如何在wpf中从高级datacontext获取datacontext

Question

我有A类和B类：

    public class A : INotifyPropertyChanged
{
    private string _ina;
    public string InA 
    {
        get
        {
            return _ina;
        }
        set
        {
            _ina = value;
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs("InA"));
            }
        }
    }
    public A()
    {
        InA = "INA";
    }
    public event PropertyChangedEventHandler PropertyChanged;
}

public class B : INotifyPropertyChanged
{
    private string _inb;
    public string INB
    {
        get
        {
            return _inb;
        }
        set
        {
            _inb = value;
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs("INB"));
            }
        }
    }
    public B()
    {
        INB = "B_inb";
    }
    public event PropertyChangedEventHandler PropertyChanged;
}

和xaml(local是类A和B所在的名称空间别名)：

    <Grid>
    <Grid.DataContext>
        <local:B/>
    </Grid.DataContext>
    <StackPanel>
        <StackPanel.DataContext>
            <local:A/>
        </StackPanel.DataContext>
        <TextBlock Text="{Binding Path=InA}"/>
        <TextBlock Text="{Binding Path=INB }"/>
    </StackPanel>
</Grid>

我知道第一个TextBlock会得到正确的值，但是第二个不能。但是如何让DataContext让第二个TextBlock从网格的DataContext而不是stackpanel的DataContext获得正确的值

Answer 1

就像你自己弄清楚的那样，

<TextBlock Text="{Binding Path=DataContext.INB,RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Grid}}}"/>

都会起作用的。它所做的就是沿着可视化树向上移动，直到找到类型为Grid的祖先，然后在该祖先中查找一个名为DataContext.INB的属性。在这种情况下，网格的数据上下文将是类B和其中定义的属性INB。