Sum with object property : Sum « LINQ « C# / CSharp Tutorial

1. C# / CSharp Tutorial
2. LINQ
3. Sum

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 EmployeeOptionEntry {
    public int id;
    public long optionsCount;
    public DateTime dateAwarded;

    public static EmployeeOptionEntry[] GetEmployeeOptionEntries() {
        EmployeeOptionEntry[] empOptions = new EmployeeOptionEntry[] {
        new EmployeeOptionEntry { 
          id = 1, 
          optionsCount = 2, 
          dateAwarded = DateTime.Parse("1999/12/31") },
        new EmployeeOptionEntry { 
          id = 101, 
          optionsCount = 2, 
          dateAwarded = DateTime.Parse("1998/12/31") }
      };
        return (empOptions);
    }
}
public class MainClass {
    public static void Main() {
        IEnumerable<EmployeeOptionEntry> options = EmployeeOptionEntry.GetEmployeeOptionEntries();
        long optionsSum = options.Sum(o => o.optionsCount);
        Console.WriteLine("The sum of the employee options is: {0}", optionsSum);
    }
}