How can I create a generic view model in MVC?

Question

I would like to use a viewmodel in MVC instead of using viewbag. Is there a way that I could create some generic viewmodel that's shared between all my controllers and then use this in my views? What kind of code would I need for this? I was thinking to maybe create something in a base controller. Is that possible?

Answer 1

I believe the predominate method for passing data between controllers and views is to create a class that represents the data you want to pass to your view and pass that model variable to the view method.

/Models/Home/IndexViewModel.cs

namespace MyProject.Models.Home
{
  public class IndexViewModel
  {
    public string Message { get; set; }
  }
}

Controllers/HomeController.cs

public class HomeController
{
  public ActionResult Index()
  {
    IndexViewModel model = new IndexViewModel();
    model.Message = "Hello World!";
    View(model);
  }
}

/Views/Home/Index.cshtml (in Razor MVC3)

@Model MyProject.Models.Home.IndexViewModel //strongly-typed view

<h1>@model.Message</h1>

Let's take this simple example, and build towards your specific request. The easy way would be to allow every view simply use the MyClass model. However, this becomes very inflexible, so here is what I would do to keep the design flexible. I'm going to assume there is some data you want to pass to many views (some or all).

Create class that represents the data you want to pass to multiple views:

/Models/SharedData.cs

namespace MyProject.Models
{
  public class SharedData
  {
    public DateTime Birthday { get; set; }
  }
}

Create an interface for models to require a SharedData class.

/Models/ISharedDataViewModel.cs

namespace MyProject.Models
{
  public interface ISharedDataViewModel
  {
    public SharedData Data { get; set; }
  }
}

Update the Home IndexViewModel to use the interface and shareddata

/Models/Home/IndexViewModel.cshtml

namespace MyProject.Models.Home
{
  public class IndexViewModel: ISharedDataViweModel
  {
    public string Message { get; set; }
    public ShardedData Data { get; set; }
  }
}

Create a Partial view that knows how to display shared data

/Views/Shared/SharedDataView.cs (in Razor MVC3)

@Model MyProject.Models.ISharedDataViewModel //strongly-typed partial view

@if (model != null && model.Data != null)
{
<h3>@model.Data.Birthday.ToString()</h3>
}

Update the Home Index page to call the Partial view

/Views/Home/Index.cshtml (in Razor MVC3)

@Model MyProject.Models.Home.IndexViewModel //strongly-typed view

<h1>@model.Message</h1>

@Html.Partial("SharedDataView", model) 

Now any page can call for the partial view if the pages model implements ISharedDataViewModel.