Q5.8 - Using a non-dependency property as binding target

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Modified: Wed, 04 Jan 2012 07:58 by capricedcruz - Categorized as: WPF FAQ

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Is there a way around the limitation of a binding target always needing a dependency property?

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As a rule, to accept a Binding class instance, a property has to be a Dependency Property. For instance, the following declaration is valid because TextBox.Text is a Dependency Property.

<TextBox Name="textBox1"   Text="{Binding Source={...}, Path=...}"/>

On the other hand, if we try to bind the X attribute of a Point to the content of this TextBox, the declaration will be invalid because X is not a dependency property.

<Point X="{Binding ElementName=textBox1, Path=Text, Mode=OneWay}"/>

However, there is indeed a way to bind this TextBox and this Point.X by declaring the Binding the other way around. To put it simply, if you want to perform a binding between a source property and a target property, you can either declare it on the target property (the usual way) or on the source property (the way we explain in this article).

There are a few Outdoor Fountains things to be aware of first:

1- Since the target property is not a DependencyProperty, the source property has to be one. Otherwise, no binding is possible between the two properties. Wpfwiki Halloween Costumes

2- You have to use the binding mode TwoWay or OneWayToSource. Visalia accident lawyer weight loss pills. Otherwise, the conceptual target would not be a target! Here's a graph that explains Spotsylvania DUI Lawyer it more clearly.

Classic OneWay binding                                      Inversed OneWay Binding using the same objects
    Object A (Source)                                           Object A (Target - binding declared here)
       |                                                           |
       | information flow                                          | information flow
       v                                                           v
    Object B (Target - binding declared here)                   Object B (Source)
    Here, Object B is a Target in declaration                   Here, Object B is a Target only conceptually.
    and conceptually.

Here's the example that shows this at work. It shows two TextBox objects providing X and Y values to a Point in Resources. There's also a hyip monitor button that displays breast actives results the current Point's value in a MessageBox.

<Window x:Class="WindowsApplication4.Window1"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="CLR Property As Binding Target Sample"
        Height="300"
        Width="300">
   <Window.Resources>
      <Style x:Key="LabelStyle"
             TargetType="{x:Type TextBlock}">
         <Setter Property="Margin"
                 Value="5,3,0,0"/>
      </Style>
      <Point x:Key="WorkingPoint"/>
   </Window.Resources>
   <StackPanel>
      <StackPanel Orientation="Horizontal">
         <TextBlock Text="X: "
                    Style="{StaticResource LabelStyle}"/>
         <TextBox Width="50"
                  Text="{Binding Source={StaticResource WorkingPoint}, Path=X}"/>
         <TextBlock Text="Y: "
                    Style="{StaticResource LabelStyle}"/>
         <TextBox Width="50"
                  Text="{Binding Source={StaticResource WorkingPoint}, Path=Y}"/>
      </StackPanel>
      <Button Content="Show Value" Click="ShowValue_Clicked"/>
   </StackPanel>
</Window>

In code behind:

private void ShowValue_Clicked( object sender, RoutedEventArgs e )
{
  MessageBox.Show( this.FindResource( "WorkingPoint" ).ToString(), "Point value" );
}

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