What is a Method?
A method (also called a function) is a block of code that performs a specific task. Methods help organize code, reduce repetition, and make programs easier to understand.
Why Use Methods?
✅ Code Reusability: Write once, use many times ✅ Organization: Break large programs into smaller parts ✅ Maintainability: Easier to update and fix ✅ Readability: Code is easier to understand
Basic Method Syntax
static returnType MethodName(parameters)
{
// Code to execute
return value; // If returnType is not void
}
Parts of a Method:
- static: Keyword (required for now)
- returnType: Type of value returned (or
voidif none) - MethodName: Name of the method (starts with uppercase)
- parameters: Input values (optional)
- return: Returns a value (if not void)
Method Without Return Value (void)
Example 1: Simple Greeting
using System;
namespace MethodsBasics
{
class Program
{
static void Main(string[] args)
{
PrintGreeting(); // Call the method
PrintGreeting(); // Can call multiple times
Console.WriteLine("\nPress any key to exit...");
Console.ReadKey();
}
static void PrintGreeting()
{
Console.WriteLine("Hello, welcome to C#!");
}
}
}
// Output:
// Hello, welcome to C#!
// Hello, welcome to C#!
Example 2: Print Line
static void Main(string[] args)
{
Console.WriteLine("Start");
PrintLine();
Console.WriteLine("Middle");
PrintLine();
Console.WriteLine("End");
Console.ReadKey();
}
static void PrintLine()
{
Console.WriteLine("========================");
}
// Output:
// Start
// ========================
// Middle
// ========================
// End
Method With Return Value
Example 1: Get Current Year
static void Main(string[] args)
{
int iYear = GetCurrentYear();
Console.WriteLine($"Current year: {iYear}");
Console.ReadKey();
}
static int GetCurrentYear()
{
return 2025;
}
Example 2: Calculate Sum
static void Main(string[] args)
{
int iResult = GetSum();
Console.WriteLine($"Sum: {iResult}");
Console.ReadKey();
}
static int GetSum()
{
int iA = 10;
int iB = 20;
int iSum = iA + iB;
return iSum;
}
Methods With Parameters
Parameters allow you to pass data into methods.
Example 1: Single Parameter
static void Main(string[] args)
{
PrintMessage("Hello World!");
PrintMessage("Welcome to C#");
PrintMessage("Methods are useful!");
Console.ReadKey();
}
static void PrintMessage(string sMsg)
{
Console.WriteLine(sMsg);
}
// Output:
// Hello World!
// Welcome to C#
// Methods are useful!
Example 2: Multiple Parameters
static void Main(string[] args)
{
PrintInfo("Alice", 25);
PrintInfo("Bob", 30);
PrintInfo("Charlie", 28);
Console.ReadKey();
}
static void PrintInfo(string sName, int iAge)
{
Console.WriteLine($"Name: {sName}, Age: {iAge}");
}
// Output:
// Name: Alice, Age: 25
// Name: Bob, Age: 30
// Name: Charlie, Age: 28
Methods With Parameters and Return Value
Example 1: Add Two Numbers
static void Main(string[] args)
{
int iResult = Add(5, 3);
Console.WriteLine($"5 + 3 = {iResult}");
int iResult2 = Add(10, 20);
Console.WriteLine($"10 + 20 = {iResult2}");
Console.ReadKey();
}
static int Add(int iA, int iB)
{
return iA + iB;
}
// Output:
// 5 + 3 = 8
// 10 + 20 = 30
Example 2: Calculate Rectangle Area
static void Main(string[] args)
{
double dArea = CalculateArea(5.0, 10.0);
Console.WriteLine($"Area: {dArea}");
Console.ReadKey();
}
static double CalculateArea(double dLength, double dWidth)
{
return dLength * dWidth;
}
Practical Examples from Course
Example 1: Temperature Conversion (From Practical Test 1)
using System;
namespace TemperatureConverter
{
class Program
{
static void Main(string[] args)
{
double dCelsius = 40.0;
double dFahrenheit = 120.0;
double dCtoF = CelsiusToFahrenheit(dCelsius);
double dFtoC = FahrenheitToCelsius(dFahrenheit);
Console.WriteLine($"{dCelsius}°C = {dCtoF:0.0}°F");
Console.WriteLine($"{dFahrenheit}°F = {dFtoC:0.0}°C");
Console.WriteLine("\nPress any key to exit...");
Console.ReadKey();
}
static double CelsiusToFahrenheit(double dCelsius)
{
return (9.0 / 5) * dCelsius + 32;
}
static double FahrenheitToCelsius(double dFahrenheit)
{
return (5.0 / 9) * (dFahrenheit - 32);
}
}
}
Example 2: Calculator Methods (From Worksheet 2)
using System;
namespace CalculatorMethods
{
class Program
{
static void Main(string[] args)
{
double dNum1, dNum2;
char cOperator;
dNum1 = GetValidNumber("Enter first number: ");
dNum2 = GetValidNumber("Enter second number: ");
cOperator = GetValidOperator();
double dResult = Calculate(dNum1, dNum2, cOperator);
Console.WriteLine($"\nResult: {dNum1} {cOperator} {dNum2} = {dResult}");
Console.WriteLine("\nPress any key to exit...");
Console.ReadKey();
}
static double GetValidNumber(string sPrompt)
{
double dNumber;
bool isValid;
do
{
Console.Write(sPrompt);
isValid = double.TryParse(Console.ReadLine(), out dNumber);
if (!isValid)
{
Console.WriteLine("\nInvalid input. Please enter a valid number.\n");
}
} while (!isValid);
return dNumber;
}
static char GetValidOperator()
{
char cOperator;
bool isValid;
do
{
Console.Write("\nEnter an operator (+, -, *, /): ");
isValid = char.TryParse(Console.ReadLine(), out cOperator) &&
(cOperator == '+' || cOperator == '-' ||
cOperator == '*' || cOperator == '/');
if (!isValid)
{
Console.WriteLine("\nInvalid operator. Please enter +, -, *, or /.");
}
} while (!isValid);
return cOperator;
}
static double Calculate(double dNum1, double dNum2, char cOperator)
{
switch (cOperator)
{
case '+':
return dNum1 + dNum2;
case '-':
return dNum1 - dNum2;
case '*':
return dNum1 * dNum2;
case '/':
if (dNum2 == 0)
{
Console.WriteLine("\nWarning: Division by zero is not allowed. Returning 0.");
return 0;
}
return dNum1 / dNum2;
default:
Console.WriteLine("\nInvalid operator. Returning 0.");
return 0;
}
}
}
}
Example 3: Ticket Pricing Methods (From Practical Test 5)
using System;
namespace TicketPricing
{
class Program
{
static void Main()
{
Console.WriteLine("Movie Theater Ticket Price Calculator");
Console.Write("Enter your age: ");
int iAge = ValidateAge(Console.ReadLine());
if (iAge == -1)
{
Console.WriteLine("\nInvalid age.");
return;
}
Console.Write("\nIs the showtime (A)fternoon or (E)vening? Enter A or E: ");
string sShowtime = Console.ReadLine().ToUpper();
decimal mPrice = CalculateTicketPrice(iAge, sShowtime);
DisplayTicketInfo(iAge, sShowtime, mPrice);
Console.WriteLine("\nPress any key to exit...");
Console.ReadKey();
}
static int ValidateAge(string sInput)
{
if (int.TryParse(sInput, out int iAge))
{
if (iAge >= 0 && iAge <= 120)
{
return iAge;
}
}
return -1; // Invalid
}
static decimal CalculateTicketPrice(int iAge, string sShowtime)
{
decimal mBasePrice;
if (sShowtime == "A")
{
mBasePrice = 8.00m;
}
else
{
mBasePrice = 12.00m;
}
if (iAge <= 12)
{
return mBasePrice * 0.60m; // 40% discount
}
else if (iAge >= 65)
{
return mBasePrice * 0.75m; // 25% discount
}
else
{
return mBasePrice;
}
}
static void DisplayTicketInfo(int iAge, string sShowtime, decimal mPrice)
{
string sShowtimeType = (sShowtime == "A") ? "Afternoon" : "Evening";
string sTicketType = GetTicketType(iAge);
Console.WriteLine("\nTicket Details:");
Console.WriteLine($"Age: {iAge}");
Console.WriteLine($"Showtime: {sShowtimeType}");
Console.WriteLine($"Ticket Type: {sTicketType}");
Console.WriteLine($"Price: R{mPrice:0.00}");
}
static string GetTicketType(int iAge)
{
if (iAge <= 12)
{
return "Child";
}
else if (iAge >= 65)
{
return "Senior";
}
else
{
return "Adult";
}
}
}
}
Method Naming Conventions
From your course requirements:
✅ Start with uppercase letter: CalculateSum(), not calculateSum()
✅ Use descriptive names: GetUserAge(), not Get()
✅ Use verbs: CalculateArea(), PrintMessage(), ValidateInput()
// Good method names
static double CalculateArea(double dLength, double dWidth)
static void PrintGreeting()
static int GetAge()
static bool ValidateEmail(string sEmail)
// Bad method names (avoid these)
static double Area(double x, double y) // Not descriptive
static void print() // Lowercase start
static int a() // Too short
Calling Methods
Direct Call
PrintMessage("Hello");
Store Result in Variable
int iSum = Add(5, 3);
Console.WriteLine(iSum);
Use Result Directly
Console.WriteLine(Add(5, 3));
Method Calling Another Method
static void Main(string[] args)
{
MethodA();
}
static void MethodA()
{
Console.WriteLine("Method A");
MethodB(); // MethodA calls MethodB
}
static void MethodB()
{
Console.WriteLine("Method B");
}
// Output:
// Method A
// Method B
Return Statement
Returning Values
static int GetNumber()
{
return 42; // Returns integer
}
static string GetName()
{
return "Alice"; // Returns string
}
static bool IsAdult(int iAge)
{
return iAge >= 18; // Returns boolean
}
Early Return
You can return early to exit a method:
static string GetGrade(int iMarks)
{
if (iMarks >= 80)
{
return "A"; // Early return
}
else if (iMarks >= 70)
{
return "B";
}
else if (iMarks >= 60)
{
return "C";
}
else if (iMarks >= 50)
{
return "D";
}
else
{
return "F";
}
}
Void Methods Don't Return Values
static void PrintMessage(string sMsg)
{
Console.WriteLine(sMsg);
// No return statement needed
}
// Or you can use return to exit early
static void CheckAge(int iAge)
{
if (iAge < 0)
{
Console.WriteLine("Invalid age");
return; // Exit method early
}
Console.WriteLine($"Valid age: {iAge}");
}
Practice Exercises
Exercise 1: Create IsEven Method
Create a method that takes an integer and returns true if even, false if odd.
Exercise 2: Create GetMax Method
Create a method that takes two integers and returns the larger one.
Exercise 3: Create PrintSquare Method
Create a method that takes a number and prints its square.
Exercise 4: Create CalculateDiscount Method
Create a method that takes a price and discount percentage, returns the final price.
Exercise 5: Create ValidatePassword Method
Create a method that checks if a password is at least 8 characters long.
Common Mistakes to Avoid
❌ Forgetting to return a value:
static int GetSum(int iA, int iB)
{
int iSum = iA + iB;
// Missing return! Compile error
}
✅ Correct:
static int GetSum(int iA, int iB)
{
int iSum = iA + iB;
return iSum;
}
❌ Wrong parameter order:
static void PrintInfo(string sName, int iAge)
{
Console.WriteLine($"{sName} is {iAge} years old");
}
// Wrong order!
PrintInfo(25, "Alice"); // ERROR!
✅ Correct:
PrintInfo("Alice", 25); // Correct order
❌ Not using returned value:
static int Add(int iA, int iB)
{
return iA + iB;
}
Add(5, 3); // Result is lost!
✅ Correct:
int iResult = Add(5, 3); // Store result
Console.WriteLine(iResult);
// Or use directly
Console.WriteLine(Add(5, 3));
Key Takeaways
✅ Methods help organize and reuse code
✅ Use void when method doesn't return a value
✅ Use specific return type when method returns a value
✅ Parameters allow passing data into methods
✅ Method names should start with uppercase
✅ Always return a value if return type is not void
✅ Call methods by name with required parameters
Next Topic: C# Methods - Part 2 (ref, out, and Recursion)