What is ViewData?

What is ViewData?
 
Introduction
 
This article demonstrates an interesting and very useful concept in ASP.NET MVC.
 
Question: What is ViewData?
 
In simple terms "ViewBag is a data holder that enables definition of a key-value pair and that holds the data that can be passed from controller to 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 ViewDataDemoApp.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 ViewDataDemoApp.Models;

 

namespace ViewDataDemoApp.Controllers

{

    public class AdditionController : Controller

    {

        //// GET: /Addition/public ActionResult Index(Addition addition)

    {

        ViewData["AddMessage"] = "Addition Result is: ";

        ViewData["Result"] = addition.FirstNumber + addition.SecondNumber;

        if ((int)ViewData["Result"] < 1)

        {

           ViewData["AddMessage"] = string.Empty;

           ViewData["Result"] = string.Empty;

        }

        return View();   

    }

  }

} 
 
Step 4: Adding New View


 

@model ViewDataDemoApp.Models.Addition@

{ ViewBag.Title = "Addition Operation Using ViewData"; }<h2>

    Addition Operation Using ViewData</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>@ViewData["AddMessage"] @ViewData["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 looks as in the following: