Passing data to the master page

In this recipe, we are going to take a look at how to pass data down to the master page. While we could pass data from a normal ActionResult to the view via the ViewData dictionary and then have the MasterPage use that data, we won't as that creates a lot of redundant code spread out over multiple actions in the controller. We could alleviate some of this action code and move it up to the OnActionExecuted method in our controller. However, if our master page is shared across multiple controllers, then this too wouldn't be a good solution. For that reason, we will instead create a controller base class and use that for creating the data for our master page.

How to do it...

  1. The first step is to create a new MVC application.
  2. Next, we will create a controller base class called BaseController. In this base controller, we will initiate a list of data for navigational purposes.

    Models/BaseController.cs: 

    public class BaseController : Controller
{
public BaseController()
{
List<string> manufacturers = new List<string>();
manufacturers.Add("Ford");
manufacturers.Add("Toyota");
manufacturers.Add("Chevy");
manufacturers.Add("Dodge");
manufacturers.Add("Nissan");
manufacturers.Add("Mazda");
manufacturers.Add("Audi");
ViewData["manufacturers"] = manufacturers;
}
}
  3. Next, we will alter our HomeController to inherit from our new BaseController.

    Controllers/HomeController.cs: 

    public class HomeController : BaseController
  4. Now that our data is being created and passed down to every view that is created from this controller, we need to update our master page to take advantage of this data.

    Views/Shared/Site.Master: 

    ...
<div id="main">
<%string menu = "";
if (ViewData["manufacturers"] != null)
{
StringBuilder sbMenu = new StringBuilder();
List<string> manufacturers = ViewData["manufacturers"] as List<string>;
foreach (string item in manufacturers)
{
sbMenu.Append(item + " - ");
}
menu = sbMenu.ToString().Substring(0, sbMenu.ToString().Length - 3);
}
%>
<%: menu %>
...
</div>
...
  5. Now you can browse to your Index and About views and you should see a new listing of auto manufacturers, which represents a navigation menu, without links. If you browse to the login or registration views, which use the Account controller, the navigation menu will disappear.

How it works...

To achieve this, we have essentially injected data that is required by our master page into the controller pipeline by inserting a controller base class. As long as our controller inherits from the base class, the ViewData will contain the navigation data. This helps us to centralize such logic and can obviously be taken in many different directions.

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