Passing Data to Views in MVC

Passing Data from a Controller to a View

ASP.NET Core MVC provides four common approaches:

1. Strongly Typed Model — Recommended

Controller:

public IActionResult Details()
{
    var product = new Product
    {
        Id = 1,
        Name = "Laptop",
        Price = 50000
    };

    return View(product);
}

View:

@model Product

<h2>@Model.Name</h2>
<p>Price: @Model.Price</p>

2. ViewBag

Controller:

ViewBag.Message = "Welcome";
return View();

View:

<h2>@ViewBag.Message</h2>

3. ViewData

Controller:

ViewData["Message"] = "Welcome";
return View();

View:

<h2>@ViewData["Message"]</h2>

4. TempData

Useful when redirecting to another action.

[HttpPost]
public IActionResult Create(Product product)
{
    TempData["SuccessMessage"] = "Product created successfully.";

    return RedirectToAction("Index");
}

View:

<p>@TempData["SuccessMessage"]</p>

Key Points

• Prefer a strongly typed Model for primary page data.
• Use a ViewModel when the View needs data from multiple models.
• ViewBag is dynamic and checked at runtime.
• ViewData uses a string-key dictionary.
• ViewBag and ViewData share the same underlying data.
• TempData retains data for the next request, making it suitable for redirects.
• Avoid passing large amounts of data through ViewBag, ViewData, or TempData.

ViewData vs ViewBag in ASP.NET Core MVC

Both ViewData and ViewBag are used to pass small amounts of data from a Controller to a View.

ViewData Example

Controller:

public IActionResult Index()
{
    ViewData["Name"] = "Syed";
    ViewData["Age"] = 40;

    return View();
}

View:

<h2>@ViewData["Name"]</h2>
<p>Age: @ViewData["Age"]</p>

For strongly typed usage, casting may be necessary:

@{
    string name = (string)ViewData["Name"];
}

ViewBag Example

Controller:

public IActionResult Index()
{
    ViewBag.Name = "Syed";
    ViewBag.Age = 40;

    return View();
}

View:

<h2>@ViewBag.Name</h2>
<p>Age: @ViewBag.Age</p>

Important Point

ViewBag is essentially a dynamic wrapper around ViewData. They share the same underlying data.

For example:

ViewData["Name"] = "Syed";

can be accessed as:

@ViewBag.Name

And:

ViewBag.City = "Chennai";

can be accessed as:

@ViewData["City"]

Interview Answer

ViewData stores values using dictionary-style string keys, while ViewBag provides dynamic property syntax over the same underlying ViewData. Both are used to pass data from a controller to a view and normally exist only for the current request.

Key point: For larger or structured data, prefer a strongly typed ViewModel instead of ViewData/ViewBag.