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Functions and Methods

Functions and Methods in C# 🚀

Functions (or methods) in C# encapsulate logic and allow code reuse. They take input parameters, process logic, and return results.

1️⃣ Defining and Calling Methods

A method in C# consists of:

Access modifier Return type Method name Parameters (optional) Method body

🔹 Basic Method

Syntax:

[AccessModifier] ReturnType MethodName(ParameterList)
{
    // Method body
    return value; // (if applicable)
}

Example:

class Program
{
    static void SayHello() // No parameters, no return type
    {
        Console.WriteLine("Hello, World!");
    }

    static void Main()
    {
        SayHello(); // Method call
    }
}

2️⃣ Methods with Parameters

🔹 Passing Arguments

Parameters allow input values to be passed to a method.

static void Greet(string name)
{
    Console.WriteLine($"Hello, {name}!");
}

static void Main()
{
    Greet("Alice"); // Output: Hello, Alice!
}

3️⃣ Methods with Return Values

🔹 Returning a Value

Methods can return values instead of void.

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

static void Main()
{
    int result = Add(5, 3);
    Console.WriteLine(result); // Output: 8
}

4️⃣ Method Overloading

Method overloading allows multiple methods with the same name but different parameters.

static int Multiply(int a, int b) => a * b;
static double Multiply(double a, double b) => a * b;

static void Main()
{
    Console.WriteLine(Multiply(2, 3));      // Calls int version → Output: 6
    Console.WriteLine(Multiply(2.5, 3.5));  // Calls double version → Output: 8.75
}

5️⃣ Optional and Named Parameters

🔹 Optional Parameters

C# allows setting default values for parameters.

static void PrintMessage(string message = "Default message")
{
    Console.WriteLine(message);
}

static void Main()
{
    PrintMessage(); // Output: Default message
    PrintMessage("Hello, C#!"); // Output: Hello, C#!
}

🔹 Named Parameters

Named parameters allow explicitly specifying parameter names.

static void DisplayUserInfo(string name, int age)
{
    Console.WriteLine($"{name} is {age} years old.");
}

static void Main()
{
    DisplayUserInfo(age: 25, name: "Bob"); // Order does not matter
}

6️⃣ Pass by Value vs Pass by Reference

🔹 Pass by Value (Default)

Changes inside the method do not affect the original variable.

static void Square(int num)
{
    num *= num;
    Console.WriteLine($"Inside method: {num}"); // Modified locally
}

static void Main()
{
    int number = 5;
    Square(number);
    Console.WriteLine($"Outside method: {number}"); // Original remains unchanged
}

🔹 Pass by Reference (ref and out)

Using ref (Requires Initialization)

The original variable is modified inside the method.

static void DoubleValue(ref int num)
{
    num *= 2;
}

static void Main()
{
    int value = 10;
    DoubleValue(ref value);
    Console.WriteLine(value); // Output: 20
}

Using out (No Need for Initialization)

The variable must be assigned inside the method.

static void GetValues(out int x, out int y)
{
    x = 5;
    y = 10;
}

static void Main()
{
    GetValues(out int a, out int b);
    Console.WriteLine($"{a}, {b}"); // Output: 5, 10
}

7️⃣ Local Functions (C# 7+)

Methods inside other methods for encapsulation.

static void Main()
{
    void LocalFunction()
    {
        Console.WriteLine("Inside Local Function");
    }

    LocalFunction(); // Call local function
}

8️⃣ Expression-Bodied Methods (C# 6+)

A shorter syntax for simple methods.

static int Square(int n) => n * n;
static void Print() => Console.WriteLine("Hello, C#!");

9️⃣ Recursive Methods

Methods calling themselves to solve problems recursively.

Example: Factorial Calculation

static int Factorial(int n)
{
    if (n == 1) return 1;
    return n * Factorial(n - 1);
}

static void Main()
{
    Console.WriteLine(Factorial(5)); // Output: 120
}

🔚 Summary

  • Methods allow reusability and better code organization
  • Parameters can be required, optional, or named
  • Return values provide results
  • Method overloading allows flexibility
  • Pass by reference (ref, out) modifies original values
  • Local and recursive functions improve modularity
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