Named Sections in Razor

10 Jun

This past week I had to build out a mostly-HTML site in MVC3. Since there wasn’t anything challenging on the backend, I decided to go all out and see how DRY I could make my view code in Razor, and to see if I ran into anything I couldn’t do that I was able to do with the WebForms view engine. The first thing that I ran into (that I didn’t know how to do) was to reproduce the same functionality as ContentPlaceHolder. Fortunately, Named Sections fit the bill perfectly.

Named Sections allow you to specify extra areas in your layout file by calling RenderSection(). These areas have a name (obviously) and can be marked as required or optional. In your view, you simply wrap the view code for a section inside Razor tags, like this:


<p>Page Content</p>

@section footer {
  <div>Footer content</div>

In a typical _Layout.cshtml file, you’ll have the basic HTML structure of your site and the Razor tag @RenderBody(). And in a View that uses this layout, you’ll have your page content in the root of the document. What I didn’t understand was that MVC is essentially treating @RenderBody() as @RenderSection(“body”) and wrapping the primary (un-nested) content of your View file in @section body { }. The idea was to make the 90% use-case scenario as easy as possible, and they definitely accomplished that goal.

But what about default content in a section? I don’t want to have to specify the same footer code on every single view in my site, just so I can override it on one page. The easy way is to call IsSectionDefined() in the layout to see if the view contains the section, but that requires wrapping a (potentially large) section of view code in an if statement.

However, it is possible to extend RenderSection to take a default content parameter. Fortunately Phil Haack (who knows a little bit about how MVC3 works) covered this in a blog about layout sections, so I don’t have to. Put simply, it’s possible to write an extension method that takes a Razor block of HTML. It’s a little convoluted, but in the right scenario it can work great.

For me, Named Sections have turned out to be incredibly useful, and will definitely save me plenty of time in the future.

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