Page 1:
myClass state = new myClass() { FirstName = "First" };
Session["Adhesion"] = state;
Page 2:
myClass obj = ((myClass)Session["Adhesion"]);
obj.LastName = "Last";
Session["Adhesion"] = obj;
Page 3:
myClass obj = ((myClass)Session["Adhesion"]);
obj.Age = 25;
Session["Adhesion"] = obj;