Two ways of generating the difference in between two lists

DiffGenerator.cs

using System.Collections.Generic;
using System.Linq;

namespace Other.Something.Core.Tasks
{
	public static class DiffGenerator
	{
		public static Diff<T> Generate<T>(IEnumerable<T> left, IEnumerable<T> right)
		{
			var added = right.Except(left);
			var removed = left.Except(right);

			var leftList = left;
			var common = right.Where(leftList.Contains);

			return new Diff<T>(added, removed, common);
		}

		public static IEnumerable<IEnumerable<T>> GenerateClassic<T>(IEnumerable<T> left, IEnumerable<T> right)
		{
			var oldList = new Queue<T>(left);
			var newList = new List<T>(right);

			var removed = new List<T>();
			var common = new List<T>();

			while (oldList.Count > 0)
			{
				var currentItem = oldList.Dequeue();

				if (newList.Contains(currentItem))
				{
					newList.Remove(currentItem);

					common.Add(currentItem);
				}
				else
				{
					removed.Add(currentItem);
				}
			}

			return new List<List<T>>()
			       	{
			       		common, newList, removed
			       	};

		}
	}

	public sealed class Diff<T>
	{
		public IEnumerable<T> Added { get; private set; }
		public IEnumerable<T> Removed { get; private set; }
		public IEnumerable<T> Common { get; private set; }

		internal Diff(IEnumerable<T> added, IEnumerable<T> removed, IEnumerable<T> common)
		{
			Added = added;
			Removed = removed;
			Common = common;
		}
	}

}