dotnet/maui · error · NotSupportedException

You are using an instance of {nameof(DataTemplateSelector)}

Error message

You are using an instance of {nameof(DataTemplateSelector)} to set the {nameof(BindableLayout)}.{BindableLayout.ItemTemplateProperty.PropertyName} property. Use {nameof(BindableLayout)}.{BindableLayout.ItemTemplateSelectorProperty.PropertyName} property instead to set an item template selector

What it means

Thrown by BindableLayout.SetItemTemplate when the object assigned to the ItemTemplate bindable property is actually a DataTemplateSelector. BindableLayout has a dedicated ItemTemplateSelector property for selectors; using the plain ItemTemplate slot for a selector is unsupported and is rejected explicitly so behavior does not silently degrade.

Source

Thrown at src/Controls/src/Core/BindableLayout/BindableLayout.cs:321

			_itemsSource = itemsSource;

			if (_itemsSource is INotifyCollectionChanged c)
			{
				_collectionChangedProxy.Subscribe(c, _collectionChangedEventHandler);
			}

			if (!_isBatchUpdate)
			{
				CreateChildren();
			}
		}

		void SetItemTemplate(DataTemplate itemTemplate)
		{
			if (itemTemplate is DataTemplateSelector)
			{
				throw new NotSupportedException($"You are using an instance of {nameof(DataTemplateSelector)} to set the {nameof(BindableLayout)}.{BindableLayout.ItemTemplateProperty.PropertyName} property. Use {nameof(BindableLayout)}.{BindableLayout.ItemTemplateSelectorProperty.PropertyName} property instead to set an item template selector");
			}

			_itemTemplate = itemTemplate;

			if (!_isBatchUpdate)
			{
				CreateChildren();
			}
		}

		void SetItemTemplateSelector(DataTemplateSelector itemTemplateSelector)
		{
			_itemTemplateSelector = itemTemplateSelector;

			if (!_isBatchUpdate)
			{
				CreateChildren();
			}

View on GitHub (pinned to f377ff1c5e)

Solutions

1. Assign the selector to BindableLayout.ItemTemplateSelectorProperty instead of ItemTemplateProperty.
2. If you intended a single template, replace the DataTemplateSelector with a plain DataTemplate on ItemTemplate.
3. Double-check XAML: the attached property must read BindableLayout.ItemTemplateSelector, not ItemTemplate.

Example fix

<!-- before -->
<StackLayout BindableLayout.ItemTemplate="{StaticResource MySelector}" />
<!-- after -->
<StackLayout BindableLayout.ItemTemplateSelector="{StaticResource MySelector}" />

// Route selectors to the correct property before assignment.
static void SetTemplate(BindableObject layout, object template)
{
    if (template is DataTemplateSelector sel)
        BindableLayout.SetItemTemplateSelector(layout, sel);
    else if (template is DataTemplate dt)
        BindableLayout.SetItemTemplate(layout, dt);
}

static bool IsSelector(object template) => template is DataTemplateSelector;

When it happens

Trigger: SetItemTemplate receives a DataTemplate whose runtime type 'is DataTemplateSelector' is true, so the NotSupportedException is thrown with the message redirecting you to ItemTemplateSelector.

Common situations: Binding a DataTemplateSelector instance to ItemTemplate in XAML by mistake; sharing a selector resource across a CollectionView (selector-aware) and a BindableLayout (needs the dedicated property); renaming a property from ItemTemplateSelector to ItemTemplate during refactor.

Related errors

• The Map.ItemTemplate property only supports DataTemplate. Se
• ItemTemplate count has exceeded the limit of {ViewTypeCount}
• DataTemplateSelector.OnSelectTemplate must not return anothe
• ItemTemplate count has exceeded the limit of {ViewTypeCount}
• InsertPageBefore is not supported globally on GTK, please us

AI-assisted analysis of dotnet/maui@f377ff1c5e (2026-08-13). Data as JSON: /api/errors/e53e00e3b5413b11. Report an issue: GitHub.