unoplatform/uno · error · XamlGenerationException

Local values are not allowed in resource dictionary with…

Error message

Local values are not allowed in resource dictionary with Source set

What it means

Thrown in the dictionary-building loop when a ResourceDictionary entry has both a Source member and _UnknownContent (i.e. local inline entries) set. WinUI/Uno semantics: a ResourceDictionary that references an external Source file cannot also contain locally-defined entries in the same element. The two are mutually exclusive because the Source fully defines the dictionary contents.

Solutions

1. Split into two elements: one <ResourceDictionary Source="..."/> inside <MergedDictionaries>, and a sibling for local entries at the parent level.
2. Move local resources into the parent ResourceDictionary (not inside the Source-referenced one).
3. If you only need the external dictionary, remove the inline entries.

Example fix

<!-- before -->
<ResourceDictionary Source="ms-appx:///Shared.xaml">
  <SolidColorBrush x:Key="Local" Color="Red"/>
</ResourceDictionary>

<!-- after -->
<ResourceDictionary>
  <ResourceDictionary.MergedDictionaries>
    <ResourceDictionary Source="ms-appx:///Shared.xaml"/>
  </ResourceDictionary.MergedDictionaries>
  <SolidColorBrush x:Key="Local" Color="Red"/>
</ResourceDictionary>

# Flag <ResourceDictionary Source="..."> that also contains child elements
Get-ChildItem -Recurse -Filter *.xaml | ForEach-Object {
  $text = Get-Content $_.FullName -Raw
  [regex]::Matches($text, '<ResourceDictionary\s+[^>]*Source="[^"]+"[^>]*>(.*?)</ResourceDirectory>', 'Singleline') |
    ForEach-Object { if ($_.Groups[1].Value -match '<') { Write-Warning "ResourceDictionary with Source has local content" } }
}

When it happens

Trigger: Writing <ResourceDictionary Source="..."> with child <Style>/<Brush> entries directly inside the same element; combining MergedDictionaries Source references with inline resources at the wrong nesting level.

Common situations: Attempting to add a local override alongside a merged dictionary in the same tag; misunderstanding that Source and local content must be in separate ResourceDictionary elements.

Related errors

• Each dictionary entry must have a 'Key'
• ' ' is not defined on
• There is already a resource with name
• Cannot assign child of type
• Dictionary item ' ' has duplicate key ' ' '" : "")}

AI-assisted analysis of unoplatform/uno@0418340488 (2026-08-13). Data as JSON: /api/errors/3b86197047e78a80. Report an issue: GitHub.

Appendix: source

Thrown at src/SourceGenerators/Uno.UI.SourceGenerators/XamlGenerator/XamlFileGenerator.cs:3046

				return;
			}

			if (isInInitializer)
			{
				writer.AppendLineInvariantIndented("{0} = {{", propertyName);
			}
			else
			{
				writer.AppendLineInvariantIndented("// {0}", propertyName);
			}

			for (int i = 0; i < dictionaries.Objects.Count; i++)
			{
				var dictObject = dictionaries.Objects[i];
				var source = dictObject.Members.FirstOrDefault(m => m.Member.Name == "Source");
				if (source != null && dictObject.Members.Any(m => m.Member.Name == "_UnknownContent"))
				{
					throw new XamlGenerationException("Local values are not allowed in resource dictionary with Source set", dictObject);
				}

				var key = GetDictionaryResourceKey(dictObject);
				if (isDict && key == null)
				{
					throw new XamlGenerationException("Each dictionary entry must have a 'Key'", dictObject);
				}

				var former = _themeDictionaryCurrentlyBuilding; //Will 99% of the time be null.
				if (isDict)
				{
					_themeDictionaryCurrentlyBuilding = key;
				}

				if (!isSetExtensionMethod)
				{
					if (!isInInitializer && !isDict)
					{

View on GitHub (pinned to 0418340488)