Create a Custom Action Filter for MVC 3

Create a Custom Action Filter for MVC 3

What is an Action Filter ?

• It's an Attribute
• Could be applied on a particular Action
• Could be applied on a Controller
• It modifies the way Action Executes
• An Action Filter is a class that inherits from the FilterAttribute base class
• Filters are used to inject an extra logic into the MVC request processing
• Filters to define logic which is used to apply add-on functionality to the application
• e.g. defining Authorization, Caching, Logging, Exception etc.

What are the Types of Action Filters ?

What is 1-2-3-4 ?

• If an Action Method has more than One Action Filter applied,
• Then the order in which they are executed
• i.e. Action Filters are Executed in the order 1-2-3-4 
• Firstly Executes Authorization Filters
• Lastly Executes Exception Filters

What is an Authorization Filter ?

• These filters are always run first before any other filters
• They implement IAuthorizationFilter interface
• Provides AuthorizeAttribute as the default class implementation

How to Do That ?

MyAuthorizationFilterAttribute.cs

using System.Web.Mvc;

namespace CustomActionFilter.CustomActionFilters

 {

 public class MyAuthorizationFilterAttribute:FilterAttribute,IAuthorizationFilter

  {

      public void OnAuthorization(AuthorizationContextfilterContext)

      {

          if(filterContext.HttpContext.Request.IsAuthenticated)

          {

              //The action filter logic

          }

      }

  }

}

HomeController.cs

using System.Web.Mvc;

using CustomActionFilter.CustomActionFilters;

namespace CustomActionFilter.Controllers

{

    public class HomeController: Controller

    {

        [MyAuthorizationFilter]

        public ActionResult Index()

        {

            ViewBag.Message = "Welcome to ASP.NET MVC!";

            returnView();

        }

    }

}

What is an Action Filter ?

• It Implements IActionFilter interface
• It Executes before and after action result is executed
• Provides ActionFilterAttribute as the default class implementation

How to Do That ?

MyActionFilterAttribute.cs

using System.Web.Mvc;

namespace CustomActionFilter.CustomActionFilters

{

    public class MyActionFilterAttribute: FilterAttribute, IActionFilter

    {

        public void OnActionExecuting(ActionExecutingContextfilterContext)

        {

            //The action filter logic - before

        }

        public void OnActionExecuted(ActionExecutedContextfilterContext)

        {

            //The action filter logic - after

        }

    }

}

HomeController.cs

using System.Web.Mvc;

using CustomActionFilter.CustomActionFilters;

namespace CustomActionFilter.Controllers

{

    public class HomeController: Controller

    {

        [MyActionFilter]

        public ActionResult Index()

        {

            ViewBag.Message = "Welcome to ASP.NET MVC!";

            returnView();

        }

    }

}

What is a Result Filter ?

• It Implements IResultFilter interface
• It Executes before and after action result is executed

How to Do That ?

MyResultFilterAttribute.cs

using System.Web.Mvc;

namespace CustomActionFilter.CustomActionFilters

{

    public class MyResultFilterAttribute: FilterAttribute, IResultFilter

    {

        public void OnResultExecuting(ResultExecutingContextfilterContext)

        {

            //The action filter logic - before

        }

        public void OnResultExecuted(ResultExecutedContextfilterContext)

        {

            //The action filter logic - after

        }

    }

}

HomeController.cs

using System.Web.Mvc;

using CustomActionFilter.CustomActionFilters;

namespace CustomActionFilter.Controllers

{

    public class HomeController: Controller

    {

        [MyResultFilter]

        public ActionResult Index()

        {

            ViewBag.Message = "Welcome to ASP.NET MVC!";

            returnView();

        }

    }

}

What is an Exception Filter ?

• It Implements IExceptionFilter interface
• It Executes only if exception is thrown by action method or an action result
• Provides HandleErrorAttribute as the default class implementation

How to Do That ?

MyExceptionFilterAttribute.cs

using System.Web.Mvc;

namespace CustomActionFilter.CustomActionFilters

{

    public class MyExceptionFilterAttribute: FilterAttribute, IExceptionFilter

    {

        public void OnException(ExceptionContextfilterContext)

        {

            if(filterContext.Exception != null)

            {

                //The action filter logic

            }

        }

    }

}

HomeController.cs

using System.Web.Mvc;

using CustomActionFilter.CustomActionFilters;

namespace CustomActionFilter.Controllers

{

    public class HomeController: Controller

    {

        [MyExceptionFilter]

        public ActionResult Index()

        {

            ViewBag.Message = "Welcome to ASP.NET MVC!";

            returnView();

        }

    }

}

Note :

• I have used VS 2010 with Asp.Net MVC 3 and C# for develop above code samples.

CustomActionFilter's Project Tree is as below :

Finally, the HomeController with All the Custom Action Filters are as below :

using System.Web.Mvc;

using CustomActionFilter.CustomActionFilters;

namespace CustomActionFilter.Controllers

{

    public class HomeController: Controller

    {

        [MyAuthorizationFilter]

        [MyActionFilter]

        [MyResultFilter]

        [MyExceptionFilter]

        public ActionResult Index()

        {

            ViewBag.Message = "Welcome to ASP.NET MVC!";

            returnView();

        }

    }

}

That's It.You're Done. 

Do you need to Download this Sample Project ?

Conclusion

• Action Filters allow you to do some extra pre or post processing to be carried out,in addition to the code written in the action methods
• Depending on your need you can implement IAuthorizationFilter, IActionFilter, IResultFilter or IExceptionFilter interfaces to make your filter an Authorization filter, Action filter, Result filter or Exception filter respectively
• These interfaces decide the order in which the action filters are executed
• Which makes your application more flexible and maintainable

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