Csharp/C Sharp/LINQ/ElementAt — различия между версиями
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Текущая версия на 14:38, 26 мая 2010
Содержание
Calling the ElementAt Operator
<source lang="csharp"> 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); }
}
</source>
The element operators extract one element from the input sequence
<source lang="csharp"> //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(); }
}
</source>
use ElementAt
<source lang="csharp"> 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); }
}
</source>
Use ElementAt to print the fourth number less that 5 in an integer array
<source lang="csharp"> using System; using System.Collections.Generic; using System.Linq; using System.Text; public class MainClass {
public static void Main() { int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 }; int fourthLowNum = ( from n in numbers where n < 5 select n) .ElementAt(3); // 3 because sequences use 0-based indexing Console.WriteLine("Fourth number < 5: {0}", fourthLowNum); }
}
</source>