Learn Do-While Loops: Ensuring Minimum Execution | While and Do-While Loops: Control and Flexibility

A do-while loop in C# is a type of loop that always executes its body at least once before checking its condition. The syntax places the condition after the loop body, which means the code inside the loop will run first, and then the condition is evaluated. This is a key difference from the while loop, where the condition is checked before any code inside the loop runs. The structure of a do-while loop looks like this:

do
{
    // Code to execute
} while (condition);

The flow of a do-while loop ensures that even if the condition is false from the beginning, the loop body will still run once. This makes do-while loops particularly useful when you need to guarantee that a block of code is executed at least one time, regardless of the initial state of the condition.

Program.cs


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using System;

namespace ConsoleApp
{
    public class Program
    {
        public static void Main()
        {
            int userInput;
            int simulatedInput = -1; // Simulated variable for demonstration

            do
            {
                // Simulate user entering a value (would be Console.ReadLine() in a real app)
                userInput = simulatedInput;
                Console.WriteLine("Enter a positive number:");
                Console.WriteLine($"(Simulated input: {userInput})");
                simulatedInput = 5; // Next input will be valid (simulate user correcting input)
            } while (userInput <= 0);

            Console.WriteLine("Thank you for entering a valid number!");
        }
    }
}

There are many scenarios where you want the loop body to run at least once before checking a condition. For example, when prompting a user for input, you often want to display the prompt and process the first input before deciding if you need to repeat the request. This is especially true for menus, confirmation dialogs, or situations where initial processing must always occur before validation.

Program.cs


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using System;

namespace ConsoleApp
{
    public class Program
    {
        public static void Main()
        {
            int choice;
            do
            {
                Console.WriteLine("Menu:");
                Console.WriteLine("1. Start Game");
                Console.WriteLine("2. Show High Scores");
                Console.WriteLine("3. Exit");
                Console.WriteLine("Enter your choice (1-3):");
                choice = 3; // Simulate user selecting 'Exit'
            } while (choice != 3);

            Console.WriteLine("Exiting menu. Goodbye!");
        }
    }
}

Choosing between a while loop and a do-while loop depends on whether you need the loop body to execute at least once. Use a do-while loop when the action must happen before any condition is checked—such as displaying a menu, asking for input, or initializing a process. In contrast, use a while loop when you might want to skip the loop entirely if the condition is false from the start. Understanding this difference helps you select the right loop for each situation and write more predictable, user-friendly programs.

1. What is the main difference between while and do-while loops?

2. When would you prefer a do-while loop over a while loop?

Everything was clear?

Thanks for your feedback!

Section 2. Chapter 3

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do
{
    // Code to execute
} while (condition);

Program.cs


              12345678910111213141516171819202122232425
            
using System;

namespace ConsoleApp
{
    public class Program
    {
        public static void Main()
        {
            int userInput;
            int simulatedInput = -1; // Simulated variable for demonstration

            do
            {
                // Simulate user entering a value (would be Console.ReadLine() in a real app)
                userInput = simulatedInput;
                Console.WriteLine("Enter a positive number:");
                Console.WriteLine($"(Simulated input: {userInput})");
                simulatedInput = 5; // Next input will be valid (simulate user correcting input)
            } while (userInput <= 0);

            Console.WriteLine("Thank you for entering a valid number!");
        }
    }
}

Program.cs


              123456789101112131415161718192021222324
            
using System;

namespace ConsoleApp
{
    public class Program
    {
        public static void Main()
        {
            int choice;
            do
            {
                Console.WriteLine("Menu:");
                Console.WriteLine("1. Start Game");
                Console.WriteLine("2. Show High Scores");
                Console.WriteLine("3. Exit");
                Console.WriteLine("Enter your choice (1-3):");
                choice = 3; // Simulate user selecting 'Exit'
            } while (choice != 3);

            Console.WriteLine("Exiting menu. Goodbye!");
        }
    }
}

1. What is the main difference between while and do-while loops?

2. When would you prefer a do-while loop over a while loop?

Everything was clear?

Thanks for your feedback!

Section 2. Chapter 3