C# Simple Example of IComparable Part-2

Definition of IComparable: IComparable compares the current instance with another object of the same type and returns an integer that indicates whether the current instance precedes, follows, or occurs in the same position in the sort order as the other object.

Example: The following code defines Employee class which implements IComparable. The CompareTo(Object? obj) method compares current this employee object with the employee object passed as argument to CompareTo method.

// Employee has Bonus
class Bonus
{
    public Bonus(int amount)
    {
        Amount = amount;
    }
    public int Amount { get; set; }
}
internal class Employee : IComparable
{
    private int _Age;
    // initialize data using CTOR
    public Employee(int id, string name, int age, int bonus)
    {
        Id = id;
        Name = name;
        Age = age;
        Bonus = new Bonus(bonus); // reference type
    }

    // to get data, we need properties
    public Bonus Bonus { get; set; }
    public int Id { get; } // read-only, Id cannot be updated
    public string? Name { get; set; }  // read-write, name can be updated
    public int Age // read-write, age can be updated
    {
        get { return _Age; }
        set
        {
            if (value < 18)
            {
                throw new ArgumentException("Age must be above 18");
            }
            else
            {
                _Age = value;
            }
        }
    }

    public int CompareTo(object? obj)
    {
        if (obj is Employee emp)
        {
            if (this.Age > emp.Age)
            {
                return 1;
            }
            else if (this.Age < emp.Age)
            {
                return -1;
            }
            else
            {
                return 0;
            }
        }
        else
        {
            throw new Exception("Invalid Data");
        }
    }

}

Code inside Main method: Five employee objects are elements of employees array. This array is passed to Array.Sort<T>(T[] array) static method. The Sort method sorts the elements in an entire System.Array using the System.IComparable. 

// employees data
Employee[] employees = new Employee[5];
employees[0] = new Employee(1001,"Bhim",35,4000);
employees[1] = new Employee(1002,"Ajay",25,3500);
employees[2] = new Employee(1003,"Vijay",43,4200);
employees[3] = new Employee(1004,"Rakesh",27,3200);
employees[4] = new Employee(1005,"Mohan",22,3100);
Console.WriteLine("original array ==>");
foreach (var emp in employees)
{
    Console.WriteLine($"Id {emp.Id}, Name {emp.Name}, Age {emp.Age}");
}
Array.Sort(employees); // sorts employees by age
Console.WriteLine("\nsorted by Age ==>");
foreach (var emp in employees)
{
    Console.WriteLine($"Age {emp.Age}, Id {emp.Id}, Name {emp.Name}");
}

OUTPUT

original array ==>

Id 1001, Name Bhim, Age 35

Id 1002, Name Ajay, Age 25

Id 1003, Name Vijay, Age 43

Id 1004, Name Rakesh, Age 27

Id 1005, Name Mohan, Age 22

sorted by Age ==>

Age 22, Id 1005, Name Mohan

Age 25, Id 1002, Name Ajay

Age 27, Id 1004, Name Rakesh

Age 35, Id 1001, Name Bhim

Age 43, Id 1003, Name Vijay

C# Simple Example of IComparable Part-1