What is ViewBag?

Introduction

This article demonstrates an interesting and very useful concept in ASP.NET MVC.

Question: What is ViewBag?

In simple terms "ViewBag is the data holder that enables the definition of a dynamic property and holds the data that can be passed from a controller to a view".

Step 1: Create a new ASP.NET MVC application

Step 2: Adding new Model

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Web;
namespace ViewBagDemoApp.Models
{
    public class Addition
    {
        [Required(ErrorMessage = "Please Enter FirstNumber")]
        public int FirstNumber { get; set; }
        [Required(ErrorMessage = "Please Enter SecondNumber")]
        public int SecondNumber { get; set; }
    }
}

Step 3: Adding new Controller

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using ViewBagDemoApp.Models;
namespace ViewBagDemoApp.Controllers
{
    public class AdditionController : Controller
    {
        //// GET: /Addition/
        public ActionResult Index(Addition addition)
        {
            ViewBag.AddMessage = "Addition Result is: ";
            ViewBag.Result = addition.FirstNumber + addition.SecondNumber;
            if (ViewBag.Result < 1)
            {
                ViewBag.AddMessage = string.Empty;
                ViewBag.Result = string.Empty;
            }
            return View();
        }
    }
}

Step 4: Adding new View

@model ViewBagDemoApp.Models.Addition
@{
ViewBag.Title = "Addition Operation Using ViewBag";
}
<h2>Addition Operation Using ViewBag</h2>
<br />
@using (Html.BeginForm())
{
@Html.ValidationSummary(true)
<fieldset>
<legend>Addition</legend>
<div class="editor-label">
@Html.LabelFor(model => model.FirstNumber)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.FirstNumber)
@Html.ValidationMessageFor(model => model.FirstNumber)
</div>
<div class="editor-label">
@Html.LabelFor(model => model.SecondNumber)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.SecondNumber)
@Html.ValidationMessageFor(model => model.SecondNumber)
</div>
<p>
@ViewBag.AddMessage @ViewBag.Result
</p>
<br />
<p>
<input type="submit" value="Add" />
</p>
</fieldset>
}
<div>
@Html.ActionLink("Back to List", "Index")
</div>
@section Scripts {
@Scripts.Render("~/bundles/jqueryval")
}

Step 5: The output for the application is as in the following

I hope this article was useful for you. I look forward to your comments and feedback. Thanks, Vijay.