using System;

using System.Xml;

using System.Xml.Serialization;

​

public class Program

{

    public static void Main()

    {

        var file = new File

        {

            NoNamespaceSchemaLocation = "myXML.xsd"

        };

​

        var xsn = new XmlSerializerNamespaces();

        xsn.Add( "NS0", "http://www.w3.org/2001/XMLSchema-instance" );

​

        var settings = new XmlWriterSettings

        {

            OmitXmlDeclaration = true,

            Indent = true

        };

​

        using var writer = XmlWriter.Create(Console.Out, settings);

​

        new XmlSerializer(typeof(File)).Serialize(writer, file, xsn);

    }

​

    public class File

    {

        [XmlAttribute("noNamespaceSchemaLocation", Namespace = "http://www.w3.org/2001/XMLSchema-instance")]

        public string NoNamespaceSchemaLocation { get; set; }

    }

}