Web and Mobile Apps Codeware: custom filters

Friday, December 5, 2014

Implementing Asp.net Custom MVC filters [Part 2]

hi in this post i will show an another way implementing custom asp.net mvc filters.

Now i will create separate class for every filter types which will inherit attributes according to type and then we will implement that inherited methods.

here we will use the name of filter class and add it on the top of action method or we can also add it to the whole controller.

Code :

Controller :

[CustomAuthorization]
public class MainController : Controller
{
//
// GET: /Main/
[CustomAction]
[CustomExceptionFilter]
public ActionResult Index()
{
int i = Convert.ToInt32(“1″) / Convert.ToInt32(“0″);
ViewBag.message = “hello world”;
return View();
}

}
class CustomAuthorization : AuthorizeAttribute
{
public override void OnAuthorization(AuthorizationContext filterContext)
{
filterContext.Controller.ViewBag.AuthorizationMsg = “From OnAuthorization method”;
}
}

class CustomAction : ActionFilterAttribute
{
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
filterContext.Controller.ViewBag.ActionExecutingMsg = “From OnActionExecuting method”;
}
public override void OnActionExecuted(ActionExecutedContext filterContext)
{
filterContext.Controller.ViewBag.ActionExecutedMsg = “From OnActionExecuted method”;
}

public override void OnResultExecuting(ResultExecutingContext filterContext)
{
filterContext.Controller.ViewBag.ResultExecutingMsg = “From OnResultExecuting method”;
}

public override void OnResultExecuted(ResultExecutedContext filterContext)
{
filterContext.Controller.ViewBag.ResultExecutedMsg = “From OnResultExecuted method”;
}
}

public class CustomExceptionFilter : FilterAttribute, IExceptionFilter
{
public void OnException(ExceptionContext filterContext)
{
filterContext.ExceptionHandled = true;
filterContext.Result = new ViewResult
{
ViewName = “error”,
};
}
}

View:

@{
Layout = null;
}

<!DOCTYPE html>

<html>
<head>
<meta name=”viewport” content=”width=device-width” />
<title>Index</title>
</head>
<body>
<div>
@ViewBag.message

<br />
@ViewBag.AuthorizationMsg
<br />
@ViewBag.ActionExecutingMsg
<br />
@ViewBag.ActionExecutedMsg
<br />
@ViewBag.ResultExecutingMsg
<br />
@ViewBag.ResultExecutedMsg
<br />
@ViewBag.ExceptionMsg
</div>
</body>
</html>

I’m adding one more view named error.cshtml , to which we will redirect when any exception occurs.

Output:

1. Without Exception

2. With Exception

Implementing Asp.net Custom MVC filters [Part 1]

hi lets implement asp.net mvc filters

Filters help us to add logic before and after a controller action which is getting called. (Like we need to log something when controller action is called)

types of filters in asp.net mvc :
1. Authorization filter
2. Action filter
3. result filter (viewresult, jsonresult etc.)
4. exception filter

example:

create a new asp.net mvc empty project. Now i will add a new controller and will return a string to the view using viewbag.

Now for implementing Custom MVC filters, we will implement methods from IAuthorizationFilter,IActionFilter,IResultFilter,IExceptionFilter
interface.

controller code

public class MainController : Controller,IAuthorizationFilter,IActionFilter,IResultFilter,IExceptionFilter
{
//
// GET: /Main/

public ActionResult Index()
{
ViewBag.message = “hello world”;
return View();
}

protected override void OnAuthorization(AuthorizationContext filterContext)
{
ViewBag.AuthorizationMsg = “From OnAuthorization method”;
}

protected override void OnActionExecuting(ActionExecutingContext filterContext)
{
ViewBag.ActionExecutingMsg = “From OnActionExecuting method”;
}

protected override void OnActionExecuted(ActionExecutedContext filterContext)
{
ViewBag.ActionExecutedMsg = “From OnActionExecuted method”;
}

protected override void OnResultExecuting(ResultExecutingContext filterContext)
{
ViewBag.ResultExecutingMsg = “From OnResultExecuting method”;
}

protected override void OnResultExecuted(ResultExecutedContext filterContext)
{
ViewBag.ResultExecutedMsg = “From OnResultExecuted method”;
}

protected override void OnException(ExceptionContext filterContext)
{
ViewBag.ExceptionMsg = “From OnException method”;
}

}

View code

<!DOCTYPE html>

<html>
<head>
<meta name=”viewport” content=”width=device-width” />
<title>Index</title>
</head>
<body>
<div>
@ViewBag.message

Output :

Below is the sequence of execution of the methods:

As View gets rendered before OnResultExecuted method , we are not able to see the onresultexecuted viewbag message.

OnException method will get called when there is any exception.