.NET Rocker

Two classes inherit from DataSourceProvider. XmlDataProvider and ObjectDataProvider. ObjectDataProvider wraps an object and allows you to bind to the wrapped object in XAML. The ObjectDataProvider has a ConstructorParameters-Property for creating an object by using a constructor with parameters.

The cool thing is that a Data Binding to the wrapped object of the ObjectDataProvider is not all. With ObjectDataProvider you can even bind to a static method or to an instance method of the wrapped object. I’ll show you an example.

Just think about a really simple ComboBox that allows the user to chose some colors. Between the name of the color a rectangle filled with the color should be displayed (In WPF this is quite easy. You haven’t to create eventhandlers like you would do in Windows Forms. There you consumed the DrawItem-event of the ComboBox and used the Graphics-object to do a little bit of GDI+. In WPF GDI+ is gone). WPF’s Color class doesn’t have a name property. So just create a static class ColorHelper with one static method GetColorNames that returns an IEnumerable<string> and uses reflection to iterate over all public static properties of the Colors class that all contain Color-objects.

public static class ColorHelper
{
  public static IEnumerable<string> GetColorNames()
  {
    foreach (PropertyInfo p
      in typeof(Colors).GetProperties(
      BindingFlags.Public | BindingFlags.Static))
    {
      yield return p.Name;
    }
  }
}

The Window in the following XAML contains an ObjectDataProvider that uses the Static GetColorNames-Method of the ColorHelper class. The ItemsSource-Property (Typ: IEnumerable) of the ComboBox is bound to the ObjectDataProvider. The ItemTemplate-Property contains a DataTemplate that specifies the Visual Tree (the "look") of an item. Thanks to TypeConverters, a SolidColorBrush-Object is created for the Fill-Property of each Rectangle specified in the DataTemplate.

<Window …
    xmlns:local="clr-namespace:SimpleObjectDataProvider">
 <Window.Resources>
  <ObjectDataProvider x:Key="colors"
   ObjectType="{x:Type local:ColorHelper}"
   MethodName="GetColorNames"/>
 </Window.Resources>
 <StackPanel>
  <ComboBox
   ItemsSource="{Binding Source={StaticResource colors}}">
   <ComboBox.ItemTemplate>
    <DataTemplate>
     <StackPanel Margin="1" Orientation="Horizontal">
      <Rectangle Fill="{Binding}" Height="10" Width="10"
        Margin="2"/>
      <TextBlock Text="{Binding}" Margin="2 0 0 0"/>
     </StackPanel>
    </DataTemplate>
   </ComboBox.ItemTemplate>
  </ComboBox>
 </StackPanel>
</Window>

The displayed, open ComboBox looks like this:

Tags: WPF, XAML

This entry was posted on Thursday, January 10th, 2008 at 8:08 am and is filed under TrivadisContent, WPF, XAML. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.