Question

简而言之，我的应用程序的一部分包含一系列绑定到Xaml中对象实例的列表框。使用IValueConverter，我能够从主对象中检索<Part>个对象的列表，并显示检索到的对象的.ToString()形式。但是，我想要做的是显示对象的Name属性。我将DisplayMemberPath设置为Name，但结果只会消除listboxitem。我已经发布了以下代码的相关部分：

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"/>

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();
    }
}

MegaWidget对象包含以下内容：

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

Location Object包含一个List，其中包含我需要查询其名称的实际对象：

 public List<Part> Contents;

找到解决方案

在继续Mate推荐的故障排除之后，我发现传递的对象是Part对象而不是ListBoxItems。这导致ListBox填充实际对象而不是ListBoxItems。通过更改ValueConverter以传递List ListBoxItems并将内容标记设置为我需要的内容，ListBox会正确填充。我在下面的问题区域中列出了解决方案：

Answer 1

在继续Mate推荐的故障排除之后，我发现传递的对象是Part对象而不是ListBoxItems。这导致ListBox被填充实际对象而不是ListBoxItems。通过更改ValueConverter以传递ListBoxItems List并将内容标记设置为我需要的内容，ListBoxes正确填充。

新的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

根据你的回答“如果我不添加DisplayMemberPath，但显示继承（system.MWidget.Part）”，我认为属性Name是空的。

要检查，请测试：

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

这里有一个示例

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; }
}

转换器

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( );
    }
}

视图模型

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>

截图

无法让DisplayMemberPath在列表框中显示绑定的对象数据

3 个答案: