What do I need to do to bind a shape's properties to a custom class or structure's properties?

Question

For some reason my object is not updating with changes in the source. The initial value is bound okay, but updating doesn't seem to occur. Here is an illustrative sample code:

(See next post for the code; formatting screwed up)

Answer 1

Hi DakkonA,

you have to repost your sample code formatted! I have tried to import the VB code in VS but it's impossible to make it run. Try it yourself.

You can format your VB.Net code with the icon </> (right of the HTML icon) in the editor.


By the way why do you using a Structure and not a Class for the CustomStructure?

Hope it helps.

Answer 2

I added the code formatted using that function, and when I edited my post it broke. And when I tried to fix it, it didn't work. Let me try again here.

I'm actually not entirely sure of the details of when to use a structure vs. a class, though I read that structures were more efficient, and didn't see any particular drawbacks, at least that I could understand.

XAML:

<Window x:Class="Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300">
    <Grid>
        <Rectangle x:Name="TestShape" Stroke="Black" />
        <Button HorizontalAlignment="Left" VerticalAlignment="Bottom" x:Name="ChangeButton">Change</Button>
        <TextBlock HorizontalAlignment="Right" VerticalAlignment="Bottom" x:Name="CurrentMarginTextBlock" />
    </Grid>
</Window>

Code-Behind:

Class Window1 

    Public CustomStructureInstance As New CustomStructure

    Private Sub Window1_Loaded(ByVal sender As Object, ByVal e As System.Windows.RoutedEventArgs) Handles Me.Loaded
        CustomStructureInstance.Margin = 50
        CurrentMarginTextBlock.Text = CStr(CustomStructureInstance.Margin)

        Dim MarginBinding As New Binding
        MarginBinding.Source = CustomStructureInstance
        MarginBinding.Path = New PropertyPath("Margin")
        TestShape.SetBinding(Rectangle.MarginProperty, MarginBinding)


    End Sub

    Private Sub ChangeButton_Click(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs) Handles ChangeButton.Click
        CustomStructureInstance.Margin = CustomStructureInstance.Margin + 10
        CurrentMarginTextBlock.Text = CStr(CustomStructureInstance.Margin)
    End Sub

End Class

Public Structure CustomStructure
    Implements System.ComponentModel.INotifyPropertyChanged

    Private MarginPrivate As Double

    Public Property Margin() As Double
        Get
            Return MarginPrivate
        End Get
        Set(ByVal value As Double)
            If Not value = MarginPrivate Then
                MarginPrivate = value
                NotifyPropertyChanged("Margin")
            End If
        End Set
    End Property

    Private Sub NotifyPropertyChanged(ByVal info As String)
        RaiseEvent PropertyChanged(Me, New System.ComponentModel.PropertyChangedEventArgs("info"))
    End Sub

    Public Event PropertyChanged(ByVal sender As Object, ByVal e As System.ComponentModel.PropertyChangedEventArgs) Implements System.ComponentModel.INotifyPropertyChanged.PropertyChanged
End Structure

Answer 3

Hi DakkonA,

thats much better :)

You have a bug in your NotifyProperyChanged method. You always fireing the event with "info". That says to WPF, hey the info property has changed. But you want "Margin".

Second, you can not use a structure you have to use a class.

Public Class CustomStructure
	Implements System.ComponentModel.INotifyPropertyChanged

	Private MarginPrivate As Double

	Public Property Margin() As Double
		Get
			Return MarginPrivate
		End Get
		Set(ByVal value As Double)
			If Not value = MarginPrivate Then
				MarginPrivate = value
				NotifyPropertyChanged("Margin")
			End If
		End Set
	End Property

	Private Sub NotifyPropertyChanged(ByVal info As String)
		RaiseEvent PropertyChanged(Me, New System.ComponentModel.PropertyChangedEventArgs(info))
	End Sub

	Public Event PropertyChanged(ByVal sender As Object, ByVal e As System.ComponentModel.PropertyChangedEventArgs) Implements System.ComponentModel.INotifyPropertyChanged.PropertyChanged
End Class

Hope this helps.

Answer 4

Thanks Guenter! The "info" error actually wasn't in my real code, but changing my structures to classes fixed the problem.