asp.net-coreRouting

Basic Routing

app.UseMvc(routes => 
{ 
    routes.MapRoute( 
    name: "default", 
    template: "{controller=Home}/{action=Index}/{id?}"); 
}); 

This will match requests for /Home/Index, /Home/Index/123 and /

Routing constraints

It is possible to create custom routing constraint which can be used inside routes to constraint a parameter to specific values or pattern.

This constrain will match a typical culture/locale pattern, like en-US, de-DE, zh-CHT, zh-Hant.

public class LocaleConstraint : IRouteConstraint
{
    private static readonly Regex LocalePattern = new Regex(@"^[a-z]{2}(-[a-z]{2,4})?$",
                                    RegexOptions.Compiled | RegexOptions.IgnoreCase);

    public bool Match(HttpContext httpContext, IRouter route, string routeKey,
                        RouteValueDictionary values, RouteDirection routeDirection)
    {
        if (!values.ContainsKey(routeKey))
            return false;

        string locale = values[routeKey] as string;
        if (string.IsNullOrWhiteSpace(locale))
            return false;

        return LocalePattern.IsMatch(locale);
    }
}

Afterwards, the Constraint needs to be registered before it can be used in routes.

services.Configure<RouteOptions>(options =>
{
    options.ConstraintMap.Add("locale", typeof(LocaleConstraint));
});

Now it can be used within routes.

Using it on Controllers

[Route("api/{culture:locale}/[controller]")]
public class ProductController : Controller { }

Using it on Actions

[HttpGet("api/{culture:locale}/[controller]/{productId}"]
public Task<IActionResult> GetProductAsync(string productId) { }

Using it in Default Routes

app.UseMvc(routes => 
{ 
    routes.MapRoute( 
        name: "default", 
        template: "api/{culture:locale}/{controller}/{id?}"); 
    routes.MapRoute( 
        name: "default", 
        template: "api/{controller}/{id?}"); 
});