using System;
using System.IO;
using System.Xml;
using System.Xml.Schema;

const string xml = "<test a=\"sdf\"/>";
//1
try
{
	using var xmlReader = XmlReader.Create(new StringReader(xml));
	xmlReader.MoveToContent();
	xmlReader.MoveToAttribute(0);

	if (xmlReader.ReadContentAs(typeof(XmlAtomicValue), null) is XmlAtomicValue xmlAtomic)
	{
//{"Content cannot be converted to the type System.Xml.Schema.XmlAtomicValue. Line 1, position 7."}
		Console.WriteLine(xmlAtomic.Value);
	}
}
catch (Exception ex)
{
	Console.WriteLine(ex);
}
//2
try
{
	using var xmlReader = XmlReader.Create(new StringReader(xml), new XmlReaderSettings {Async = true});
	await xmlReader.MoveToContentAsync();
	xmlReader.MoveToAttribute(0);

	if (await xmlReader.ReadContentAsAsync(typeof(XmlAtomicValue), null) is XmlAtomicValue xmlAtomic)
	{
//ok
		Console.WriteLine(xmlAtomic.Value);
	}
}
catch (Exception ex)
{
	Console.WriteLine(ex);
}