C# Online Compiler | .NET Fiddle

using System;
using System.ComponentModel.DataAnnotations;

namespace HelloWorldMvcApp
{
	public class SampleViewModel
	{

	}
}

<!DOCTYPE html>
<html>
<head>
    <title>ImageShapes</title>
	<script src="https://code.jquery.com/jquery.min.js"></script>
	<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css" rel="stylesheet" type="text/css" />
	<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>
	<meta charset="utf-8">
</head>
<body>
	
@using (Html.BeginForm())
{
  <div class="container">

   
    <h2>ImageShapes</h2>

	Choose ImageShapes:
    @Html.DropDownList("ImageShape",
                        (SelectList)ViewBag.ImageShapesList, 
	  					"N/A", 
                        new { 

                            onchange = "this.form.submit()" 
                        })

    <br /><br />

	<pre id="imgHtml"></pre>
	  
    <img src="http://image.slidesharecdn.com/dev208-asp-130926011519-phpapp01/95/dev208-aspnet-mvc-5-1-638.jpg?cb=1380158517"
         alt="Discover ASP.NET MVC 5 New Features"
         class="@ViewBag.ImageShape" />

	  
  </div>
}

	<script>
		$(function() { 
			$('#imgHtml').text($('img')[0].outerHTML);
		});
	</script>

</body>
</html>

 
<!DOCTYPE html>
<html>
<head>
    <title>ImageShapes</title>
    <script src="https://code.jquery.com/jquery.min.js"></script>
    <link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css" rel="stylesheet" type="text/css" />
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>
    <meta charset="utf-8">
</head>
<body>
    
@using (Html.BeginForm())
{
  <div class="container">
​
   
    <h2>ImageShapes</h2>
​
    Choose ImageShapes:
    @Html.DropDownList("ImageShape",
                        (SelectList)ViewBag.ImageShapesList, 
                        "N/A", 
                        new { 
​

using System;
using System.Web.Mvc;
using System.Collections.Generic;

namespace HelloWorldMvcApp
{
	public class HomeController : Controller
	{

        public ActionResult Index(string ImageShape)
        {
            var options = new List<string>();
            options.Add("img-rounded");
            options.Add("img-circle");
            options.Add("img-thumbnail");

            ViewBag.ImageShapesList = new SelectList(options);

            if (String.IsNullOrEmpty(ImageShape))
            {
                ImageShape = null;
            }
            ViewBag.ImageShape = ImageShape;

            return View();
        }
	}
}

 
using System;
using System.Web.Mvc;
using System.Collections.Generic;
​
namespace HelloWorldMvcApp
{
    public class HomeController : Controller
    {
​
        public ActionResult Index(string ImageShape)
        {
            var options = new List<string>();
            options.Add("img-rounded");
            options.Add("img-circle");
            options.Add("img-thumbnail");
​
            ViewBag.ImageShapesList = new SelectList(options);
​
            if (String.IsNullOrEmpty(ImageShape))
            {
                ImageShape = null;
            }
            ViewBag.ImageShape = ImageShape;
​
            return View();
        }
    }
}