dotnet/maui · error · BuildException

XC0041

XC0041

Error message

Binding: Indexer did not contain closing bracket.

What it means

Thrown while parsing a compiled-binding path when a path segment contains '[' but no matching ']'. The parser uses LastIndexOf(']') and throws BindingIndexerNotClosed when it returns -1.

Source

Thrown at src/Controls/src/Build.Tasks/SetPropertiesVisitor.cs:831

			if (string.IsNullOrWhiteSpace(path))
				return true;

			path = path.Trim(' ', '.'); //trim leading or trailing dots
			var parts = path.Split(['.'], StringSplitOptions.RemoveEmptyEntries);
			var properties = new List<(PropertyDefinition property, TypeReference propDeclTypeRef, string indexArg)>();

			var previousPartTypeRef = tSourceRef;
			foreach (var part in parts)
			{
				var p = part;
				string indexArg = null;
				var lbIndex = p.IndexOf('[');
				if (lbIndex != -1)
				{
					var rbIndex = p.LastIndexOf(']');
					if (rbIndex == -1)
						throw new BuildException(BindingIndexerNotClosed, lineInfo, null);

					var argLength = rbIndex - lbIndex - 1;
					if (argLength == 0)
						throw new BuildException(BindingIndexerEmpty, lineInfo, null);

					indexArg = p.Substring(lbIndex + 1, argLength).Trim();
					if (indexArg.Length == 0)
						throw new BuildException(BindingIndexerEmpty, lineInfo, null);

					p = p.Substring(0, lbIndex);
					p = p.Trim();
				}

				if (p.Length > 0)
				{
					var property = previousPartTypeRef.GetProperty(context.Cache, pd => pd.Name == p && pd.GetMethod != null && pd.GetMethod.IsPublic && !pd.GetMethod.IsStatic, out var propDeclTypeRef);
					if (property is null)
					{

View on GitHub (pinned to f377ff1c5e)

Solutions

1. Add the missing closing ']' to complete the indexer.
2. Re-check the whole path string for balanced brackets.
3. If you did not intend an indexer, remove the '['.

Example fix

<!-- before -->
<Label Text="{Binding Items[0}" />

<!-- after -->
<Label Text="{Binding Items[0]}" />

// A binding path segment with '[' must have a closing ']'
static bool IndexersClosed(string path)
    => path.Split('.').All(seg => seg.Count(c => c == '[') == 0
        || seg.Contains(']'));

When it happens

Trigger: A binding path with an unterminated indexer, e.g. `{Binding Items[0}`.

Common situations: Manual editing of a binding path that drops the closing bracket; malformed copy-paste.

Related errors

• XC0042
• XC0043
• XC0044
• XC0102
• XC0020

AI-assisted analysis of dotnet/maui@f377ff1c5e (2026-08-13). Data as JSON: /api/errors/06eab6e386761e89. Report an issue: GitHub.