string myXml = "<test><a i=\"1\"/><a i=\"2\"/></a></a></test>";
System.IO.MemoryStream ms = new System.IO.MemoryStream(System.Text.Encoding.UTF8.GetBytes(myXml));
System.Xml.XmlReader xr = System.Xml.XmlReader.Create(ms);

int firstIValue = 0;

while (xr.Read())
{
  if(xr.NodeType == System.Xml.XmlNodeType.Element)
    if (xr.Name == "a")
    {
      firstIValue = Convert.ToInt32(xr["i"]);
      break;
    }
}