[c#] How to convert List<string> to List<int>?

My question is part of this problem:

I recieve a collection of id's from a form. I need to get the keys, convert them to integers and select the matching records from the DB.

[HttpPost]
public ActionResult Report(FormCollection collection)
{
    var listofIDs = collection.AllKeys.ToList();  
    // List<string> to List<int>
    List<Dinner> dinners = new List<Dinner>();
    dinners= repository.GetDinners(listofIDs);
    return View(dinners);
}