osu-lazer/osu.Game/Extensions/CollectionExtensions.cs

// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
// See the LICENCE file in the repository root for full licence text.

using System.Collections.Generic;

namespace osu.Game.Extensions
{
    public static class CollectionExtensions
    {
        public static void AddRange<T>(this ICollection<T> collection, IEnumerable<T> items)
        {
            // List<T> has a potentially more optimal path to adding a range.
            if (collection is List<T> list)
                list.AddRange(items);
            else
            {
                foreach (T obj in items)
                    collection.Add(obj);
            }
        }
    }
}