有没有办法在c＃中获得两组对象之间的区别？

Question

我想在c＃中获得两组int之间的区别。给定s1和s2我想返回那些在s1而不在s2中的int。我可以做一些事情，比如：

    List<int> s1 = new List<int>();
    List<int> s2 = new List<int>();

    foreach (int i in s1)
    {
        if (s1.Contains(i))
        {
            //
        }
        else
        {
            //
        }
    }

但我想知道是否有人能指出更清洁的东西。我想做点什么

List<int> omitted = s1.Difference(s2);

不确定是否有任何人可能指出的现有方法或LINQ结构？谢谢。

Answer 1

我想你想要HashSet.Except。也就是说，使用HashSets，而不是使用Lists，然后操作可用。如果您所代表的内容实际上是一个“设置”，这是一个更好的类型。 （如果你已经有了一个列表，你可以创建一个'新的HashSet'。）

Answer 2

IEnumerable<T> a, b;

var added = a.Except(b);
var removed = b.Except(a);

Answer 3

List<int> s1 = new List<int>();
List<int> s2 = new List<int>();

return sl.FindAll( i => !s2.Contains(i) )

Answer 4

from x in s1
where ! s2.contains(x)
select x

Answer 5

当你需要找到两个IEnumerable之间的无序差异时，这两个扩展方法可能很方便（它与leppie包装器给扩展方法给出的答案大致相同）：

public class EnumerableDifferences<T>
{
    public IEnumerable<T> Added { get; }
    public IEnumerable<T> Removed { get; }

    public EnumerableDifferences(IEnumerable<T> added, IEnumerable<T> removed)
    {
        Added = added;
        Removed = removed;
    }
}

public static class EnumerableExtensions
{
    public static HashSet<TSource> ToHashSet<TSource>(this IEnumerable<TSource> source, IEqualityComparer<TSource> comparer)
    {
        return new HashSet<TSource>(source, comparer);
    }

    public static IEnumerable<TSource> ExceptBy<TSource, TKey>(this IEnumerable<TSource> first, IEnumerable<TSource> second, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> keyComparer = null)
    {
        return first
            .ExceptBy(keySelector, second.Select(keySelector), keyComparer);
    }

    public static IEnumerable<TSource> ExceptBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEnumerable<TKey> keys, IEqualityComparer<TKey> keyComparer = null)
    {
        var secondKeys = keys.ToHashSet(keyComparer);

        foreach (var firstItem in source)
        {
            var firstItemKey = keySelector(firstItem);

            if (!secondKeys.Contains(firstItemKey))
            {
                yield return firstItem;
            }
        }
    }

    public static EnumerableDifferences<TSource> DifferencesBy<TSource, TKey>(this IEnumerable<TSource> first, IEnumerable<TSource> second, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> keyComparer = null)
    {
        keyComparer = keyComparer ?? EqualityComparer<TKey>.Default;

        var removed = first.ExceptBy(second, keySelector, keyComparer);
        var added = second.ExceptBy(first, keySelector, keyComparer);

        var result = new EnumerableDifferences<TSource>(added, removed);

        return result;
    }

    public static EnumerableDifferences<TSource> Differences<TSource>(this IEnumerable<TSource> first, IEnumerable<TSource> second, IEqualityComparer<TSource> comparer = null)
    {
        return first
            .DifferencesBy(second, x => x, comparer);
    }
}

public static class Program
{
    public static void Main(params string[] args)
    {
        var l1 = new[] { 'a', 'b', 'c' };
        var l2 = new[] { 'a', 'd', 'c' };

        var result = l1.Differences(l2);

        Console.ReadKey();
    }
}

Answer 6

另一个有用的API，获得对称差异：

HashSet.SymmetricExceptWith()