private static List<t> RemoveDoubleItems</t><t>(List</t><t> list)
{
    List</t><t> newList = new List</t><t>();
    Dictionary</t><t , string> keyList = new Dictionary</t><t , string>();
 
    foreach (T item in list)
    {
        if (!keyList.ContainsKey(item))
        {
            keyList.Add(item, string.Empty);
            newList.Add(item);
        }
    }
 
    return newList;
}</t>