測試

新建一個Person類

public class Person
    {
        public Person(string name,int id)
        {
            Name = name;
            Id = id;
        }
        public string Name { get; set; }
        public int Id { get; set; }

    }

初始化List中有一百萬條資料，然後分別通過每種方法判斷xiaoming是否在List中，程式碼如下

static void Main(string[] args)
        {
            List<Person> persons = new List<Person>();
            //初始化persons資料
            for (int i = 0; i < 1000000; i++)
            {
                Person person = new Person("My" + i,i);
                persons.Add(person);
            }
            Person xiaoming=new Person("My999999", 999999);
            
            //下面通過三種方法判斷persons中是否包含xiaoming
            Stopwatch watch = new Stopwatch();
            watch.Start();
            bool a = persons.Contains(xiaoming);
            watch.Stop();

            Stopwatch watch1 = new Stopwatch();
            watch1.Start();
            bool b = persons.Exists(x=>x.Id==xiaoming.Id);
            watch1.Stop();

            Stopwatch watch2 = new Stopwatch();
            watch2.Start();
            bool c = persons.Where(x=>x.Id==xiaoming.Id).Any();
            watch2.Stop();

            Stopwatch watch3 = new Stopwatch();
            watch3.Start();
            bool d = persons.Any(x => x.Id == xiaoming.Id);
            watch3.Stop();

            Console.WriteLine("Contains耗時：" + watch.Elapsed.TotalMilliseconds);
            Console.WriteLine("Exists耗時：" + watch1.Elapsed.TotalMilliseconds);
            Console.WriteLine("Where耗時：" + watch2.Elapsed.TotalMilliseconds);
            Console.WriteLine("Any耗時：" + watch3.Elapsed.TotalMilliseconds);
            Console.ReadLine();
        }
 

執行結果如下圖所示

結論

通過上圖可以看出效能排序為
Contains > Exists > Where > Any

注意：
Contains中不能帶查詢條件