Auto Upgrade MVC 3 To MVC 4

Install-Package UpgradeMvc3ToMvc4

http://nugetmusthaves.com/Package/UpgradeMvc3ToMvc4
Hope this help you !

Showing loading animation in center of page while making a call to Action method in MVC

Now, use javascript to show it in and hide, when an ajax request starts. 
<script type="text/javascript">
    $(document).ajaxStart(function () {
        $('#spinner').show();
    }).ajaxStop(function () {
        $('#spinner').hide();
    });
</script>


Style the div element to position it on the centre of the browser.
<style>
div#spinner
{
    display: none;
    width:100px;
    height: 100px;
    position: fixed;
    top: 50%;
    left: 50%;
    text-align:center;
    margin-left: -50px;
    margin-top: -100px;
    z-index:2;
    overflow: auto;
}  
</style>


Put the html for the loader in the page.
<div id="spinner">
    <img src="~/Images/googleLarge.gif" alt="Loading..."/>
</div>

Hope this help you !