unoplatform/uno · error · ArgumentNullException

type

Error message

type

What it means

Thrown by ValueSerializer.GetSerializerFor(Type, IValueSerializerContext) when the type argument is null. The method needs the type to consult the context and to check whether it is a known MarkupExtension, so it rejects null up front.

Source

Thrown at src/SourceGenerators/System.Xaml/System.Windows.Markup/ValueSerializer.cs:74

			if (context != null)
			{
				return context.GetValueSerializerFor (descriptor);
			}

			var tc = descriptor.Converter;
			if (tc != null && tc.GetType () != typeof (TypeConverter))
			{
				return new TypeConverterValueSerializer (tc);
			}

			return null;
		}

		public static ValueSerializer GetSerializerFor (Type type, IValueSerializerContext context)
		{
			if (type == null)
			{
				throw new ArgumentNullException ("type");
			}

			if (context != null)
			{
				return context.GetValueSerializerFor (type);
			}

			// Standard MarkupExtensions are serialized without ValueSerializer.
			if (typeof (MarkupExtension).IsAssignableFrom (type) && XamlLanguage.AllTypes.Any (x => x.UnderlyingType == type))
			{
				return null;
			}

			// DateTime is documented as special.
			if (type == typeof (DateTime))
			{
				return new DateTimeValueSerializer ();
			}

View on GitHub (pinned to 0418340488)

Solutions

1. Resolve the Type (via GetType/UnderlyingType) and null-check before calling.
2. Skip members whose UnderlyingType is null rather than passing null through.
3. Use GetSerializerFor(PropertyDescriptor,...) when only a descriptor is available.

Example fix

// before
Type t = member.UnderlyingType; // may be null
var ser = ValueSerializer.GetSerializerFor(t, ctx); // throws

// after
Type t = member.UnderlyingType;
var ser = t != null ? ValueSerializer.GetSerializerFor(t, ctx) : null;

Type t = member.UnderlyingType;
if (t == null) return null; // nothing to serialize
var ser = ValueSerializer.GetSerializerFor(t, ctx);

static bool HasSerializableType(Type t) => t != null;

When it happens

Trigger: Calling GetSerializerFor((Type)null, context), commonly when the type was derived from a null-valued property or an unresolved reflection result.

Common situations: Serialization code that walks a member list where UnderlyingType can be null (e.g. attached properties, directives); typeof lookups that returned null on a trimmed/AOT scenario.

Related errors

• descriptor
• typeName
• type
• serviceProvider
• assembly

AI-assisted analysis of unoplatform/uno@0418340488 (2026-08-13). Data as JSON: /api/errors/7d355a0f29f9ec41. Report an issue: GitHub.