Chapter 4 · Lesson 1

Defining Methods

Defining Methods in C#

Methods encapsulate reusable logic. Every C# method lives inside a class or struct.

Access modifiers

public – accessible everywhere.
private – accessible only within the containing type (default).
protected – accessible within the type and its subclasses.
internal – accessible within the same assembly.

Return types and void Every method declares a return type. Use void when nothing is returned.

out and ref parameters

ref — pass a variable by reference (caller must initialize).
out — pass a reference for the method to assign (caller need not initialize).

Expression-bodied methods For single-expression methods, use the => syntax:

csharp

public int Add(int a, int b) => a + b;

Key points:

C# methods follow PascalCase naming by convention.
static methods belong to the type, not an instance.
out parameters are commonly used in the Try-Parse pattern: int.TryParse(s, out int result).

Code Examples

Methods with out parameterscsharp

using System;
class MathUtils {
    public static bool TryDivide(int dividend, int divisor, out double result) {
        if (divisor == 0) { result = 0; return false; }
        result = (double)dividend / divisor;
        return true;
    }

    public static (int Min, int Max) MinMax(int[] arr) {
        int min = arr[0], max = arr[0];
        foreach (var n in arr) {
            if (n < min) min = n;
            if (n > max) max = n;
        }
        return (min, max);
    }

    static void Main() {
        if (TryDivide(10, 3, out double r))
            Console.WriteLine($"10 / 3 = {r:F2}");

        TryDivide(5, 0, out double r2);
        Console.WriteLine($"5 / 0 succeeded: false");

        var (min, max) = MinMax(new[] { 3, 1, 4, 1, 5, 9 });
        Console.WriteLine($"Min: {min}, Max: {max}");
    }
}

out parameters let a method return multiple values. Tuples are another idiomatic approach in modern C#.

Expression-bodied methodscsharp

using System;
class Geometry {
    public double Radius { get; }
    public Geometry(double radius) => Radius = radius;

    public double Area() => Math.PI * Radius * Radius;
    public double Circumference() => 2 * Math.PI * Radius;
    public override string ToString() => $"Circle(r={Radius})";

    static void Main() {
        var c = new Geometry(5);
        Console.WriteLine(c);
        Console.WriteLine($"Area: {c.Area():F2}");
        Console.WriteLine($"Circumference: {c.Circumference():F2}");
    }
}

Expression-bodied members use => for concise one-liners. They work for methods, properties, constructors, and more.

Quick Quiz

1. What is the difference between `out` and `ref` parameters?

2. What is the default access modifier for a C# class method?

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Defining Methods in C#

Methods encapsulate reusable logic. Every C# method lives inside a class or struct.

Access modifiers

public – accessible everywhere.

private – accessible only within the containing type (default).

protected – accessible within the type and its subclasses.

internal – accessible within the same assembly.