static void Main(string[] args)

{

List<Customer> custs = new List<Customer>();

custs.Add(new Customer() { ID = 1 });

custs.Add(new Customer() { ID = 5 });

custs.First(new Func<Customer, bool>(delegate(Customer x) { return x.ID == 5; }));

custs.First(new Func<Customer, bool>((Customer x) => x.ID == 5));

custs.First(delegate(Customer x) { return x.ID == 5; });

custs.First((Customer x) => x.ID == 5);

custs.First(x => x.ID == 5);

custs.First(Customer.Test);

List<Customer> newCusts = custs.Where(x => x.ID == 5).ToList();//找到集合中满足指定条件的元素

int sum = custs.Sum(x => x.ID);//计算和

List<Customer> ofType = custs.OfType<Customer>().ToList();//根据指定类型，筛选集合中的元素

List<int> select = custs.Select(x => x.ID + 1).ToList();//将集合中的每个元素投影的新集合中

List<string> selectMany = custs.SelectMany(x => new List<string>() { "id:", x.ID.ToString() }).ToList();//将序列的每个元素投影到一个序列中，最终把所有的序列合并

List<ulong> select= custs.ConvertAll(item => Convert.ToUInt64(item));

//LINQ

sum= custs.Where(x => x.ID != 10).Sum(x => x.ID);

sum = (from v in custs where v.ID != 1 select v).Sum(x => x.ID);

}

 

class Customer

{

public int ID { get; set; }

public static bool Test(Customer x)

{

return x.ID == 5;

}

}