asp.net mvc: how to create custom binding for models when using LINQ to Entities

Question

I've got a number of tables in my db that share common cols: modified by, modified date, etc. Not every table has these cols. We're using LINQ to Enties to generate the

I'd like to create a custom binder class that can handle the automatic binding of these fields. Is there a way to do this without having a custom binding class for each entity class?

Here's the code I have:

In global.asax.cs, Application_Start():

  ModelBinders.Binders.Add(typeof(Foo),new FooBinder());

Then in FooBinder.cs:

public override Object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
  var obj = (Foo)base.BindModel(controllerContext, bindingContext);
  var user = controllerContext.HttpContext.User.Identity;
  obj.modified_by = user.Name;
  obj.modified_date = DateTime.Now;
  return obj;
}

Is there a way to generalize this so it can handle multiple types?

Answer 1

We do this in the repository, not in the binder. We have an interface with the common fields (Modified on). We implement the interface in partial classes which we codegen for our entities using a T4 template.

Answer 2

You can use reflection to set fields by name, so that you can do foreach over property names. This is not a big deal since model binder uses reflection itself to get to the properties, anyway. Then you can just register binder for each of the "common" types - which is also OK to do using reflection, for example by checking that entity has all fields required present - so it works even if you add new such entities.

Just have your binder call default one and then update the fields.