unoplatform/uno · error · ObjectDisposedException

reader

Error message

reader

What it means

Thrown by XamlObjectReader.Read as an ObjectDisposedException (object name 'reader') when IsDisposed is true. This indicates the reader was disposed (via Close/Dispose) and Read() was called afterward — the underlying node stream is gone and reading is no longer valid.

Source

Thrown at src/SourceGenerators/System.Xaml/System.Xaml/XamlObjectReader.cs:175

			get { return sctx; }
		}

		public override XamlType Type {
			get { return NodeType == XamlNodeType.StartObject ? nodes.Current.Object.Type : null; }
		}

		public override object Value {
			get {
				if (NodeType != XamlNodeType.Value)
					return null;
				return nodes.Current.Value;
			}
		}

		public override bool Read ()
		{
			if (IsDisposed)
				throw new ObjectDisposedException ("reader");
			if (IsEof)
				return false;
			
			if (ns_iterator == null)
				ns_iterator = PrefixLookup.Namespaces.GetEnumerator ();
			if (ns_iterator.MoveNext ())
				return true;
			if (nodes == null)
				nodes = new XamlObjectNodeIterator (root, sctx, value_serializer_context).GetNodes ().GetEnumerator ();
			if (nodes.MoveNext ())
				return true;
			if (!is_eof)
				is_eof = true;
			return false;
		}
	}
}

View on GitHub (pinned to 0418340488)

Solutions

1. Do not call Read() after the reader is disposed — scope all reads within the using block.
2. Track disposal state in your pipeline and skip or recreate the reader for subsequent passes.
3. Create a fresh XamlObjectReader for each read pass rather than reusing a disposed one.

Example fix

// before
using (var reader = new XamlObjectReader(obj, sctx))
{
    while (reader.Read()) Process(reader);
} // disposed here
reader.Read(); // throws ObjectDisposedException

// after
using (var reader = new XamlObjectReader(obj, sctx))
{
    while (reader.Read()) Process(reader);
}
// if you need to read again, create a new reader
using (var reader2 = new XamlObjectReader(obj, sctx))
{
    while (reader2.Read()) Process(reader2);
}

if (reader.IsDisposed) throw new ObjectDisposedException("reader was disposed");
reader.Read();

try { reader.Read(); }
catch (ObjectDisposedException) { /* recreate reader */ }

When it happens

Trigger: Calling Read() after Close() or Dispose() on the same XamlObjectReader instance. Or holding a stale reader reference in a reused pipeline and calling Read in a second pass.

Common situations: XAML processing loops that use using(var reader = ...) blocks but then attempt to read outside the block. Reader pooling/reuse that calls Read after a prior consumer disposed the reader. Error-recovery paths that dispose on failure but continue iterating.

Related errors

• There is already an object of type {0} named as '{1}'. Objec
• schemaContext
• instance type '{0}' must be public and non-nested.
• instance type '{0}' has no default constructor.
• typeArguments array contains one or more null XamlTypeName

AI-assisted analysis of unoplatform/uno@0418340488 (2026-08-13). Data as JSON: /api/errors/b9adc3766255bb1c. Report an issue: GitHub.