If-else execution flow in C Sharp (C#)

Introduction

If-else helps your program make choices. It runs different code depending on conditions.

Deciding if a user is old enough to access a website

Checking if a number is positive or negative

Choosing what message to show based on the time of day

Turning on a light if it is dark outside

Syntax

C Sharp (C#)

if (condition)
{
    // code runs if condition is true
}
else
{
    // code runs if condition is false
}

The condition is a true or false question your program asks.

Only one block runs: either the if part or the else part.

Examples

This checks if age is 18 or more. It prints a message based on that.

C Sharp (C#)

int age = 18;
if (age >= 18)
{
    Console.WriteLine("You can vote.");
}
else
{
    Console.WriteLine("You are too young to vote.");
}

This checks if number is positive or not and prints accordingly.

C Sharp (C#)

int number = -5;
if (number > 0)
{
    Console.WriteLine("Positive number");
}
else
{
    Console.WriteLine("Zero or negative number");
}

Sample Program

This program asks the user for their age. It then uses if-else to print if they are an adult or a minor.

C Sharp (C#)

using System;

class Program
{
    static void Main()
    {
        Console.Write("Enter your age: ");
        int age = int.Parse(Console.ReadLine() ?? "0");

        if (age >= 18)
        {
            Console.WriteLine("You are an adult.");
        }
        else
        {
            Console.WriteLine("You are a minor.");
        }
    }
}

Important Notes

Make sure the condition inside if is something that results in true or false.

You can have many if statements, but only one else per if.

Summary

If-else lets your program choose between two paths.

The if block runs when the condition is true.

The else block runs when the condition is false.