高效的LINQ語句有哪些

小編給大家分享一下高效的LINQ語句有哪些，相信大部分人都還不怎么了解，因此分享這篇文章給大家參考一下，希望大家閱讀完這篇文章后大有收獲，下面讓我們一起去了解一下吧！

Model層的類如下:

public class Order
    {
        public int Id { get; set; }
        public decimal Amount { get; set; }
        public string CustomerName { get; set; }
        public string Status { get; set; }
    }

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

Program.cs代碼如下:

 class Program
    {
        //AutoResetEvent 允許線程通過發信號互相通信。通常，此通信涉及線程需要獨占訪問的資源。
        //線程通過調用 AutoResetEvent 上的 WaitOne 來等待信號。如果 AutoResetEvent 處于非終止狀態，則該線程阻塞，并等待當前控制資源的線程,通過調用 Set 發出資源可用的信號。
        //調用 Set 向 AutoResetEvent 發信號以釋放等待線程。AutoResetEvent 將保持終止狀態，直到一個正在等待的線程被釋放，然后自動返回非終止狀態。如果沒有任何線程在等待，則狀態將無限期地保持為終止狀態。
        //可以通過將一個布爾值傳遞給構造函數來控制 AutoResetEvent 的初始狀態，如果初始狀態為終止狀態，則為 true；否則為 false。

        //通俗的來講只有等myResetEven.Set()成功運行后,myResetEven.WaitOne()才能夠獲得運行機會;Set是發信號，WaitOne是等待信號，只有發了信號，等待的才會執行。如果不發的話，WaitOne后面的程序就永遠不會執行。
        private static AutoResetEvent autoSet = new AutoResetEvent(false);


        private static List<Person> list = new List<Person>()
        {
            new Person() {Name = "Rose", Age = 19},
            new Person() {Name = "Steve", Age = 45},
            new Person() {Name = "Jessica", Age = 20},
        };


        private static void Main(string[] args)
        {
            //CheckOrders();
            //Common();
            //RemoveFromList();
            //ExceptionHandling();
            //-----------------------------------------------------------------
            //--------------------------------模擬非線程安全----------------------------

            Thread t1 = new Thread(() =>
            {
                //確保等待t2開始之后才運行下面的代碼
                autoSet.WaitOne();
                foreach (var item in list)
                {
                    Console.WriteLine("t1:" + item.Name);
                    Thread.Sleep(1000);
                }
            });
            t1.Start();
            Thread t2 = new Thread(() =>
            {
                //通知t1可以執行代碼
                autoSet.Set();
                //沉睡1秒是為了確保刪除操作在t1的迭代過程中
                Thread.Sleep(1000);
                list.RemoveAt(2);
            });
            t2.Start();

            Console.ReadKey();
        }

        public static void CheckOrders()
        {
            List<Order> orders = new List<Order>()
            {
                new Order { Id = 123, Amount = 29.95m, CustomerName = "Mark", Status = "Delivered" },
                new Order { Id = 456, Amount = 45.00m, CustomerName = "Steph", Status = "Refunded" },
                new Order { Id = 768, Amount = 32.50m, CustomerName = "Claire", Status = "Delivered" },
            };

            bool anyRefunded = orders.Any(o => o.Status == "Refunded");
            if (anyRefunded)
            {
                Console.WriteLine("There are refunded orders");
            }
            else
            {
                Console.WriteLine("No refunds");
            }

            bool allDelivered = orders.All(o => o.Status == "Delivered");
            if (allDelivered)
            {
                Console.WriteLine("Everything was delivered");
            }
            else
            {
                Console.WriteLine("Not everything was delivered");
            }
        }

        public static void Common()
        {
            //距離圣誕節的天數
            var daysToChristmas = (new DateTime(DateTime.Today.Year, 12, 25) - DateTime.Today).TotalDays;
            Console.WriteLine(daysToChristmas);

            //-----------------------------------------------------------------
            int SUM = "10,5,0,8,10,1,4,0,10,1"
                .Split(',')
                .Select(int.Parse)
                .OrderBy(n => n)
                .Skip(3)
                .Sum();
            Console.WriteLine(SUM);
            //-----------------------------------------------------------------
            var customers = new[] {
                new { Name = "Annie", Email = "annie@test.com" },
                new { Name = "Ben", Email = "" },
                new { Name = "Lily", Email = "lily@test.com" },
                new { Name = "Joel", Email = "joel@test.com" },
                new { Name = "Sam", Email = "" },
            };
            foreach (var customer in
                from c in customers
                where !String.IsNullOrEmpty(c.Email)
                select c)
            {
                Console.WriteLine("Sending email to {0}", customer.Name);
            }
            //效果同上
            foreach (var customer in customers.Where(c => !String.IsNullOrEmpty(c.Email)))
            {
                Console.WriteLine("Sending email to {0}", customer.Name);
            }
        }

        public static void RemoveFromList()
        {
            Func<List<string>> makeList = () => Enumerable.Range(1, 10000000).Select(n => ("Item " + n + "")).ToList();
            var itemsToRemove = new[] { "Item 0", "Item 1", "Item 50", "Item 1000", "Item 999999", "Item 9999999" };
            var stopwatch = new Stopwatch();
            var list = makeList();

            stopwatch.Start();
            foreach (var item in itemsToRemove)
            {
                list.Remove(item);
            }
            stopwatch.Stop();

            Console.WriteLine(list.Count + "Foreach took {0}ms", stopwatch.ElapsedMilliseconds);

            list = makeList();


            stopwatch.Restart();
            var newList = list.Except(itemsToRemove).ToList(); //效率極低
            stopwatch.Stop();

            Console.WriteLine(newList.Count + "Except took {0}ms", stopwatch.ElapsedMilliseconds);
        }


        public static void ExceptionHandling()
        {
            var numbers = Enumerable.Range(1, 10)
                    .Select(n => 5 - n)
                    .Select(n =>
                    {
                        try
                        {
                            return 10 / n;
                        }
                        catch (Exception e)
                        {
                            Console.WriteLine("Error in lambda: " + e.Message);
                            return -1;
                        }
                    });

            foreach (var n in numbers)
            {
                Console.WriteLine(n);
            }
        }

    }

以上是“高效的LINQ語句有哪些”這篇文章的所有內容，感謝各位的閱讀！相信大家都有了一定的了解，希望分享的內容對大家有所幫助，如果還想學習更多知識，歡迎關注億速云行業資訊頻道！