Call Method (Function) after some seconds using C# in ASP.Net

How to call function after 3 second

i am calling this funciton on page load, but i want to add time delay so it calls after 3 second after page ls completed loaded

pls advice

thanks

i have this function 

        public void getparentcat()
        {
            var q=(from c in db.category_master
                       where c.IsPublished==true && c.IsShowHomePage==true && c.parent_category_id==0
                   select c).ToList() ;


            ListView1.DataSource = q.ToList();
            ListView1.DataBind();
        }