ASP.NET ViewData
last modified April 3, 2025
In this article, we explore the ViewData dictionary in ASP.NET 8. ViewData is a fundamental mechanism for passing data from controllers to views in MVC apps.
ASP.NET MVC provides several ways to transfer data between controllers and views. ViewData is one of the simplest and most straightforward approaches available.
Basic Definition
ViewData is a dictionary object derived from ViewDataDictionary class. It allows passing data from a controller to a view during the request-response cycle.
The ViewData dictionary uses string keys to store and retrieve data. The data is accessible only during the current request and is cleared when the request ends.
ViewData requires typecasting when retrieving values since it stores objects. It's ideal for small amounts of data that don't need complex model binding.
ASP.NET ViewData Example
The following example demonstrates how to use ViewData in an ASP.NET MVC app.
var builder = WebApplication.CreateBuilder(args);
builder.Services.AddControllersWithViews();
var app = builder.Build();
app.UseStaticFiles();
app.MapControllerRoute(
name: "default",
pattern: "{controller=Home}/{action=Index}/{id?}");
app.Run();
This sets up a basic ASP.NET MVC application. The AddControllersWithViews
method enables MVC with view support. The default route maps to HomeController.
using Microsoft.AspNetCore.Mvc;
public class HomeController : Controller
{
public IActionResult Index()
{
ViewData["Title"] = "Welcome to our Store";
ViewData["Message"] = "Today's special offers:";
var products = new List<string>
{
"Laptop - 15% off",
"Smartphone - 10% off",
"Headphones - 20% off"
};
ViewData["Products"] = products;
ViewData["DiscountDate"] = DateTime.Now.AddDays(1);
return View();
}
}
The controller sets several ViewData values: a title string, a message string, a list of products, and a discount expiration date. These values will be accessible in the corresponding view.
@{
Layout = "_Layout";
}
<h2>@ViewData["Title"]</h2>
<p>@ViewData["Message"]</p>
<ul>
@foreach (var product in (List<string>)ViewData["Products"])
{
<li>@product</li>
}
</ul>
<p>
Offers valid until:
@(((DateTime)ViewData["DiscountDate"]).ToString("MMMM dd, yyyy"))
</p>
The view retrieves and displays all ViewData values. Note the explicit casting required for the list of products and the DateTime value. The title and message are displayed directly.
This example shows ViewData's flexibility in handling different data types. However, remember that ViewData values are not strongly typed, which can lead to runtime errors if casting is incorrect.
Source
Microsoft ASP.NET MVC Views Documentation
In this article, we have explored the ViewData dictionary in ASP.NET 8. This simple yet powerful feature enables easy data transfer between controllers and views.
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