Part 3: C# Fundamentals: Operators and Expressions
In this lesson, we’ll explore operators and expressions in C#. These are fundamental concepts that allow you to perform calculations, make decisions, and create logic in your programs.
Operators are symbols used to perform operations, while expressions combine operators and values to produce results. Let’s dive in!
Types of Operators
C# provides a wide range of operators, categorized by their purpose.
1. Arithmetic Operators
These operators are used to perform basic mathematical calculations.
| Operator | Description | Example | Result |
|---|---|---|---|
+ | Addition | 10 + 3 | 13 |
- | Subtraction | 10 - 5 | 5 |
* | Multiplication | 6 * 3 | 18 |
/ | Division | 8 / 2 | 4 |
% | Modulus (remainder) | 10 % 3 | 1 |
⚠ Important Note: Division by Zero ⚠
If you attempt to divide a number by zero, you’ll encounter an error or a special value like Infinity. Always check the divisor before performing the division.
int numerator = 10, divisor = 0;
if (divisor != 0)
{
Console.WriteLine(numerator / divisor);
}
else
{
Console.WriteLine("Error: Division by 0.");
}
2. Relational Operators
These operators are used to compare values. The result of a comparison is either true or false.
| Operator | Description | Example | Result |
|---|---|---|---|
== | Equal to | 7 == 7 | true |
!= | Not equal to | 5 != 2 | true |
< | Less than | 4 < 8 | true |
> | Greater than | 9 > 7 | true |
<= | Less than or equal | 5 <= 5 | true |
>= | Greater or equal | 8 >= 12 | false |
3. Logical Operators
Logical operators allow you to combine boolean expressions (true/false) to make more complex decisions.
| Operator | Description | Example | Result |
|---|---|---|---|
&& | Logical AND | true && false | false |
II | Logical OR | true II false | true |
! | Logical NOT | !true | false |
Example:
string day = "Saturday";
bool isWeekend = day == "Saturday" || day == "Sunday";
Console.WriteLine($"Is it the weekend? {isWeekend}"); // true
4. Ternary Operator
The ternary operator is a compact and elegant way to make decisions in a single line of code.
The structure is:
condition ? valueIfTrue : valueIfFalse;
Example:
int age = 18; string message = age >= 18 ? "You are an adult" : "You are a minor"; Console.WriteLine(message); // Output: You are an adult
Additional Example: Determine the Sign of a Number
int number = -5;
string state = number > 0 ? "positive" : (number < 0 ? "negative" : "zero");
Console.WriteLine($"The number {number} is {state}."); // negative
Example: Basic Calculator
Let’s create a calculator that allows the user to perform basic arithmetic operations.
using System;
class BasicCalculator
{
static void Main(string[] args)
{
Console.WriteLine("Enter the first number:");
double number1 = Convert.ToDouble(Console.ReadLine());
Console.WriteLine("Enter the operator (+, -, *, /):");
char operatorChar = Console.ReadLine()[0];
Console.WriteLine("Enter the second number:");
double number2 = Convert.ToDouble(Console.ReadLine());
double result = operatorChar switch
{
'+' => number1 + number2,
'-' => number1 - number2,
'*' => number1 * number2,
'/' => number2 != 0 ? number1 / number2 : double.NaN,
_ => double.NaN
};
Console.WriteLine($"The result is: {result}");
}
}
