WPF datatemplateselector not getting called

Question

Hello I'm trying to dynamically change datatemplate but my method SelectTemplate in class TreeViewItemTemplateSelector never getting called (I've checked it by debugger) :( please help me :)

Code from xaml MainWindow:

Code in code behind:

Answer 1

Your problem seems to be that your TreeViewCustomItem is inheriting from TreeViewItem. (As seen in http://pastebin.com/jnP2nWMF)

Removing that inheritance (and the dependency property) causes the template selector to fire fine. What were/are you trying to achieve with the node item?

Looking at the OutputWindow, I get this message:

System.Windows.Data Error: 26 : ItemTemplate and ItemTemplateSelector are ignored for items already of the ItemsControl's container type; Type='TreeViewCustomItem'

You don't have to have items inherit from the TreeViewItem in order to bind them to a TreeView, TreeViewItem is something that the TreeView uses to hold the data, and then the DataTemplate is used to present the data.

Answer 2

Move DataTemplates from TreeView.Resources to Window.Resources

         <Window.Resources><DataTemplate x:Key="DefaultTemplate">
            <TextBlock Text="{Binding Header}"></TextBlock>
        </DataTemplate><DataTemplate x:Key="Regulation">
            <TextBlock Text="{Binding Path=Header}" FontWeight="Bold"></TextBlock>
        </DataTemplate>

        <DataTemplate x:Key="Article">
            <TextBlock Text="{Binding Path=Header}" Foreground="Green"></TextBlock>
        </DataTemplate>        
<local:TreeViewItemTemplateSelector x:Key="TemplateSelector" DefaultTemplate="{StaticResource DefaultTemplate}"  ArticleTemplate="{StaticResource Article}" RegulationTemplate="{StaticResource Regulation}"  />

and make change

 <TreeView ItemTemplateSelector="{StaticResource TemplateSelector}" Height="409" HorizontalAlignment="Left" Margin="10,10,0,0" Name="treeView1" VerticalAlignment="Top" Width="277" ItemsSource="{Binding}"/>

Update code and we will see. I put similar code into VS and it works so we need to take a closer look. So i checked this and changed

public class TreeViewCustomItem
{
    public string Header { get; set; }
}

and this

 listmy = new ObservableCollection<TreeViewCustomItem> { new TreeViewCustomItem { Header = "xD" }, new TreeViewCustomItem { Header = "xxD" } };
        //treeView1.ItemsSource = listmy;
        this.DataContext = listmy;

 public class selector : DataTemplateSelector
{

    public DataTemplate RegulationTemplate { get; set; }

    public DataTemplate DefaultTemplate { get; set; }

    public override DataTemplate SelectTemplate(object item, DependencyObject container)
    {
        TreeViewCustomItem treeViewItem = item as TreeViewCustomItem;
        if (treeViewItem.Header == "xD")
        {
            return RegulationTemplate;
        }

        else
        {
            return DefaultTemplate;

        }
    }
}

and in XAML looks like this

         xmlns:local="clr-namespace:WpfApplication1.Views">
    <Window.Resources>
        <DataTemplate x:Key="DefaultTemplate">
            <TextBlock Text="{Binding Header}"></TextBlock>
        </DataTemplate>
        <DataTemplate x:Key="Regulation">
            <TextBlock Text="{Binding Path=Header}" FontWeight="Bold"></TextBlock>
        </DataTemplate>
    <local:selector x:Key="selector_" DefaultTemplate="{StaticResource DefaultTemplate}" RegulationTemplate="{StaticResource Regulation}"/>
</Window.Resources>
    <Grid>
        <TreeView Height="409" HorizontalAlignment="Left" Margin="10,10,0,0" Name="treeView1" VerticalAlignment="Top" Width="277"  
           ItemsSource="{Binding}" ItemTemplateSelector="{StaticResource selector_}"/>      

</Grid>

And it works so my presumption is that problem is inside TreeViewCustomItem.