TextBox Placeholder text while also Binding to ListBox.SelectedItem

Question

如何将文本框绑定到ListBox的Selected Item，我怎么还有一个占位符文本（.Text =“Whatever”）？

Answer 1

When do you want this placeholder text to display? When there is no SelectedItem?

You could use PriorityBinding which will allow you to provide a list of bindings and it will use the first that produces a result.

Something like:

<TextBox> 
   <TextBox.Text>
     <PriorityBinding>
       <Binding Path="myListBox.SelectedItem"/>
       <Binding Source="Default Text"/>
     </PriorityBinding>
   </TextBox.text>
 </TextBox>