HierarchicalDataTemplate.ItemContainerStyleSelector Property

Definition

Namespace:

System.Windows

Assembly:

PresentationFramework.dll

Gets or sets custom style-selection logic for a style that can be applied to each item container.

public:
 property System::Windows::Controls::StyleSelector ^ ItemContainerStyleSelector { System::Windows::Controls::StyleSelector ^ get(); void set(System::Windows::Controls::StyleSelector ^ value); };

public System.Windows.Controls.StyleSelector ItemContainerStyleSelector { get; set; }

member this.ItemContainerStyleSelector : System.Windows.Controls.StyleSelector with get, set

Public Property ItemContainerStyleSelector As StyleSelector

Property Value

StyleSelector

A StyleSelector that chooses which style to use as the ItemContainerStyle. The default is null.

Examples

The following example creates a TreeView that uses the ItemContainerStyle of a HierarchicalDataTemplate to choose between two styles for items in the second level of the TreeView.

<StackPanel Name="sp1" x:FieldModifier="public">
  <StackPanel.Resources>
    <src:TreeViewData x:Key="dataItems"/>

    <Style x:Key="TreeViewItemStyle1"  TargetType="TreeViewItem">
      <Setter Property="Foreground" Value="Navy"/>
      <Setter Property="FontStyle" Value="Italic"/>
    </Style>

    <Style x:Key="TreeViewItemStyle2"  TargetType="TreeViewItem">
      <Setter Property="Foreground" Value="Green"/>
      <Setter Property="FontWeight" Value="Bold"/>
    </Style>

    <src:TreeViewItemStyleSelector x:Key="tviSelector"/>
    
    <HierarchicalDataTemplate DataType="{x:Type src:ItemsForTreeView}"
                              ItemsSource="{Binding Path=SecondLevelItems}"
                              ItemContainerStyleSelector="{StaticResource tviSelector}">

      <!--Display the TopLevelName property in the first level.-->
      <TextBlock Text="{Binding Path=TopLevelName}"/>
      
      <!--Display each string in the SecondLevelItems property in
          the second level.-->
      <HierarchicalDataTemplate.ItemTemplate>
          <DataTemplate>
              <TextBlock Text="{Binding}"/>
          </DataTemplate>
      </HierarchicalDataTemplate.ItemTemplate>
      
    </HierarchicalDataTemplate>
  </StackPanel.Resources>

  <TreeView Height="200" ItemsSource="{Binding Source={StaticResource dataItems}}"
            VirtualizingStackPanel.IsVirtualizing="True">
    <TreeView.ItemContainerStyle>

      <!--Expand each TreeViewItem in the first level.-->
      <Style TargetType="TreeViewItem">
        <Setter Property="IsExpanded" Value="True"/>
      </Style>
    </TreeView.ItemContainerStyle>
  </TreeView>
</StackPanel>

The following example shows the StyleSelector that is used in the previous example.

public class TreeViewItemStyleSelector : StyleSelector
{
    public override Style SelectStyle(object item, DependencyObject container)
    {
        string itemString = item as string;

        string[] strings = itemString.Split(null);
        int value;
        
        if (!Int32.TryParse(strings[strings.Length - 1], out value))
        {
            return null;
        }

        StackPanel sp = ((Window1) Application.Current.MainWindow).sp1;

        if (value < 5)
        {
            return sp.FindResource("TreeViewItemStyle1") as Style;
        }
        else
        {
            return sp.FindResource("TreeViewItemStyle2") as Style;
        }
    }
}

Public Class TreeViewItemStyleSelector
    Inherits StyleSelector
    Public Overloads Overrides Function SelectStyle(ByVal item As Object, ByVal container As DependencyObject) As Style
        Dim itemString As String = TryCast(item, String)

        Dim strings As String() = itemString.Split(Nothing)
        Dim value As Integer

        If Not Int32.TryParse(strings(strings.Length - 1), value) Then
            Return Nothing
        End If

        Dim win1 As Window1 = CType(Application.Current.MainWindow, Window1)
        Dim sp As StackPanel = win1.sp1

        If value < 5 Then
            Return TryCast(sp.FindResource("TreeViewItemStyle1"), Style)
        Else
            Return TryCast(sp.FindResource("TreeViewItemStyle2"), Style)
        End If

    End Function
End Class

The following example creates the data that is used in the previous example.

public class TreeViewData : ObservableCollection<ItemsForTreeView>
{

    public TreeViewData()
    {
        for (int i = 0; i < 100; ++i)
        {
            ItemsForTreeView item = new ItemsForTreeView();
            item.TopLevelName = "item " + i.ToString();
            Add(item);
        }
    }
}

public class ItemsForTreeView
{
    public string TopLevelName { get; set; }
    private ObservableCollection<string> level2Items;

    public ObservableCollection<string> SecondLevelItems
    {
        get 
        {
            level2Items ??= new ObservableCollection<string>();
            return level2Items;
        }
    }

    public ItemsForTreeView()
    {
        for (int i = 0; i < 10; ++i)
        {
            SecondLevelItems.Add("Second Level " + i.ToString());
        }
    }
}

Public Class TreeViewData
    Inherits ObservableCollection(Of ItemsForTreeView)

    Public Sub New()
        For i As Integer = 0 To 99
            Dim item As New ItemsForTreeView()
            item.TopLevelName = "item " & i.ToString()
            Add(item)
        Next
    End Sub
End Class


Public Class ItemsForTreeView
    Private _TopLevelName As String
    Public Property TopLevelName() As String
        Get
            Return _TopLevelName
        End Get
        Set(ByVal value As String)
            _TopLevelName = value
        End Set
    End Property
    Private level2Items As ObservableCollection(Of String)

    Public ReadOnly Property SecondLevelItems() As ObservableCollection(Of String)
        Get
            If level2Items Is Nothing Then
                level2Items = New ObservableCollection(Of String)()
            End If
            Return level2Items
        End Get
    End Property

    Public Sub New()
        For i As Integer = 0 To 9
            SecondLevelItems.Add("Second Level " & i.ToString())
        Next
    End Sub
End Class

Remarks

You use the ItemContainerStyle property to set a style to affect the appearance of the elements that contain the data items. For example, for TreeView, the generated containers are TreeViewItem controls; for Menu, they are MenuItem controls. If you have more than one style defined and need to supply logic to choose which one to apply, then you use the ItemContainerStyleSelector property instead of the ItemContainerStyle property. Note that this property is ignored if the ItemContainerStyle property is set.