無法讓DisplayMemberPath在列表框中顯示綁定對象數據

Question

長話短說我有一段應用程序，其中包含一系列綁定到Xaml中的對象實例的列表框。使用IValueConverter，我能夠從主對象中檢索出<Part>對象的列表，並顯示檢索到的對象的.ToString()形式。然而，我想要做的是顯示對象的Name屬性。我將DisplayMemberPath設置爲Name，但結果只顯示listboxitem。我已經張貼下面的代碼的相關部分：

XAML：

<Window.Resources> 
    <local:LocationtoEquipmentCOnverter x:Key="locationEquipmentFiller" /> 
</Window.Resources> 
<Window.DataContext> 
    <local:MegaWdiget/> 
</Window.DataContext> 
<ListBox x:Name="listboxFront" HorizontalAlignment="Left" Margin="180,45,0,0" VerticalAlignment="Top" Width="82" Opacity="0.5" ItemsSource="{Binding ConverterParameter=Front, Converter={StaticResource locationEquipmentFiller}, Mode=OneWay}" DisplayMemberPath="Name"/> 

的ValueConverter：

public class LocationtoEquipmentCOnverter : IValueConverter 
{ 
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) 
    { 
     MegaWidget MWidget = (MegaWidget)value; 
     Location loc = MWidget.Locations[(string)parameter]; 
     return loc.Contents; 
    } 

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) 
    { 
     throw new NotImplementedException(); 
    } 
} 

的MegaWidget對象包含以下內容：

[XmlElement] 
public Dictionary<string, Location> Locations { get; set; } 

的位置對象包含一個列表，其中包含我需要查詢其名稱的實際對象：

public List<Part> Contents; 

發現的解決方案

沿着伴侶建議排除故障的線路繼續後，我發現，正在傳遞的對象是部分的對象，而不是ListBoxItems。這導致ListBox被填充實際對象而不是ListBoxItems。通過更改ValueConverter以傳遞ListBoxItems的List並將content標籤設置爲我需要的值，ListBoxes正確填充。我已經在下面的問題區域列出瞭解決方案：

Answer 1

一起排除故障由伴侶推薦線路繼續後，我發現，正在傳遞的對象是部分的對象，而不是ListBoxItems。這導致ListBox被實際對象填充而不是ListBoxItems。通過將ValueConverter更改爲傳遞一個ListBoxItems列表，其內容標籤設置爲我所需要的，ListBoxes正確填充。

新ValueConverter：

public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) 
{ 
    MegaWidget MWidget = (MegaWidget)value; 
    Location loc = MWidget.Locations[(string)parameter]; 
    List<ListBoxItem> displayContent = new List<ListBoxItem>(); 

    foreach (Part item in loc.Contents) 
    { 
     ListBoxItem lbi = new ListBoxItem(); 
     lbi.Content = item.Name; 
     displayContent.Add(lbi); 
    } 

    return displayContent; 
} 

Answer 2

根據您的迴應「如果我不添加DisplayMemberPath，但顯示繼承（system.MWidget.Part）」，我想屬性Name將變空。

要進行檢查，請測試：

public class LocationtoEquipmentCOnverter : IValueConverter 
{ 
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) 
    { 
     MegaWidget MWidget = (MegaWidget)value; 
     Location loc = MWidget.Locations[(string)parameter]; 

     //Refers to Class "Content" used in loc.Contents collection. I do not know what the name that you have used 
     foreach (Content item in loc.Contents) 
     { 
      item.Name += "***"; 
     } 

     return loc.Contents; 
    } 

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) 
    { 
     throw new NotImplementedException(); 
    } 
} 

Answer 3

這裏的示例HOWTO

• 模型

  public class MegaWidget 
  { 
      public Dictionary<string, Location> Locations { get; set; } 
  } 
  
  public class Location 
  { 
      public List<Part> Contents { get; set; } 
  } 
  
  public class Part 
  { 
      public int Id { get; set; } 
      public string PartName { get; set; } 
  } 
  

• 轉換

  public class LocationEquipmentConverter : IValueConverter 
  { 
      public object Convert(object value, Type targetType, object parameter, CultureInfo culture) 
      { 
       MegaWidget widget = value as MegaWidget; 
       string location = (string) parameter; 
       return widget?.Locations[ location ]?.Contents; 
      } 
  
      public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) 
      { 
       throw new NotImplementedException(); 
      } 
  } 
  

• 視圖模型

  public class FooViewModel : ViewModelBase 
  { 
      public FooViewModel() 
      { 
       Widget = new MegaWidget 
       { 
        Locations = new Dictionary<string, Location> 
        { 
         [ "Front" ] = new Location 
         { 
          Contents = new List<Part> 
          { 
           new Part { Id = 1, PartName = "Part 01" }, 
           new Part { Id = 2, PartName = "Part 02" }, 
           new Part { Id = 3, PartName = "Part 03" }, 
          } 
         }, 
         [ "Back" ] = new Location 
         { 
          Contents = new List<Part> 
          { 
           new Part { Id = 11, PartName = "Part 11" }, 
           new Part { Id = 12, PartName = "Part 12" }, 
           new Part { Id = 13, PartName = "Part 13" }, 
          } 
         }, 
        } 
       }; 
      } 
  
      public MegaWidget Widget { get; } 
  
      #region Property FrontPart 
      private Part _frontPart; 
  
      public Part FrontPart 
      { 
       get { return _frontPart; } 
       set { SetProperty(ref _frontPart, value); } 
      } 
      #endregion 
  
      #region Property BackPart 
      private Part _backPart; 
  
      public Part BackPart 
      { 
       get { return _backPart; } 
       set { SetProperty(ref _backPart, value); } 
      } 
      #endregion 
  } 
  

• 查看

  <Window x:Class="WPG.WpfApp.FooView" 
       xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
       xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
       xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
       xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
       xmlns:ViewModel="clr-namespace:WPG.WpfApp.ViewModel" 
       xmlns:local="clr-namespace:WPG.WpfApp" 
       mc:Ignorable="d" 
       Title="FooView" Height="300" Width="300"> 
      <Window.Resources> 
       <ViewModel:LocationEquipmentConverter x:Key="LocationEquipmentConverter"/> 
      </Window.Resources> 
      <Window.DataContext> 
       <ViewModel:FooViewModel/> 
      </Window.DataContext> 
      <Grid> 
       <StackPanel> 
        <ListBox ItemsSource="{Binding Widget, ConverterParameter=Front, Converter={StaticResource LocationEquipmentConverter}, Mode=OneWay}" 
          SelectedItem="{Binding Path=FrontPart}" 
          DisplayMemberPath="PartName"/> 
        <ListBox ItemsSource="{Binding Widget, ConverterParameter=Back, Converter={StaticResource LocationEquipmentConverter}, Mode=OneWay}" 
          SelectedItem="{Binding Path=BackPart}" 
          DisplayMemberPath="PartName"/> 
       </StackPanel> 
      </Grid> 
  </Window> 
  

• 截圖