When I tried to get the values of session objects in web service then the session variable returns null value.
I have tried different way to solve this glitch but after searching on google and msdn finally i found the solution and i modified the code as below and it worked for me.
[WebMethod(EnableSession = true)]
public void getcustomers()
Session["cust"] = new test();
cust = Session["cust"] as test;
Once you have done this, you able to access session objects similar to aspx pages.