What is view engine? What does it actually do?

Question

I started learning ASP.NET MVC3.

So, while reading tutorials online and in books, I came across this term "view engine" quite frequently. I don't know what it is.

What does it actually do?

Why should it matter to me at all?

Answer 1

The view engine is responsible for creating HTML from your views. Views are usually some kind of mixup of HTML and a programming language. The pattern behind most of these is called two-step view.

For example, ASP.NET comes with its own view engine out of the box. That is the one where views have lots of tags like <% %> and <%: %>. It uses the .aspx file extension.

With ASP.NET MVC3, another out-of-the-box view engine was added, Razor, which has a more appealing syntax, e.g. <div>@Model.UserName</div>.

The choice of view engine is important, because the feature sets of view engines are quite different. Some support rendering to PDF files, for instance; some can't be used outside a web context (this is true for the old ASP.NET view engine), while others can (e.g. Razor). 'Offline' rendering of views comes in handy when you want to create HTML emails the same way you build your views and those emails should be sent from a background worker rather than a web application.

There's a nice comparison of asp.net view engines here on SO.

The good news is that you can use multiple view engines in parallel in ASP.NET MVC, though I wouldn't recommend it unless necessary.

There are some very nice extension points in the Razor engine already. For example, you can provide a custom view base class, a powerful concept that makes it easy to add a lot of functionality in the right place without having to mess with all the gritty details that you'd have to cope with otherwise.

I'd currently go for Razor.

Answer 2

The view engine is what's responsible for rendering your view, and converting your code into glorious HTML. As such, they are directly responsible for HOW you need to write code in your views.

There's basically two ones you need to care about: ASPX and Razor. Razor is, in my opinion, much sleeker and easier to use, at the cost of only being supported in MVC3.

For example, a code block in ASPX might look like this:

<% foreach(var item in Model) { %>     <tr>         <td><%: item.Name %></td>     </tr> <% } %> 

Whereas the Razor equivalent will look like this:

@foreach(var item in Model) {     <tr>         <td>@item.Name</td>     </tr> }