<Create>
  <Test Id="01" Marks="40" Rank="4"/>
  <Test Id="02" Marks="60" Rank="5"/>
  <Test Id="03" Marks="80" Rank="2"/>
</Create>

var xmlString = "<Create><Test Id="01" Marks="40" Rank="4"/><Test Id="02" Marks="60" Rank="5"/><Test Id="03" Marks="80" Rank="2"/></Create>";
var xml = new XmlDocument();
xml.LoadXml(xmlString);
var nodes = xml.SelectNodes("Create/Test");
foreach (XmlNode node in nodes)
{
    Console.WriteLine(string.Format("Id: {0}; Marks: {1}; Rank: {2}", node.Attributes["Id"].Value, node.Attributes["Marks"].Value, node.Attributes["Rank"].Value));
}