如何告诉我的DataTemplate绑定到PARENT ViewModel中的属性？ [英] How can I tell my DataTemplate to bind to a property in the PARENT ViewModel?

问题描述

我有以下 MainView.xaml 文件，可以作为MVVM菜单切换器使用。我有这些对：

I've got the following MainView.xaml file that works well as a MVVM menu switcher. I've got these pairs:

• Page1View / Page1ViewModel


• Page2View / Page2ViewModel
我的 MainViewModel 中的

• Page1View / Page1ViewModel
• Page2View / Page2ViewModel

我用两个ViewModels填充了一个ObservableCollection，当用户点击 Next 按钮，它调用MainViewModel中的 NextPageCommand ，它用一个新的ViewModel切换 CurrentPageViewModel ，然后使用适当的视图显示。

in my MainViewModel I fill an ObservableCollection with both ViewModels, then when the user clicks the Next button, it calls NextPageCommand in MainViewModel which switches out CurrentPageViewModel with a new ViewModel which is then displayed with an appropriate View, works nicely.

我还有一个菜单中填充了来自Observable集合中ViewModels的所有标题，这也很好用。

I also have a Menu being filled with all the titles from the ViewModels in the Observable collection, which also works nicely.

然而，每个MenuItem有一个Command ={Binding SwitchPageCommand}，它应该在 MainViewModel 上调用SwitchPageCommand，而不是例如 Page1ViewModel 或 Page2ViewModel 。

However, each MenuItem has a Command="{Binding SwitchPageCommand}" which SHOULD call SwitchPageCommand on the MainViewModel and not on e.g. Page1ViewModel or Page2ViewModel.

那么如何在模板中指出不要绑定到当前ViewModel，但是ViewModel 包含 ViewModel，例如如下所示：

So how can I indicate in the template not to bind to the current ViewModel but the ViewModel which contains that ViewModel, e.g. something like this:

PSEUDO-CODE:

<DataTemplate x:Key="CodeGenerationMenuTemplate">
    <MenuItem 
        Command="{Binding <parentViewModel>.SwitchPageCommand}" 
        Header="{Binding Title}" 
        CommandParameter="{Binding Title}"/>
</DataTemplate>

这里是 MainViewModel ：

<Window x:Class="TestMenu234.Views.MainView"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:c="clr-namespace:TestMenu234.Commands"
    xmlns:vm="clr-namespace:TestMenu234.ViewModels"
    xmlns:v="clr-namespace:TestMenu234.Views"
    Title="Main Window" Height="400" Width="800">

    <Window.Resources>
        <DataTemplate x:Key="CodeGenerationMenuTemplate">
            <MenuItem Header="{Binding Title}" Command="{Binding SwitchPageCommand}" CommandParameter="{Binding Title}"/>
        </DataTemplate>
        <DataTemplate DataType="{x:Type vm:Page1ViewModel}">
            <v:Page1View/>
        </DataTemplate>
        <DataTemplate DataType="{x:Type vm:Page2ViewModel}">
            <v:Page2View/>
        </DataTemplate>
    </Window.Resources>

    <DockPanel>

        <Menu DockPanel.Dock="Top">
            <MenuItem Header="Code _Generation" ItemsSource="{Binding AllPageViewModels}"
                      ItemTemplate="{StaticResource CodeGenerationMenuTemplate}"/>
        </Menu>

        <StackPanel DockPanel.Dock="Top" Orientation="Horizontal">
            <Button Margin="5" Content="Next Page" Command="{Binding NextPageCommand}"/>
        </StackPanel>

        <ContentControl
            Content="{Binding CurrentPageViewModel}"/>

    </DockPanel>
</Window>

推荐答案

答案是这样的：

<DataTemplate x:Key="CodeGenerationMenuTemplate">
    <MenuItem 
        Header="{Binding Title}" 
        Command="{Binding DataContext.SwitchPageCommand,
    RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Menu}}}" 
        CommandParameter="{Binding Title}"/>
</DataTemplate>

我刚刚看到，Nir给了我解决上述问题的语法：什么是最好的在MVVM中构建一个显示各种页面的菜单？。

I just saw that Nir had given me the syntax to solve the above issue on this question: What is the best way in MVVM to build a menu that displays various pages?.

这篇关于如何告诉我的DataTemplate绑定到PARENT ViewModel中的属性？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！