Question

Is there any built-in Ordered Collection which support Move-Up and Move-Down of items ?

i wanna have Ordered Collection(could be List) where i can be sure that when i insert items it will be

inserted at the end of the Collection, then i want to be able to do something like this

Col.MoveUp(Item1);//Takes Item1 and move its index one step up.
                  //if its index is 3 it will be 2 and item on index 2 will be 3
Col.MoveDown(item2);

Answer 1

It is very easy to build up your own. Here I made them as extension methods. Another option is to define your own collection, inherit it from List and insert these methods there.

public static class ListExtensions
{
    public static void MoveUp<T>(this List<T> list, T item)
    {
        int index = list.IndexOf(item);

        if (index == -1)
        {
            // item is not in the list
            throw new ArgumentOutOfRangeException("item");
        }

        if (index == 0)
        {
            // item is on top
            return;
        }

        list.Swap(index, index - 1);
    }

    public static void MoveDown<T>(this List<T> list, T item)
    {
        int index = list.IndexOf(item);

        if (index == -1)
        {
            // item is not in the list
            throw new ArgumentOutOfRangeException("item");
        }

        if (index == list.Count - 1)
        {
            // item is no bottom
            return;
        }

        list.Swap(index, index + 1);
    }

    private static void Swap<T>(this List<T> list, int i1, int i2)
    {
        T temp = list[i1];
        list[i1] = list[i2];
        list[i2] = temp;
    }
}