    new BItemViewModel()
   }
  }
 }
}

class GroupViewModel 
{
 static readonly GroupViewModel GroupA = new GroupViewModel(0);
 static readonly GroupViewModel GroupB = new GroupViewModel(1);

 int GroupIndex;
 GroupViewModel(int groupIndex) 
 {
  this.GroupIndex = groupIndex;
 }

 string DisplayName
 {
  get { return "This is group " + GroupIndex.ToString(); }
 }
}

class ItemGroupTypeConverter : IValueConverter
{
 object Convert(object value, Type targetType, object parameter, CultureInfo culture)
 {
  if (value is AItemViewModel)
   return GroupViewModel.GroupA;
  else 
   return GroupViewModel.GroupB;
 }
}

这个XAML

<UserControl.Resources>
 <vm:ItemsGroupTypeConverter x:Key="ItemsGroupTypeConverter "/>
 <CollectionViewSource x:Key="GroupedItems" Source="{Binding Items}">
  <CollectionViewSource.GroupDescriptions>
   <PropertyGroupDescription Converter="{StaticResource ItemsGroupTypeConverter }"/>
  </CollectionViewSource.GroupDescriptions>
 </CollectionViewSource>
</UserControl.Resources>
<ListBox ItemsSource="{Binding Source={StaticResource GroupedItems}}">
 <ListBox.GroupStyle>
  <GroupStyle>
   <GroupStyle.HeaderTemplate>
    <DataTemplate>
     <TextBlock Text="{Binding DisplayName}" FontWeight="bold" />
    </DataTemplate>
   </GroupStyle.HeaderTemplate>
  </GroupStyle>              
 </ListBox.GroupStyle>
 <ListBox.ItemTemplate>
  <DataTemplate>
   <TextBlock Text="{Binding DisplayName}" />
  </DataTemplate>
 </ListBox.ItemTemplate>
</ListBox>

这可以以某种方式起作用，例如HeaderTemplate的绑定不起作用的事实.无论如何，我都希望省略TypeConverter和CollectionViewSource.没有办法使用ViewModel的属性进行分组吗?

This works somehow, exept of the fact that the binding of the HeaderTemplate does not work. Anyhow I'd prefer omitting the TypeConverter and the CollectionViewSource. Isn't there a way to use a property of the ViewModel for Grouping?

我知道，在此示例场景中，将GroupViewModel替换为可以正常工作的字符串很容易，但这不是一个选择.那么如何将HeaderTemplate绑定到GroupViewModel?

I know that in this sample scenario it would be easy to replace the GroupViewModel with a string an have it working, but that's not an option. So how can I bind the HeaderTemplate to the GroupViewModel?

推荐答案

好，我终于自己解决了.

Ok, I finally solved it myself.

首先不需要TypeConverter，因为PropertyGroupDescription可以绑定到PropertyName上.因此，我向IItemViewModel添加了一个属性"Group"，并按如下所示修改了XAML:

First of all the TypeConverter is unnecessary, because the PropertyGroupDescription can be bound on a PropertyName. So I added a Property 'Group' to IItemViewModel and modified XAML as follows:

<UserControl.Resources>
 <CollectionViewSource x:Key="GroupedItems" Source="{Binding Items}">
  <CollectionViewSource.GroupDescriptions>
   <PropertyGroupDescription PropertyName="Group"/>
  </CollectionViewSource.GroupDescriptions>
 </CollectionViewSource>
</UserControl.Resources>

此外，HeaderTemplate的DataContext是CollectionViewGroupInternal，绑定必须看起来像这样:

Furthermore the HeaderTemplate's DataContext is a CollectionViewGroupInternal and the binding has to look like this:

<DataTemplate>
 <TextBlock Text="{Binding Name.DisplayName}" FontWeight="bold" />
</DataTemplate>

此处CollectionViewGroupInternal.Name解析实际的GroupViewModel.

Here CollectionViewGroupInternal.Name resolves the actual GroupViewModel.

这篇关于使用分组绑定WPF中的列表框的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！