how to add default parameters to attribute routes in asp.net mvc

Question

I am trying to change this convention based route:

routes.MapRoute(
    "MovieByReleaseDate",
    "movies/released/{year}/{month}",
    new { controller = "Movies", action = "ByReleasedDate" },
);

to attribute route:

[Route("movies/released/{year}/{month}")]

but I can't see how I can define default parameters like in the first way.

Superfine

Answer 1

You can use multiple [Route] attributes coupled with nullable parameters to achieve your goal.

[HttpGet]
[Route("movies/released/")]
[Route("movies/released/{year}")]
[Route("movies/released/{year}/{month}")]
public string Test(int? year = 2018, int? month = 1)
{
    return "The year is " + year;
}

When you send a request to movies/released without a year, the default value is used for the year. When you send a request to movies/released/2000, the URL parameter overrides the default value.

Somnambulism

worked great - only thing I stumbled across is that it's important that the parameter is marked as nullable, providing a default value is not sufficient. Kinda makes sense if you think about it, I think default values are used at the call site to fill in the blanks. Anyway, something to watch out for – Triturate

Answer 2

You can define route constriants in attributte routing to allow only some value

[Route("movies/released/{year:regex(2015|2016)}/{month:regex(\\d{2}):range(1,12)}")]
    public ActionResult ByReleasedDate(int year, int month)
    {
        return Content($"year {year} and month {month}");
    }

by using {year:regex(2015|2016)} it allows only 2015 or 2016 in year parameter

by using {month:regex(\\d{2}):range(1,12)} it allows only 2 digit for month and range from 1 to 12

Hope this helps

Perspicacity

Works like a charm. I was searching for the same. – Casandracasanova