var xelement = XElement.Load("http://localhost:1694/newtest.xml");
var query = (from m in xelement.Descendants("BankName")
where m.Attribute("BankName").Value == "jinesh" && m.Attribute("TemplateModel").Value == "sam"
from b in m.Element("XandYPosition").Elements("column")
where b.Attribute("Name").Value == "ChqDate"
select b).FirstOrDefault();
if (query != null)
{
query.Attribute("X").SetValue("1000");
query.Attribute("Y").SetValue("2000");
}