Anonymous delegates in C # and examples of lambda expressions

I. C # from 1.0 to 4.0, with the support of LINQ, Generics, the code is getting simpler and more elegant

1 int[] Nums = {5, 4, 1, 3, 9, 8, 6, 7, 2, 0}; 2             ienumerable<int> newnums = from n in nums where n > 0 select N; 3             newnums = newnums.where (New func<i Nt,int, bool> (delegate (int I,int index) {return i < Index;})); 4             newnums = Newnums.where (new func<int, int, bool> ((int i, int index) = = < index)); 5             newnums = Newnu Ms. Where (delegate (int i, int index) {return i < index;}); 6             newnums = Newnums.where ((i, index) = = < index), 7             foreach (var i in newnums) 8             {9                 Console.Write Line (i);             

Two. Collection operation, also suitable for EF database operation

1. Creation of two entity classes

1 Public     class Store 2     {3 public         string Id, 4 public         string Name, 5     } 6 public class person     7
  
   {8 Public         string name {get, set;} 9 public         int Age {get; set;} Ten public         string StoreId {get; set;} One     }
  

2. Inserting data

1             var Stores = new list<store> () 2             {3                 new store () {id= "1", name= "1 Class"}, 4                 new Store () {id= "2", name= "Class 2"} 5             }; 6  7             var Persons = new list<person> () 8             {9                 new person () {name= "P1", Age=1, storeid= "1"},10                 New Person () {name= ' P2 ', age=2, storeid= ' 1 '},11                 new Person () {name= ' P3 ', age=3, storeid= ' 1 '},12                 new person () { Name= "P4", Age=4, storeid= "2"},13                 new Person () {name= ' P5 ', age=5, storeid= ' 1 '},14                 new Person () {name= ' P6 ', Age=6, storeid= "2"},15                 new Person () {name= ' P7 ', age=7, storeid= ' 1 '},16                 new Person () {name= ' P8 ', age=8, Storeid= "1"}17             };

3. Check the number of people younger than 3 years of age 1 and 2 classes respectively

1             var plst = persons.where (o = o.age > 3). GroupBy (o = O.storeid). Select (g = new {StoreId = G.key, Count = G.count ()}). Join (Stores, S = = S.storeid, p = = p.id, (s, p) = = new {S.storeid, storeName = P.name, s.count}); 2             foreach ( var p in Plst) 3             {4                 Console.WriteLine (P.storename + "with" + P.count + "personal"); 5             }

4. Output

There are 2 people in Class 2 and 3 in Class 1.