DocumentWindow with ContentTemplateSelector

public MainWindow()
        {
            InitializeComponent();

            var docWin = new DocumentWindow()
                                        {
                                            Title = "title1",
                                            ContentTemplateSelector = (TemplateSelector)Resources["TSelector"],
                                            Content = "1"
                                        };
            grid.Children.Add(docWin);
        }

<Window.Resources>
        <DataTemplate x:Key="FirstDataTemplate">
            <Label>FirstDataTemplate</Label>
        </DataTemplate>

        <DataTemplate x:Key="OtherDataTemplate">
            <Label>OtherDataTemplate</Label>
        </DataTemplate>

        <DockSiteTest:TemplateSelector x:Key="TSelector" 
                                       FirstDataTemplate="{StaticResource FirstDataTemplate}"
                                       OtherDataTemplate="{StaticResource OtherDataTemplate}">
        </DockSiteTest:TemplateSelector>
    </Window.Resources>
    
    <Grid x:Name="grid">
    </Grid>

public class TemplateSelector : DataTemplateSelector
    {
        public DataTemplate FirstDataTemplate
        {
            get; set;
        }

        public DataTemplate OtherDataTemplate
        {
            get;
            set;
        }

        public override DataTemplate SelectTemplate(object item, DependencyObject container)
        {
            if (item.ToString() == "1")
            {
                return FirstDataTemplate;
            }

            return OtherDataTemplate;
        }
    }