using System;

​

public class Program

{

    public static void Main()

    {

        System.Xml.XmlDocument doc = new System.Xml.XmlDocument();

        var root = doc.CreateElement("root");

        doc.AppendChild(root);

        root.SetAttribute("xmlns:mc", "http://schemas.openxmlformats.org/markup-compatibility/2006");

        var inner = doc.CreateElement("inner");

        root.AppendChild(inner);

        inner.SetAttribute("Ignorable", "http://schemas.openxmlformats.org/markup-compatibility/2006", "p14 a14 p15 p16 a16 thm15 adec ahyp v");

        var list = inner.Attributes;

        foreach (System.Xml.XmlAttribute attr in list)

            Console.WriteLine(attr.Name);

    }

}