[ASP.NET Core] Routing

 ASP.NET Core   Routing    Attribute Routing

▌Introduction

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We will learn how to set routing in ASP.NET Core MVC, including of

1.  Template and defaults

2.  Catch-all

3.  Constraint

4.  Custom constraint

5.  Attribute routing

▌Environment

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▋.NET Core 2.0.0 preview 1

▌Template and Defaults

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After we create a ASP.NET Core MVC template, we will find the default routing in Startup.cs : Configure method as following

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

Which equals (Skip app.UseMvc)

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

▋Result

/Products/Details/13  => OK

/Products/Details/toy => OK

/Products/Index/       => OK

▌Catch-all

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▋Routing sample

routes.MapRoute(             name: "help",             template: "HelpMe/{*question}",             defaults: new { controller = "Home", action = "Help" });

And here is the MVC Controller.

public IActionResult Help(string question) {             ViewBag.Question = question;             return View(); }

▋Result

▌Constraint

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▋Routing sample

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

▋Result

/Products/Details/13  => OK

/Products/Details/toy => 404

/Products/Index/       => 404

How about

template: "{controller=Home}/{action=Index}/{id:int?}"); ?
You can have a try.

Here are some standard Constraints for routing. See more details on docs.microsoft.com.

Type	Constraint	Example
String	minlength	{id:minlength(5)}
	maxlength	{id:maxlength(10)}
	length	{id:length(7)} {id:length(5, 10)}
Integer	min	{age:min(18)}
	max	{age:max(65)}
	range	{age:range(18, 65)}
Regular expression	regex(expression)

▋Routing sample

routes.MapRoute(         name: "default",         template: "{controller=Home}/{action=Index}/{id:min(10)}");

▋Result

/Products/Details/13      => OK

/Products/Details/5       =>  404 

/Products/Details         =>  404

/Products/Details/15.5    =>  404

If we need two or more constraints on a routing, write the route like this,

template: "{controller=Home}/{action=Index}/{id:min(10):max(20)}");

▋Custom constraint

Step 1. Implement IRouteConstraint

Step 2. Register custom constraint

▋Create custom routing class

public class CustomRouteConstraint : IRouteConstraint {     private readonly string[] constraints = new string[]{"peter","jack","mary"};     public bool Match(HttpContext httpContext, IRouter route, string routeKey, RouteValueDictionary values, RouteDirection routeDirection)     {         object value;         if (values.TryGetValue(routeKey, out value) && value != null)         {             return constraints.Contains(value.ToString().ToLower());         }         return false;     } }

▋Register custom routing in Startup.cs

public void ConfigureServices(IServiceCollection services) {             //Register custom routing             services.AddRouting(options =>                 options.ConstraintMap.Add("Custom", typeof(CustomRouteConstraint))); }

▋Use custom constraint

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

▋Result

/Home/Index/Peter     => OK

/Home/Index/MARY      => OK

/Home/Index/Steven    => 404

/Home/Index            => 404

▌Attribute Routing

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▋Routing sample

[Route("[controller]/[action]/{name:Custom}")] public IActionResult Index(string name) {             _logger.Debug($"Name={name}");             return View(); }

▌Reference

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▋Routing in ASP.NET Core