how to call global asax route on code behind button click

Question

 i have a button click event from i am doing to redirect in same page with different url  and i have a route for that url in global asax file but its not working on button click

 

its only working on html anchor tag only how can i do that 

my code as follows

 

 global asax route

routes.MapPageRoute("mmmm2", "hotels/{id}/", "~/products.aspx"); 

routes.MapPageRoute("maincat123", "hotels/{id}/{city}/", "~/products.aspx"); 

 

 code behind

string subcat = Page.RouteData.Values["id"].ToString();

HtmlButton btn = sender as HtmlButton;

HtmlInputText txt = btn.Parent.FindControl("Text2") as HtmlInputText;

string city = txt.Value;

string url = "hotels/" + subcat + "/" + city + "/";

Session["temp"] = url;

Response.Redirect(url);