Modelbinding database entities in ASPNET MVC

Question

I'm having trouble trying to think what the best way is to recreate a database object in a controller Action.

I want to make use of ModelBinders so in my action I have access to the object via a parameter, rather than having to repeat code to get an object from the database based on an identifier parameter. So I was thinking of having a ModelBinder that performs a call to the dataaccess layer to obtain the original object (or creates a new one if it doesn't exist in the database), then binds any properties to the database object to update it. However I've read that the ModelBinders shouldn't make database queries (first comment of this article).

If the ModelBinder shouldn't perform a database query (so just using the DefaultModelBinder) then what about database objects that have properties that are other db objects? These would never get assigned.

Saving an object after the user has edited it (1 or 2 properties are editable in the view) the ModelBinded object would be missing data, so saving it as it is would result in data in the database being overwritten with invalid values, or NOT-NULL constraints failing.

So, whats the best way to get an object in a controller action from the database bound with the form data posted back from the view?

Note im using NHibernate.

Answer 1

I get the model object from the database, then use UpdateModel (or TryUpdateModel) on the object to update values from the form parameters.

public ActionResult Update( int id )
{
     DataContext dc = new DataContext();
     MyModel model = dc.MyModels.Where( m => m.ID == id ).SingleOrDefault();

     string[] whitelist = new string[] { "Name", "Property1", "Property2" };

     if (!TryUpdateModel( model, whitelist )) {
        ... model error handling...
        return View("Edit");
     }

     ViewData.Model = model;

     return View("Show");
}