মেথডস (Methods)

// Method that returns a value
static int Add(int a, int b)
{
    return a + b;
}

// Method that returns nothing (void)
static void Greet(string name)
{
    Console.WriteLine($"Hello, {name}! Welcome aboard.");
}

// Expression-bodied method (short version with =>)
static double CircleArea(double radius) => Math.PI * radius * radius;

// Calling the methods
int sum = Add(5, 3);
Console.WriteLine($"5 + 3 = {sum}");

Greet("Laboni");

double area = CircleArea(5);
Console.WriteLine($"Circle area (r=5): {area:F2}");

5 + 3 = 8
Hello, Laboni! Welcome aboard.
Circle area (r=5): 78.54

// ref — modifies the original variable
static void DoubleIt(ref int number)
{
    number *= 2;
}

// out — must assign a value inside the method
static void Divide(int a, int b, out int quotient, out int remainder)
{
    quotient = a / b;
    remainder = a % b;
}

// Optional parameters with defaults
static string MakeTag(string text, string color = "blue", int size = 14)
{
    return $"<span style='color:{color}; font-size:{size}px'>{text}</span>";
}

// Using ref
int value = 10;
DoubleIt(ref value);
Console.WriteLine($"After DoubleIt: {value}");

// Using out
Divide(17, 5, out int q, out int r);
Console.WriteLine($"17 / 5 = {q} remainder {r}");

// Using optional params
Console.WriteLine(MakeTag("Hello"));                   // uses defaults
Console.WriteLine(MakeTag("Warning", "red"));          // override color
Console.WriteLine(MakeTag("Title", "green", 24));      // override both

After DoubleIt: 20
17 / 5 = 3 remainder 2
<span style='color:blue; font-size:14px'>Hello</span>
<span style='color:red; font-size:14px'>Warning</span>
<span style='color:green; font-size:24px'>Title</span>

// Same method name, different parameter lists
static string Describe(int number)
    => $"{number} is a whole number";

static string Describe(double number)
    => $"{number} is a decimal number";

static string Describe(string text)
    => $"\"{text}\" is a string with {text.Length} characters";

static string Describe(int a, int b)
    => $"{a} and {b} add up to {a + b}";

// C# picks the right overload based on what you pass
Console.WriteLine(Describe(42));
Console.WriteLine(Describe(3.14));
Console.WriteLine(Describe("hello"));
Console.WriteLine(Describe(10, 20));

42 is a whole number
3.14 is a decimal number
"hello" is a string with 5 characters
10 and 20 add up to 30