I'm new to coding and trying my best but I got stuck. Again. So. I need to calculate the product of some random numbers using do while. You type the numbers and when you type x, the loop needs to close showing the result. If you ONLY type x, it needs to show "1".

I can't manage to only show "1" when you type "x".

I have this:

int product = 1;

Console.WriteLine();
String input = Console.ReadLine();

do
{
    int n = Convert.ToInt32(input);
    product = product * n;
    input = Console.ReadLine();
} while (!input.ToLower().Equals("x"));
            
Console.WriteLine(product);
Console.ReadLine();

CodePudding user response：

for and while breaks in the start of the loops and do while break at the end, sometimes you have to break it the middle (here after the input was entered, if it's x) and before the accumulation.

The best way to manage this is an infinite loop for(;;) or while(true) and uses of break:

var product = 1;

for(;;)
{
    var input = Console.ReadLine();
    if (input is null || input.Equals("x", StringComparison.OrdinalIgnoreCase))
        break;

    product *= Convert.ToInt32(input);
}

Console.WriteLine(product);
Console.ReadLine();

Or you can try to make it fit (mostly double calls to ReadLine).

A for version that looks ugly:

var product = 1;
for (var input = Console.ReadLine(); input != "x"; input = Console.ReadLine())
{
    product *= int.Parse(input);
}

Console.WriteLine(product);
Console.ReadLine();

A while version:

var product = 1;
var input = Console.ReadLine();

while (!input.ToLower().Equals("x"))
{
    product *= Convert.ToInt32(input);
    input = Console.ReadLine();
} 

Console.WriteLine(product);
Console.ReadLine();

Another while version that avoid ReadLine at multiple places:

var product = 1;

string input;

// an affectation actually evaluate to the value affected
// avoid this since it's not easily readable (= and == mismatch)
while ((input = Console.ReadLine()) != "x")
{
    product *= Convert.ToInt32(input);
} 

Console.WriteLine(product);
Console.ReadLine();

A do while version:

I add it because it's in the question title, otherwise I didn't consider it a good solution.
Based on

CodePudding user response：

        ConsoleKeyInfo continueProgram = new ConsoleKeyInfo();
        ConsoleKeyInfo continueInput = new ConsoleKeyInfo();

        List<int> products = new List<int>();

        do
        {
            Console.Clear();
            
            do
            {
                Console.Write("\nPlease enter new number . . . ");
                if (int.TryParse(Console.ReadLine(), out int result))
                {
                    products.Add(result);
                    Console.WriteLine("\nNew Product Added!");
                }
                else
                {
                    Console.WriteLine("\nYou have entered a value that is not an integer!\n");
                }

                Console.Write("\nDo you want to enter an other value (press Y) or any key to exit . . . ");
                continueInput = Console.ReadKey();
                Console.WriteLine();
            }
            while (continueInput.Key == ConsoleKey.Y);

            Console.WriteLine();

            foreach (var item in products)
            {
                Console.WriteLine(item.ToString());
            }

            Console.ReadLine();

            Console.Write("\n\nPress 'Y' to continue or any other key to exit! . . . ");
            continueProgram = Console.ReadKey();

        } while (continueProgram.Key == ConsoleKey.Y);

CodePudding user response：

The problem is that Console.ReadLine() gets called twice before checking for x. The first input gets eaten up.

What you need to do is inside the loop ask and process the input, and exit the loop when the condition is met.

One way of doing this is by keeping a boolean value called done indicating when to exit the loop'

    static void Main(string[] args)
    {
        int product = 1;
        bool done = false;
        do
        {
            Console.WriteLine("Enter number or 'x' to calculate result.");
            string input = Console.ReadLine();
            done = input.ToLower() == "x";
            if (int.TryParse(input, out int value))
            {
                product *= value;
            }
            else
            {
                Console.WriteLine("Input ignored.");
            }
        } while (!done);

        Console.WriteLine($"The product is {product}");

    }

Another more succinct way is to use the break; statement

    static void Main(string[] args)
    {
        int product = 1;
        do
        {
            Console.WriteLine("Enter number or 'x' to calculate result.");
            string input = Console.ReadLine();
            if (input.ToLower() == "x")
            {
                // this exits the loop
                break;
            }
            if (int.TryParse(input, out int value))
            {
                product *= value;
            }
            else
            {
                Console.WriteLine("Input ignored.");
            }
        } while (true);

        Console.WriteLine($"The product is {product}");

    }

Also, it is recommended to use int.TryParse(string, out integer) for better handling weird user inputs instead of Convert.ToInt32(). See the pattern above on how it is used.