unoplatform/uno · error · ArgumentNullException

assembly

Error message

assembly

What it means

Thrown by XamlAccessLevel.AssemblyAccessTo(Assembly) when the assembly argument is null. The method extracts assembly.GetName() to build the access level, so a null assembly has no identity to record.

Source

Thrown at src/SourceGenerators/System.Xaml/System.Xaml.Permissions/XamlAccessLevel.cs:38

// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Reflection;
using Uno.Xaml;

namespace Uno.Xaml.Permissions
{
	[SerializableAttribute]
	public class XamlAccessLevel
	{
		public static XamlAccessLevel AssemblyAccessTo (Assembly assembly)
		{
			if (assembly == null)
			{
				throw new ArgumentNullException ("assembly");
			}

			return new XamlAccessLevel (assembly.GetName ());
		}
		public static XamlAccessLevel AssemblyAccessTo (AssemblyName assemblyName)
		{
			if (assemblyName == null)
			{
				throw new ArgumentNullException ("assemblyName");
			}

			return new XamlAccessLevel (assemblyName);
		}

		public static XamlAccessLevel PrivateAccessTo (string assemblyQualifiedTypeName)
		{
			if (assemblyQualifiedTypeName == null)
			{

View on GitHub (pinned to 0418340488)

Solutions

1. Resolve the assembly via type.Assembly or Assembly.Load and verify non-null before calling.
2. Use the AssemblyName overload when you only have identity metadata.
3. Guard at the boundary: if (asm == null) throw your own domain error with context.

Example fix

// before
var asm = Assembly.Load(name); // may be null
var lvl = XamlAccessLevel.AssemblyAccessTo(asm); // throws

// after
var asm = Assembly.Load(name) ?? throw new FileNotFoundException(name);
var lvl = XamlAccessLevel.AssemblyAccessTo(asm);

var asm = type.Assembly ?? throw new InvalidOperationException("no assembly");
var lvl = XamlAccessLevel.AssemblyAccessTo(asm);

static bool IsAssemblyKnown(Assembly a) => a != null;

When it happens

Trigger: Calling AssemblyAccessTo with a null Assembly, e.g. from a type whose Assembly property resolved to null in a reflection-less/AOT environment, or from a partially-loaded module.

Common situations: Dynamic loading where Assembly.Load returned null; sandboxing code that constructs XamlAccessLevel from caller-supplied assemblies without validation; trimmed binaries where type.Assembly is null.

Related errors

• assemblyName
• assemblyQualifiedTypeName
• type
• typeName
• type

AI-assisted analysis of unoplatform/uno@0418340488 (2026-08-13). Data as JSON: /api/errors/83086a37a19790c4. Report an issue: GitHub.