Main

1 static void Main(string[] args)2         {3             BasicConcept();4 5             QuerySyntax();6 7             QueryOperations();8             Console.ReadLine();9         }

1、Query Syntax、Method Syntax

1 private static void BasicConcept() 2         { 3             int[] numbers = { 5, 10, 8, 3, 6, 12 }; 4             //1、Query syntax 5             var numQuery1 = from num in numbers 6                             where num % 2 == 0 7                             orderby num 8                             select num; 9             foreach (var i in numQuery1)10             {11                 Console.Write(i + " ");12             }13             Console.WriteLine();14             //2、Method syntax15             var numQuery2 = numbers.Where(p => p % 2 == 0).OrderBy(p => p);16             foreach (var i in numQuery2)17             {18                 Console.Write(i + " ");19             }20         }

2、Query Syntax语法

1 private static void QuerySyntax() 2         { 3             //1、Data Source 4             int[] numbers = { 0, 1, 2, 3, 4, 5, 6 }; 5  6             //2、Query creation 7             var numQuery = from num in numbers 8                            where num % 2 == 0 9                            select num;10 11             //3、Query execution12             foreach (var num in numQuery)13             {14                 Console.Write("{0,1} ", num);15             }16         }

3、关键字group by、join、let、into

1 private static void QueryOperations() 2         { 3             List
      
        custorms = new List
       
        (); 4             custorms.Add(new Customer() { Name = "Jack", City = "Beijing" }); 5             custorms.Add(new Customer() { Name = "Joy", City = "Beijing" }); 6             custorms.Add(new Customer() { Name = "Tom", City = "Shanghai" }); 7  8             List
        
          employees = new List
         
          (); 9             employees.Add(new Employee() { Name = "Jack", ID = 101 });10             employees.Add(new Employee() { Name = "Jackson", ID = 102 });11 12             var query = from c in custorms13                         group c by c.City into cusGroup14                         where cusGroup.Count() >= 215                         select new { City = cusGroup.Key, Number = cusGroup.Count() };16 17             //foreach (var cg in query)18             //{19             //    Console.WriteLine(cg.Key);20             //    foreach (var c in cg)21             //    {22             //        Console.WriteLine(" {0}", c.Name);23             //    }24             //}25 26             foreach (var c in query)27             {28                 Console.WriteLine("{0} Count {1}", c.City, c.Number);29             }30 31             var queryJoin = from c in custorms32                             join e in employees on c.Name equals e.Name33                             select new { PersonName = c.Name, PersonID = e.ID, PersonCity = c.City };34 35             foreach (var p in queryJoin)36             {37                 Console.WriteLine("{0} {1} {2}", p.PersonName, p.PersonID, p.PersonCity);38             }39 40             string[] strings = { "Hello World", "This is Friday", "Are you happy?" };41             var stringQuery = from s in strings42                               let words = s.Split(' ')43                               from word in words44                               let w = word.ToUpper()45                               select w;46             foreach (var s in stringQuery)47             {48                 Console.Write(s + " ");49             }50         }51 class Customer52         {53             public string Name54             {55                 get;56                 set;57             }58             public string City59             {60                 get;61                 set;62             }63         }64 65         class Employee66         {67             public string Name { get; set; }68             public int ID { get; set; }69         }