有点时候，需要利用UserControl占位模板，动态替换的情况，绑定后无法获取DataContext的问题

Posted 2021-02-28 xuling-297769461

有点时候，需要利用UserControl占位模板，动态替换的情况，绑定后无法获取DataContext的问题，特此备注下

效果如下：

关键的地方是，下面第3行，需要把当前的上下文传递到Content，生成绑定的ContentTemplate才能获取到绑定在UserControl的DataContext

1 <Style TargetType="UserControl">
2             <Setter Property="ContentTemplate" Value="{StaticResource SingleDataTemplate}" />
3             <Setter Property="Content" Value="{Binding}" />
4             <Style.Triggers>
5                 <DataTrigger Binding="{Binding ElementName=rabtn,Path=IsChecked}" Value="false">
6                     <Setter Property="ContentTemplate" Value="{StaticResource MultipleTemplate}" />
7                 </DataTrigger>
8             </Style.Triggers>
9         </Style>

下面是完成的前后端代码：

 1 <Window x:Class="VideoAndAudioDemo.MainWindow"
 2         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
 3         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
 4         xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
 5         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
 6         xmlns:local="clr-namespace:VideoAndAudioDemo"
 7         mc:Ignorable="d"
 8         Title="MainWindow" Height="450" Width="800">
 9     <Window.Resources>
10         <DataTemplate x:Key="SingleDataTemplate">
11             <RadioButton Content="{Binding Name}" />
12         </DataTemplate>
13         <DataTemplate x:Key="MultipleTemplate">
14             <CheckBox Content="{Binding Name}" />
15         </DataTemplate>
16         <Style TargetType="UserControl">
17             <Setter Property="ContentTemplate" Value="{StaticResource SingleDataTemplate}" />
18             <Setter Property="Content" Value="{Binding}" />
19             <Style.Triggers>
20                 <DataTrigger Binding="{Binding ElementName=rabtn,Path=IsChecked}" Value="false">
21                     <Setter Property="ContentTemplate" Value="{StaticResource MultipleTemplate}" />
22                 </DataTrigger>
23             </Style.Triggers>
24         </Style>
25     </Window.Resources>
26     <Grid>
27         <StackPanel>
28             <StackPanel Orientation="Horizontal">
29                 <TextBlock Text="我是模板：" />
30                 <UserControl/>
31             </StackPanel>
32             <StackPanel Orientation="Horizontal" Margin="0 20 0 0">
33                 <RadioButton x:Name="rabtn" IsChecked="True" GroupName="selected" Content="单选" />
34                 <RadioButton GroupName="selected" Content="多选" />
35             </StackPanel>
36         </StackPanel>
37     </Grid>
38 </Window>

View Code

 1 using System;
 2 using System.Collections.Generic;
 3 using System.ComponentModel;
 4 using System.Linq;
 5 using System.Media;
 6 using System.Text;
 7 using System.Threading.Tasks;
 8 using System.Windows;
 9 using System.Windows.Controls;
10 using System.Windows.Data;
11 using System.Windows.Documents;
12 using System.Windows.Input;
13 using System.Windows.Media;
14 using System.Windows.Media.Imaging;
15 using System.Windows.Navigation;
16 using System.Windows.Shapes;
17 
18 namespace VideoAndAudioDemo
19 {
20     /// <summary>
21     /// MainWindow.xaml 的交互逻辑
22     /// </summary>
23     public partial class MainWindow : Window
24     {
25         public MainWindow()
26         {
27             InitializeComponent();
28             var vm = new MainWindowViewModel();
29             DataContext = vm;
30 
31             vm.Name = "测试";
32         }
33     }
34 
35     public class MainWindowViewModel : INotifyPropertyChanged
36     {
37         public event PropertyChangedEventHandler PropertyChanged;
38         private string name;
39 
40         public string Name
41         {
42             get => name;
43             set
44             {
45                 name = value;
46                 PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(Name)));
47             }
48         }
49     }
50 }

View Code