Chapter 3.1. Simple Conditions

In this chapter, we will discuss the conditional statements in the C# language, through which our program may have different effects, depending on a condition. We'll explain the syntax of conditional operators for checks (if and if-else) with appropriate examples and we will see in what range a variable (its scope) lives. Finally, we will go through debugging techniques to track the path that runs through our program during implementation.

Video: Chapter Overview

Watch the video lesson about what we will learn in this chapter: https://youtu.be/sstA00rIWk0.

Introduction to Simple Conditions by Examples

In programming we can check conditions and execute different blocks of code depending on the check. This is typically performed using the if-else constructs:

var size = decimal.Parse(Console.ReadLine());
if (size < 0)
    Console.WriteLine($"Negative size: {size}");
else if (size > 1000)
    Console.WriteLine($"Size too big: {size}");
else
{
    Console.WriteLine($"Size accepted: {size}");
    Console.WriteLine($"Area: {size * size}");
}

Run the above code example: https://repl.it/@nakov/size-checker-if-else-csharp.

When executed, the above code will enter a decimal number and will check its value several times. Depending on the above conditions, it will display different messages. Examples are shown below.

If we enter -20 as input, the output will be as follows:

Negative size: -20

If we enter 150 as input, the output will be as follows:

Size accepted: 150
Area: 22500

If we enter 3200 as input, the output will be as follows:

Size too big: 3200

Let's explain in greater detail how to use simple if-else conditions in C#.