C# Programming Labs

Your Task: Create a program that works with an array of integers - declaring, initializing, accessing elements, and calculating statistics.

Detailed Requirements:
1. Declare an integer array "numbers" - Initialize with at least 5 values. In C#, arrays are fixed-size collections. You can declare arrays in several ways:
   • int[] numbers = {10, 25, 8, 42, 15}; - Array initializer (most common)
   • int[] numbers = new int[5]; - Creates array with default values (0)
   • int[] numbers = new int[] {10, 25, 8, 42, 15}; - Explicit new keyword

2. Print array length - Use the .Length property: numbers.Length returns the number of elements. This is a property, not a method, so no parentheses!

3. Access individual elements - Arrays are zero-indexed, meaning the first element is at index 0:
   • numbers[0] → First element (10)
   • numbers[4] → Fifth element (15)
   • numbers[numbers.Length - 1] → Last element

4. Loop through all elements - Use a foreach loop (preferred) or traditional for loop:
   • foreach (int num in numbers) { Console.WriteLine(num); }
   • for (int i = 0; i < numbers.Length; i++) { ... }

5. Calculate sum and average - Loop through to add all values, then divide by length for average.

💡 Pro Tips:
• For dynamic-size collections, use List<int> instead of arrays
• Use Array.Sort(numbers) to sort in-place
• Use Array.Reverse(numbers) to reverse order
• LINQ provides shortcuts: numbers.Sum(), numbers.Average(), numbers.Max()

Expected Output:
Array length: 5 First element: 10 Last element: 15 All elements: 10 25 8 42 15 Sum: 100 Average: 20

Your Task: Create several methods to perform calculations and demonstrate method concepts including parameters, return values, and method overloading.

Detailed Requirements:
1. Create a method "Add" that takes two integers and returns their sum:
static int Add(int a, int b) { return a + b; }    • static - Method belongs to the class, not an instance
   • int - Return type (what the method gives back)
   • Add - Method name (use PascalCase in C#)
   • (int a, int b) - Parameters (inputs)

2. Create a method "Greet" that takes a name and prints a greeting:
static void Greet(string name) { Console.WriteLine($"Hello, {name}!"); }    • void - No return value (just performs an action)

3. Create an overloaded "Multiply" method:
Method overloading means having multiple methods with the same name but different parameters:
static int Multiply(int a, int b) { return a * b; } static int Multiply(int a, int b, int c) { return a * b * c; }

4. Create a method with a default parameter:
static void PrintMessage(string msg, int times = 1) { for (int i = 0; i < times; i++) Console.WriteLine(msg); }

💡 Pro Tips:
• Methods should do ONE thing well (Single Responsibility)
• Use descriptive names: CalculateTotal() not Calc()
• Return early to avoid deeply nested code
• Consider using out or ref parameters for multiple returns

Expected Output:
Sum: 15 Hello, Alice! Product of 2 numbers: 20 Product of 3 numbers: 60 Message printed once Message printed 3 times

Your Task: Master essential string operations in C# including length, case conversion, substring, and searching.

Detailed Requirements:
1. Create a string variable and get its length:
string message = "Hello, C# World!"; int length = message.Length;

2. Convert to uppercase and lowercase:
string upper = message.ToUpper(); // "HELLO, C# WORLD!" string lower = message.ToLower(); // "hello, c# world!" Note: These methods return NEW strings (strings are immutable in C#).

3. Extract substrings:
string sub1 = message.Substring(0, 5); // "Hello" (start, length) string sub2 = message.Substring(7); // "C# World!" (from index 7 to end)

4. Find characters and substrings:
int index = message.IndexOf("C#"); // 7 (position of "C#") bool contains = message.Contains("World"); // true bool starts = message.StartsWith("Hello"); // true bool ends = message.EndsWith("!"); // true

5. Replace and trim:
string replaced = message.Replace("World", "Universe"); string trimmed = " spaces ".Trim(); // "spaces"

6. Split and join:
string[] words = message.Split(' '); // Split by space string joined = string.Join("-", words); // Join with dash

💡 Pro Tips:
• Strings are immutable - methods return new strings
• Use StringBuilder for many concatenations (better performance)
• string.IsNullOrEmpty(str) checks for null or ""
• string.IsNullOrWhiteSpace(str) also checks for whitespace
• Use @"string" for verbatim strings (ignores escape chars)

Expected Output:
Original: Hello, C# World! Length: 16 Uppercase: HELLO, C# WORLD! Lowercase: hello, c# world! Substring: Hello Contains 'C#': True Index of 'World': 10 Replaced: Hello, C# Universe!