12 minlesson

Return Values

Return Values

Methods can compute and return values to the calling code. This makes them even more powerful and flexible.

The return Statement

Use return to send a value back from a method:

csharp
1static int Add(int a, int b)
2{
3    return a + b;
4}
5

6int result = Add(3, 5);
7Console.WriteLine(result);  // 8

Return Type

The return type is declared before the method name:

csharp
1// Returns an integer
2static int GetAge()
3{
4    return 25;
5}
6

7// Returns a string
8static string GetName()
9{
10    return "Alice";
11}
12

13// Returns a boolean
14static bool IsValid()
15{
16    return true;
17}
18

19// Returns a double
20static double CalculateTax(double amount)
21{
22    return amount * 0.08;
23}

void vs Return Type

  • void: Method doesn't return anything
  • Other types (int, string, etc.): Method returns a value
csharp
1// void - no return value
2static void PrintMessage()
3{
4    Console.WriteLine("Hello");
5    // No return needed (or use 'return;' to exit early)
6}
7

8// int - returns a value
9static int Square(int n)
10{
11    return n * n;  // Must return an int
12}

Using Return Values

Return values can be:

Stored in Variables

csharp
1int doubled = Double(5);
2Console.WriteLine(doubled);  // 10
3

4static int Double(int n) => n * 2;

Used Directly in Expressions

csharp
1Console.WriteLine(Add(3, 4));  // 7
2Console.WriteLine($"Sum: {Add(10, 20)}");  // Sum: 30
3

4int total = Add(1, 2) + Add(3, 4);  // 3 + 7 = 10

Passed to Other Methods

csharp
1int squared = Square(Double(3));  // Double(3)=6, Square(6)=36
2

3static int Double(int n) => n * 2;
4static int Square(int n) => n * n;

Used in Conditions

csharp
1if (IsEven(10))
2{
3    Console.WriteLine("10 is even");
4}
5

6static bool IsEven(int n) => n % 2 == 0;

Early Return

return immediately exits the method:

csharp
1static int Divide(int a, int b)
2{
3    if (b == 0)
4    {
5        Console.WriteLine("Cannot divide by zero!");
6        return 0;  // Exit early
7    }
8    return a / b;  // Normal return
9}
10

11static string GetGrade(int score)
12{
13    if (score < 0 || score > 100)
14    {
15        return "Invalid";  // Exit early for invalid input
16    }
17

18    if (score >= 90) return "A";
19    if (score >= 80) return "B";
20    if (score >= 70) return "C";
21    if (score >= 60) return "D";
22    return "F";
23}

Returning Complex Types

Returning Arrays

csharp
1static int[] CreateRange(int start, int count)
2{
3    int[] result = new int[count];
4    for (int i = 0; i < count; i++)
5    {
6        result[i] = start + i;
7    }
8    return result;
9}
10

11int[] numbers = CreateRange(5, 3);  // [5, 6, 7]

Returning Tuples

Return multiple values without out parameters:

csharp
1static (int min, int max) GetMinMax(int[] numbers)
2{
3    int min = numbers[0];
4    int max = numbers[0];
5

6    foreach (int n in numbers)
7    {
8        if (n < min) min = n;
9        if (n > max) max = n;
10    }
11

12    return (min, max);
13}
14

15int[] data = { 5, 2, 8, 1, 9 };
16var result = GetMinMax(data);
17Console.WriteLine($"Min: {result.min}, Max: {result.max}");
18

19// Or deconstruct
20var (minimum, maximum) = GetMinMax(data);
21Console.WriteLine($"Min: {minimum}, Max: {maximum}");

Named Tuple Elements

csharp
1static (string name, int age, string city) GetPerson()
2{
3    return ("Alice", 30, "New York");
4}
5

6var person = GetPerson();
7Console.WriteLine($"{person.name} is {person.age} from {person.city}");

Practical Examples

Calculate Average

csharp
1static double CalculateAverage(int[] numbers)
2{
3    if (numbers.Length == 0)
4        return 0;
5

6    int sum = 0;
7    foreach (int n in numbers)
8    {
9        sum += n;
10    }
11    return (double)sum / numbers.Length;
12}
13

14int[] scores = { 85, 90, 78, 92, 88 };
15double avg = CalculateAverage(scores);
16Console.WriteLine($"Average: {avg:F2}");  // Average: 86.60

Password Validator

csharp
1static bool IsValidPassword(string password)
2{
3    if (password.Length < 8)
4        return false;
5

6    bool hasUpper = false;
7    bool hasLower = false;
8    bool hasDigit = false;
9

10    foreach (char c in password)
11    {
12        if (char.IsUpper(c)) hasUpper = true;
13        if (char.IsLower(c)) hasLower = true;
14        if (char.IsDigit(c)) hasDigit = true;
15    }
16

17    return hasUpper && hasLower && hasDigit;
18}
19

20Console.WriteLine(IsValidPassword("weak"));       // False
21Console.WriteLine(IsValidPassword("StrongPass1")); // True

Temperature Converter

csharp
1static double CelsiusToFahrenheit(double celsius)
2{
3    return celsius * 9 / 5 + 32;
4}
5

6static double FahrenheitToCelsius(double fahrenheit)
7{
8    return (fahrenheit - 32) * 5 / 9;
9}
10

11Console.WriteLine($"0°C = {CelsiusToFahrenheit(0)}°F");      // 32
12Console.WriteLine($"100°C = {CelsiusToFahrenheit(100)}°F");  // 212
13Console.WriteLine($"98.6°F = {FahrenheitToCelsius(98.6):F1}°C"); // 37.0

Chaining Methods

csharp
1static string FormatName(string name)
2{
3    return name.Trim().ToUpper();
4}
5

6static string Greet(string name)
7{
8    return $"Hello, {FormatName(name)}!";
9}
10

11static string CreateMessage(string name, int visits)
12{
13    string greeting = Greet(name);
14    return $"{greeting} This is visit #{visits}.";
15}
16

17string message = CreateMessage("  alice  ", 5);
18Console.WriteLine(message);  // Hello, ALICE! This is visit #5.

Summary

In this lesson, you learned:

  • Methods return values using the return statement
  • Return type is declared before the method name
  • void means no return value; other types require a return
  • Return values can be used in expressions, stored, or passed to other methods
  • Early returns can simplify code with conditions
  • Tuples allow returning multiple values

Next, we'll learn about method overloading.

Return Values - Anko Academy