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Action Result in ASP.NET MVC

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21 Jun 2018CPOL
In this article, you will learn about basic foremost concepts about Action Results in ASP.NET MVC 5. Hope you'll enjoy this. Feel free to give your feedback.

Introduction and Background

This article will tell you the basic to advanced foremost concepts about 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

According to the first part of the question, why there is ContentResult data type in the action method, to understand this, you have to understand about 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 ActionResult.

Let’s get started with Action Result.

Action Result

Action Result is actually a data type. When it is used with action method, then it is called return type. As you know, an action referred to a method of the controller. So 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
    {
        //
        // Summary:
        //     Initializes a new instance of the System.Web.Mvc.ActionResult class.
        protected ActionResult();
    }
}

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

To see inside the assembly, you can either follow the steps given below after downloading ILSpy or you can view my GIF file named as ILSpy.gif after clicking here.

Steps are as follows:

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

Image 1

Now you can see, the ActionResult 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
    {
        //
        // Summary:
        //     Initializes a new instance of the System.Web.Mvc.ActionResult class.
        protected ActionResult();
    }
}

It is an abstract class because actions of a 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, same action method “Index” returning two different types named Content and View. So 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?”

The answer is, choosing a 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.

Image 2

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

  1. Content Returning Results
  2. Redirection Results
  3. Status Results

Let’s understand each.

Content Returning Results

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

  1. ViewResult
  2. PartialViewResult
  3. ContentResult
  4. EmptyResult
  5. FileResult
  6. JsonResult
  7. 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 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.

Output

Image 3

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 in the figure below that we “Second View” page in views folder:

Image 4

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 the action name.

Output

Image 5

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>

Output

Image 6

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 the 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 an 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:

Image 7

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 have content of layout page. See figure below:

Image 8

So here, you can use PartialViewResult datatype.

ContentResult

The ContentRresult 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>");
    }
}

Output

Image 9

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

public class HomeController : Controller
{
    public ContentResult Index()
    {
        return Content("<h3>Zain Ul Hassan</h3>", "text/html");
    }
}

The output is the same as above:

Image 10

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:

Image 11

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:

Image 12

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 same as above:

Image 13

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 the 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");
    }
}

Output

Image 14

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:

Image 15

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:

Image 16

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 derived 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 the following code:

<script type="text/javascript" src="@Url.Action("Index")"></script>

The output is as shown below:

Image 17

Redirection Results

This type of ActionResult is used for redirection purpose, which you will 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:

Image 18

RedirectionResult is better for redirection to live URLs mean to say 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 overloaded. 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:

Image 19

Now if you are in the same controller and don’t want to give the name of the 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:

Image 20

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.

Status Result

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

  1. HttpStatusCodeResult
  2. HttpUnauthorizedResult
  3. 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:

Image 21

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

Image 22

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

If you don’t want to use System.Net namespace, then HttpStatusCodeResult has such an overload whose output will be the 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 looks 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

Image 23

Summary

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

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Syed Zain Shah
Web Developer
Pakistan Pakistan
Software Engineering Student, C# Trainer, Blogger and an Active Learner. I am a very ardent about learning new technologies and implementing technologies in a professional environment. I am a community speaker and has spoken at 50+ technology sessions for last 1 year at UE IT Society in the University of Education.

I knows about:
Front End: HTML 5, jQuery, CSS 3, Ajax, JavaScript, Bootstrap
Back End: C#, Java, SQL Server, ASP.NET MVC 5, Entity Framework, Angular2

I enjoys very much learning new technologies, starting new projects and meeting new challenges.
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Comments and Discussions

 
PraiseNicely described. Pin
_ZaiT_9-Aug-18 1:46
member_ZaiT_9-Aug-18 1:46 
PraiseI find this explanation very helpful Pin
JohnDonnelly26-Jun-18 13:00
memberJohnDonnelly26-Jun-18 13:00 
GeneralRe: I find this explanation very helpful Pin
Syed Zain Shah26-Jun-18 20:13
groupSyed Zain Shah26-Jun-18 20:13 

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Posted 21 Jun 2018

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