4.1 Defining Methods

A fundamental concept for structuring and reusing code.

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📌 1. What is a Method?

A method is a block of code that performs a specific task.

• Helps avoid repetition

• Makes code modular and readable

• Can accept parameters and return values

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📌 2. Basic Syntax

[access_modifier] [return_type] MethodName([parameters])
{
    // Method body
}

• access_modifier → public, private, protected, etc. (who can access the method)

• return_type → data type the method returns (void if it returns nothing)

• MethodName → any valid identifier

• parameters → input values (optional)

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📌 3. Example: Void Method

// No return value
public void Greet(string name)
{
    Console.WriteLine($"Hello, {name}!");
}
 
// Usage
Greet("Alice");  // Output: Hello, Alice!

• void → method does not return anything

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📌 4. Example: Method with Return Value

public int Add(int a, int b)
{
    int sum = a + b;
    return sum;
}
 
// Usage
int result = Add(5, 3);
Console.WriteLine(result); // 8

• int → return type

• return → sends the value back to the caller

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📌 5. Method Overloading

You can define multiple methods with the same name but different parameters.

public int Add(int a, int b) => a + b;
public double Add(double a, double b) => a + b;
 
Console.WriteLine(Add(5, 3));     // 8 (int)
Console.WriteLine(Add(5.5, 3.2)); // 8.7 (double)

• Compiler chooses the correct method based on parameter types

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📌 6. Optional Parameters and Default Values

public void PrintMessage(string message = "Hello World")
{
    Console.WriteLine(message);
}
 
PrintMessage();            // Hello World
PrintMessage("Hi there!"); // Hi there!

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📌 7. Expression-bodied Methods (C# 6+)

For short methods, you can use =>:

public int Square(int x) => x * x;
 
Console.WriteLine(Square(5)); // 25

• Similar to lambda expressions but for named methods

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📌 8. Pass by Reference vs Value

• By default, parameters are passed by value:

void Increment(int x)
{
    x++;
}
 
int num = 5;
Increment(num);
Console.WriteLine(num); // 5 (unchanged)

• To modify the original variable, use ref or out. See Difference Between Ref and Out:

void Increment(ref int x)
{
    x++;
}
 
int num = 5;
Increment(ref num);
Console.WriteLine(num); // 6

• out → similar to ref but must be initialized inside method. See Initialising Before Passing

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📌 9. Summary Table

Feature	Example / Notes
No return (void)	void Greet()
Return value	int Add(int a, int b)
Parameters	(int a, int b)
Optional parameters	(string msg = "Hello")
Method overloading	Same name, different parameters
Expression-bodied method	int Square(int x) => x * x;
Pass by reference	ref or out

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✅ Tip:

• Methods should do one thing and be reusable.

• Keep parameter lists short and meaningful.