SelectFromList

public static List<T> SelectRandom<T>(List<T> SomeList, int Need)
{
    int NeedSelect = Need;

    if (NeedSelect > SomeList.Count) { return new List<T>(SomeList); }
    if (NeedSelect <= 0) { new List<T>(); }

    List<T> Result = new List<T>(NeedSelect);

    while (NeedSelect > 0)
    {
        // дроп листа
        Result.Clear();
        // восстановление числа выборок
        NeedSelect = Need;

        for (int i = 0; i < SomeList.Count; i++)
        {
            if (DropDice(NeedSelect, (SomeList.Count - Result.Count)))
            {
                NeedSelect--;
                Result.Add(SomeList[i]);

                if (NeedSelect == 0) break;
            }
        }
    }

    return Result;
}

public static List<T> SelectRandomExclude<T>(List<T> SomeList, int Need)
{
    int NeedExclude = SomeList.Count - Need;

    if (NeedExclude > SomeList.Count) { return new List<T>(); }
    if (NeedExclude <= 0) { return new List<T>(SomeList);  }

    // копирование
    List<T> Result = new List<T>(SomeList);

    while (NeedExclude > 0)
    {
        for (int i = Result.Count - 1; i >=0 ; i--)
        {
            if (DropDice(NeedExclude, Result.Count))
            {
                NeedExclude--;
                Result.RemoveAt(i);

                if (NeedExclude == 0) break;
            }
        }
    }

    return Result;
}

private static bool DropDice(int Need, int Avaiable)
{
    return (DevilEngine.Tools.RandomGlobal.SatanGlobalRandomGenerator.NextDouble() < ((float)Need / (float)Avaiable));
}