Action Result In ASP.NET MVC

Tóm Tắt

Introduction and Background

This article will demonstrate the basic to advanced concepts of action results in ASP.NET MVC. Last week, one of my friends asked the question “Why there is ContentResult data type in the action method and what is its purpose?” I am dedicating this article to him. I hope he will like this.

The topics to be covered are,

What is ActionResult?

Content Returning Results

Redirection Results

Status Results

The Question

The first part of the question is: “Why there is ContentResult data type in the action method?”. To understand this, you have to understand the data types in ASP.NET MVC 5 because the ContentResult is a data type whose base data type is ActionResult, hence you have to understand Action Result.

Let’s get started with Action Result.

Action Result in ASP.NET MVC

Action Result is actually a data type. When it is used with action method, it is called return type. As you know, an action is referred to as a method of the controller, the Action Result is the result of action when it executes. In fact, Action Result is a return type. This return type has many other derived types. First, look at the base and derived types of ActionResult.

namespace

System.Web.Mvc
{
public

abstract

class

ActionResult
{
protected

ActionResult();
}
}

As we see in the Visual Studio, the ActionResult type is coming from System.Web.Mvc assembly. And the problem is that we can’t see inside this assembly with “Go to Definition” feature of Visual Studio.

To see inside the assembly, you can either follow the following steps after downloading ILSpy or you can watch this video by clicking here.

Steps are as follows.

I am giving you the direct link to download the ILSpy. Click here.
If you don’t have the System.Web.Mvc assembly, then you can download after clicking here.
Run ILSpy after extracting it.
Click on File (on the top-left-corner)
Select “Open” option and open the assembly from where you downloaded it.
After selecting, the assembly will load in ILSpy software.
Expand the assembly, you will see ActionResult, expand it also, you will see the base and derived types also.
The types of ActionResult is shown in the image below:

Now, you can see that the Action Result is a base data type whose derived types are HttpStatusCodeResult, JavaScriptResult, FileResult, ContentResult, JsonResult, EmptyResult, RedirectResult, RedirectToRouteResult, ViewResult. And, there must be a helper method against each data type (either base or derived type).

When we go into ActionResult, we see that it is an abstract class.

namespace

System.Web.Mvc
{
public

abstract

class

ActionResult
{
protected

ActionResult();
}
}

It is an abstract class because actions of controller can return different types of data at the same time. So, it has to be abstract so that every HTTP request could handle properly. See the code below,

public

ActionResult Index()
{
bool

answer = DateTime.Now.Day + 2 == 5;
if

(answer)
{
return

Content(

“Correct”

);
}
else
{
return

View();
}
}

As you can see, the same action method “Index” is returning two different types named Content and View; if you want to return multiple types, you have to use base type as ActionResult.

The above concept also answers the question “When to choose base type ActionResult or derived type?”

Choosing the derived type for a specific result is a good practice, but when you want that your action method should return multiple types, then you have to use base type ActionResult.

Now, the important concept comes. There are three categories for the derived types. Let’s take a look at it.

As you can see, there are three categories of data types of ActionResult,

Content Returning Results
Redirection Results
Status Results

Let’s understand each.

Content Returning Results

As the name depicts these results are used for returning the content to the browser. There are 7 types of content returning results:

ViewResult
PartialViewResult
ContentResult
EmptyResult
FileResult
JsonResult
JavaScriptResult

ViewResult

ViewResult is a datatype which is responsible for returning the View. Let’s look at its example.

public

class

HomeController : Controller
{
public

ViewResult Index()
{
return

View();
}
}

And the code of Index view is as follows,

<

h2

>
This is Index View.
</

h2

>

As you can see in the above code, index action method is returning the View using ViewResult type. After this, MVC will find the View having name “Index” from the “Home” folder in the Views folder. And the output is as follows,

The interesting thing with ViewResult type is, you can return a different View regardless of using View having the same name as that of the action method. Look at an example.

public

class

HomeController : Controller
{
public

ViewResult Index()
{
return

View(“Second View” );
}
}

You can see the figure below that we “Second View” page in views folder,

And the code of “Second View” page is as follows,

<

h2

>

This is Second View but having action name “Index”

</

h2

>

You can see above, now MVC will find the view having name “Second View” rather than finding the view having the same name as that of the action name. Output is as follows,

Hence, you can call any other view using different action name with the help of ViewResult type.

PartialViewResult

It is the type which is used to return the partial view page rather than returning the regular view page. Look at its example.

public

class

HomeController : Controller
{
public

PartialViewResult Index()
{
return

PartialView(

“Second View”

);
}
}

And the code of “Second View” is shown below.

<

h2

>

This is Second View but having action name “Index”

</

h2

>

Now the output is different, let’s see below,

As you can see the output is the same as in the previous example. But the difference is here we can’t see the line “© 2018 – My ASP.NET Application” because it is the line from Layout page, which is absent here due to the usage of PartialViewResult datatype.

As you can see the output of PartialViewResult is same as that of ViewResult. But the content of layout page is missing. It is just an example. This is not the real-time example.

Now, let’s look at the example where we’ll see layout page. Make a new controller named as “Student” and an action method named as “Name”, as shown below,

public

class

StudentController : Controller
{
public

PartialViewResult Name()
{
return

View(

“_SecondView”

);
}
}

There is no need to make the View for “Name”. Because here the Name action method is calling a different View page. See the folder structure below,

The proper way of creating partial view page is, it should be used inside the regular view, having the name start with _, and should reside in the Shared folder.

Now, when you execute it, you will see the same output but having content of layout page. See the figure below.

So here you can use PartialViewResult datatype.

ContentResult

“Content” result is a datatype which is responsible for the returning of content. But the point of interest is, you will have proper control over the returned content. I mean to say that you have to add the content in the “Content” helping method of ContentResult type. Here you can pass the contents like HTML content, Javascript content or any other content. Let’s understand it with examples.

Code of Home controller is given below,

public

class

HomeController : Controller
{
public

ContentResult Index()
{
return

Content(

“<h3>Zain Ul Hassan </h3>”

);
}
}

Its output will be,

You can also give MIME (Multipurpose Internet Mail Extensions) type in Content helper method to tell the MVC to take appropriate action after recognizing the content. Code is as shown below,

public

class

HomeController : Controller
{
public

ContentResult Index()
{
return

Content(

“<h3>Zain Ul Hassan</h3>”

,

“text/html”

);
}
}

Output is the same as above,

You can also give Javascript content which will return by ContentResult type. Let’s take an example.

public

class

HomeController : Controller
{
public

ContentResult Index()
{
return

Content(
“<script> alert(‘Hi! I am Zain Ul Hassan’) </script>”
);
}
}

The output will have an alert as shown below,

So you can use ContentResult datatype in the above way.

EmptyResult

This type is genuinely for returning nothing. But the problem is, this EmptyResult type doesn’t have any helper method. So we can use it by making its object, as shown below,

public

class

HomeController : Controller
{
public

EmptyResult Index()
{
return

new

EmptyResult();
}
}

But you want to use ActionResult then MVC will automatically perceive that it is of EmptyResult. For code, see below,

public

class

HomeController : Controller
{
public

ActionResult Index()
{
return

null

;
}
}

So it is the use of EmptyResult type.

FileResult

FileResult is a type which is used to return the file to the browser. The helper method for this type is File, and has many overloads. So if we use the following overload and specify only the URL of the file and the MIME (Multipurpose Internet Mail Extensions) type then we should see the content of the file in the browser. Let’s take an example.

The overload we use is,

protected

internal

FilePathResult File(

string

fileName,

string

contentType);

And the code for action method using FileResult type is as follows,

public

class

HomeController : Controller
{
public

FileResult Index()
{
return

File(

“~/Files/text.txt”

,

“text/plain”

);
}
}

This file is included in the project and the URL is given above. And the output is given below,

Now if you want to return the file in byte array then you have to use following code,

public

class

HomeController : Controller
{
public

FileResult Index()
{
byte

[] fileBytes = System.IO.File.ReadAllBytes(Server.MapPath(

“~/Files/text.txt”

));
return

File(fileBytes,

“text/plain”

);
}
}

The output is the same as above,

Now if you don’t want to show the file in the browser and want that your file should be asked to download then you have to use following overload the file helper method,

protected

internal

virtual

FilePathResult File(

string

fileName,

string

contentType,

string

fileDownloadName);

The code of action using FileResult is given below,

public

class

HomeController : Controller
{
public

FileResult Index()
{
return

File(Url.Content(

“~/Files/text.txt”

),

“text/plain”

,

“testFile.txt”

);
}
}

Then the output will be as shown below,

Hence it is the use of FileResult in different scenarios.

JsonResult

It is the derived type of ActionResult which is used to represent the JSON data. To see how can we JSONify any data, you can see code below:

public

JsonResult Index()
{
return

Json(

new

{ Name =

“Zain Ul Hassan”

, ID = 1 });
}

Its output is as follows,

You will get this error after executing the above code. Now understand what the problem here is.

As you know, JSON contains your encoded data that can be precious, so MVC strictly stops the sharing of information over a GET request. In fact, MVC is trying to prevent you from JSON Hijacking.

So if you want to share the information over the GET request then you have to use the code shown below,

public

JsonResult Index()
{
return

Json(

new

{ Name =

“Zain Ul Hassan”

, ID = 1 }, JsonRequestBehavior.AllowGet);
}

The output will become,

So, JsonRequestBehavior.AllowGet permits the MVC to share the information over the GET request. But you should use the above feature when you are sure that your JSON data doesn’t contain sensitive data.

JavaScriptResult

This derive type is used for returning the javascript code from the controller. When it executes we see the javascript code as we mentioned in the controller’s action method. For details, let’s take an example,

public

JavaScriptResult Index()
{
return

JavaScript(

“alert(‘Zain Ul hassan’)”

);
}

And the View named as Index has following code,

<script type=

“text/javascript”

src=

“@Url.Action(“

Index

“)”

></script>

The output is as shown below,

Redirection Results

This type of ActionResult is used for redirection purpose, which will you see with examples here. There are 2 types of redirection results,

RedirectResult
Redirect to Action Result

RedirectionResult

If you use this type then it’ll redirect to the URL specified by you. An example is given below,

public

RedirectResult Index()
{
return

Redirect(

“https://www.c-sharpcorner.com/members/zain-ul-hassan2”

);
}

In the output, the specified URL will open, as shown below,

RedirectionResult is better for redirection to live URLs which means it is not a best practice to use it for redirection to the local pages of the current app. For this purpose use RedirectionToRouteResult as explained below,

RedirectionToRouteResult

It is responsible for the redirection to the actions within the application. There are many helper methods in it which are actually overloads. We use RedirectToRoute which redirect us to the action within the specified controller. Let’s look at its example.

public

RedirectToRouteResult Index()
{
return

RedirectToRoute(

new

{ controller =

“Student”

, action =

“Name”

});
}

We have Name action method within the Student controller, and the code of Name view is given below,

<

h2

>

Redirection Successfull

</

h2

>

So the output is as follows,

Now if you are in the same controller and don’t want to give the name of controller then the better option of is, RedirectToAction helper method. Look at the code below,

public

class

HomeController : Controller
{
public

RedirectToRouteResult Index()
{
return

RedirectToAction(

“SecondIndex”

);
}
public

ActionResult SecondIndex()
{
return

View();
}
}

And the View of SecondIndex’s code is below,

<

h3

>

This is the SecondIndex of the same controller named as “Home”

</

h3

>

The output is as follows,

Status Result

Its responsibility is to give the status code to the browser. There are three types of this set explained below,

HttpStatusCodeResult
HttpUnauthorizedResult
HttpNotFoundResult

HttpStatusCodeResult

This type is used to give HTTP status code to the browser. Look at its example.

public

HttpStatusCodeResult Index()
{
return

new

HttpStatusCodeResult(HttpStatusCode.Unauthorized);
}

The output is as shown below,

You can show your own message after using the overloaded version of the type HttpStatusCodeResult.

public

HttpStatusCodeResult Index()
{
return

new

HttpStatusCodeResult(HttpStatusCode.Unauthorized,

“Sorry! You don’t have access.”

);
}

Output

Here HttpStatusCode is coming from System.Net namespace. And it contains all the HTTP status codes.

If you don’t want to use System.Net namespace then HttpStatusCodeResult has an overload whose output will be same as above. See the code below:

public

HttpStatusCodeResult Index()
{
return

new

HttpUnauthorizedResult(

“Sorry! You don’t have access.”

);
}

The output is the same as above but the code is looking more readable.

HttpNotFoundResult

This is also an overload of HttpStatusCodeResult but it has the helper method, we don’t have to make an anonymous object. The code is as follows:

public

HttpNotFoundResult Index()
{
return

HttpNotFound(

“Sorry! You don’t have access.”

);
}

Output

Summary

These were the basic and foremost things to understand about Action Results. If you have any query then feel free to contact me in the comments. Also, give feedback either positive or negative, it will help me to make my articles better and increase my enthusiasm to share my knowledge.

As you can see, the helper method RedirectToAction is used for calling action within the current controller so if MVC doesn’t find that, 404 error will occur. RedirectToAction has many overloads, you can give controllers, actions, route values and much more. So you have to use according to your scenario.

Introduction and Background

Action Result in ASP.NET MVC

Content Returning Results

ViewResult

PartialViewResult

ContentResult

EmptyResult

FileResult

JsonResult

JavaScriptResult

Redirection Results

RedirectionResult

RedirectionToRouteResult

Status Result

HttpStatusCodeResult

HttpNotFoundResult

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