using System; using System.Linq; using System.Collections; using System.Collections.Generic; public class Employee { public int id; public string firstName; public string lastName; public static ArrayList GetEmployeesArrayList() { ArrayList al = new ArrayList(); al.Add(new Employee { id = 1, firstName = "J", lastName = "R" }); al.Add(new Employee { id = 2, firstName = "W", lastName = "G" }); al.Add(new Employee { id = 3, firstName = "A", lastName = "H" }); al.Add(new Employee { id = 4, firstName = "D", lastName = "L" }); al.Add(new Employee { id = 101, firstName = "K", lastName = "F" }); return (al); } public static Employee[] GetEmployeesArray() { return ((Employee[])GetEmployeesArrayList().ToArray(typeof(Employee))); } } public class MainClass { public static void Main() { Employee emp = Employee.GetEmployeesArray().ElementAtOrDefault(3); Console.WriteLine(emp == null ? "NULL" :string.Format("{0} {1}", emp.firstName, emp.lastName)); } }
ElementAtOrDefault Operator with an Invalid Index
using System; using System.Linq; using System.Collections; using System.Collections.Generic; public class Employee { public int id; public string firstName; public string lastName; public static ArrayList GetEmployeesArrayList() { ArrayList al = new ArrayList(); al.Add(new Employee { id = 1, firstName = "J", lastName = "R" }); al.Add(new Employee { id = 2, firstName = "W", lastName = "G" }); al.Add(new Employee { id = 3, firstName = "A", lastName = "H" }); al.Add(new Employee { id = 4, firstName = "D", lastName = "L" }); al.Add(new Employee { id = 101, firstName = "K", lastName = "F" }); return (al); } public static Employee[] GetEmployeesArray() { return ((Employee[])GetEmployeesArrayList().ToArray(typeof(Employee))); } } public class MainClass { public static void Main() { Employee emp = Employee.GetEmployeesArray().ElementAtOrDefault(5); Console.WriteLine(emp == null ? "NULL" : string.Format("{0} {1}", emp.firstName, emp.lastName)); } }
Return an Empty Sequence of Strings
using System; using System.Linq; using System.Collections; using System.Collections.Generic; public class MainClass { public static void Main() { IEnumerable<string> strings = Enumerable.Empty<string>(); foreach (string s in strings) Console.WriteLine(s); Console.WriteLine(strings.Count()); } }
Use Generation Operators: Range
using System; using System.Collections.Generic; using System.Linq; using System.Text; public class MainClass { public static void Main() { var numbers = from n in Enumerable.Range(100, 50) select new { Number = n, OddEven = n % 2 == 1 ? "odd" : "even" }; foreach (var n in numbers) { Console.WriteLine("The number {0} is {1}.", n.Number, n.OddEven); } } }
use ElementAt
using System; using System.Collections; using System.Collections.Generic; using System.Text; using System.Linq; public class MainClass{ public static void Main(){ int[] numbers = {1, 2, 3, 4, 5, 6, 7, 8, 9}; var query = numbers.ElementAt(4); Console.Write(query); } }
The element operators extract one element from the input sequence
//First, Last, Single, and ElementAt using System; using System.Collections.Generic; using System.Linq; public class MainClass { public static void Main() { int[] numbers = { 10, 9, 8, 7, 6 }; int firstNumber = numbers.First(); int lastNumber = numbers.Last(); int secondNumber = numbers.ElementAt(1); int lowestNumber = numbers.OrderBy(n => n).First(); } }
Calling the ElementAt Operator
using System; using System.Linq; using System.Collections; using System.Collections.Generic; public class Employee { public int id; public string firstName; public string lastName; public static ArrayList GetEmployeesArrayList() { ArrayList al = new ArrayList(); al.Add(new Employee { id = 1, firstName = "J", lastName = "R" }); al.Add(new Employee { id = 2, firstName = "W", lastName = "G" }); al.Add(new Employee { id = 3, firstName = "A", lastName = "H" }); al.Add(new Employee { id = 4, firstName = "D", lastName = "L" }); al.Add(new Employee { id = 101, firstName = "K", lastName = "F" }); return (al); } public static Employee[] GetEmployeesArray() { return ((Employee[])GetEmployeesArrayList().ToArray(typeof(Employee))); } } public class MainClass { public static void Main() { Employee emp = Employee.GetEmployeesArray().ElementAt(3); Console.WriteLine("{0} {1}", emp.firstName, emp.lastName); } }