Csharp/C Sharp/LINQ/GroupJoin

GroupJoin 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());
   }

} 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() {
       Employee[] employees = Employee.GetEmployeesArray();
       EmployeeOptionEntry[] empOptions = EmployeeOptionEntry.GetEmployeeOptionEntries();
       var employeeOptions = employees
         .GroupJoin(
           empOptions,
            e => e.id,
            o => o.id,
            (e, os) => new {
                id = e.id,
                name = string.Format("{0} {1}", e.firstName, e.lastName),
                options = os.Sum(o => o.optionsCount)
            });
       foreach (var item in employeeOptions)
           Console.WriteLine(item);
   }

}

</source>