Update pattern for MVC + Dal

FooController.cs

[HttpPost]
[ValidateAntiForgeryToken]
public async Task<ActionResult> Edit(EditFooVm vm)
{
    if (!ModelState.IsValid)
    {
        SaveModelState();
        return RedirectToAction("Edit", new {id = vm.FooId});
    }

    if (!await _auth.CheckAccessAsync(User, vm.FooId, AccessFlags.Update))
    {
        return HttpNotFound(MessageFooNotFoundOrNotAuthorized);
    }

    await _versions.UpdateAsync(vm.FooId, w =>
    {
        w.Label = vm.Label;
        // ..and other properties exposed by FooDal.UpdateWhitelist
    });
    return RedirectToAction("Index");
}

FooDal.cs

public async Task UpdateAsync(Guid id, [NotNull] Action<UpdateWhitelist> update)
{
    if (update == null) throw new ArgumentNullException("update");

    Foo existing = await _db.Foos.FindAsync(id);
    if (existing == null)
        throw new NotFoundException("Foo not found. Id: " + id);

    update(new UpdateWhitelist(existing));
    existing.LastModified = DateTimeOffset.UtcNow;

    await _db.SaveChangesAsync();
}

FooDal.UpdateWhitelist.cs

// Nested type of FooDal, in a separate file using partial class
public class UpdateWhitelist
{
    private readonly Foo _existing;

    public UpdateWhitelist([NotNull] Foo existing)
    {
        if (existing == null) throw new ArgumentNullException("existing");
        _existing = existing;
    }

    public string Label
    {
        get { return _existing.Label; }
        set { _existing.Label = value; }
    }
    
    // .. other white listed properties
}