Handling “extra” params in ASP.Net MVC5 routing

Question

I have this path that I need to handle:

http://mpdev.website.com/Account/ExternalLogOn?LogonTicket=c3792319c8711a0dd465bbd6f6b31ea913b42db7&PID=1137565&ReturnUrl=/Home/CompReq?EC=151120TXAM

The ExternalLogon action in the Account Controller automatically logs the user in based on a check between the LogonTicket and the PID. Then it is supposed to redirect to the ReturnUrl.

How would I fix the /Home/CompReq route to handle the EC parameter and how to modify the Action in the Home Controller?

I have only one route in my RouteConfig:

public static void RegisterRoutes(RouteCollection routes)
{
    routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

    routes.MapRoute(
        name: "Default",
        url: "{controller}/{action}/{id}",
        defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
    );
}

This link works perfectly but I know I don't have any params on it.

http://mpdev.website.com/Account/ExternalLogOn?LogonTicket=c3792319c8711a0dd465bbd6f6b31ea913b42db7&PID=1137565&ReturnUrl=/Home/MyInfo

Home Controller Action definition is like this:

public ActionResult CompReq(string eventcode)

ExternalLogon definition:

ExternalLogOn(string LogonTicket, int? PID, string User, string EC, String State, string ReturnUrl)

Answer 1

ReturnUrl value should be url encoded:

http://mpdev.website.com/Account/ExternalLogOn?LogonTicket=c3792319c8711a0dd465bbd6f6b31ea913b42db7&PID=1137565&ReturnUrl=%2FHome%2FCompReq%3FEC%3D151120TXAM

CompReq action should have same function parameter name as query parameter name:

public ActionResult CompReq(string EC)

ExternalLogon action should have proper parameters:

ExternalLogOn(string LogonTicket, int? PID, string ReturnUrl)

In ExternalLogOn you do a redirect to ReturnUrl param:

return Redirect(ReturnUrl);