Operators in C#

# CHAPTER 5

Operators in C# #

1. Introduction #

2. Learning Objectives #

• Use Arithmetic operators for calculations.

• Use Comparison and Logical operators for decision-making.

• Use Assignment operators to update variables.

• Understand the Null-coalescing operator (??).

• Use the Ternary operator (?:) as a shorthand.

3. Arithmetic Operators #

Important Note on Division: If you divide two integers, C# truncates the decimal. 5 / 2 results in 2. To get 2.5, at least one number must be a double: 5.0 / 2.

4. Assignment Operators #

5. Comparison Operators #

6. Logical Operators #

7. The Ternary Operator (?:) #

int age = 20;
string status = (age >= 18) ? "Adult" : "Minor";
Console.WriteLine(status); // Prints "Adult"

8. The Null-Coalescing Operator (??) #

string defaultName = "Guest";
string userName = null; // Imagine this came from an empty database field

// If userName is null, use defaultName instead
string displayName = userName ?? defaultName;

Console.WriteLine(displayName); // Prints "Guest"

*(Note: C# 8.0 introduced the ??= operator, which assigns the right value to the left variable ONLY if the left variable is currently null).*

9. Common Mistakes #

• Confusing = and ==: x = 5 assigns the value 5 to x. x == 5 checks if x is equal to 5.

• Modulus on Doubles: The % operator is almost exclusively used with integers (e.g., checking if a number is even by doing x % 2 == 0).

10. Best Practices #

• Always use parentheses () when combining multiple logical operators to make the order of operations explicitly clear. Example: if ((age > 18) && (hasLicense == true))

11. Exercises #

1. 1. Write a program that calculates the area and perimeter of a rectangle (Area = width * height, Perimeter = 2 * (width + height)).

1. 2. Create an integer variable points = 100. Use the += operator to add 50 points, then print the result.

1. 3. Use the ternary operator to check if a number is even or odd, and print the result.

12. MCQs with Answers #

13. Interview Questions #

• Q: Explain short-circuit evaluation in C# logical operators (&& and ||).

• Q: What is the difference between i++ (postfix) and ++i (prefix)?

• Q: Describe a real-world scenario where the null-coalescing operator (??) is highly beneficial.

14. Summary #

15. Next Chapter Recommendation #