Learn C# Programming

do
{
    // Code to execute
    // This runs at least once
} while (condition);

// while loop - may not execute at all
int x = 10;
while (x < 5)
{
    Console.WriteLine("This will never print");
    x++;
}

// do...while loop - executes at least once
int y = 10;
do
{
    Console.WriteLine("This will print once: " + y);
    y++;
} while (y < 5);

// Output: "This will print once: 10"

int choice;

do
{
    Console.WriteLine("\n=== MENU ===");
    Console.WriteLine("1. Option 1");
    Console.WriteLine("2. Option 2");
    Console.WriteLine("3. Option 3");
    Console.WriteLine("0. Exit");
    Console.Write("Enter your choice: ");
    
    if (int.TryParse(Console.ReadLine(), out choice))
    {
        switch (choice)
        {
            case 1:
                Console.WriteLine("You selected Option 1");
                break;
            case 2:
                Console.WriteLine("You selected Option 2");
                break;
            case 3:
                Console.WriteLine("You selected Option 3");
                break;
            case 0:
                Console.WriteLine("Goodbye!");
                break;
            default:
                Console.WriteLine("Invalid choice. Please try again.");
                break;
        }
    }
    else
    {
        Console.WriteLine("Invalid input. Please enter a number.");
        choice = -1; // Force loop to continue
    }
    
    } while (choice != 0);

// Output: "This will print once: 10"