unoplatform/uno · error · ArgumentNullException

type

Error message

type

What it means

Thrown by XamlAccessLevel.PrivateAccessTo(Type) when the type argument is null. The method reads type.AssemblyQualifiedName to forward to the string overload, so a null type is rejected first.

Source

Thrown at src/SourceGenerators/System.Xaml/System.Xaml.Permissions/XamlAccessLevel.cs:67

			return new XamlAccessLevel (assemblyName);
		}

		public static XamlAccessLevel PrivateAccessTo (string assemblyQualifiedTypeName)
		{
			if (assemblyQualifiedTypeName == null)
			{
				throw new ArgumentNullException ("assemblyQualifiedTypeName");
			}

			return new XamlAccessLevel (assemblyQualifiedTypeName);
		}

		public static XamlAccessLevel PrivateAccessTo (Type type)
		{
			if (type == null)
			{
				throw new ArgumentNullException ("type");
			}

			return new XamlAccessLevel (type.AssemblyQualifiedName);
		}

		internal XamlAccessLevel (AssemblyName assemblyAccessToAssemblyName)
		{
			AssemblyAccessToAssemblyName = assemblyAccessToAssemblyName;
		}

		internal XamlAccessLevel (string privateAccessToTypeName)
		{
			PrivateAccessToTypeName = privateAccessToTypeName;
		}

		public AssemblyName AssemblyAccessToAssemblyName { get; private set; }
		public string PrivateAccessToTypeName { get; private set; }
	}

View on GitHub (pinned to 0418340488)

Solutions

1. Resolve the Type with a non-failing lookup and null-check before calling.
2. Catch TypeLoadException at the resolution step and surface a clearer domain error.
3. Use the string overload only when you have a verified assembly-qualified name.

Example fix

// before
var t = Type.GetType("Missing.Foo, Missing"); // null
var lvl = XamlAccessLevel.PrivateAccessTo(t); // throws

// after
var t = Type.GetType("Missing.Foo, Missing") ?? throw new TypeLoadException();
var lvl = XamlAccessLevel.PrivateAccessTo(t);

var t = Type.GetType(qualifiedName) ?? throw new TypeLoadException(qualifiedName);
var lvl = XamlAccessLevel.PrivateAccessTo(t);

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

When it happens

Trigger: Calling PrivateAccessTo((Type)null), typically from a reflection path that returned null (e.g. Type.GetType on an unresolvable name).

Common situations: Loading XAML access settings from config that names a type not present at runtime; cross-platform code where a type is conditionally compiled out; AOT/trimming that removed the type.

Related errors

• assembly
• assemblyName
• assemblyQualifiedTypeName
• typeName
• type

AI-assisted analysis of unoplatform/uno@0418340488 (2026-08-13). Data as JSON: /api/errors/dff80a22d369f1f8. Report an issue: GitHub.