unoplatform/uno · error · XamlGenerationException

The value '{value}' is an invalid value for 'Name' property

Error message

The value '{value}' is an invalid value for 'Name' property

What it means

Thrown by ValidateName when the x:Name value is not a valid C# identifier per Roslyn's SyntaxFacts.IsValidIdentifier. The x:Name becomes a generated backing field name, so it must be a legal identifier (letters, digits, underscores; not starting with a digit; no spaces or special chars).

Source

Thrown at src/SourceGenerators/Uno.UI.SourceGenerators/XamlGenerator/XamlFileGenerator.cs:3736

			void BuildCustomMarkupExtensionPropertyValue(IIndentedStringBuilder writer, XamlMemberDefinition member, string closure, string? resourceOwner)
			{
				var propertyValue = GetCustomMarkupExtensionValue(member, closure, resourceOwner);
				if (!propertyValue.IsNullOrEmpty())
				{
					writer.AppendIndented($"{closure}.{member.Member.Name} = {propertyValue};\r\n");
				}
			}
		}

		private static bool IsNotFrameworkElementButNeedsSourceLocation(XamlObjectDefinition objectDefinition)
			=> objectDefinition.Type.Name is "VisualState" or "AdaptiveTrigger" or "StateTrigger";

		private void ValidateName(string? value, IXamlLocation location)
		{
			// Nullable suppressions are due to https://github.com/dotnet/roslyn/issues/55507
			if (!SyntaxFacts.IsValidIdentifier(value!))
			{
				throw new XamlGenerationException($"The value '{value}' is an invalid value for 'Name' property", location);
			}

			if (!CurrentScope.DeclaredNames.Add(value!))
			{
				throw new XamlGenerationException($"The name '{value}' is already defined in this scope", location);
			}
		}

		private IPropertySymbol? FindLazyContentProperty(XamlMemberDefinition? implicitContentChild, INamedTypeSymbol? elementType)
		{
			if (implicitContentChild != null && elementType != null)
			{
				var contentProperty = FindContentProperty(elementType);

				if (contentProperty != null && IsLazyVisualStateManagerProperty(contentProperty) && !HasDescendantsWithXName(implicitContentChild))
				{
					return contentProperty;
				}

View on GitHub (pinned to 0418340488)

Solutions

1. Rename to a valid C# identifier: start with a letter or underscore, use only alphanumerics and underscores.
2. Avoid C# reserved keywords as names.
3. Use PascalCase or camelCase consistent with the codebase.

Example fix

<!-- before -->
<TextBox x:Name="1st-name"/>

<!-- after -->
<TextBox x:Name="FirstName"/>

# Validate x:Name values are legal C# identifiers
Add-Type -AssemblyName 'Microsoft.CodeAnalysis.CSharp' -ErrorAction SilentlyContinue
# Fallback regex equivalent of a valid C# identifier:
Get-ChildItem -Recurse -Filter *.xaml | ForEach-Object {
  Select-String -Path $_.FullName -Pattern 'x:Name="([^"]+)"' |
    ForEach-Object {
      $n = $_.Matches[0].Groups[1].Value
      if ($n -notmatch '^[A-Za-z_][A-Za-z0-9_]*$') { Write-Warning "$($_.Filename):$($_.LineNumber): invalid x:Name '$n'" }
    }
}

When it happens

Trigger: x:Name starting with a digit (x:Name="1stItem"); containing spaces, dots, or hyphens; using a C# keyword as a name in some cases; empty or whitespace-only names.

Common situations: Auto-generated names from a designer that include invalid characters; naming by a non-programmer convention; copy-paste from HTML id attributes that contain hyphens.

Related errors

• The name '{value}' is already defined in this scope
• Unable to find type '{objectDefinition.Type}'
• The {0} string passed in the colorString argument is not a r
• The {0} string passed in the colorString argument is not a r
• The {0} string passed in the colorString argument is not a r

AI-assisted analysis of unoplatform/uno@0418340488 (2026-08-13). Data as JSON: /api/errors/6796c045e00c8330. Report an issue: GitHub.