dotnet/maui · error · ArgumentOutOfRangeException

indexPath

Error message

indexPath

What it means

ListSource is a single-section IItemsViewSource wrapping a plain list. Its indexer rejects any NSIndexPath whose Section is greater than 0, because ListSource only ever holds one section. This protects against a caller handing it a multi-section path that the backing data cannot satisfy.

Source

Thrown at src/Compatibility/Core/src/iOS/CollectionView/ListSource.cs:38

		{
			foreach (object item in enumerable)
			{
				Add(item);
			}
		}

		public void Dispose()
		{

		}

		public object this[NSIndexPath indexPath]
		{
			get
			{
				if (indexPath.Section > 0)
				{
					throw new ArgumentOutOfRangeException(nameof(indexPath));
				}

				return this[(int)indexPath.Item];
			}
		}

		public int GroupCount => 1;

		public int ItemCount => Count;

		public NSIndexPath GetIndexForItem(object item)
		{
			for (int n = 0; n < Count; n++)
			{
				if (this[n] == item)
				{
					return NSIndexPath.Create(0, n);
				}

View on GitHub (pinned to f377ff1c5e)

Solutions

1. Bind a GroupedItemsSource / use GroupHeaderTemplate when your data or layout is grouped.
2. Verify NSIndexPath.Section == 0 before indexing into a non-grouped ItemsViewSource.
3. Ensure the items layout (Linear/Grid) matches a flat source and only use Grouped layout with group data.

Example fix

// before
var item = source[indexPath];
// after
if (indexPath.Section == 0)
    item = source[indexPath];

// Before indexing:
if (indexPath.Section != 0) return; // ListSource is single-section

static bool IsSingleSectionPath(NSIndexPath p) => p.Section == 0;

When it happens

Trigger: Accessing ListSource[NSIndexPath] with indexPath.Section > 0; typically an upstream caller that assumes multi-section grouping while ItemsView is bound to a flat non-grouped source.

Common situations: Switching a grouped ItemsView layout to a non-grouped one without rebinding; feeding grouped-style index paths from a header/footer supplementary view into a ListSource-backed collection; a custom layout computing paths in section 1+.

Related errors

• group
• indexPath
• view
• renderer
• self

AI-assisted analysis of dotnet/maui@f377ff1c5e (2026-08-13). Data as JSON: /api/errors/2b0a04655af1ad0e. Report an issue: GitHub.