StyleSelector.SelectStyle Method (Object, DependencyObject)

 

When overridden in a derived class, returns a Style based on custom logic.

Namespace:   System.Windows.Controls
Assembly:  PresentationFramework (in PresentationFramework.dll)

Public Overridable Function SelectStyle (
	item As Object,
	container As DependencyObject
) As Style

Parameters

item
Type: System.Object

The content.

container
Type: System.Windows.DependencyObject

The element to which the style will be applied.

Return Value

Type: System.Windows.Style

Returns an application-specific style to apply; otherwise, null.

To create a StyleSelector that applies a style based on custom logic, create a subclass of the StyleSelector class and implement the SelectStyle method.

The following example shows how to define a StyleSelector that defines a Style for a row. This example defines the Background color according to the row index.

Public Class ListViewItemStyleSelector
	Inherits StyleSelector
	Public Overrides Function SelectStyle(ByVal item As Object, ByVal container As DependencyObject) As Style
		Dim st As New Style()
		st.TargetType = GetType(ListViewItem)
		Dim backGroundSetter As New Setter()
		backGroundSetter.Property = ListViewItem.BackgroundProperty
		Dim listView As ListView = TryCast(ItemsControl.ItemsControlFromItemContainer(container), ListView)
		Dim index As Integer = listView.ItemContainerGenerator.IndexFromContainer(container)
		If index Mod 2 = 0 Then
			backGroundSetter.Value = Brushes.LightBlue
		Else
			backGroundSetter.Value = Brushes.Beige
		End If
		st.Setters.Add(backGroundSetter)
		Return st
	End Function
End Class

The following example shows how to define a ResourceKey for the StyleSelector. The namespc prefix maps to a CLR namespace and the corresponding assembly where the StyleSelector is defined. For more information, see XAML Namespaces and Namespace Mapping for WPF XAML.

<namespc:ListViewItemStyleSelector x:Key="myStyleSelector"/>

The following example shows how to set the ItemContainerStyleSelector property of a ListView to this StyleSelector resource.

<ListView 
      ItemsSource="{Binding Source={StaticResource EmployeeData}, 
                                        XPath=Employee}"
      ItemContainerStyleSelector="{DynamicResource myStyleSelector}" >      
  <ListView.View>
    <GridView>
      <GridViewColumn DisplayMemberBinding="{Binding XPath=FirstName}" 
                      Header="First Name" Width="120"/>
      <GridViewColumn DisplayMemberBinding="{Binding XPath=LastName}" 
                      Header="Last Name" Width="120"/>
      <GridViewColumn DisplayMemberBinding="{Binding XPath=FavoriteCity}" 
                      Header="Favorite City" Width="120"/>
    </GridView>
  </ListView.View>
</ListView>

For an example of how to create a selector to choose a defined style resource, see the implementation of DataTemplateSelector.SelectTemplate, which allows you to use custom logic to select a DataTemplate, based on a similar concept.

.NET Framework
Available since 3.0
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