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().Where(e => e.id == 5).SingleOrDefault(); Console.WriteLine(emp == null ? "NULL" : string.Format("{0} {1}", emp.firstName, emp.lastName)); } }
Author: coder
SingleOrDefault after where clause
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().Where(e => e.id == 4).SingleOrDefault(); Console.WriteLine(emp == null ? "NULL" : string.Format("{0} {1}", emp.firstName, emp.lastName)); } }
SingleOrDefault with object property reference
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().SingleOrDefault(e => e.id == 4); Console.WriteLine(emp == null ? "NULL" : string.Format("{0} {1}", emp.firstName, emp.lastName)); } }
LastOrDefault: Where an Element Is Not Found
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().LastOrDefault(e => e.id == 5); Console.WriteLine(emp == null ? "NULL" : string.Format("{0} {1}", emp.firstName, emp.lastName)); } }
Use SingleOrDefault
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.SingleOrDefault(n => n > 9); Console.Write(query); } }
Single with condition
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().Single(e => e.id == 3); Console.WriteLine("{0} {1}", emp.firstName, emp.lastName); } }
SequenceEqual Operator with string array
using System; using System.Linq; using System.Collections; using System.Collections.Generic; public class MyStringifiedNumberComparer : IEqualityComparer<string> { public bool Equals(string x, string y) { return (Int32.Parse(x) == Int32.Parse(y)); } public int GetHashCode(string obj) { return Int32.Parse(obj).ToString().GetHashCode(); } } public class MainClass { public static void Main() { string[] stringifiedNums1 = { "101", "49", "017", "1080", "00027", "2" }; string[] stringifiedNums2 = {"1", "1049", "17", "080", "27", "02" }; bool eq = stringifiedNums1.SequenceEqual(stringifiedNums2,new MyStringifiedNumberComparer()); Console.WriteLine(eq); } }