WPF 相对源行为

Question

我在理解上有些问题 RelativeSource绑定(bind)行为。
下面是绑定(bind)Label的代码内容到 StackPanel正确标记:

<Window x:Class="Binding_RelativeSource.MainWindow" Tag="Window Tag">
    <Grid Tag="Grid Tag">
        <StackPanel Tag="StackPanel Tag" Height="100" HorizontalAlignment="Left" Margin="156,97,0,0" Name="stackPanel1" VerticalAlignment="Top" Width="200">
            <Label Content="{Binding Path=Tag,RelativeSource={RelativeSource Mode=FindAncestor,AncestorLevel=1,AncestorType=StackPanel},FallbackValue=BindingFailed}" Height="28" Name="label1" />
        </StackPanel>
    </Grid>
</Window>

以上代码不绑定(bind) Grid标记，如果我更改 AncestorType=Grid和 AncestorLevel=2 .
我有两个问题:

我想我应该将 AncestorLevel 更改为 2，以绑定(bind)到 Grid。但它
为AncestorLevel=1工作.为什么？

我也无法将标签绑定(bind)到窗口标签。请建议。

Answer 1

AncestorLevel用于查找要绑定(bind)的正确祖先，这是因为该类型的祖先可能不止一个。

这是一个显示这一点的场景:

<Grid Tag="AncestorLevel 3">
    <Grid Tag="AncestorLevel 2">
        <Grid Tag="AncestorLevel 1">
            <StackPanel Tag="StackPanel Tag" Height="100" HorizontalAlignment="Left" Margin="156,97,0,0" Name="stackPanel1" VerticalAlignment="Top" Width="200">
                <Label Content="{Binding Path=Tag,RelativeSource={RelativeSource Mode=FindAncestor,AncestorLevel=1,AncestorType=Grid},FallbackValue=BindingFailed}" Height="28"  />
                <Label Content="{Binding Path=Tag,RelativeSource={RelativeSource Mode=FindAncestor,AncestorLevel=2,AncestorType=Grid},FallbackValue=BindingFailed}" Height="28"  />
                <Label Content="{Binding Path=Tag,RelativeSource={RelativeSource Mode=FindAncestor,AncestorLevel=3,AncestorType=Grid},FallbackValue=BindingFailed}" Height="28"  />
            </StackPanel>
        </Grid>
    </Grid>
</Grid>

结果:



替代方法

但是你可以使用 ElementName 来简化代码。绑定(bind)，这使用 Name元素的

例子:

<Window x:Class="WpfApplication9.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525" Name="MyWindow" Tag="This is the window">
    <Grid Name="Grid1" Tag="First grid">
        <Grid Name="Grid2" Tag="Second grid">
            <Grid Name="Grid3" Tag="ThirdGrid">
                <StackPanel Name="stackPanel1" Tag="StackPanel Tag" Height="160" HorizontalAlignment="Left" Margin="156,97,0,0" VerticalAlignment="Top" Width="200">
                    <Label Content="{Binding ElementName=MyWindow, Path=Tag}" Height="28"  />
                    <Label Content="{Binding ElementName=Grid1, Path=Tag}" Height="28"  />
                    <Label Content="{Binding ElementName=Grid2, Path=Tag}" Height="28"  />
                    <Label Content="{Binding ElementName=Grid3, Path=Tag}" Height="28"  />
                    <Label Content="{Binding ElementName=stackPanel1, Path=Tag}" Height="28"  />
                </StackPanel>
            </Grid>
        </Grid>
    </Grid>
</Window>

结果:



如果要绑定(bind)回 Window您仍然可以使用 FindAncestor

<Window x:Class="WpfApplication9.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525" Tag="This is the window">
    <Grid>
        <StackPanel Height="100" HorizontalAlignment="Left" Margin="156,97,0,0" Name="stackPanel1" VerticalAlignment="Top" Width="200">
            <Label Content="{Binding Path=Tag,RelativeSource={RelativeSource Mode=FindAncestor,AncestorType=Window},FallbackValue=BindingFailed}" Height="28"  />
        </StackPanel>
    </Grid>

结果: