Methods and Parameters in C#

# CHAPTER 11

Methods and Parameters #

1. Introduction #

2. Learning Objectives #

• Define and call custom methods.

• Understand Return Types (void, int, string, etc.).

• Pass data using Parameters.

• Implement Method Overloading.

• Use Optional and Named Parameters.

3. Declaring and Calling a Method #

Syntax: AccessModifier ReturnType MethodName(Parameters) { // body }

using System;

class Program
{
    // Method Definition
    static void SayHello() 
    {
        Console.WriteLine("Hello from a custom method!");
    }

    static void Main(string[] args)
    {
        // Method Call
        SayHello(); 
        SayHello(); // Can be reused!
    }
}

*(Note: We use static here because Main is static, and static methods can only directly call other static methods).*

4. Return Types #

class Program
{
    // Returns an integer
    static int GetLuckyNumber() 
    {
        return 7;
    }

    static void Main()
    {
        int myNum = GetLuckyNumber();
        Console.WriteLine(myNum); // Prints 7
    }
}

5. Parameters and Arguments #

class Program
{
    // Takes two parameters: string and int
    static void GreetUser(string name, int age) 
    {
        Console.WriteLine($"Hello {name}, you are {age} years old.");
    }

    static void Main()
    {
        GreetUser("Alice", 25); // "Alice" and 25 are the Arguments
    }
}

6. Method Overloading #

class Program
{
    static int Add(int a, int b) 
    {
        return a + b;
    }

    // Overloaded Method
    static double Add(double a, double b) 
    {
        return a + b;
    }

    static void Main()
    {
        Console.WriteLine(Add(5, 5));       // Calls the 'int' version
        Console.WriteLine(Add(2.5, 3.5));   // Calls the 'double' version
    }
}

7. Optional and Named Parameters #

class Program
{
    // 'country' is an optional parameter
    static void Register(string name, string country = "USA") 
    {
        Console.WriteLine($"{name} is from {country}");
    }

    static void Main()
    {
        Register("John");           // "John is from USA"
        Register("Maria", "Spain"); // "Maria is from Spain"
        
        // Named Parameters (C# feature for clarity)
        Register(country: "Japan", name: "Kenji"); 
    }
}

8. OOP and Memory Explanation #

9. Common Mistakes #

• Forgetting return: If your method signature says static int Calculate(), the compiler will throw an error if you forget to return an integer.

• Confusing Parameters with Arguments: Parameters are the variables in the method definition (int x). Arguments are the actual values passed during the call (5).

10. Best Practices #

• Single Responsibility Principle: A method should do exactly ONE thing. If a method is 100 lines long and formats data, saves to a database, and sends an email, break it down into three separate methods.

• PascalCase Naming: In C#, method names should always start with a capital letter (CalculateTotal, not calculateTotal).

11. Exercises #

1. 1. Write a method called Multiply that takes two int parameters and returns their product. Test it in Main().

1. 2. Create an overloaded version of Multiply that takes three int parameters.

12. MCQs with Answers #

13. Interview Questions #

• Q: Explain Method Overloading. Is changing the return type enough to overload a method? (Answer: No, the parameter list must differ).

• Q: Explain the difference between Passing by Value and Passing by Reference (ref and out keywords).

14. Summary #

15. Next Chapter Recommendation #