using System;

using System.IO;

using System.Xml;

public class Program

{

    public static void Main()

    {

        var ctx = new XmlParserContext(null, new XmlNamespaceManager(new NameTable()), null, XmlSpace.None);

        var set = new XmlReaderSettings() { IgnoreComments = true, IgnoreProcessingInstructions = true, IgnoreWhitespace = true };

​

        using (var xml = new StringReader(

            "<?xml version=\"1.0\" encoding=\"utf-8\"?>" +

            "<rdf:RDF " +

            "  xmlns:rdf=\"http://www.w3.org/1999/02/22-rdf-syntax-ns#\"> " +

            "  <rdf:Description rdf:about=\"x\" /> " +

            "</rdf:RDF>"))

        using (var rdr = XmlReader.Create(xml, set, ctx))

        {

            rdr.MoveToContent();

​

            Console.WriteLine(rdr.Name);

            Console.WriteLine(rdr.LookupNamespace("rdf"));

            Console.WriteLine(ctx.NamespaceManager.HasNamespace("rdf"));    // True

            rdr.Read();

            Console.WriteLine(rdr.Name);

            Console.WriteLine(rdr.LookupNamespace("rdf"));

            Console.WriteLine(ctx.NamespaceManager.HasNamespace("rdf"));    // False

            rdr.Read();

            Console.WriteLine(rdr.Name);

            Console.WriteLine(rdr.LookupNamespace("rdf"));

            Console.WriteLine(ctx.NamespaceManager.HasNamespace("rdf"));    // True

        }

    }

}