Attribute Routing With ASP.net MVC 5 - Route Constraints

Introduction

• This Article shows how to use the Latest ASP.net MVC 5 Attribute Routing's Route Constraints with your Application.
• You can read the first part of this Article here 'Attribute Routing With ASP.net MVC 5'

How to set Route Constraints ?

• It allows you to restrict the parameters in the route template are matched
• The syntax is {parameter:constraint}

     PetController.cs

     public class PetController : Controller
      {

        // eg: /Pet/8

        [Route("Pet/{petId:int}")]

        public ActionResult GetSpecificPetById(int petId)

        {

            return View();

         }

     }

Key points of the above code

• In the above example, /Pet/8 will Route to the “GetSpecificPetById” Action.
• Here the route will only be selected, if the "petId" portion of the URI is an integer.

Above Route on Browser is as below

The following diagram shows the constraints that are supported

How to apply multiple constraints to a parameter ?

• You can apply multiple constraints to a parameter, separated by a colon.
• Well,It's like this  [Route("Pet/{petId:int:min(1)}")]

 PetController.cs

     public class PetController : Controller
      {

        // eg: /Pet/8

        [Route("Pet/{petId:int:min(1)}")]

        public ActionResult GetSpecificPetById(int petId)

        {

            return View();

         }

     }

Key points of the above code

• In the above example,You can't use  /Pet/10000000000 ,because it is larger than int.MaxValue
• And also you can't use /Pet/0 ,because of the min(1) constraint.

How to Specifying that a parameter is Optional ? 

• You can do it by Specifying that a parameter is Optional (via the '?' modifier).
• This should be done after inline constraints.
• Well,it's like this  [Route("Pet/{message:maxlength(4)?}")]

              
        PetController.cs

        // eg: /Pet/good

        [Route("Pet/{message:maxlength(4)?}")]

        public ActionResult PetMessage(string message)

        {

            return View();

        }

Key points of the above code

• In the above example, /Pet/good and /Pet will Route to the “PetMessage” Action.
• The route /Pet also works hence of the Optional modifier.
• But /Pet/good-bye will not route above Action , because of the maxlength(4) constraint.

Above Routes on Browser are as below

Used Dev. Environment in Article's Source Code

• Visual Studio 2013 Express
• .Net Framework 4.5.1
• ASP.net MVC 5
• C#

Conclusion

• You saw that how easily can configure the URI Route Constraints with Attribute Routing
• In my next article I will show how to apply Attribute Routing with Custom Route Constraints and Areas
• So enjoy this Awesome New Feature of ASP.net MVC 5

I hope this helps to You.Comments and feedback greatly appreciated.

If you feel it was a good article,Give me a +1.Thank You.

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