Real-Time Example Of Extension Method In C#

In most C# interviews, the interviewer asks about a real-time example of extension method. So, here we will have a real time example of extension method for long data types, step by step.

 

This article demonstrates how to create extension method for long data types in C#. A few month ago I came across one of the requirements where I needed to display long data type numbers in a shortened format due to space constraints in the page. The number should be displayed in the page as below with a shortened fomat with suffix k, B and M (K indicates thousands, M - millions and B - Billions). Then I decided to create an extension method for long type and I am going to explain that here. 

 

Requierment is to display numbers as below with suffix K,M,B.

• 999 then 999
• 1000 then 1k
• 12000 then 12k
• 110000 then 110K 
• 1120000 then 1.12M
• 12300000 then 12.3M
• 123400000 then 123.4M 
• 1234500000 then 1.235B and so on 

Extension method allows you to add a new method to any existing type/class which were not part of the class. Extension method will help developer to extend the functionality of existing type without creating a new derived type, without changing existing type or without modifying existing type/orignal type.

  

Here I will explain how to create extension method for int type in C# step by step. A few points to remember while creating extension methods,

• Class shoud be marked as static.
• Method should be marked as static.
• First parameter of extension method must be a type which you want to extend. In parameter this keyword is used to bind with what you want to extend.

Step 1

 

Let's start with window console application.

 

 

Step 2

 

Go to Add and click on New project then give project Name as ExtensionMethod and click on ok.

 

 

Step 3

 

Click on add new items and add new class.

 

Step 4

 

Write Extension method for long type. 

public static class LongExtension
    {
        public static string FormatNumberKMB(this long num)
        {
            if (num >= 100000000000)
            {
                return (num / 1000000000).ToString("0.#B");
            }
            if (num >= 1000000000)
            {
                return (num / 1000000000).ToString("0.##B");
            }
            if (num >= 100000000)
            {
                return (num / 1000000).ToString("0.#M");
            }
            if (num >= 1000000)
            {
                return (num / 1000000).ToString("0.##M");
            }
            if (num >= 100000)
            {
                return (num / 1000).ToString("0.#k");
            }
            if (num >= 10000)
            {
                return (num / 1000).ToString("0.##k");
            }
            if (num >= 1000)
            {
                return (num / 1000).ToString("0.#k");
            }

            return num.ToString("#,0");
        }
    }

Step 5

 

After adding extension method put logic with static method inside static class. As in the below image all long type numbers are applicable to use the above-created extension method. Once  applied to any long type then this method will be able to be used on long type.

 

 

Step 6

 

How to use long extension method in application.

class Program
 {
     static void Main(string[] args)
     {
         long number = 999;

         Console.WriteLine(number.ToString() + " Shorten To " + number.FormatNumberKMB());
         Console.WriteLine("-----------------------------------");

         number = 1000;
         Console.WriteLine(number.ToString() + " Shorten To " + number.FormatNumberKMB());
         Console.WriteLine("-----------------------------------");

         number = 12000;
         Console.WriteLine(number.ToString() + " Shorten To " + number.FormatNumberKMB());
         Console.WriteLine("-----------------------------------");

         number = 110000;
         Console.WriteLine(number.ToString() + " Shorten To " + number.FormatNumberKMB());
         Console.WriteLine("-----------------------------------");

         number = 1120000;
         Console.WriteLine(number.ToString() + " Shorten To " + number.FormatNumberKMB());
         Console.WriteLine("-----------------------------------");

         number = 12300000;
         Console.WriteLine(number.ToString() + " Shorten To " + number.FormatNumberKMB());
         Console.WriteLine("-----------------------------------");

         number = 123400000;
         Console.WriteLine(number.ToString() + " Shorten To " + number.FormatNumberKMB());
         Console.WriteLine("-----------------------------------");

         number = 1234560000;
         Console.WriteLine(number.ToString() + " Shorten To " + number.FormatNumberKMB());
         Console.WriteLine("-----------------------------------");

         number = 12345670000;
         Console.WriteLine(number.ToString() + " Shorten To " + number.FormatNumberKMB());
         Console.WriteLine("-----------------------------------");

         number = 123456780000;
         Console.WriteLine(number.ToString() + " Shorten To " + number.FormatNumberKMB());
         Console.WriteLine("-----------------------------------");

         Console.ReadLine();
     }
 }

Step 7

 

Let's have a look at the final result for the above scenarios.

 

 

Conclusion

 

Extension method allows you to add a new method without creating a new derived type, and without changing existing type. Here I have created long data types. In the same way you can create other types like int, decimal, string etc. I hope this article will help you to understand extension method with real time examples.