IsEmpty
is being resolved from CollectionView.IsEmpty
how?
I applied high tracing for the binding
Visibility="{Binding ElementName=entry,
PresentationTraceSources.TraceLevel=High,
Path=Text.IsEmpty,
Converter={StaticResource BooleanToVisibilityConverter}}"
and here is the result
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'
interesting lines from the above trace
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)
so you can see that indeed type String
does not have IsEmpty
for String.IsEmpty found accessor <null>
but the view for the string is an EnumerableCollectionView
which does have IsEmpty
and the binding resolved to the same
for EnumerableCollectionView.IsEmpty found accessor RuntimePropertyInfo(IsEmpty)
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