Question

I am just getting into .NET MVC2 (.NET in general even) and I am having a hard time getting familiar with the “flow” of things. The MVC framework, I get.. for the most part. The part that I am getting tripped up on is applying standard programming practices to .NET MVC.

For example

public ActionResult Index()
{
   var dataContext = new SiteContentDataContext();
   var data = from c in dataContext.SiteContents where c.Slug == "home-page" select c;
   // call/return getMainNav()
   // call/return getSubNav()
   return View(data);
}

public ActionResult SiteContent(string strSlug)
{
   var dataContext = new SiteContentDataContext();
   var data = from c in dataContext.SiteContents where c.Slug == strSlug select c;
   // call/return getMainNav()
   // call/return getSubNav()
   return View(data);
}

private void getSubNav()
{
   // get subnav records from db.
   // return subnav records.
}

private void getMainNav()
{
   // get main nav records from db.
   // return main nav records.
}

The Index and SiteContent view are identical except for the fact that the Index view uses a different master page. Both views have a subnav and a main nav that will be dynamic content from a database.

The question, finally, is how would I go about populating the getSubNav and getMainNav functions and second, how would I return that data to the view properly?

Answer 1

Look into ViewModel objects, objects you create whose purpose in life is to carry data to and from your Views. The Models folder created for you by default in a new MVC project would hold exactly those classes.

You have options besides the ViewModel object methodology, but none are as clean. (The ViewData dictionary is around to help but it’s not intended to be the primary means of providing data to your views.) Here’s an example of how to set the Model property of the ViewData object to an instantiated, populated viewmodel instance:

    public ActionResult SiteContent(string strSlug) {
        SiteContentVM model = new SiteContentVM();
        SiteService siteService = new SiteService();
        model.Slug = siteService.GetALittleSlimyCreature(strSlug);
        model.List1 = siteService.GetList1();
        model.List2 = siteService.GetList2();
        ViewData.Model = model;
        return View();
    }

You can now create a strongly typed view (complete with intellisense) to reference any properties of your ViewModel object instance from within your view simply through the Model property:

<% foreach (var item in Model.List1) { %>
    <% Html.Encode(item.StringField) %> <!-- <= writing a property -->
    <% Html.RenderPartial("PartialNameHere", item); %> <!-- <= the equivalent of a usercontrol -->
<% } %>

As you see above the process of getting data from the database does not change for MVC. You do it just as you would in a normal webforms project. (…usually this involves instantiating a business logic or service class of some sort rather than actually writing the code in the MVC project.)

Enjoy MVC!