C# List＜T＞的Contains, Exists, Any，Where性能对比

测试

新建一个Person类

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中有一百万条数据，然后分别通过每种方法判断xiaoming是否在List中，代码如下

static void Main(string[] args)         {             List<Person> persons = new List<Person>();             //初始化persons数据             for (int i = 0; i < 1000000; i++)             {                 Person person = new Person("My" + i,i);                 persons.Add(person);             }             Person xiaoming=new Person("My999999", 999999);                          //下面通过三种方法判断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耗时：" + watch.Elapsed.TotalMilliseconds);             Console.WriteLine("Exists耗时：" + watch1.Elapsed.TotalMilliseconds);             Console.WriteLine("Where耗时：" + watch2.Elapsed.TotalMilliseconds);             Console.WriteLine("Any耗时：" + watch3.Elapsed.TotalMilliseconds);             Console.ReadLine();         } 

执行结果如下图所示

结论

通过上图可以看出性能排序为
Contains > Exists > Where > Any

注意：
Contains中不能带查询条件