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Exam Notes

Week 2 C# Fundamentals: Control Flow, Loops, and Methods

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1. Control Flow in C#

If Statements: Executes a block of code only if the condition is true.

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if (condition) {

// Code executes if condition is true

}

If-Else Statements: Provides an alternative block of code if the condition is false.

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if (condition) {

// Executes if condition is true

} else {

// Executes if condition is false

}

Else If Statements: Used to check multiple conditions in sequence.

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if (condition1) {

// Executes if condition1 is true

} else if (condition2) {

// Executes if condition2 is true

} else {

// Executes if neither condition1 nor condition2 are true

}

Switch Statements: Tests a single expression against multiple values.

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switch (variable) {

case value1:

// Code for value1

break;

case value2:

// Code for value2

break;

default:

// Code if no cases match

break;

}

Key Points:

Use break to exit a case and prevent "fall-through" (unintentional execution of subsequent cases).

The default case is optional but recommended as a fallback when no cases match.

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2. Loops in C#

Loops allow repeating a block of code as long as a condition is met.

While Loop: Executes as long as the condition is true. If the condition is false initially, the loop does not execute.

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while (condition) {

// Loop body

}

Do-While Loop: Executes the loop body at least once since the condition is checked after the loop body.

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do {

// Loop body

} while (condition);

For Loop: Commonly used when the number of iterations is known in advance.

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for (initialization; condition; update) {

// Loop body

}

Example:

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for (int i = 0; i < 5; i++) {

Console.WriteLine(i);

}

Foreach Loop: Simplifies iterating over collections and arrays by automatically accessing each element in the collection.

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foreach (var item in collection) {

// Loop body

}

Example:

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int[] numbers = { 1, 2, 3 };

foreach (int num in numbers) {

Console.WriteLine(num);

}

Note: Values accessed in a foreach loop are read-only within the loop, so they cannot be modified directly.

Jump Statements in Loops:

break: Immediately exits the nearest loop or switch.

continue: Skips the rest of the code in the current loop iteration and proceeds to the next iteration.

return: Exits the method and, if specified, returns a value (applicable only within methods, not loops).

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3. Methods in C#

Methods are reusable blocks of code that perform specific tasks. They can accept parameters, execute code, and optionally return values.

Defining a Method:

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returnType MethodName(parameterList) {

// Method body

}

Example:

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public int Add(int a, int b) {

return a + b;

}

Method Components:

Return Type: Specifies the type of value the method returns (e.g., int, string, void).

Method Name: Follows PascalCase naming convention.

Parameter List: Defines parameters passed to the method with types and names, separated by commas.

Return Statement: Ends method execution and returns a value (if specified).

Calling a Method:

Example of calling a method with parameters and capturing the return value:

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int result = Add(5, 3); // Calls the Add method with arguments 5 and 3

Examples of Method Types:

Method with Parameters and Return Type:

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public int Multiply(int x, int y) {

return x * y;

}

Void Method: A void method does not return a value.

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public void DisplayMessage() {

Console.WriteLine("Hello, World!");

}

Overloading Methods:

You can create multiple methods with the same name but different parameter lists. This is called method overloading.

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public int Add(int a, int b) {

return a + b;

}

public double Add(double a, double b) {

return a + b;

}

Note: Overloaded methods must differ in their parameter lists (number or types of parameters).

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4. Arrays and Collections

Arrays and collections store groups of elements in C#.

Arrays: A fixed-size, ordered collection of elements of the same type.

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int[] numbers = new int[3] { 1, 2, 3 };

Accessing Elements: Array elements are accessed by index, starting at 0. For example, numbers[0] would give 1.

Iterating Over Arrays:

Using a for loop:

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for (int i = 0; i < numbers.Length; i++) {

Console.WriteLine(numbers[i]);

}

Using foreach loop (simpler for read-only access):

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foreach (int num in numbers) {

Console.WriteLine(num);

}

Collections: Dynamic data structures like List, Dictionary, and Queue are more flexible than arrays.

List: A resizable array-like collection.

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List<int> numbers = new List<int>() { 1, 2, 3 };

numbers.Add(4); // Adds 4 to the list

Dictionary: Stores key-value pairs.

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Dictionary<string, int> ages = new Dictionary<string, int>();

ages.Add("Alice", 25);

ages.Add("Bob", 30);

Summary: Key Points for Week 2

Control Flow: Use if, else, and switch statements for conditional execution.

Loops:

Use for and while loops for repeated execution.

Use foreach loops for simpler iteration over arrays and collections.

Understand break (exit loop/switch), continue (skip to next iteration), and return (exit method).

Methods:

Define methods with a return type, name, and optional parameters.

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