Custom modelbinder results in new database insert

Question

I've got this issue in ASP.NET MVC model binding. I have an address object with a country child object. However - I'm using auto-complete for the country name. So in my view I've got something like this:

@Html.EditorFor(model => model.Country)

And I wrote a custom binder here:

    public class CountryBinder : IModelBinder
{
    public CountryBinder(DataContext db)
    {
        this.Db = db;
    }

    protected DataContext Db { get; set; }

    public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        var countryName = controllerContext.HttpContext.Request[bindingContext.ModelName];
        var result = Db.Countries.SingleOrDefault(
            country => country.EnglishShortName.Equals(countryName) | country.Translation_NL.Equals(countryName));
        return result;
    }
}

The data context is injected like this:

kernel.Bind<IDBContext>().To<DataContext>().InRequestScope();

Controller looks like this:

        var model = this.participationRepository.Single(p => p.Id == participation.Id);
        if (!participation.IsCancelled)
        {
            this.TryUpdateModel(model);

etc...

Every time I save - a new Country is created, with the exact specs of the country that we found in the binder, but with new id. Any clues?