How to implement IComparable interface in our own C# class.
Implement IComparable interface in C# class
In this article we will learn how to implement IComparable
interface in our own C# class and what are the advantage on that? IComparable will allow us to sort object of
that class if we implement IComparable interface in it. When a class implements
IComparable interface we must add the method CompareTo(T). The T may be any
Type.
Implement IComparable
Lets implement IComparable interface in our own class to see
how it works? Have a look on below code.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Diagnostics;
using System.Reflection;
namespace TestDomain
{
class Person :IComparable<Person>
{
public string Name { get; set; }
public int Age { get; set; }
public int CompareTo(Person tmp)
{
//Alphabetic sort if age is equal. [A to Z]
if (this.Age == tmp.Age)
{
return this.Name.CompareTo(tmp.Name);
}
//Default to Age sort. [High to low]
return tmp.Age.CompareTo(this.Age);
}
public override string ToString()
{
//String representation.
return this.Age.ToString() + "," + this.Name;
}
}
class Program
{
public static void Main(String[] args)
{
List<Person> list = new List<Person>();
list.Add(new Person() { Name = "Ram", Age =50});
list.Add(new Person() { Name = "Shyam", Age =60 });
list.Add(new Person() { Name = "Jadu", Age =30 });
list.Add(new Person() { Name = "Hari", Age =80 });
list.Add(new Person() { Name = "Martin", Age =70 });
//Uses IComparable.CompareTo() internally
list.Sort();
//Uses Person.ToString
foreach (var element in list)
{
Console.WriteLine(element);
}
Console.ReadLine();
}
}
}
Here is sample output.
So, In output we are seeing that the list has sorted
according to Age, (Descending order) . The question is how it has done? Where
we did not write any logic for sorting operation?
In Person class we have implemented IComparable interface
like below
Class Person : IComparable<Person>
The IComparable interface is parameterized interface (or
generic interface) and it takes parameter T (means any type). We are passing
Person class as parameter because we want to implement it in Person class and
want to sort object of Person class.
The person class is very simple it contains only two
properties those are Name and Age. Here we want to sort collection of Person
class according to their Age. As we have discussed earlier we have to define
CompareTo function if we want to implement IComparable interface in our own
class.
public int CompareTo(Person tmp)
{
//Alphabetic sort if age is equal. [A to Z]
if (this.Age == tmp.Age)
{
return this.Name.CompareTo(tmp.Name);
}
//Default to Age sort. [High to low]
return tmp.Age.CompareTo(this.Age);
}
The return type of CompareTo function is
integer and parameter type is T. We have define the logic that if two person
has same age then use their name to sort otherwise it will sort according to
Age.
Within Main() function we are creating List of Person class
and calling Sort() method which calls CompareTo() method internally. If we want
to change the order, means want to sort in ascending order then we have to make
change in CompareTo() method. This is the method to show data in ascending order
by Age.
public int CompareTo(Person tmp)
{
//Alphabetic sort if age is equal. [A to Z]
if (this.Age == tmp.Age)
{
return tmp.Name.CompareTo(this.Name);
}
//Default to Age sort. [High to low]
return this.Age.CompareTo(tmp.Age);
}
Here is output
Conclusion:-
In this article we have implemented IComparable interface in our own C# class. Hope you have understood then advantage of IComparable interface.