C# Else if Statement

Using the C# Else if statements, we can increase the execution speed over simple if statements. That means when we use Else if control flow statements, the compiler will check all the comparisons in the sequence only until the given condition is satisfied. Once the condition is satisfied, rather than going for the next comparison, it will exit there itself.

Syntax

The Else if control statements will overcome the performance issues with the simple if expressions. And the syntax behind this C# else if statement is as shown below.

if <condition>
{
  Statements //These are executed if condition is true
}
else if <condition>
{
  Statements //These are executed when this else if condition is true
}
else if <condition>
{
  Statements //These sare executed when this else if condition is true
}
else
  <Default statements> //These are executed in case when neither of the above conditions is true. 

C# Else If Example

Let us write a simple example using the else if statement. It is the same example that you saw in the if condition.

This example read numbers from 1 to 4 and printed in words. If the user-given number is not in between 1 to 4, then print it as an invalid number.

using System;
class Program
{
    static void Main()
    {
        int i = int.Parse(Console.ReadLine());


        if (i == 1)
        {
            Console.WriteLine("input number is one");
        }
        else if (i == 2)
        {
            Console.WriteLine("input number is two");
        }
        else if (i == 3)
        {
            Console.WriteLine("input number is three");
        }
        else if (i == 4)
        {
            Console.WriteLine("input number is four");
        }
        else
        {
            Console.WriteLine("input number is invalid");
        }
    }
}

ANALYSIS

Here i = 2 is given as input.

First, it checks for 2==1, which is false.

2==2 returns true

Hence it prints: input number is two.

And it quit from the loop without executing the next line.