WPF：我如何调试绑定错误？ [英] WPF: How do I debug binding errors?

问题描述

我在我的输出窗口得到这个：

  

System.Windows.Data错误：4：无法为参照的RelativeSource FindAncestor，AncestorType ='System.Windows.Controls.ItemsControl'，AncestorLevel ='1'的结合找到源头。 BindingEx pression：路径= VerticalContentAlignment;的DataItem = NULL;目标元素是'ListBoxItem的'（名称=''）;目标属性是'VerticalContentAlignment（输入VerticalAlignment'）

这是我的XAML，它运行时看起来是正确的。

 ＆LT;分组框标题=准许/拒绝报告＆GT;
            ＆LT; ListBox中的ItemsSource ={结合转换器= {StaticResource的MethodBinder}，ConverterParameter = GrantDeny，模式=单向}＆GT;
                ＆LT; ListBox.ItemTemplate＆GT;
                    ＆LT;＆DataTemplate的GT;
                        ＆LT; StackPanel的方向=横向＆GT;
                            ＆LT;标签内容={结合实体}/＆GT;
                            ＆LT;标签内容={结合HasPermission}/＆GT;
                        ＆LT; / StackPanel的＆GT;
                    ＆LT; / DataTemplate中＆GT;
                ＆LT; /ListBox.ItemTemplate>
            ＆LT; /列表框＆GT;
        ＆LT; /分组框中＆GT;
 

解决方案

我也打算建议比亚Stollnitz的文章，但乔纳森 - 阿伦得到了他的职务，而在我还在打字这一个。我还建议在<一个链接href=\"http://wpfdisciples.word$p$pss.com/2008/04/04/debugging-in-wpf-wpf-disciples-tips-and-tricks/\">this博客条目。

在这种特殊情况下，你可以看到某处ListBoxItem中有FindAncestor绑定到失败一个ItemsControl。告诉你马上有一个ListBoxItem的地方，可以是：

1. 不要在可视化树，或


2. 不在一个ItemsControl（列表框是一个ItemsControl）

另外，你知道有人在什么地方，是一个ListBoxItem中的VerticalContentAlignment属性绑定到FindAncestor。

纵观系统主题（随前pression Blend和也可通过NET的反射的BAMLViewer加载项），我们可以看到这一点：

 ＆LT;风格X：键={X：输入一个ListBoxItem}＆GT;
  ＆LT; setter属性=VerticalContentAlignment
          VALUE ={绑定路径= VerticalContentAlignment，的RelativeSource = {的RelativeSource AncestorType = {X：类型的ItemsControl}}/＆GT;
 

这说明那里的约束力从何而来。是，是如何被创建的下一个问题一个ListBoxItem中不是一个列表框（或其他的ItemsControl）下？

有些事情要查找：

• 您在构建code ListBoxItems地方？


• 有没有在你的XAML明确指定的？任何一个ListBoxItem


• 请您有任何code是手工操作在ListBox中的项目？

希望这将头你在正确的方向。

I'm getting this in my output Window:

System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='System.Windows.Controls.ItemsControl', AncestorLevel='1''. BindingExpression:Path=VerticalContentAlignment; DataItem=null; target element is 'ListBoxItem' (Name=''); target property is 'VerticalContentAlignment' (type 'VerticalAlignment')

This is my XAML, which when run looks correct

        <GroupBox Header="Grant/Deny Report">
            <ListBox ItemsSource="{Binding  Converter={StaticResource MethodBinder}, ConverterParameter=GrantDeny, Mode=OneWay}">
                <ListBox.ItemTemplate>
                    <DataTemplate>
                        <StackPanel Orientation="Horizontal">
                            <Label Content="{Binding Entity}"/>
                            <Label Content="{Binding HasPermission}"/>
                        </StackPanel>
                    </DataTemplate>
                </ListBox.ItemTemplate>
            </ListBox>
        </GroupBox>

解决方案

I was also going to recommend Bea Stollnitz's article but Jonathan Allen got his post in while I was still typing this one. I also recommend the links in this blog entry.

In this particular case you can see that somewhere a ListBoxItem has a FindAncestor binding to an ItemsControl that is failing. That tells you right away there is a ListBoxItem somewhere that is either:

1. Not in the visual tree, or
2. Not under an ItemsControl (a ListBox is an ItemsControl)

In addition, you know that someone, somewhere, is binding a ListBoxItem's VerticalContentAlignment property to FindAncestor.

Looking at the system themes (shipped with Expression Blend and also available through NET Reflector's BAMLViewer Add-in), we see this:

<Style x:Key="{x:Type ListBoxItem}">
  <Setter Property="VerticalContentAlignment"
          Value="{Binding Path=VerticalContentAlignment,RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}" />

This explains where the binding comes from. The next question is, how is a ListBoxItem being created that is not under a ListBox (or other ItemsControl)?

Some things to look for:

• Are you constructing ListBoxItems in code anywhere?
• Is there any ListBoxItem explicitly specified in your XAML?
• Do you have any code that manually manipulates the items in ListBox?

Hopefully this will head you in the right direction.

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