I have created a DataTemplate as part of a resource of a user control with the following XAML:

<UserControl x:Class="XamDataTreeApp.SystemSettingsView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<UserControl.Resources>
<ResourceDictionary>
<DataTemplate x:Key="AppSettingsProviderDataTemplate">
<StackPanel Orientation="Horizontal">
<ContentPresenter Grid.Column="1" Content="{Binding Icon}" Margin="4,1,0,1" />
<TextBlock Grid.Column="2" Margin="4,1,0,1" FontWeight="Normal" Text="{Binding Alias, Mode=OneWay}" VerticalAlignment="Center" />
</StackPanel>
</DataTemplate>
</ResourceDictionary>
</UserControl.Resources><Border><ContentPresenter TreeViewContainer/></Border></UserControl>

and code behind.

public partial class SystemSettingsView
{
public SystemSettingsView(ITreeViewFactory treeViewFactory)
{
InitializeComponent();

Loaded += (sender, args) =>
{
if (TreeView == null)
{
var treeCreationCtx = new TreeViewCreationContext
{
Name = "SystemSettingsView",
DataContext = DataContext,
ItemSourceBinding = new Binding("SettingProviders"),
ItemDataTemplate = (DataTemplate)Resources["AppSettingsProviderDataTemplate"],
OnSelectionChanged = (selectedItem) =>
{
var systemSettingsViewModel = DataContext as SystemSettingsViewModel;
if (systemSettingsViewModel != null)
systemSettingsViewModel.SelectedSettingsProvider = (IAppSettingsProvider) selectedItem;
}
};

TreeView = treeViewFactory.GetTreeView(treeCreationCtx);
}
};
}

public FrameworkElement TreeView
{
get { return TreeViewContainer.Child as FrameworkElement; }
set
{
TreeViewContainer.Child = value;
}
}
}
}

When I attempt to programmatically create an instance of xamDataTree that users this template with the following constructs:

public FrameworkElement GetTreeView(TreeViewCreationContext creationContext)
{
if (creationContext == null)
throw new ArgumentNullException("creationContext");
if (creationContext.IsInvalid())
throw new InvalidDataException("creation context is not valid");

var tree = new XamDataTree()
{
Name = creationContext.Name,
NodeLineVisibility = Visibility.Visible,
DataContext = creationContext.DataContext
};

tree.SetBinding(XamDataTree.ItemsSourceProperty, creationContext.ItemSourceBinding);

if (creationContext.SelectedItemBinding != null)
tree.SetBinding(XamDataTree.SelectedDataItemsProperty, creationContext.SelectedItemBinding);

if (creationContext.ItemDataTemplate != null)
{
var nodeLayout = new NodeLayout();
nodeLayout.ItemTemplate = creationContext.ItemDataTemplate;
tree.GlobalNodeLayouts.Add(nodeLayout);
}

if (creationContext.OnSelectionChanged != null)
{
tree.SelectedNodesCollectionChanged += (sender, args) => creationContext.OnSelectionChanged.Invoke(tree.SelectedDataItems.First());
}

return tree;
}

public class TreeViewCreationContext
{
public string Name { get; set; }
public object DataContext { get; set; }
public Binding ItemSourceBinding { get; set; }
public DataTemplate ItemDataTemplate { get; set; }
public Action<object> OnSelectionChanged { get; set; }
public Binding SelectedItemBinding { get; set; }

public bool IsValid()
{
return !IsInvalid();
}

public bool IsInvalid()
{
if (DataContext == null)
return true;
if (ItemSourceBinding == null)
return true;
if (ItemDataTemplate == null)
return true;

return false;
}
}

I get the following exception: "A NodeLayout with this key is already in this collection."

If I do the same thing using WPF native treeview as follows:

public FrameworkElement GetTreeView(TreeViewCreationContext creationContext)
{
if (creationContext == null)
throw new ArgumentNullException("creationContext");
if (creationContext.IsInvalid())
throw new InvalidDataException("creation context is not valid");

var tv = new TreeView { Name = creationContext.Name, DataContext = creationContext.DataContext };
tv.SetBinding(ItemsControl.ItemsSourceProperty, creationContext.ItemSourceBinding);

if (creationContext.ItemDataTemplate != null)
tv.ItemTemplate = creationContext.ItemDataTemplate;

if (creationContext.SelectedItemBinding != null)
tv.SetBinding(BindableSelectedItemBehavior.SelectedItemProperty, creationContext.SelectedItemBinding);

if (creationContext.OnSelectionChanged != null)
{
tv.SelectedItemChanged += (sender, args) => creationContext.OnSelectionChanged.Invoke(tv.SelectedItem);
}

var behaviors = Interaction.GetBehaviors(tv);
behaviors.Add(new BindableSelectedItemBehavior());
return tv;
}

I do not have this problem.

Any tips?