/// <summary>
/// Retrieve an unused ActiveKey for this Login.
/// </summary>
private static ActiveKey RetrieveUnusedKey(CSSDataContext db, Login login)
{
var random = new Random();
var earliest = DateTime.Now.AddHours(-ActiveKey.PreferredMinLifetime);
var availableKeys = db.AvailableKey(login.Id)
.Where(p => p.DateCreated > earliest && p.IsValid == true);
var length = availableKeys.Count();
if (length == 0)
{
return(null);
}
//Find a key (at random) which this Login has not already used.
var index = random.Next(0, length - 1);
var keyresult = availableKeys.Skip(index).Take(1).FirstOrDefault();
return(db.ActiveKeys.FirstOrDefault(p => p.Id == keyresult.Id));
}