What causes "x:Bind event path cannot be empty" in unoplatform/uno?

Provide a handler method path in the x:Bind, e.g. Click="{x:Bind OnClick}".

unoplatform/uno · error · XamlGenerationException

x:Bind event path cannot be empty

Error message

x:Bind event path cannot be empty

What it means

Thrown in the x:Bind event-handling code path when XBindExpressionParser.RestoreSinglePath returns null for the bind's first member value — i.e. the x:Bind expression on an event has no path/method name at all (e.g. Click="{x:Bind}" or an empty path). An event binding must name a handler method to invoke.

Source

Thrown at src/SourceGenerators/Uno.UI.SourceGenerators/XamlGenerator/XamlFileGenerator.cs:3812

				.DelegateInvokeMethod
				?.Parameters
				.Select(p => p.Name)
				.ToArray();

			if (member.Objects.FirstOrDefault() is XamlObjectDefinition bind && bind.Type.Name == "Bind")
			{
				if (componentDefinition is null)
				{
					// 500 - Internal XAML Code gen error
					throw new XamlGenerationException("The component definition cannot be null", bind);
				}

				CurrentScope.XBindExpressions.Add(bind);

				var path = XBindExpressionParser.RestoreSinglePath(bind.Members.First().Value?.ToString());
				if (path is null)
				{
					throw new XamlGenerationException("x:Bind event path cannot be empty", bind);
				}

				INamedTypeSymbol GetTargetType()
				{
					if (template.isInside)
					{
						var dataTypeObject = FindMember(template.xamlObject!, "DataType", XamlConstants.XamlXmlNamespace);
						if (dataTypeObject?.Value == null)
						{
							// Check if this is a static method binding (path starts with a namespace prefix like "local:Type")
							// Static bindings don't require x:DataType because they don't access the DataContext
							var pathParts = path.Split('.');
							var isStaticBinding = pathParts.FirstOrDefault()?.Contains(":") ?? false;

							if (isStaticBinding)
							{
								// Extract the type from the static path (e.g., "local:StaticHandler" from "local:StaticHandler.OnClick")
								return GetType(RewriteNamespaces(pathParts[0]));

View on GitHub (pinned to 0418340488)

Solutions

Provide a handler method path in the x:Bind, e.g. Click="{x:Bind OnClick}".
Ensure the named method exists on the bind target (the page or the x:DataType).
If binding a property (not an event), use the normal {x:Bind PropertyPath} form on a non-event attribute.

Example fix

<!-- before -->
<Button Click="{x:Bind}"/>

<!-- after -->
<Button Click="{x:Bind OnClick}"/>

Defensive patterns

Strategy: validation

Validate before calling

# Flag empty x:Bind on event attributes
Get-ChildItem -Recurse -Filter *.xaml | ForEach-Object {
  Select-String -Path $_.FullName -Pattern '\{x:Bind\s*\}' |
    ForEach-Object { Write-Warning "$($_.Filename):$($_.LineNumber): empty x:Bind path" }
}

Prevention

Event x:Bind must name a handler method, e.g. {x:Bind OnClick}.
Distinguish event binding (method) from property binding (path).

When it happens

Trigger: Writing an event attribute as {x:Bind} with no member path; a malformed x:Bind whose path parses to null; an empty x:Bind expression string.

Common situations: Authoring a binding in the editor and not finishing the path; refactor that empties a binding expression; misunderstanding that event x:Bind requires a method name, not a property path.

Related errors

AI-assisted analysis of unoplatform/uno@0418340488 (2026-08-13). Data as JSON: /api/errors/94145d470b3cbfe8. Report an issue: GitHub.