unoplatform/uno · error · XamlGenerationException

Unable to find x:DataType in enclosing DataTemplate for x:Bi

Error message

Unable to find x:DataType in enclosing DataTemplate for x:Bind event

What it means

Thrown in the x:Bind event GetTargetType() logic when the binding is inside a DataTemplate (template.isInside) but the DataTemplate has no x:DataType attribute, and the path is not a static binding (does not start with a namespace prefix like 'local:'). x:Bind inside a DataTemplate is compiled and strongly typed, so it requires x:DataType to know the data type of each item; without it (and not being static) the generator cannot resolve the handler.

Source

Thrown at src/SourceGenerators/Uno.UI.SourceGenerators/XamlGenerator/XamlFileGenerator.cs:3833

				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]));
							}

							throw new XamlGenerationException("Unable to find x:DataType in enclosing DataTemplate for x:Bind event", bind);
						}

						return GetType(dataTypeObject.Value.ToString() ?? "");
					}
					else if (_xClassName?.Symbol is not null)
					{
						return _xClassName.Symbol;
					}
					else if (Generation.AutoGeneratedCodeBehindFiles.TryGetValue(_fileDefinition.UniqueID, out var autoGenBaseType))
					{
						// Use the XAML-derived base type when code-behind is auto-generated
						return autoGenBaseType;
					}
					else
					{
						throw new XamlGenerationException($"Unable to find the type '{_xClassName?.Namespace}.{_xClassName?.ClassName}'", bind);
					}
				}

View on GitHub (pinned to 0418340488)

Solutions

Add x:DataType="local:MyItemViewModel" to the DataTemplate, matching the item type.
If the handler is a static method, qualify the path with a namespace prefix, e.g. Click="{x:Bind local:Handlers.OnClick}" — this bypasses the x:DataType requirement.
Move the handler to the page/code-behind and reference the page-level type instead of a template-scoped binding.

Example fix

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

<!-- after -->
<DataTemplate x:DataType="local:ItemViewModel">
  <Button Click="{x:Bind Delete}"/>
</DataTemplate>

Defensive patterns

Strategy: validation

Validate before calling

# Flag DataTemplate containing {x:Bind} without x:DataType (and not static)
Get-ChildItem -Recurse -Filter *.xaml | ForEach-Object {
  $text = Get-Content $_.FullName -Raw
  [regex]::Matches($text, '<DataTemplate(?![^>]*x:DataType)(.*?)</DataTemplate>', 'Singleline') |
    ForEach-Object {
      if ($_.Groups[1].Value -match '\{x:Bind(?!.*:)') {
        Write-Warning "DataTemplate with x:Bind but no x:DataType (and non-static path)"
      }
    }
}

Prevention

Always set x:DataType on any DataTemplate that uses {x:Bind}.
For static handlers, qualify the path with a namespace prefix (local:Type.Method) to bypass x:DataType.
Remember x:Bind is compiled/strongly-typed and does not inherit DataContext like {Binding}.

When it happens

Trigger: Using {x:Bind SomeMethod} on an event inside a <DataTemplate> that has no x:DataType; a DataTemplate used for an ItemsControl where x:DataType was omitted.

Common situations: Adding x:Bind to a templated item without setting x:DataType; porting from {Binding} (late-bound) to {x:Bind} (compiled) and forgetting the type annotation; assuming DataContext propagates into templates for x:Bind (it does not — x:Bind uses x:DataType).

Related errors

AI-assisted analysis of unoplatform/uno@0418340488 (2026-08-13). Data as JSON: /api/errors/352ca4e8baba69ff. Report an issue: GitHub.