unoplatform/uno · error · XamlGenerationException

Unable to find type '{objectDefinition.Type}'

Error message

Unable to find type '{objectDefinition.Type}'

What it means

Thrown when processing an x:Name member (line 3490 branch): the generator needs the object's type symbol to register a backing field (RegisterBackingField), but FindType(objectDefinition.Type) returns null. This differs from 309 — here the object passed earlier checks but specifically the Name-backing-field registration requires a resolvable type and it is missing.

Source

Thrown at src/SourceGenerators/Uno.UI.SourceGenerators/XamlGenerator/XamlFileGenerator.cs:3497

							{
								ValidateName(value, member);

								writer.AppendLineIndented($@"__nameScope.RegisterName(""{value}"", {writer.AppliedParameterName});");
							}

							if (
								member.Member.Name == "Name"
								&& !IsAttachedProperty(member)
								&& !isMemberInsideResourceDictionary.isInside
							)
							{
								nameMember = member;

								var type = FindType(objectDefinition.Type)?.GetFullyQualifiedTypeIncludingGlobal();

								if (type == null)
								{
									throw new XamlGenerationException($"Unable to find type '{objectDefinition.Type}'", objectDefinition);
								}

								writer.AppendLineInvariantIndented("__that.{0} = {1};", value, writer.AppliedParameterName);
								// value is validated as non-null in ValidateName call above.
								RegisterBackingField(type, value!, FindObjectFieldAccessibility(objectDefinition));
							}
							else if (member.Member.Name == "Name"
								&& member.Member.PreferredXamlNamespace == XamlConstants.XamlXmlNamespace)
							{
								writer.AppendLineInvariantIndented("// x:Name {0}", member.Value, member.Value);
							}
							else if (member.Member.Name == "Key")
							{
								writer.AppendLineInvariantIndented("// Key {0}", member.Value, member.Value);
							}
							else if (member.Member.Name == "DeferLoadStrategy"
								&& member.Member.PreferredXamlNamespace == XamlConstants.XamlXmlNamespace)
							{

View on GitHub (pinned to 0418340488)

Solutions

1. Resolve the type exactly as for error 309: fix the xmlns prefix, add the project/PackageReference, correct any typo.
2. Confirm the element's type compiles on the current UnoTargetFrameworkOverride (TFM).
3. Remove the x:Name if the element type is intentionally unresolved/optional, or gate the XAML by platform.

Example fix

<!-- before -->
<Page xmlns:w="using:Missing.Lib">
  <w:BadControl x:Name="MyControl"/>
</Page>

<!-- after -->
<Page xmlns:w="using:Real.Lib">
  <w:RealControl x:Name="MyControl"/>
</Page>

# Same as 309: ensure every type used in XAML resolves. Additionally, list x:Name'd elements
# and confirm their types compile:
Get-ChildItem -Recurse -Filter *.xaml | ForEach-Object {
  Select-String -Path $_.FullName -Pattern '<(\w+:)?([\w.]+)\b[^>]*x:Name' |
    ForEach-Object { Write-Host "Named element of type: $($_.Matches[0].Groups[2].Value)" }
# Then build and resolve any CS0246 alongside the XAML error.

When it happens

Trigger: An element with x:Name whose type cannot be resolved by the compilation (undeclared xmlns, missing assembly reference, typo); an element inside a ResourceDictionary that also has x:Name but whose type is unknown.

Common situations: Naming a control whose type comes from an unreferenced assembly; renaming/moving a control type without updating xmlns; platform-conditional types referenced on a TFM where they don't exist.

Related errors

• The type '{objectDefinition.Type}' could not be found
• The value '{value}' is an invalid value for 'Name' property
• The name '{value}' is already defined in this scope
• Unable to find the type '{_xClassName?.Namespace}.{_xClassNa
• Type '{0}' is not resolved as a valid type by the type resol

AI-assisted analysis of unoplatform/uno@0418340488 (2026-08-13). Data as JSON: /api/errors/9a7d3fa19ca9d5fe. Report an issue: GitHub.