Implement Equals for DropDownListFor with a non-primitive object

Question

I have an object Modem with the property Protocol which is bound to a DropDownListFor. The value of Modem in the DropDownList isn't selected.

public class Modem {

   public Protocol Protocol { get; set; }

}

public class Protocol {
    public string Name { get; set; }
    public string Value { get; set; }
}

My Controller code

var modem = new Modem{ Protocol = new Protocol { Name = "UDP", Value = "The udp protocol" } };
var protocols = new List<Protocol>{ new Protocol { Name = "TCP", Value = "The tcp protocol" }, new Protocol { Name = "UDP", Value = "The udp protocol" } };
ViewBag.Protocols = protocols.Select(p => new SelectListItem{ Value = p.Name, Text = p.Value });

return View(modem);

My View code

@Html.DropDownListFor(modem => modem.Protocol, (IEnumerable<SelectListItem>) ViewBag.Protocols)

If I manually set the selected protocol that doesn't work. So can I implement Equals like this (already tried doing this with Protocol, but it didn't work...)

public bool Equals(object obj){
    if(obj == null){
        return false;
    }
    var protocol = obj as Protocol;
    return protocol != null && protocol.Name == Name;
}

Update : I tried using

@Html.DropDownListFor(modem => modem.Protocol, new SelectList(ViewBag.Protocols, "Name", "Value", Model.Protocol))

But didn't work too :(.

Update 2 : Using reflector, I have found this line :

HashSet<string> set = new HashSet<string>(from value in enumerable.Cast<object>() select Convert.ToString(value, CultureInfo.CurrentCulture), StringComparer.OrdinalIgnoreCase);

So DropDownListFor uses the ToString method to do the set of the default value. With this ToString method, I could do what I wanted :

public override string ToString()
{
    return Name;
}

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