C#中比较两个List是否相等的常见方法

var list1 = new List<int> { 1, 2, 3 };
var list2 = new List<int> { 1, 2, 3 };

bool areEqual = list1.SequenceEqual(list2); // ✅ true

var list1 = new List<int> { 1, 2, 3 };
var list2 = new List<int> { 3, 2, 1 };

bool areEqual = list1.OrderBy(x => x).SequenceEqual(list2.OrderBy(x => x)); // ✅ true

list3.Sort();
list4.Sort();
Console.WriteLine(list3.SequenceEqual(list4)); // 输出: True

public class Person
{
    public string Name { get; set; }
    public int Age { get; set; }

    public override bool Equals(object? obj)
    {
        if (obj is Person person)
        {
            return Name == person.Name && Age == person.Age;
        }
        return false;
    }

    public override int GetHashCode()
    {
        return HashCode.Combine(Name, Age);
    }
}

Console.WriteLine(person1.SequenceEqual(person2)); // 输出: True

public class Person
{
    public string Name { get; set; }
    public int Age { get; set; }
}

public class PersonComparer : IEqualityComparer<Person>
{
    public bool Equals(Person? x, Person? y)
    {
        return x?.Name == y?.Name && x?.Age == y?.Age;
    }

    public int GetHashCode(Person obj)
    {
        return HashCode.Combine(obj.Name, obj.Age);
        // 还有一种写法：
        // return obj.Name.GetHashCode() ^ obj.Age.GetHashCode();
    }
}

var list1 = new List<Person>
{
    new Person { Name = "Alice", Age = 25 },
    new Person { Name = "Bob", Age = 30 }
};

var list2 = new List<Person>
{
    new Person { Name = "Alice", Age = 25 },
    new Person { Name = "Bob", Age = 30 }
};

bool areEqual = list1.SequenceEqual(list2, new PersonComparer()); // ✅ true

bool setEqual = list1.Count == list2.Count &&
                !list1.Except(list2).Any() &&
                !list2.Except(list1).Any();

bool areEqual = new HashSet<int>(list1).SetEquals(list2);

HashSet<int> set1 = new HashSet<int>(list3);
HashSet<int> set2 = new HashSet<int>(list4);

bool isEqual = set1.SetEquals(set2);
Console.WriteLine(isEqual); // 输出: True

List<int>? list5 = null;
List<int>? list6 = null;
Console.WriteLine(list5 == list6); // 输出: True

List<string?> list7 = new List<string?> { "a", null };
List<string?> list8 = new List<string?> { "a", null };
Console.WriteLine(list7.SequenceEqual(list8)); // 输出: True