创建上下文绑定 XAML [英] Creating ContextBinding XAML

问题描述

我在为 stackPanel 内的所有字段设置 DataContext 时遇到问题.我想做的是将数据上下文设置为 vm:ViewModel.但它不起作用，当我向 VS 寻求 DataBinding 的帮助时，它会在 TextBox 内显示 TextBox.DataContext.有没有办法只设置一次，或者我必须为每个控件设置它?

I'm having problems setting the DataContext for all fields that are inside a stackPanel. What I would like to do is set the Data Context as vm:ViewModel. But it's not working and when I ask VS for assistance with DataBinding it Displays the TextBox.DataContext inside the TextBox. Is there a way to only set it once or do I have to set it for each control?

    <StackPanel DataContext="vm:ViewModel">
    <TextBox Text="{Binding FirstNumber}" HorizontalAlignment="Left" Height="23" Margin="206,45,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="120">
            <TextBox.DataContext>
                <vm:ViewModel/>
            </TextBox.DataContext>
        </TextBox>
    </StackPanel>

推荐答案

你需要让你的 DataContext 引用你的 ViewModel 的一个实例.

You need to get your DataContext to refer to an instance of your ViewModel.

DataContext="vm:ViewModel" 不是创建 ViewModel 的实例...它只是设置一个字符串.

DataContext="vm:ViewModel" is not creating an instance of the ViewModel...it's just setting a string.

改用属性元素语法:

    <StackPanel>
    <StackPanel.DataContext>
        <vm:ViewModel/>
    </StackPanel.DataContext>
    <TextBox Text="{Binding FirstNumber}" HorizontalAlignment="Left" Height="23" Margin="206,45,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="120"/>
    </StackPanel>

如果你这样做，那么就没有必要/事实上，在你的 TextBox.DataContext 中创建另一个可能是错误的......你只想继承 StackPanel 的 DataContext.

And if you do that, then there's no need/in fact it's probably wrong to create another one in your TextBox.DataContext...you just want to inherit the DataContext of the StackPanel.

我将向您展示另一种创建 ViewModel 并引用它的实例的方法，以便您有一个更大的了解.....那就是在资源中创建它，然后在资源中引用该资源绑定...这是一个例子:

I'll just show you another way to create a ViewModel and to refer to the instance of it so you have a bigger picture.....that is to create it in resources, and then refer to that resource in the binding...here's an example:

<Window x:Class="WpfApplication8.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:vm="clr-namespace:WpfApplication8"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <vm:ViewModel x:Key="myviewmodel"/>
    </Window.Resources>
        <StackPanel x:Name="stackp" DataContext="vm:ViewModel">
        <TextBox Text="{Binding Source={StaticResource myviewmodel}, Path=FirstNumber}" HorizontalAlignment="Left" Height="23" Margin="206,45,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="120"/>
    </StackPanel>
</Window>

将 DataContext 设置在树中更高级别的另一个示例:

Another example that sets the DataContext at a higher level in the tree:

<Window x:Class="WpfApplication8.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:vm="clr-namespace:WpfApplication8"
        Title="MainWindow" Height="350" Width="525">
    <Window.DataContext>
        <vm:ViewModel/>
    </Window.DataContext>
    <StackPanel>
        <TextBox Text="{Binding FirstNumber}" HorizontalAlignment="Left" Height="23" Margin="206,45,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="120"/>
    </StackPanel>
</Window>

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