**Course Title:** Mastering C#: From Fundamentals to Advanced Programming **Section Title:** Control Structures and Functions **Topic:** Loops: for, while, foreach. ### Introduction to Loops In the previous topic, we explored conditional statements, which allowed us to control the flow of our program based on certain conditions. In this topic, we will delve into loops, a fundamental concept in programming that enables us to execute a block of code repeatedly for a specified number of iterations or until a certain condition is met. Loops are essential in programming as they help us perform repetitive tasks efficiently and accurately. C# provides several types of loops, including `for`, `while`, and `foreach`. Each type of loop has its own strengths and is suited for specific use cases. ### For Loop A `for` loop is used when we know the number of iterations in advance. It consists of three main components: 1. Initialization: This is where we declare and initialize a loop counter variable. 2. Condition: This is the condition that is evaluated before each iteration. If the condition is true, the loop executes; otherwise, it terminates. 3. Increment/Decrement: This is where we update the loop counter variable after each iteration. The general syntax of a `for` loop is as follows: ```csharp for (int i = 0; i < 10; i++) { Console.WriteLine($"Iteration {i}"); } ``` In this example, the loop initializes a variable `i` to 0, checks if `i` is less than 10, and if so, executes the code inside the loop. After each iteration, `i` is incremented by 1. **Example 1: Sum of numbers using a for loop** ```csharp int sum = 0; for (int i = 1; i <= 10; i++) { sum += i; } Console.WriteLine($"Sum of numbers from 1 to 10: {sum}"); ``` In this example, the `for` loop iterates from 1 to 10, and in each iteration, it adds the current number to the `sum` variable. ### While Loop A `while` loop is used when we don't know the number of iterations in advance. It consists of a condition and a code block. The loop continues to execute the code block as long as the condition is true. The general syntax of a `while` loop is as follows: ```csharp int i = 0; while (i < 10) { Console.WriteLine($"Iteration {i}"); i++; } ``` In this example, the loop checks if `i` is less than 10, and if so, executes the code inside the loop. After each iteration, `i` is incremented by 1. **Example 2: Reading user input using a while loop** ```csharp string userInput = string.Empty; while (userInput.ToLower() != "exit") { Console.Write("Enter a string (or 'exit' to exit): "); userInput = Console.ReadLine(); Console.WriteLine($"You entered: {userInput}"); } ``` In this example, the `while` loop continues to read user input until the user enters the string 'exit'. ### Foreach Loop A `foreach` loop is used to iterate over collections or arrays. It provides a more readable and concise way to iterate over a collection without the need to manually increment a loop counter. The general syntax of a `foreach` loop is as follows: ```csharp int[] numbers = { 1, 2, 3, 4, 5 }; foreach (int number in numbers) { Console.WriteLine($"Number: {number}"); } ``` In this example, the `foreach` loop iterates over the `numbers` array and executes the code inside the loop for each number in the array. **Example 3: Sum of numbers in an array using a foreach loop** ```csharp int[] numbers = { 1, 2, 3, 4, 5 }; int sum = 0; foreach (int number in numbers) { sum += number; } Console.WriteLine($"Sum of numbers: {sum}"); ``` In this example, the `foreach` loop iterates over the `numbers` array and adds each number to the `sum` variable. ### Key Concepts * Loops allow us to execute a block of code repeatedly for a specified number of iterations or until a certain condition is met. * `for` loops are used when we know the number of iterations in advance. * `while` loops are used when we don't know the number of iterations in advance. * `foreach` loops are used to iterate over collections or arrays. ### Practical Takeaways * Use `for` loops when you need to perform a task a specific number of times. * Use `while` loops when you need to perform a task until a certain condition is met. * Use `foreach` loops when you need to iterate over a collection or array. ### Quiz Test your understanding of loops by answering the following questions: * What is the primary difference between a `for` loop and a `while` loop? * What is the purpose of the `foreach` loop? * Write a `for` loop that iterates from 1 to 10 and prints the sum of each number. * Write a `while` loop that reads user input until the user enters the string 'exit'. ### Additional Resources For more information on loops in C#, refer to the official [Microsoft Documentation: Loops](https://docs.microsoft.com/en-us/dotnet/csharp/tour-of-csharp/loops). **How was your experience learning about loops in C#? Do you have any questions or need further clarification on any of the topics covered? Leave a comment below or ask for help.** In the next topic, we will explore **Creating and using methods (functions)**.