Saturday, July 15, 2017

Part 38 - Attribute routing in asp.net MVC



In this video you will find the basic concept of an Attribute routing. We have included several example of attribute routing which will help you to understand from the depth.

What is attribute routing ?
- MVC-5 has included a new type of routing, which is known as attribute routing. 
- Attribute routing uses attributes to define routes. 
- Attribute routing gives you more control over the URI' s in your web application.
   
Example -


[Route("Student/{Id}")]

 public int GetStudent(int Id)

 {

       return Id;

 }
  
How to enable attribute routing?
-  Open your RouteConfig.cs which is present under App_Start folder. Then you have to  add MapMvcAttributeRoutes()” method into this . Please refer below screenshot.  

Can we use attribute routing with convention-based routing ?
  -    Yes, we can use both of them.

#Various example of attribute routing 

 1. Optional parameter and default value:
We can set parameter as optional and can set default value for this. To set optional parameter we  used "?" character in [Route]. Example: [Route("Student/Name/{Name?}")].
we can also set the default value for this. Example: [Route("Student/Name/{Name=Ashish}")].
Now below method can be accessed by below url pattern
1. Student/Name/YourName" 
2.  Student/Name"

    //Optional URI parameter
  [Route("Student/Name/{Name?}")]
  public string GetStudent(string Name)
  {
      return "Student with Name =" + Name;
   }

   //Default URI parameter value
   [Route("Student/Name/{Name=Ashish}")]
  public string GetStudent(string Name)
  {
    return "Student with Name =" + Name;
   }

2.  Route Prefixes: 
 -   You can use route prefix at method level as well as at controller level. 
    
a). Route prefix at method level 
 In [Route("Student")] and [Route("Student/{Id}")], the Student text is acting like route prefix 

 
 [Route("Student")]
 public string GetStudent()
 {
    return "All";
 }

 [Route("Student/{Id}")]
 public string GetStudent(int Id)
 {
    return "Student with Id=" + Id;
 }

b). Route prefix at controller level 
Route prefix can be added at controller level. Here we have added  [RoutePrefix("Home")]
on the top of TestController class. Now we can access the Index method with below url pattern. 
 Home/Index
namespace MVCTutorial.Controllers
{
    [RoutePrefix("Home")]   
    public class TestController : Controller
    {

        public ActionResult Index()
        {
            return View();
        }

     
    }
}

3.  Default Route :
We can set the default route at controller level. Example  [Route("{action=Index}")]

namespace MVCTutorial.Controllers
{
    [RoutePrefix("Home")]
    [Route("{action=Index}")]
    public class TestController : Controller
    {

        public ActionResult Index()
        {
            return View();
        }

     
    }
}

5.  Route Constraints
Route constraints let you restrict how the parameters in the route template are matched. The general syntax is {parameter:constraint}. For example, in the below code, there are three "GetStudent()" methods. Now see below cases in which we have shown that which url pattern will be used to call "GetStudent()" method.

 case (a). Test/Student/11  - It will call first GetStudent() method as we passed an integer value as an optional parameter i.e. "11" . Also "11" does not lie between 3 and 10. So, there is no chance for calling third GetStudent() method. So,  this route will work :  [Route("Student/{Id:int}")]
case (b). Test/Student/Ashish - It will call the second method as we have passed a string value as an optional parameter. i.e "Ashish". In this case [Route("Student/{Name}")] will be working.
case (c). Test/Student/4  - It will call the third GetStudent() method as we have passed an integer as an optional parameter and its also lies  between 3 to 10. So, this route will be working in this case : [Route("Student/{Id:int:min(3):max(10)}")] 

namespace MVCTutorial.Controllers
{
      
    public class TestController : Controller
    {
        public ActionResult Index()
        {
            return View();
        }
        [Route("Student/{Id:int}")]    //case (a)
        public string GetStudent(int Id)
        {
            return "Student with Id=" + Id;
        }

        [Route("Student/{Name}")]     // case (b)
        public string GetStudent(string Name)
        {
            return "Student with Name=" + Name;
        }

        [Route("Student/{Id:int:min(3):max(10)}")]  // case (c)
        public string GetStudent(int Id)
        {
            return "Student with Id=" + Id;
        }


        [Route("Student/Message/{Message:maxlength(5)}")]
        public string GetMessage(string Message)
        {
            return "Student message=" + Message;
        }

    }

}

Below constraint chart will help you to apply constraint against different URL











 
 
 
 
 


  

 SN


  

 Constraint


  

 Description 


  

 Example


 



  

ü1


  

alpha


  

Matches uppercase or lowercase
  Latin alphabet characters (a-z, A-Z)


  

{x:alpha}


 



  

ü2


  

bool


  

Matches a Boolean value.


  

{x:bool}


 



  

ü3


  

datetime


  

Matches a DateTime value.


  

{x:datetime}


 



  

ü4


  

decimal


  

Matches a decimal value.


  

{x:decimal}


 



  

ü5


  

double


  

Matches a 64-bit floating-point
  value.


  

{x:double}


 



  

ü6


  

float


  

Matches a 32-bit floating-point
  value.


  

{x:float}


 



  

ü7


  

guid


  

Matches a GUID value.


  

{x:guid}


 



  

ü8


  

int


  

Matches a 32-bit integer value.


  

{x:int}


 



  

ü9


  

length


  

Matches a string with the
  specified length or within a specified range of lengths.


  

{x:length(6)} 

    {x:length(1,20)}


 



  

ü10


  

long


  

Matches a 64-bit integer value.


  

{x:long}


 



  

ü11


  

max


  

Matches an integer with a maximum
  value.


  

{x:max(10)}


 



  

ü12


  

maxlength


  

Matches a string with a maximum
  length.


  

{x:maxlength(10)}


 



  

ü13


  

min


  

Matches an integer with a minimum
  value.


  

{x:min(10)}


 



  

ü14


  

minlength


  

Matches a string with a minimum
  length.


  

{x:minlength(10)}


 



  

ü15


  

range


  

Matches an integer within a range
  of values.


  

{x:range(10,50)}


 



  

ü16


  

regex


  

Matches a regular expression.


  

{x:regex(^\d{3}-\d{3}-\d{4}$)}



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