其中是此XAML代码中的IsEmpty引用/成员

本文关键字：IsEmpty 引用 成员 代码 XAML | 更新日期: 2023-09-27 18:20:56

我无法理解IsEmpty在这段代码（Path=Text.IsEmpty）（关于水印TextBox）中的来源：

<Grid Grid.Row="0" Background="{StaticResource brushWatermarkBackground}" 
                   Style="{StaticResource EntryFieldStyle}" >
    <TextBlock Margin="5,2" Text="Type to search ..." Foreground="Gray"
               Visibility="{Binding ElementName=entry, Path=Text.IsEmpty, 
                          Converter={StaticResource BooleanToVisibilityConverter}}"/>
    <TextBox Name="entry" Background="Transparent"/>
</Grid>

您可以看到一个字符串没有任何IsEmpty属性。DependencyProperty也不具有任何IsEmpty成员。我甚至尝试在对象浏览器窗口中搜索IsEmpty，但没有任何相关的结果来解释代码。

你能向我解释一下这里的IsEmpty参考资料吗？（任何关于它的参考链接都很棒）。

其中是此XAML代码中的IsEmpty引用/成员

正在从CollectionView.IsEmpty 解析IsEmpty

如何

我为绑定应用了高跟踪

Visibility="{Binding ElementName=entry,
                     PresentationTraceSources.TraceLevel=High, 
                     Path=Text.IsEmpty, 
                     Converter={StaticResource BooleanToVisibilityConverter}}"

这是的结果

System.Windows.Data Warning: 56 : Created BindingExpression (hash=40147308) for Binding (hash=39658150)
System.Windows.Data Warning: 58 :   Path: 'Text.IsEmpty'
System.Windows.Data Warning: 60 : BindingExpression (hash=40147308): Default mode resolved to OneWay
System.Windows.Data Warning: 61 : BindingExpression (hash=40147308): Default update trigger resolved to PropertyChanged
System.Windows.Data Warning: 62 : BindingExpression (hash=40147308): Attach to System.Windows.Controls.TextBlock.Visibility (hash=2939094)
System.Windows.Data Warning: 67 : BindingExpression (hash=40147308): Resolving source 
System.Windows.Data Warning: 70 : BindingExpression (hash=40147308): Found data context element: <null> (OK)
System.Windows.Data Warning: 74 :     Lookup name entry:  queried TextBlock (hash=2939094)
System.Windows.Data Warning: 65 : BindingExpression (hash=40147308): Resolve source deferred
System.Windows.Data Warning: 67 : BindingExpression (hash=40147308): Resolving source 
System.Windows.Data Warning: 70 : BindingExpression (hash=40147308): Found data context element: <null> (OK)
System.Windows.Data Warning: 74 :     Lookup name entry:  queried TextBlock (hash=2939094)
System.Windows.Data Warning: 78 : BindingExpression (hash=40147308): Activate with root item TextBox (hash=46768536)
System.Windows.Data Warning: 108 : BindingExpression (hash=40147308):   At level 0 - for TextBox.Text found accessor DependencyProperty(Text)
System.Windows.Data Warning: 104 : BindingExpression (hash=40147308): Replace item at level 0 with TextBox (hash=46768536), using accessor DependencyProperty(Text)
System.Windows.Data Warning: 101 : BindingExpression (hash=40147308): GetValue at level 0 from TextBox (hash=46768536) using DependencyProperty(Text): ''
System.Windows.Data Warning: 108 : BindingExpression (hash=40147308):   At level 1 - for String.IsEmpty found accessor <null>
System.Windows.Data Warning: 108 : BindingExpression (hash=40147308):   At level 1 - for EnumerableCollectionView.IsEmpty found accessor RuntimePropertyInfo(IsEmpty)
System.Windows.Data Warning: 104 : BindingExpression (hash=40147308): Replace item at level 1 with EnumerableCollectionView (hash=40847598), using accessor RuntimePropertyInfo(IsEmpty)
System.Windows.Data Warning: 101 : BindingExpression (hash=40147308): GetValue at level 1 from EnumerableCollectionView (hash=40847598) using RuntimePropertyInfo(IsEmpty): 'True'
System.Windows.Data Warning: 80 : BindingExpression (hash=40147308): TransferValue - got raw value 'True'
System.Windows.Data Warning: 82 : BindingExpression (hash=40147308): TransferValue - user's converter produced 'Visible'
System.Windows.Data Warning: 89 : BindingExpression (hash=40147308): TransferValue - using final value 'Visible'

上述跟踪中有趣的行

System.Windows.Data Warning: 108 : BindingExpression (hash=40147308):   At level 1 - for String.IsEmpty found accessor <null>
System.Windows.Data Warning: 108 : BindingExpression (hash=40147308):   At level 1 - for EnumerableCollectionView.IsEmpty found accessor RuntimePropertyInfo(IsEmpty)

所以你可以看到类型String实际上没有IsEmpty

for String.IsEmpty found accessor <null>

但是该字符串的视图是具有CCD_ 12的CCD_

for EnumerableCollectionView.IsEmpty found accessor RuntimePropertyInfo(IsEmpty)
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