using System;

using System.Xml;

using System.Text;

​

public class Program

{

    public static void Main()

    {

        var xmldoc = @"<Block ID=""Ar0010100"" BOX=""185 211 825 278"" ELEMENT_TYPE=""h1"" SEQ_NO=""0"" />";

        var filedoc = new XmlDocument();

        filedoc.LoadXml(xmldoc);

        XmlNodeList elemList = filedoc.GetElementsByTagName("Block");

        for (int i = 0; i < elemList.Count; i++)

        {

            string attrVal = elemList[i].Attributes["ID"].Value;

            Console.WriteLine(attrVal);

        }

    }

}