Converting a Regular ReadOnly Property to a ReadOnly DependencyProperty

Question

I have a UserControl that contains several properties that are ReadOnly (the Get method returns a generated value rather than a value that is explicitly set). I need to bind to these properties in my XAML, so I need to convert these properties to DependencyProperty(s). I have used regular DependencyProperty(s) before, but I have never used ReadOnly DependencyProperty(s). I have looked at the documentation, but found it somewhat confusing, and wasn't quite sure how convert my regular ReadOnly property (especially since the value is generated). Is there anywhere that I can see an example/comparison of a regular ReadOnly property (that generates the value) and what it would look like when converted to a ReadOnly DependencyProperty? Thanks.

Answer 1

Hi @Nathan Sokalski ,

The Windows Runtime does not provide a way to register a custom dependency property as read-only.

The alternative solution are as follows.

Public Class TestUserControl  
	Inherits UserControl  
  
	Public ReadOnly Property Value As Double  
		Get  
			Return _Value  
		End Get  
	End Property  
	Private _Value As Double = 1  
  
End Class  
  
  
Public Class TestReadonlyUserControl  
	Inherits UserControl  
  
	Public Property Value As Double  
		Get  
			Return CType(GetValue(ValueProperty), Double)  
		End Get  
		Private Set(value As Double)  
			SetValue(ValueProperty, value)  
		End Set  
	End Property  
  
	Protected Shared ReadOnly ValueProperty As DependencyProperty _  
			= DependencyProperty.Register _  
				("Value" _  
				, GetType(Double) _  
				, GetType(TestReadonlyUserControl) _  
				, New PropertyMetadata(CType(1, Double))  
				)  
  
	Public Sub New()  
		Dim g As New Grid()  
		g.Background = New SolidColorBrush(Windows.UI.Colors.Red)  
		AddHandler g.Tapped, Sub()  
								 Me.Value += 1  
							 End Sub  
		Me.Content = g  
  
		Me.Width = 100  
		Me.Height = 100  
	End Sub  
End Class  

---
<StackPanel>
<local:TestReadonlyUserControl x:Name="uc" />
<TextBlock Text="{Binding ElementName=uc, Path=Value}" />
</StackPanel>

Answer 2

Maybe I was unclear about my question. The documentation I was referring to is

https://learn.microsoft.com/en-us/dotnet/framework/wpf/advanced/read-only-dependency-properties

And here is an example of what a regular ReadOnly property might look like:

Public ReadOnly Property FirstPlusSecond() As Integer  
	Get  
		Return Me.First + Me.Second  
	End Get  
End Property  

Note that the Get returns a generated value (it does not use GetValue like a regular DependencyProperty would). I want to be able to bind to this property in my XAML. How would I make this property bindable?