1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4
5 namespace Linq101
6 {
7 class Element
8 {
9 /// <summary>
10 /// This sample uses First to return the first matching element as a Product, instead of as a sequence containing a Product.
11 /// </summary>
12 public void Linq58()
13 {
14 List<Data.Product> products = Data.GetProductList();
15
16 Data.Product product12 = (from p in products
17 where p.ProductID == 12
18 select p).First();
19
20 ObjectDumper.Write(product12);
21 }
22
23 /// <summary>
24 /// This sample uses First to find the first element in the array that starts with 'o'.
25 /// </summary>
26 public void Linq59()
27 {
28 string[] strings = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };
29
30 string startsWithO = strings.First(s => s[0] == 'o');
31
32 Console.WriteLine("A string starting with 'o': {0}", startsWithO);
33 }
34
35 /// <summary>
36 /// This sample uses FirstOrDefault to try to return the first element of the sequence, unless there are no elements, in which case the default value for that type is returned.
37 /// </summary>
38 public void Linq60()
39 {
40 int[] numbers = { };
41
42 int firstNumOrDefault = numbers.FirstOrDefault();
43
44 Console.WriteLine(firstNumOrDefault);
45 }
46
47 /// <summary>
48 /// This sample uses FirstOrDefault to return the first product whose ProductID is 789 as a single Product object, unless there is no match, in which case null is returned.
49 /// </summary>
50 public void Linq61()
51 {
52 List<Data.Product> products = Data.GetProductList();
53
54 Data.Product product789 = products.FirstOrDefault(p => p.ProductID == 789);
55
56 Console.WriteLine("Product 789 exists: {0}", product789 != null);
57 }
58
59 /// <summary>
60 /// This sample uses ElementAt to retrieve the second number greater than 5 from an array.
61 /// </summary>
62 public void Linq62()
63 {
64 int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
65
66 int number = (from n in numbers
67 where n > 5
68 select n).ElementAt(1);
69
70 Console.WriteLine("Second number > 5: {0}", number);
71 }
72 }
73 }
