列表项是值类型/结构并包含重复项的列表框的选择错误? [英] Selection bug for listbox where the list items are value types / structs and contain duplicates?

问题描述

我将 Horizo​​ntal ItemsControl 转换为 Listbox，以便能够选择单个项目，但发现选择已损坏.花了一些时间来提炼出问题所在.

I turned an Horizontal ItemsControl to a Listbox so that I am able to select individual items but found that the selection was broken. Took some time to distill out the problematic bit.

Books = new[] { new Book{Id=1, Name="Book1"},
                                 new Book{Id=2, Name="Book2"},
                                 new Book{Id=3, Name="Book3"},
                                 new Book{Id=4, Name="Book4"},
                                 new Book{Id=3, Name="Book3"},
            };

            <DataTemplate DataType="{x:Type WPF_Sandbox:Book}">
                <TextBlock Text="{Binding Name}"/>
            </DataTemplate>

<ListBox ItemsSource="{Binding Books}"/>

如果 Book 是一个结构，如果您选择的项目在列表中具有等效结构，则列表框选择(默认模式:单)会出错.例如 Book3

If Book is a struct, the listbox selection (default mode : single) goes awry if you select an item which has an equivalent struct in the list. e.g Book3

如果 Book 变成一个类(具有非值类型语义)，则选择是固定的.

If Book is turned into a class (with non-value type semantics), selection is fixed.

选择(到目前为止，不喜欢其中任何一个):

Choices (so far, don't like any of them):

• 我选择了结构体，因为它是一个小型数据结构，并且值类型语义在比较两个实例是否相等时很有用.将其更改为类会导致我失去值类型语义.我不能再使用默认的 Equals 或覆盖它以进行成员比较.
• 添加一个独特的 Book 属性，纯粹是为了让列表框选择起作用(例如，一个索引).
• 消除重复.. 不可能.

WPF 列表框:选择问题:声明列表框正在设置 SelectedItem，并且在为此更新 UI 时，它只是点亮列出列表中 Equal(SelectedItem) 的所有项目.不知道为什么.. 突出 SelectedIndex 会使这个问题消失；也许我错过了一些东西.ListBox 甚至在 SelectionMode="Single" 中也选择了许多项目:当列表项目是字符串(值类型语义)时显示相同的问题

WPF listbox : problem with selection : states that the Listbox is setting SelectedItem and while updating the UI for this, it just lights up all items in the list that Equal(SelectedItem). Not sure why.. highlighting SelectedIndex would make this problem go away; maybe I am missing something. ListBox is selecting many items even in SelectionMode="Single" : shows the same problem when list items are strings (value type semantics)

推荐答案

为什么不简单地使用更好的集合类作为数据源来解决问题

Why not simply use a better collection class as your datasource to overcome the problem

var collection = new[]
 {
     new Book {Id = 1, Name = "Book1"},
     new Book {Id = 2, Name = "Book2"},
     new Book {Id = 3, Name = "Book3"},
     new Book {Id = 4, Name = "Book4"},
     new Book {Id = 3, Name = "Book3"},
 };
 var Books = collection.ToDictionary(b => Guid.NewGuid(), b => b);
 DataContext = Books;

这将是您的数据模板

<ListBox ItemsSource="{Binding}">
  <ListBox.ItemTemplate>
    <DataTemplate>
      <TextBlock Text="{Binding Value.Name}"/>
    </DataTemplate>
  </ListBox.ItemTemplate>

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