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ViewData, ViewBag and TempData in MVC


ViewData, ViewBag and TempData in MVC explained


ViewBag and ViewData are used to pass the data from Controller action to View and TempData is used to pass the data from action to another action or one Controller to another Controller.

ViewData and ViewBag are used for the same purpose that is, to transfer data from controller to view.  ViewData is nothing but a dictionary of objects and it is accessible by string as key. ViewData is a property of controller that exposes an instance of the 

ViewDataDictionary class. ViewBag is very similar to ViewData, but ViewBag is a dynamic property (dynamic keyword is introduced in .net framework 4.0). ViewBag is able to set and get value dynamically and able to add any number of additional fields without converting it to strongly typed. ViewBag is just a wrapper around the ViewData.

ViewData

1.       ViewData is derived from the ViewDataDictionary class and is basically a Dictionary object i.e. Keys and Values where Keys are String while Values will be objects.
2.       Data is stored as Object in ViewData.
3.       We need to cast data back to its original type since the data is stored as object in ViewData. Also it required NULL checking while retrieving.
4.       ViewData is used for passing value from Controller to View.
5.       ViewData is available only for Current Request. It will be destroyed on redirection.

Example

In the example that follows, a string value is set in the ViewData object in Controller and it is then displayed in View.

Controller

public class CsharpnaijaController : Controller
{
    // GET: Csharpnaija
    public ActionResult Index()
    {
        ViewData["Message"] = "C# Naija, Hello!";
        return View();
    }
}

View

<html>
<head>
    <meta name="viewport" content="width=device-width"/>
    <title>Index</title>
</head>
<body>
    <div>
        @ViewData["Message"]
    </div>
</body>
</html>

ViewBag

ViewBag is a dynamic object to pass the data from Controller to View. And, this will pass the data as a property of object ViewBag. And we have no need to typecast to read the data or for null checking. The scope of ViewBag is permitted to the current request and the value of ViewBag will become null while redirecting.

Example

Controller

public class CsharpnaijaController : Controller
{
    // GET: First
    public ActionResult Index()
    {
        ViewBag.Message = "C# Naija, Hello";
        return View();
    }
}

View

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

TempData

TempData is a dictionary object to pass data from one action to other action in the same Controller or different Controller. Usually, TempData object will be stored in a session object. Tempdata is also required to typecast and null check before reading data from it. TempData scope is limited to the next request and if we want Tempdata to be available even further, we should use Keep and peek.

Example

In the following example, a string value is set in the TempData object in Controller and it is redirected to another Controller and finally displayed in View.

Employee Controller

public class  EmployeeController : Controller
{
    // GET: Employee
    public ActionResult Index()
    {
        TempData["Message"] = "Hello, C# Naija ";
        return new RedirectResult(@"~\Department\");
    }
}

Department Controller


public class DepartmentController : Controller
{
    // GET: Department
    public ActionResult Index()
    {
        return View();
    }
}

View of Department Controller


<html>
<head>
    <meta name="viewport" content="width=device-width"/>
    <title>Index</title>
</head>
<body>
    <div>
        @TempData["Message"];
    </div>
</body>
</html>

I hope this article helped you understand, the concept of ViewData, ViewBag and TempData.

This article referenced the work of Mudassar Khan, SATISH KUMAR and JIGNESHTRIVEDI



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Location: Abuja, Nigeria

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