wpf - WPF 相对源行为

Question

我在理解RelativeSource绑定行为方面遇到了一些问题。以下是将内容正确绑定Label到StackPanelTag 的代码：

<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>

上面的代码不绑定Grid标签，如果我改变AncestorType=Grid和AncestorLevel=2. 我有两个问题：

1. 我想我应该将 AncestorLevel 更改为 2，以绑定到 Grid。但它适用于AncestorLevel=1. 为什么？

2. 我也无法将标签绑定到窗口标签。请建议。

Answer 1

用于查找要绑定的AncestorLevel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

ElementName但是您可以通过使用绑定来简化代码，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：

如果你想绑定回Window你仍然可以使用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：

Answer 2

我的最终结论是：VS2010 设计器的问题是它没有更新 Window 标签的 RelativeSource 绑定。它更新设计器中其他控件的绑定（我检查了 Grid 和 StackPanel），但对于 Winodw，它会在运行时更新。微软已经在 VS2012 中为此做了解决方法。