Monday, March 10, 2014

Step By Step How to make Ajax calls using PartialViews in MVC 4

        By Carmel Schvartzman


In this tutorial we'll learn how to make Ajax calls using PartialViews in MVC 4. We'll use several ActionLink Html Helpers to asynchronously render data from database, sent by some Action methods from the web server.

We'll be using three ActionLink Html Helpers.  As you know, an Html Helper is a class designed for rendering HTML controls to the Views. It supports several extension methods representing the different controls such as forms, textboxes, labels, dropdownlists, routelinks ( "< a >" ) , actionlinks ( "< a >" ) ,textareas, passwords, listboxes, checkboxes, radiobuttons, hidden fields, editors, and validation code.

We'll want to render a PartialView, via Ajax requests, showing up as follows:




The web page we're going to build, will display a list of blog posts, stored in database in a "Blog" table, and included in the Entity Framework context as follows:



By the other side, we'll need a Partial View containing a list of the posts in the Blog table. We'll make a AJAX call from the Index View, in order to populate a <div> with the contents of the PartialView. Add a new View to the "Shared" folder:

Set this as a "Partial View" , strongly typed according to the "Blog" Model class:


Because we don't need all the controls scaffolded in the View, delete the ones marked with red and retain those marked with green:


Now add the <img> tag in order to properly display the images in the page:




Now we'll build the controller to handle the user's interactions. This controller will render a simple View with a <div> placeholder in which display the Partial View, and three Ajax enabled links to call three different Action methods that filter the contents for that Partial View. Therefore, add a new Controller to the Controllers folder:


Name it "PostList", and leave it as an empty controller:




Leave the Index Action method as it is:


Now take a look again at the Model type the Partial View is expecting:



According to that, let's write another Action method to send the IEnumerable<Blog> collection to the Partial View:


The new Partial View will return a PartialViewResult with the collection obtained from a Repository we build in a previous Tutorial.

Now, for the View rendered by the Index Action method, add a new View right clicking inside the Index Action method:




Leave it as a simple View not strongly typed:


Open the Content tag and find the "Index" <F2>:


Change the title to "Posts List" and insert an Ajax.ActionLink control:


First Action Link we code, will send an GET request to the "AllPosts" Action method, and will insert the response inside the "DivPosts" update target, REPLACING its contents:



Buid (F6) and run your app (CTL-F5) , to get this presentation UI:




Click the link , and you'll see all the data ajax loaded without refreshing the web page:




Now we'll add another two Action methods to render filtered data. Notice that all we did was copy-paste the original "AllPosts" action method, adding a filter, and an HTTP POST attribute to handle POST requests:




The second Action Link we code, will send a POST request to the "Last3Posts" Action method, and will insert the response inside the "DivPosts" update target, REPLACING its contents:



Accordingly, the third Action Link we code, will send a GET request to the "AllPostsDescending" Action method, and will insert the response inside the "DivPosts".

Buid (F6) and run your app (CTL-F5) , and click the second link, to see ONLY 3 LAST posts:



Open the Developer Tools (F12) and in the NETWORK tab you'll see a POST request was sent:


And this was the response received:


You see, it's an HTML made to fit and replace the <div> tag content holder.

Now click the third link, to see all posts but SORTED descending by date posts, sending the following request:




The response received is indeed sorted descending:



And this is the ajax rendered table inside the <div> :





In this tutorial we've learned how to make Ajax calls using PartialViews in MVC 4, with several ActionLink Html Helpers used to asynchronously render filtered data from database
That's all!! 
Happy programming.....


כתב: כרמל שוורצמן