UWP Treeview C# 中的无效转换异常答案

【问题标题】：Invalid Cast Exception in UWP Treeview C#UWP Treeview C# 中的无效转换异常
【发布时间】：2020-05-28 13:32:38
【问题描述】：

使用绑定到三层分层集合（订单 - SKU - 位置）的树视图时。我正在使用 DataTemplateSelector 来选择要使用的 TreeViewItem 模板。当我滚动时，我得到一个与post 完全相同的无效异常 - 如果我滚动得更快，异常似乎发生得更快。

我在该帖子中尝试了两种建议的解决方案（将树视图包装在滚动查看器中，以及自定义用户控件）。包装 TreeView 没有帮助，我无法让自定义用户控件解决方案为我正常工作，我想知道这是否与我有一个三层集合而不是两层的事实有关。自定义 UserControl 的代码与链接帖子中的代码完全相同，只是针对我的收藏进行了修改。当我尝试它时，它只会将集合的一层绑定到树视图。我正在寻找的是一种解决方案，可以防止框架代码重用模板，这似乎是导致异常的原因。

这是我的 XAML 和当前产生异常的 TreeView 的代码：

<Page
x:Class="PickSheetManager.Views.PickSheetManagerPage"
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:winui="using:Microsoft.UI.Xaml.Controls"
xmlns:model="using:PickSheetManager.Core.Models"
xmlns:behaviors="using:PickSheetManager.Behaviors"
xmlns:templateSelectors="using:PickSheetManager.TemplateSelectors"
xmlns:controls="using:Microsoft.Toolkit.Uwp.UI.Controls"
xmlns:controls1="using:PickSheetManager.Controls"
xmlns:ic="using:Microsoft.Xaml.Interactions.Core"
xmlns:i="using:Microsoft.Xaml.Interactivity"
Style="{StaticResource PageStyle}"
behaviors:NavigationViewHeaderBehavior.HeaderMode="Never"
mc:Ignorable="d">

<Page.Resources>        
    <DataTemplate x:Key="OrderTemplate" x:DataType="model:Order">
        <winui:TreeViewItem
            AutomationProperties.Name="{x:Bind PoIDx}"
            ItemsSource="{x:Bind SKUs}" IsExpanded="True">
            <StackPanel x:Name="stack" Orientation="Horizontal">
            <i:Interaction.Behaviors>
                <ic:DataTriggerBehavior Binding ="{x:Bind NotEnoughInventory}" Value="True">
                    <ic:ChangePropertyAction TargetObject="{Binding ElementName=stack}" PropertyName="Background" Value="Red" />
                </ic:DataTriggerBehavior>
            </i:Interaction.Behaviors>
            <CheckBox IsChecked="{x:Bind IsSelected, Mode=TwoWay}" Padding="5" MinWidth="0"/>
            <TextBlock Text="PoIDx: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
            <TextBlock Text="{x:Bind PoIDx}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
            <TextBlock Text="Delivery: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
            <TextBlock Text="{x:Bind DeliveryType}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
            <TextBlock Text="Delivery: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
            <TextBlock Text="{x:Bind DeliveryType}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
            <TextBlock Text="Type: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
            <TextBlock Text="{x:Bind OrderType}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
            <TextBlock Text="Total Quantity: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
            <TextBlock Text="{x:Bind TotalQuantity}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
            <TextBlock Text="Printed: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
            <TextBlock Text="{x:Bind IsPrinted}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
            <TextBlock Text="Notes: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
            <TextBox Text="{x:Bind Notes, Mode=TwoWay}" Margin="{StaticResource XXSmallTopRightBottomMargin}" Width="150"/>
        </StackPanel>
        </winui:TreeViewItem>
    </DataTemplate>        

    <DataTemplate x:Key="SKUTemplate" x:DataType="model:SKU">
        <winui:TreeViewItem
            AutomationProperties.Name="{x:Bind SKUNum}"
            ItemsSource="{x:Bind Locations}" IsExpanded="True">
            <StackPanel x:Name="stack2" Orientation="Horizontal">
                <i:Interaction.Behaviors>
                    <ic:DataTriggerBehavior Binding ="{x:Bind NotEnoughInventory}" Value="True">
                        <ic:ChangePropertyAction TargetObject="{Binding ElementName=stack2}" PropertyName="Background" Value="Yellow" />
                    </ic:DataTriggerBehavior>
                </i:Interaction.Behaviors>
                <CheckBox IsChecked="{x:Bind IsSelected, Mode=TwoWay}" Padding="5" MinWidth="0" />
                <TextBlock Text="SKU: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="{x:Bind SKUNum}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="Needed: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="{x:Bind NeedQuantity}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="Available: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="{x:Bind AvailableQuantity}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
            </StackPanel>
        </winui:TreeViewItem>
    </DataTemplate>        

    <DataTemplate x:Key="LocationTemplate" x:DataType="model:Location">
        <winui:TreeViewItem
            AutomationProperties.Name="{x:Bind LocationName}"
            IsExpanded="True">
            <StackPanel Orientation="Horizontal">
                <CheckBox IsChecked="{x:Bind IsSelected, Mode=TwoWay}" Padding="5" MinWidth="0" />
                <TextBlock Text="{x:Bind LocationName}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="Pick Type: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="{x:Bind PickType}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="Pick Quantity: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="{x:Bind PickQuantity}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="Available Quantity: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="{x:Bind AvailableQuantity}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBox Text="{x:Bind Notes, Mode=TwoWay}" Margin="{StaticResource XXSmallTopRightBottomMargin}" Width="150" />
            </StackPanel>
        </winui:TreeViewItem>
    </DataTemplate>      


    <templateSelectors:SampleDataTemplateSelector x:Key="TreeViewTemplateSelector"
        OrderDetailTemplate="{StaticResource OrderTemplate}"
        SKUDetailTemplate="{StaticResource SKUTemplate}"
        LocationDetailTemplate="{StaticResource LocationTemplate}" />
</Page.Resources>

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition x:Name="treeViewColumn" Width="6*" />
        <ColumnDefinition x:Name="detailViewColumn" Width="4*" />
    </Grid.ColumnDefinitions>
    <Grid Grid.Column="0">
        <Grid.RowDefinitions>
            <RowDefinition x:Name="treeViewRow" Height="8*" />
            <RowDefinition x:Name="controlRow" Height="2*" />
        </Grid.RowDefinitions>
        <ScrollViewer x:Name="WrapViewer" Grid.Row="0" Grid.Column="0" Padding="{StaticResource DetailPageMargin}">
        </ScrollViewer>
        <winui:TreeView
            x:Name="treeView"
            Grid.Row="0"
            SelectionMode="Single"
            ItemsSource="{x:Bind ViewModel.openOrders}"
            ItemTemplateSelector="{StaticResource TreeViewTemplateSelector}">
            <i:Interaction.Behaviors>
                <behaviors:TreeViewCollapseBehavior x:Name="collapseBehavior" />
                <ic:EventTriggerBehavior EventName="ItemInvoked">
                    <ic:InvokeCommandAction Command="{x:Bind ViewModel.ItemInvokedCommand}" />
                </ic:EventTriggerBehavior>
            </i:Interaction.Behaviors>
        </winui:TreeView>
    </Grid>
    <Grid Grid.Column="1">
        <Grid.RowDefinitions>
            <RowDefinition x:Name="detailViewRow" Height="4*" />
            <RowDefinition x:Name="iarRow" Height="4*" />
            <RowDefinition x:Name="controlRow2" Height="2*" />
        </Grid.RowDefinitions>
    </Grid>
</Grid>

被绑定的集合

 public ObservableCollection<Order> openOrders { get; } = new ObservableCollection<Order>();


 public async Task LoadDataAsync()
 {           
     var data2 = await OrderDataLoader.GetTreeViewDataAsync();
     foreach (var item in data2)
     {
         openOrders.Add(item);
     }                   
 }

以及 DataTemplateSelector 代码：

public class SampleDataTemplateSelector : DataTemplateSelector
{
    public DataTemplate OrderDetailTemplate { get; set; }

    public DataTemplate SKUDetailTemplate { get; set; }

    public DataTemplate LocationDetailTemplate { get; set; }

    protected override DataTemplate SelectTemplateCore(object item)
    {
        return GetTemplate(item) ?? base.SelectTemplateCore(item);
    }

    protected override DataTemplate SelectTemplateCore(object item, DependencyObject container)
    {
        return GetTemplate(item) ?? base.SelectTemplateCore(item, container);
    }

    private DataTemplate GetTemplate(object item)
    {
        switch (item)
        {
            case Order order:
                return OrderDetailTemplate;
            case SKU sku:
                return SKUDetailTemplate;
            case Location location:
                return LocationDetailTemplate;
        }

        return null;
    }
}

更新

我实际上已经尝试了两种不同的尝试来使用户控件正常工作。两者都只显示了一层。

尝试 #1 用户控件 XAML：

<UserControl
    x:Class="PickSheetManager.Controls.OrderTreeItemControl"
    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:winui="using:Microsoft.UI.Xaml.Controls"
    xmlns:model="using:PickSheetManager.Core.Models"
    xmlns:behaviors="using:PickSheetManager.Behaviors"
    xmlns:templateSelectors="using:PickSheetManager.TemplateSelectors"
    xmlns:controls="using:Microsoft.Toolkit.Uwp.UI.Controls"
    xmlns:controls1="using:PickSheetManager.Controls"
    xmlns:ic="using:Microsoft.Xaml.Interactions.Core"
    xmlns:i="using:Microsoft.Xaml.Interactivity"
    mc:Ignorable="d">

    <UserControl.Resources>
        <DataTemplate x:Name="OrderTemplate" x:DataType="model:Order">
            <StackPanel x:Name="stack" Orientation="Horizontal">
                <i:Interaction.Behaviors>
                    <ic:DataTriggerBehavior Binding ="{x:Bind NotEnoughInventory}" Value="True">
                        <ic:ChangePropertyAction TargetObject="{Binding ElementName=stack}" PropertyName="Background" Value="Red" />
                    </ic:DataTriggerBehavior>
                </i:Interaction.Behaviors>
                <CheckBox IsChecked="{x:Bind IsSelected, Mode=TwoWay}" Padding="5" MinWidth="0"/>
                <TextBlock Text="PoIDx: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="{x:Bind PoIDx}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="Delivery: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="{x:Bind DeliveryType}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="Delivery: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="{x:Bind DeliveryType}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="Type: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="{x:Bind OrderType}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="Total Quantity: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="{x:Bind TotalQuantity}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="Printed: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="{x:Bind IsPrinted}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="Notes: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBox Text="{x:Bind Notes, Mode=TwoWay}" Margin="{StaticResource XXSmallTopRightBottomMargin}" Width="150"/>
            </StackPanel>
        </DataTemplate>
        <DataTemplate x:Name="SKUTemplate" x:DataType="model:SKU">            
            <StackPanel x:Name="stack2" Orientation="Horizontal">
                <i:Interaction.Behaviors>
                    <ic:DataTriggerBehavior Binding ="{x:Bind NotEnoughInventory}" Value="True">
                        <ic:ChangePropertyAction TargetObject="{Binding ElementName=stack2}" PropertyName="Background" Value="Yellow" />
                    </ic:DataTriggerBehavior>
                </i:Interaction.Behaviors>
                <CheckBox IsChecked="{x:Bind IsSelected, Mode=TwoWay}" Padding="5" MinWidth="0" />
                <TextBlock Text="SKU: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="{x:Bind SKUNum}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="Needed: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="{x:Bind NeedQuantity}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="Available: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="{x:Bind AvailableQuantity}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
            </StackPanel>            
        </DataTemplate>
        <DataTemplate x:Name="LocationTemplate" x:DataType="model:Location">
            <StackPanel Orientation="Horizontal">
                <CheckBox IsChecked="{x:Bind IsSelected, Mode=TwoWay}" Padding="5" MinWidth="0" />
                <TextBlock Text="{x:Bind LocationName}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="Pick Type: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="{x:Bind PickType}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="Pick Quantity: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="{x:Bind PickQuantity}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="Available Quantity: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBlock Text="{x:Bind AvailableQuantity}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                <TextBox Text="{x:Bind Notes, Mode=TwoWay}" Margin="{StaticResource XXSmallTopRightBottomMargin}" Width="150" />
            </StackPanel>            
        </DataTemplate>
    </UserControl.Resources>

    <Grid>
        <ContentControl x:Name="MainContent"/>
    </Grid>
</UserControl>

尝试 #1 .cs

    namespace PickSheetManager.Controls
{
    public sealed partial class OrderTreeItemControl : UserControl
    {
        public OrderTreeItemControl()
        {
            this.InitializeComponent();
        }

        public Order Data
        {
            get { return (OpenOrdersBase)GetValue(DataProperty); }
            set { SetValue(DataProperty, value); }
        }

        public static readonly DependencyProperty DataProperty =
            DependencyProperty.Register("Data", typeof(OpenOrdersBase), typeof(OrderTreeItemControl), new PropertyMetadata(null, new PropertyChangedCallback(Data_Changed)));

        private static void Data_Changed(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            if (e.NewValue != null)
            {
                var instance = d as OrderTreeItemControl;
                if (e.NewValue is Location)
                {
                    instance.MainContent.ContentTemplate = instance.LocationTemplate;
                }
                else if (e.NewValue is SKU)
                {
                    instance.MainContent.ContentTemplate = instance.SKUTemplate;
                }
                else
                {
                    instance.MainContent.ContentTemplate = instance.OrderTemplate;
                }
            }
        }
    }
}

尝试 #1 模型类

public class OpenOrdersBase
{
    public ObservableCollection<Order> Orders { get; } = new ObservableCollection<Order>();
}
public class Order : OpenOrdersBase
{
    public bool IsSelected { get; set; }
    public string OrderNumber { get; set; }
    public string PoIDx { get; set; }
   ...
    public ICollection<SKU> SKUs { get; set; }

}
public class SKU : OpenOrderBase
{
    public bool IsSelected { get; set; }
    public string SKUNum { get; set; }
    ...
    public ICollection<Location> Locations { get; set; }
}
public class Location : OpenOrdersBase
{
    public bool IsSelected { get; set; }
    ...
    public string Notes { get; set; }
}

尝试 #1 页面 XAML

<DataTemplate x:Key="BaseTemplate" x:DataType="model:Order">
            <winui:TreeViewItem
                IsExpanded="False"
                ItemsSource="{x:Bind SKUs}">
                <controls1:TestControl Data="{Binding}"/>
             </winui:TreeViewItem>                        
         </DataTemplate>
...
<winui:TreeView
            x:Name="treeView"
            Grid.Row="0"
            SelectionMode="Single"
            Margin="10,10,10,10"
            ItemsSource="{x:Bind ViewModel.openOrders}"
            ItemTemplate="{StaticResource BaseTemplate}">
            <i:Interaction.Behaviors>
                <behaviors:TreeViewCollapseBehavior x:Name="collapseBehavior" />
                <ic:EventTriggerBehavior EventName="ItemInvoked">
                    <ic:InvokeCommandAction Command="{x:Bind ViewModel.ItemInvokedCommand}" />
                </ic:EventTriggerBehavior>
            </i:Interaction.Behaviors>
        </winui:TreeView>

尝试 #2 最大的区别在于 UserControl XAML 和模型中用户控件 XAML

    <UserControl
    x:Class="PickSheetManager.Controls.OrderTreeItemControl"
    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:winui="using:Microsoft.UI.Xaml.Controls"
    xmlns:model="using:PickSheetManager.Core.Models"
    xmlns:behaviors="using:PickSheetManager.Behaviors"
    xmlns:templateSelectors="using:PickSheetManager.TemplateSelectors"
    xmlns:controls="using:Microsoft.Toolkit.Uwp.UI.Controls"
    xmlns:controls1="using:PickSheetManager.Controls"
    xmlns:ic="using:Microsoft.Xaml.Interactions.Core"
    xmlns:i="using:Microsoft.Xaml.Interactivity"
    mc:Ignorable="d">

    <UserControl.Resources>

        <DataTemplate x:Name="OrderTemplate" x:DataType="model:Order">
            <winui:TreeViewItem
                AutomationProperties.Name="{x:Bind PoIDx}"
                ItemsSource="{x:Bind SKUs}"
                IsExpanded="True">
                <StackPanel x:Name="stack" Orientation="Horizontal">
                    <i:Interaction.Behaviors>
                        <ic:DataTriggerBehavior Binding ="{x:Bind NotEnoughInventory}" Value="True">
                            <ic:ChangePropertyAction TargetObject="{Binding ElementName=stack}" PropertyName="Background" Value="Red" />
                        </ic:DataTriggerBehavior>
                    </i:Interaction.Behaviors>
                    <CheckBox IsChecked="{x:Bind IsSelected, Mode=TwoWay}" Padding="5" MinWidth="0"/>
                    <TextBlock Text="PoIDx: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="{x:Bind PoIDx}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="Delivery: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="{x:Bind DeliveryType}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="Delivery: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="{x:Bind DeliveryType}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="Type: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="{x:Bind OrderType}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="Total Quantity: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="{x:Bind TotalQuantity}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="Printed: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="{x:Bind IsPrinted}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="Notes: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBox Text="{x:Bind Notes, Mode=TwoWay}" Margin="{StaticResource XXSmallTopRightBottomMargin}" Width="150"/>
                </StackPanel>
            </winui:TreeViewItem>

        </DataTemplate>
        <DataTemplate x:Name="SKUTemplate" x:DataType="model:SKU">
            <winui:TreeViewItem
                AutomationProperties.Name="{x:Bind SKUNum}"
                ItemsSource="{x:Bind Locations}"
                IsExpanded="True">
                <StackPanel x:Name="stack2" Orientation="Horizontal">
                    <i:Interaction.Behaviors>
                        <ic:DataTriggerBehavior Binding ="{x:Bind NotEnoughInventory}" Value="True">
                            <ic:ChangePropertyAction TargetObject="{Binding ElementName=stack2}" PropertyName="Background" Value="Yellow" />
                        </ic:DataTriggerBehavior>
                    </i:Interaction.Behaviors>
                    <CheckBox IsChecked="{x:Bind IsSelected, Mode=TwoWay}" Padding="5" MinWidth="0" />
                    <TextBlock Text="SKU: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="{x:Bind SKUNum}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="Needed: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="{x:Bind NeedQuantity}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="Available: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="{x:Bind AvailableQuantity}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                </StackPanel>
            </winui:TreeViewItem>
        </DataTemplate>
        <DataTemplate x:Name="LocationTemplate" x:DataType="model:Location">
            <winui:TreeViewItem
                AutomationProperties.Name="{x:Bind LocationName}"                
                IsExpanded="True">
                <StackPanel Orientation="Horizontal">
                    <CheckBox IsChecked="{x:Bind IsSelected, Mode=TwoWay}" Padding="5" MinWidth="0" />
                    <TextBlock Text="{x:Bind LocationName}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="Pick Type: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="{x:Bind PickType}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="Pick Quantity: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="{x:Bind PickQuantity}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="Available Quantity: " Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBlock Text="{x:Bind AvailableQuantity}" Margin="{StaticResource XXSmallTopRightBottomMargin}" />
                    <TextBox Text="{x:Bind Notes, Mode=TwoWay}" Margin="{StaticResource XXSmallTopRightBottomMargin}" Width="150" />
                </StackPanel>
            </winui:TreeViewItem>
        </DataTemplate>
    </UserControl.Resources>

    <Grid>
        <ContentControl x:Name="MainContent"/>
    </Grid>
</UserControl>

在用户控件的代码中，我只是将 OpenOrdersBase 更新为 Order，因为我从所有模型中删除了继承。

最终页面 XAML 以这种方式更改

<DataTemplate x:Key="BaseTemplate" x:DataType="model:Order">
    <controls1:TestControl Data="{Binding}"/>                                        
</DataTemplate>

【问题讨论】：

你好，对于更复杂的数据结构，使用UserControl在控件内部进行判断是一种思路。你需要根据你的数据结构调整UserControl的写法，你说UserControl只显示一层，你能说明你是怎么写这个UserControl的吗？
我明天一上班就会把代码贴出来。谢谢。

标签： c# uwp treeview

【解决方案1】：

实际上，您的尝试 1 已经非常接近成功，只需要稍作修改即可。

这个问题出在类的定义上：

Order、SKU、Location 有一个共同的基类OpenOperBase，这很好，但是基类应该提供一个共同的属性，而不是一个特殊的Order 集合。

试试这个：

public class OpenOrdersBase
{
    public ObservableCollection<OpenOrdersBase> Children { get; set; } = new ObservableCollection<OpenOrdersBase>();
}

在你的Order 和SKU 类中，有一个子集合属性，将它们提取为单独的基类集合属性，稍后在数据绑定中看到效果。

现在您可以删除Order.SKUs 和SKU.Locations。

绑定时，TestControl的内容不需要改变（保持尝试#1的写法），但是TreeViewItem模板需要改变DataType

<DataTemplate x:DataType="models:OpenOrdersBase" x:Key="BaseTemplate">
    <TreeViewItem ItemsSource="{x:Bind Children}">
        <controls:TestControl Data="{Binding}"/>
    </TreeViewItem>
</DataTemplate>

我们的总体思路如下：

由于TreeViewItem 仅作为TreeView.Children 的子级直接有效，因此尝试#2 的方法不可取。
TreeView.ItemTemplate 属性影响所有内部子级，因此在绑定TreeViewItem.ItemsSource 时，最好绑定一个基类集合，而不是特定类型的集合（如SKUs）
如果你想根据数据类型显示不同的模板，创建UserControl并在内部判断类型是一种可行的方法（你已经做过了）。

谢谢。

【讨论】：

非常感谢您的明确答复。我真的很感激。