wpf - 为什么这个数据模板在设计时不起作用？

Question

以下简单数据模板仅在运行时有效。在设计时它什么也不显示。为什么会这样？

<DataTemplate x:Key="SomeEnumDataTemplate">
    <ListBox Name="list" Width="20" IsSynchronizedWithCurrentItem="True" SelectedIndex="{Binding Mode=OneWay, Converter={StaticResource EnumToIntConverter}}">
        <ListBox.Template>
            <ControlTemplate TargetType="ListBox">
                <ContentPresenter Content="{TemplateBinding SelectedItem}" />
            </ControlTemplate>
        </ListBox.Template>
        <Rectangle Height="10" Width="10" Fill="Red" />
        <Rectangle Height="10" Width="10" Fill="Green" />
        <Rectangle Height="10" Width="10" Fill="Yellow" />
    </ListBox>
</DataTemplate>

我在另一个 DataTemplate 中这样使用它：

<HierarchicalDataTemplate x:Key="NodeDataTemplate" ItemsSource="{Binding Children}">
    <StackPanel Orientation="Horizontal" ToolTip="{Binding Description}">            
        <ContentControl ContentTemplate="{StaticResource SomeEnumDataTemplate}" Content="{Binding Mode}" Margin="3,0,0,0" />
        <TextBlock Text="{Binding Name}" />
    </StackPanel>
</HierarchicalDataTemplate>

再次在具有设计时数据的 UserControl 中使用：

<UserControl x:Class="MyProject.Views.MyView"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:ViewModels="clr-namespace:MyProject.ViewModels" mc:Ignorable="d" 
             d:DesignHeight="780" d:DesignWidth="400" d:DataContext="{x:Static ViewModels:SampleData.RootNode}">     
 <TreeView ItemsSource="{Binding}" ItemTemplate="{StaticResource NodeDataTemplate}">
     <TreeView.ItemContainerStyle>
      <Style TargetType="TreeViewItem">
       <Setter Property="IsExpanded" Value="True" />
   </Style>   
  </TreeView.ItemContainerStyle>
 </TreeView>
</UserControl>

score 3 · Accepted Answer

您可以轻松创建设计时数据：

创建您的数据模型：

public class Person
{
    public string Name { get; set; }

    public int  Age { get; set; }
}

public class PersonCollection : List<Person>
{
    public PersonCollection()
    {

    }
}

创建一个.xaml包含以下扩展名的文件：

设计时间树数据.xaml

    <local:PersonCollection xmlns:local="clr-namespace:Test_TreeWithDesignData">
        <local:Person Name="Joan Solo" Age="32" />
        <local:Person Name="Amara Skywalker" Age="31" />
    </local:PersonCollection>

使用d:DataContextandd:DesignData来使用您在 DesignTimeTreeData.xaml 中指定的数据：

主窗口.xaml

    <Window x:Class="Test_TreeWithDesignData.MainWindow"
            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:local="clr-namespace:Test_TreeWithDesignData"
            Title="MainWindow"
            Height="350"
            Width="525"
            mc:Ignorable="d">
        <Grid>
            <TreeView
                d:DataContext="{d:DesignData Source=./DesignTimeTreeData.xaml}"
                ItemsSource="{Binding}">
                <TreeView.Resources>
                    <DataTemplate DataType="{x:Type local:Person}" >
                        <StackPanel Orientation="Horizontal" Height="25">
                            <Label Content="{Binding Name}"/>
                            <Label Content="{Binding Age}" Margin="3,0,0,0"/>
                        </StackPanel>
                    </DataTemplate>
                </TreeView.Resources>
            </TreeView>
        </Grid>
    </Window>

由于通常Window.DataContext属性设置为 aViewModel并且 theTreeView.DataContext是它的集合，为了让两个数据源都工作，您可以用设置为集合的a包围TreeViewa 。GridDataContextViewModel

DummyViewModel.cs

    public class DummyViewModel : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
        {
            var handler = PropertyChanged;
            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        public PersonCollection Persons { get; set; }

        public DummyViewModel()
        {
            this.Persons = new PersonCollection();
        }
    }

主窗口.xaml

    <Window x:Class="Test_TreeWithDesignData.MainWindow"
            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:local="clr-namespace:Test_TreeWithDesignData"
            Title="MainWindow"
            Height="350"
            Width="525"
            mc:Ignorable="d">
        <Window.DataContext>
            <local:DummyViewModel />
        </Window.DataContext>

        <Grid Name="RootGrid">
            <Grid Name="TreeGrid" DataContext="{Binding Persons}">
                <TreeView d:DataContext="{d:DesignData Source=./DesignTimeTreeData.xaml}"
                    ItemsSource="{Binding}">
                    <TreeView.Resources>
                        <DataTemplate DataType="{x:Type local:Person}" >
                            <StackPanel Orientation="Horizontal" Height="25">
                                <Label Content="{Binding Name}"/>
                                <Label Content="{Binding Age}" Margin="3,0,0,0"/>
                            </StackPanel>
                        </DataTemplate>
                    </TreeView.Resources>
                </TreeView>
            </Grid>
        </Grid>
    </Window>

结果：

在此处输入图像描述

编辑

下一个问题是：如何在 Designer 中展开项目？

这Person将有一个人的集合：

public class Person
{
    public string Name { get; set; }

    public int  Age { get; set; }

    public PersonCollection Childs { get; set; }
}

设计时数据将有一个孩子

设计时间树数据.xaml

    <local:PersonCollection xmlns:local="clr-namespace:Test_TreeWithDesignData">
        <local:Person Name="Joan Solo" Age="32" />
        <local:Person Name="Amara Skywalker" Age="31">
            <local:Person.Childs>
                <local:PersonCollection>
                    <local:Person Name="Han Skywalker" Age="10" />
                </local:PersonCollection>
            </local:Person.Childs>
        </local:Person>
    </local:PersonCollection>

树现在将有一个 HierarchicalDataTemplate：

<HierarchicalDataTemplate
    DataType="{x:Type local:Person}"
    ItemsSource="{Binding Childs}">
    <StackPanel Orientation="Horizontal" Height="25">
        <Label Content="{Binding Name}"/>
        <Label Content="{Binding Age}" Margin="3,0,0,0"/>
    </StackPanel>
</HierarchicalDataTemplate>

并且TreeView将绑定到DesignerProperties.IsInDesignMode扩展设计器中的项目：

<TreeView.ItemContainerStyle>
    <Style TargetType="TreeViewItem">
        <Style.Triggers>
            <DataTrigger
                    Binding="{Binding RelativeSource={RelativeSource Self}, Path=(pf:DesignerProperties.IsInDesignMode)}"
                    Value="true"
                    >
                <Setter Property="IsExpanded" Value="True" />
            </DataTrigger>
        </Style.Triggers>
    </Style>
</TreeView.ItemContainerStyle>

这是窗口的 xaml：

主窗口.xaml

    <Window x:Class="Test_TreeWithDesignData.MainWindow"
            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:local="clr-namespace:Test_TreeWithDesignData"
            xmlns:pf="clr-namespace:System.ComponentModel;assembly=PresentationFramework"
            Title="MainWindow"
            Height="250"
            Width="325"
            mc:Ignorable="d"
            >
        <Window.DataContext>
            <local:DummyViewModel />
        </Window.DataContext>

        <Grid Name="RootGrid">

            <Grid Name="TreeGrid" DataContext="{Binding Persons}">
                <TreeView
                    d:DataContext="{d:DesignData Source=./DesignTimeTreeData.xaml}"
                    ItemsSource="{Binding}"
                    >
                    <TreeView.ItemContainerStyle>
                        <Style TargetType="TreeViewItem">
                            <Style.Triggers>
                                <DataTrigger
                                        Binding="{Binding RelativeSource={RelativeSource Self}, Path=(pf:DesignerProperties.IsInDesignMode)}"
                                        Value="true"
                                        >
                                    <Setter Property="IsExpanded" Value="True" />
                                </DataTrigger>
                            </Style.Triggers>
                        </Style>
                    </TreeView.ItemContainerStyle>
                    <TreeView.Resources>
                        <HierarchicalDataTemplate
                            DataType="{x:Type local:Person}"
                            ItemsSource="{Binding Childs}"
                            >
                            <StackPanel Orientation="Horizontal" Height="25">
                                <Label Content="{Binding Name}"/>
                                <Label Content="{Binding Age}" Margin="3,0,0,0"/>
                            </StackPanel>
                        </HierarchicalDataTemplate>
                    </TreeView.Resources>
                </TreeView>
            </Grid>
        </Grid>
    </Window>

这是结果：

在此处输入图像描述

score 0 · Accepted Answer

一旦你开始绑定，设置 DataContext、ItemSource 等，设计师就会对你大发雷霆。只需删除所有绑定（看起来像 3），您的设计器就会工作。把它全部排好，或者做任何你需要做的事情，然后重新添加绑定。

wpf - 为什么这个数据模板在设计时不起作用？

2 回答 2

编辑

Related

Reference