difference between viewbag and viewdata and tempdata in mvc3

the main difference below,

ViewData:

• ViewData is a dictionary of objects that is derived from ViewDataDictionary class and accessible using strings as keys

• It’s required type casting for complex data type and check for null values to avoid error.

ViewBag: 

• ViewBag doesn’t require typecasting for complex data type.
• ViewBag is a dynamic property that takes advantage of the new dynamic features in C# 4.0. 

Check the following example:

public class HomeController : Controller

{

    public ActionResult Index()

    {

        var emp = new Employee

        {

            EmpID=101,

            Name = "Deepak",

            Salary = 35000,

            Address = "Delhi"

        };

        ViewData["emp"] = emp;

        ViewBag.Employee = emp;

        return View(); 

    }

}

And the code for View is as follows:

@model MyProject.Models.EmpModel;

@{ 

 Layout = "~/Views/Shared/_Layout.cshtml"; 

 ViewBag.Title = "Welcome to Home Page";

 var viewDataEmployee = ViewData["emp"] as Employee; //need type casting

}

<h2>Welcome to Home Page</h2>

This Year Best Employee is!

<h4>@ViewBag.emp.Name</h4>

<h3>@ViewData.Employee.Name</h3>