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Basic IComparable example in C#

This tutorial explains how to compare 2 classes using Icomparable interface.

Objective of this Tutorial

The objective of this tutorial is to demonstrate how to use IComparable interface for comparing similar objects.

Prerequisites

Software

Visual studio (any version) is installed on your machine.

Technical knowledge

In order to understand this tutorial you must have the basic knowledge of C#.

Steps Involved

In order to achieve our goal we will follow these steps:

1. Create a class which implements Icomparable interface

2. Invoke CompareTo method in Main method

Before we start working on each step here is a piece of information that you need to know:

IComparable comes into picture when there is a need to make objects sortable and for comparing them. IComparable is a generalized comparison method that is implemented by a value type or class.

In order to implement the IComparable class, it is important to implement CompareTo() method. It is in this method that we actually define how objects will be compared.

The declaration syntax for this interface is as follows

public interface IComparable<T>

It defines CompareTo() method (check the function signature below)

int CompareTo (T com)

The return value of CompareTo method depends upon the comparison result

1. If both the objects are equal then CompareTo method returns zero.

2. If both the objects are not equal then CompareTo method returns a non zero value(it can be positive or negative).

In the example given below we are comparing the data related to people. The comparison method will differ for different scenarios depending on what type of data is being compared.

Let’s start working on each step

Step 1: Create a class which implements

Icomparable interface

public class Person: IComparable < Person > {
	public Person() {}

	public Person(string PersonName, int Age, string Address) {
		this.PersonName = PersonName;
		this.Age = Age;
		this.Address = Address;
	}

	public int CompareTo(Person other) {
		bool isEqual = true;

		if (this.PersonName.CompareTo(other.PersonName) != 0) isEqual = false;

		if (this.Age != other.Age) isEqual = false;

		if (this.Address.CompareTo(other.Address) != 0) isEqual = false;

		return isEqual == true ? 1 : 0;
	}

	public string PersonName {
		get;
		set;
	}
	public int Age {
		get;
		set;
	}
	public string Address {
		get;
		set;
	}
}

Step 2: Invoke CompareTo method in Main method

We will now define the main method to invoke the CompareTo() method and to display results as shown below:

static void Main(string[] args) {
	Person p1 = new Person("Karan Gupta", 32, "Gurgaon");
	Person p2 = new Person("Karan Gupta", 32, "Gurgaon");

	Console.WriteLine(p1.CompareTo(p2));
	Console.WriteLine(Environment.NewLine);

	Person p3 = new Person("Karan Gupta", 32, "Gurgaon");
	Person p4 = new Person("Karan Gupta", 32, "Delhi");

	Console.WriteLine(p3.CompareTo(p4));
	Console.ReadLine();
}

In the code above p1 and p2 are identical objects therefore their comparison generates a value of 0 where as that is not the case with comparison of p3 and p4. As a result, when the program is executed the results are shown as displayed below.

Picture showing the output of the IComparable interface in C#

Click to Enlarge

Posted By -	Karan Gupta

Posted On -	Thursday, March 6, 2014

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