检查两个列表是否相等 [英] Check if two lists are equal

问题描述

我有一个类如下:

public class Tag {
    public Int32 Id { get; set; }
    public String Name { get; set; }
}

我有两个标签列表:

List<Tag> tags1;
List<Tag> tags2;

我使用 LINQ 的选择来获取每个标签列表的 Id.然后:

I used LINQ's select to get the Ids of each tags list. And then:

List<Int32> ids1 = new List<Int32> { 1, 2, 3, 4 };
List<Int32> ids2 = new List<Int32> { 1, 2, 3, 4 };
List<Int32> ids3 = new List<Int32> { 2, 1, 3, 4 };
List<Int32> ids4 = new List<Int32> { 1, 2, 3, 5 };
List<Int32> ids5 = new List<Int32> { 1, 1, 3, 4 };

ids1 应该等于 ids2 和 ids3 ... 两者具有相同的数字.

ids1 should be equal to ids2 and ids3 ... Both have the same numbers.

ids1 不应等于 ids4 和 ids5 ...

ids1 should not be equal to ids4 and to ids5 ...

我尝试了以下方法:

var a = ints1.Equals(ints2);
var b = ints1.Equals(ints3);

但两者都给我错误.

检查标签列表是否相等的最快方法是什么?

What is the fastest way to check if the lists of tags are equal?

更新

我正在寻找标签与书籍中的标签完全相同的帖子.

I am looking for POSTS which TAGS are exactly the same as the TAGS in a BOOK.

IRepository repository = new Repository(new Context());

IList<Tags> tags = new List<Tag> { new Tag { Id = 1 }, new Tag { Id = 2 } };

Book book = new Book { Tags = new List<Tag> { new Tag { Id = 1 }, new Tag { Id = 2 } } };

var posts = repository
  .Include<Post>(x => x.Tags)
  .Where(x => new HashSet<Int32>(tags.Select(y => y.Id)).SetEquals(book.Tags.Select(y => y.Id)))
  .ToList();

我正在使用 实体框架，但出现错误:

I am using Entity Framework and I get the error:

mscorlib.dll 中出现类型为System.NotSupportedException"的异常，但未在用户代码中处理

An exception of type 'System.NotSupportedException' occurred in mscorlib.dll but was not handled in user code

附加信息:LINQ to Entities 无法识别方法 'Boolean SetEquals(System.Collections.Generic.IEnumerable`1[System.Int32])' 方法，并且该方法无法转换为存储表达式.

Additional information: LINQ to Entities does not recognize the method 'Boolean SetEquals(System.Collections.Generic.IEnumerable`1[System.Int32])' method, and this method cannot be translated into a store expression.

我该如何解决这个问题?

How do I solve this?

推荐答案

使用 SequenceEqual 检查序列是否相等，因为 Equals 方法检查引用相等.

var a = ints1.SequenceEqual(ints2);

或者，如果您不关心元素顺序，请使用 Enumerable.All 方法:

Or if you don't care about elements order use Enumerable.All method:

var a = ints1.All(ints2.Contains);

第二个版本还需要对 Count 进行另一次检查，因为即使 ints2 包含的元素多于 ints1，它也会返回 true.所以更正确的版本应该是这样的:

The second version also requires another check for Count because it would return true even if ints2 contains more elements than ints1. So the more correct version would be something like this:

var a = ints1.All(ints2.Contains) && ints1.Count == ints2.Count;

为了检查不等式只需反转All方法的结果:

In order to check inequality just reverse the result of All method:

var a = !ints1.All(ints2.Contains)

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