You have basically two options:
Either create that file
or use routing to map that address to a desired file
.
Example of the second approach:
protected void Application_Start(object sender, EventArgs e)
{
RegisterRoutes(RouteTable.Routes);
}
private void RegisterRoutes(RouteCollection routes)
{
routes.MapPageRoute("customer-reservation", // name of the route
"Customer/Reservation", // url to look for
"~/Pages/reservation.aspx"); // existing file to map to
}
Note you need at least .NET version 4 or higher if you're using webforms, or use MVC for this to work. If you're using lower .NET version and not using MVC, you'd need an url rewrite module (search for it on Google, returns plenty of results).
Note2: this example belongs inside Global.asax.cs
file.
Note3: another examples can be found here for instance: http://weblogs.asp.net/jalpeshpvadgama/archive/2011/12/11/easy-url-rewriting-in-asp-net-4-0-web-forms.aspx
If you need to find more resources on this topic, just type "asp.net routing" which shall give you enough results to learn from.