ASP.NET MVC自定义可选参数

Question

How is it possible to define a route in ASP.NET MVC 5 that will ignore static prefixes/suffixes (like "zip-" , "-county" ) for optional parameters if the latter not set?

So that in this case for example:

routes.Add("Search",
    new LowercaseDashedRoute(
    "search/{searchType}/{state}/{county}-county/{city}",
    new RouteValueDictionary(new {
        controller = "Home",
        action = "Search",            
        county = UrlParameter.Optional,
        city = UrlParameter.Optional }),
    new RouteValueDictionary(new { searchType = searchTypeConstraint }),
    new LowercaseDashedRouteHandler()));

when county is missing the URL would be like /search/sale/ca/los-angeles but not /search/sale/ca/-county/los-angeles

Answer 1

You can set a constraint for your county parameter and then create another route without it:

routes.Add("Search",
    new LowercaseDashedRoute(
    "search/{searchType}/{state}/{county}/{city}",
    new RouteValueDictionary(new {
        controller = "Home",
        action = "Search",            
        county = UrlParameter.Optional,
        city = UrlParameter.Optional }),
    new RouteValueDictionary(new { searchType = searchTypeConstraint, county="\\S+-county" }),
    new LowercaseDashedRouteHandler()));

Route 2:

routes.Add("Search",
    new LowercaseDashedRoute(
    "search/{searchType}/{state}/{city}",
    new RouteValueDictionary(new {
        controller = "Home",
        action = "Search",
        city = UrlParameter.Optional }),
    new RouteValueDictionary(new { searchType = searchTypeConstraint }),
    new LowercaseDashedRouteHandler()));

The downside is that "-county" suffix will be added to the parameter, but you can easily handle this in your controller.

Answer 2

It is not possible to have 2 optional parameters on a single route or to combine an optional parameter with a literal part in a segment.

However, to get the desired effect, you can just add another route to handle the case with no county (and remove the county as an optional parameter).

// Matches:
//     /search/sale/ca/los-angeles-county/los-angeles
//     /search/sale/ca/los-angeles-county
routes.Add("SearchCounty",
    new LowercaseDashedRoute(
    "search/{searchType}/{state}/{county}-county/{city}",
    new RouteValueDictionary(new {
        controller = "Home",
        action = "Search",            
        city = UrlParameter.Optional }),
    new RouteValueDictionary(new { searchType = searchTypeConstraint }),
    new LowercaseDashedRouteHandler()));

// Matches:
//     /search/sale/ca/los-angeles
routes.Add("Search",
    new LowercaseDashedRoute(
    "search/{searchType}/{state}/{city}",
    new RouteValueDictionary(new {
        controller = "Home",
        action = "Search" }),
    new RouteValueDictionary(new { searchType = searchTypeConstraint }),
    new LowercaseDashedRouteHandler()));

The routing engine will only match the first route if <something>-county is passed in as the 4th segment, so it will be able to distinguish that case from just passing a city argument.