dotnet/maui · error · NotSupportedException

The Map.ItemTemplate property only supports DataTemplate…

Error message

The Map.ItemTemplate property only supports DataTemplate. Set the Map.ItemTemplateSelector property instead to use a DataTemplateSelector

What it means

The Map control separates its templating into two properties: ItemTemplate (for a single DataTemplate) and ItemTemplateSelector (for a DataTemplateSelector that chooses templates per-item). Assigning a DataTemplateSelector instance to ItemTemplate throws NotSupportedException because the internal CreatePinItems logic only handles uniform DataTemplate rendering, and silently ignoring the selector would produce wrong results.

Solutions

1. Use Map.ItemTemplateSelector instead of Map.ItemTemplate when you need per-item template selection.
2. If you only need one template, assign it to Map.ItemTemplate directly.
3. Verify the type of the object you are assigning: if it is a DataTemplateSelector subclass, use ItemTemplateSelector.

Example fix

// before
map.ItemTemplate = new PinTemplateSelector(); // DataTemplateSelector subclass

// after
map.ItemTemplateSelector = new PinTemplateSelector();

// Check before assigning
if (template is DataTemplateSelector)
    map.ItemTemplateSelector = (DataTemplateSelector)template;
else
    map.ItemTemplate = template;

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

When it happens

Trigger: Setting `map.ItemTemplate = new MyDataTemplateSelector()` where MyDataTemplateSelector derives from DataTemplateSelector. This can happen when a developer is unaware of the two-property split and assigns a selector to the simpler property.

Common situations: Copy-pasting a DataTemplateSelector from a ListView/CollectionView sample into Map.ItemTemplate instead of Map.ItemTemplateSelector. Refactoring code that previously used a single template to use a selector without moving the assignment. Misreading the API surface.

Related errors

• ItemTemplate count has exceeded the limit of
• You are using an instance of
• Cannot call CreateContent directly on a DataTemplateSelector
• DataTemplateSelector.OnSelectTemplate must not return…
• internal ElementTemplate

AI-assisted analysis of dotnet/maui@f377ff1c5e (2026-08-13). Data as JSON: /api/errors/bbde335440f6938f. Report an issue: GitHub.

Appendix: source

Thrown at src/Controls/Maps/src/Map.cs:287

			if (oldItemsSource is INotifyCollectionChanged ncc)
			{
				ncc.CollectionChanged -= OnItemsSourceCollectionChanged;
			}

			if (newItemsSource is INotifyCollectionChanged ncc1)
			{
				ncc1.CollectionChanged += OnItemsSourceCollectionChanged;
			}

			_pins.Clear();
			CreatePinItems();
		}

		void OnItemTemplatePropertyChanged(DataTemplate oldItemTemplate, DataTemplate newItemTemplate)
		{
			if (newItemTemplate is DataTemplateSelector)
			{
				throw new NotSupportedException(
					$"The {nameof(Map)}.{ItemTemplateProperty.PropertyName} property only supports {nameof(DataTemplate)}." +
					$" Set the {nameof(Map)}.{ItemTemplateSelectorProperty.PropertyName} property instead to use a {nameof(DataTemplateSelector)}");
			}

			_pins.Clear();
			CreatePinItems();
		}

		void OnItemTemplateSelectorPropertyChanged()
		{
			_pins.Clear();
			CreatePinItems();
		}

		void OnItemsSourceCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
		{
			e.Apply(
				insert: (item, _, __) => CreatePin(item),

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