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Calculating product of numbers using do while

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();

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 yassinMi answer.
var product = 1;
var input = "1";
do
{
product *= int.Parse(input);
input = Console.ReadLine();
} while (input != "x");
Console.WriteLine(product);
Console.ReadLine();
A Linq version:
var product = Enumerable.Range(0, int.MaxValue) // many elements
.Select(_ => Console.ReadLine()) // discard them and take the console input
.TakeWhile(s => s != "x") // stop on 'x'
.Select(int.Parse) // parse to int
.Aggregate(1, (a, b) => a * b); // accumulate from 1 and by making the product
Console.WriteLine(product);
Console.ReadLine();

a simple fix: change the line
String input = Console.ReadLine();
to
String input = "1";
otherwise you would use the while loop, or add extra if statement..

Welcome to C#!
Your issue is most likely due to an error while converting a value. You are trying to convert "x" to int, but "x" is a letter, which cannot be converted to a number.
Cause of the issue
The problem of this program is that you are trying to convert a letter to a number. This is not possible in real life, and less possible in programming! A computer is not able to convert a number to a letter, unless you are explaining to it how, or if your handle the error properly.
The following line:
int n = Convert.ToInt32(input);
...Does not check for what has been entered. Convert.ToInt32() will throw an exception if the string? (From Console.ReadLine()) could not be converted.
The fix
To fix this issue, you need to handle the input of the user. Literally anything is accepted by Console.ReadLine() but you want a value that can be converted to a int.
The int type has a built-in function to convert a value without throwing an exception if it couldn't be converted, instead, it returns a bool (Either true or false).
So the following changes need to be brought to your program:
int product = 1;
string ? input;
do {
input = Console.ReadLine();
// Try to parse to integer, if it couldn't be parsed to integer, continue.
if (!int.TryParse(input, out int n)) {
continue;
}
product = product * n;
} while (!input.Equals("x", StringComparison.InvariantCultureIgnoreCase));
Console.WriteLine(product);
// End of the program
Console.WriteLine("Press any key to quit the program.");
Console.ReadKey();
Trying to parse a string to an integer
The method int.TryParse(string? input, out int output); allows you to try to convert a string to a int.
If the method fails, instead of throwing an Exception, it will returns false.
Getting the output value
The output value can be obtained from out int output, out allows you to output a value from a function.
The logic would be that if int.TryParse(...) returns true, the value can be used, otherwise you can continue.
The continue statement tells your loop that the current loop should be skipped and goes to the next one (= At the beginning of your loop).
Other changes
I've brought to your program some changes to make it more readable and easier to edit.
Firstly, you'd want to use Equals(input, StringComparison.InvariantCultureIgnoreCase) instead of ToLowerCase(), the result is the same and it is cleaner! 🙂
Also, you can directly ask the input within your while loop since this will be repeated each time, you just need to position it correctly so the value can be verified.
Final program

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);

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.

What is wrong with my while statement? Else statement won't write

Everything runs correctly except the else statement. It gets skipped over once the numbers are equal to each other. It doesn't say "You got it" at the end.
//declare variables
int number = 4;
int guessCount = 0;
int guess;
//get first number
Console.WriteLine("Guess a number between 1 and 10:");
guess = Convert.ToInt32(Console.ReadLine());
guessCount = guessCount + 1; //increment counter
while (guess != number) //keep repeating until number is chosen
{
guessCount = guessCount + 1; //increment counter
if (guess < number) //if statement if guess is less than number
{
Console.WriteLine("Your guess is too low.");
}
else if (guess > number) //if statement if guess is more than number
{
Console.WriteLine("Your guess is too high.");
}
else //
{
Console.WriteLine("You got it!!");
}
//end of while to ask for a new guess
Console.WriteLine("Guess again: ");
guess = Convert.ToInt32(Console.ReadLine());
}
//display output
Console.WriteLine("You figured it out in " + guessCount + " guesses.");
Console.ReadLine(); //keep window open

Your while expression states: guess != number which is true as long as the user does not type in 4 (your hardcoded value). You are setting guess right before the while expression gets checked, so if the user types in the right number, the while expression will be false and it will be jumped over. I commented your code at the problems' locations.
//declare variables
int number = 4;
int guessCount = 0;
int guess;
//get first number
Console.WriteLine("Guess a number between 1 and 10:");
// Problem A: user types in 4 -> guess becomes equal to number -> while expression gets false -> while body will not be executed
guess = Convert.ToInt32(Console.ReadLine());
while (guess != number) //keep repeating until number is chosen
{
guessCount = guessCount + 1; //increment counter
if (guess < number) //if statement if guess is less than number
{
Console.WriteLine("Your guess is too low.");
}
else if (guess > number) //if statement if guess is more than number
{
Console.WriteLine("Your guess is too high.");
}
else //
{
Console.WriteLine("You got it!!");
}
//end of while to ask for a new guess
Console.WriteLine("Guess again: ");
// Problem B: user types in 4 -> guess becomes equal to number -> while expression gets false -> loop ends
guess = Convert.ToInt32(Console.ReadLine());
}

When it is coming into the while loop, it means that guess is != number and the only state that is possible here is guess < number and guess > number that you have already checked for, and guess = number is meaningless because if the guess is equal to number it doesn't even comes into the while loop. This is why your else statement never executes because the only state that your else statement is checking for is guess == number.

"Prove" that string is immutable in c#

I already knew that in C#, string are reference type that are handled mostly like a value type, but I recently discover this:
http://net-informations.com/faq/general/immutable.htm
I'm trying to "prove" that string are immutable by printing the reference to a string variable anytime a concatenation occurs:
string s = string.Empty;
for (int i = 0; i < 10; i++)
{
s += " " + i;
// Console.WriteLine(&s);
}
As you can guess, the code doesn't compile if the line is uncommented (Compiler Error CS0208: Cannot take the address of, get the size of, or declare a pointer to a managed type ('type')).
I also tried the GetHashCode(), but apparently for string it returns the same value based on the... String value itself (ie. it will always return the same result for "0" for instance).
Is there a way to do that? It won't be for a coding purpose, just for an understanding purpose... If not, how can you know that it will "really" create n instances of a string at each concatenation? Appart from "knowing it"...
EDIT: probably not a duplicate of C# memory address and variable, because I want to know how to get the address of a reference type, and apparently that thread deals only with value type.

If you want to check that a new instance was created, just compare it to the previous instance:
string s = string.Empty;
for (int i = 0; i < 10; i++)
{
var saved = s;
s += " " + i;
if (ReferenceEquals(saved, s))
Console.WriteLine("oops, no new instance created?");
}
You'll see that this won't print anything.

You can use the ObjectIDGenerator to generate ids for the strings and see if the ids are the same.
var string1 = "Jerry";
ObjectIDGenerator generator = new ObjectIDGenerator();
bool string1FirstTime;
long string1Id = generator.GetId(string1, out string1FirstTime);
bool string2FirstTime;
var string2 = string1 + " Seinfeld";
long string2Id = generator.GetId(string2, out string2FirstTime);
Below will return false because they are not the same.
var same = string1Id == string2Id;

You can copy the string to another variable, and compare their references and value before and after modification:
string s = string.Empty;
for (int i = 0; i < 10; i++)
{
var copy = s;
// true
Console.WriteLine("both are the same reference: {0}", Object.ReferenceEquals(s, copy));
// true
Console.WriteLine("both are the same value: {0}", s.Equals(copy));
s += " " + i;
// false
Console.WriteLine("both are the same reference: {0}", Object.ReferenceEquals(s, copy));
// false
Console.WriteLine("both are the same value: {0}", s.Equals(copy));
}

Using int in try outside of context

Console.Write("Write a number: ");
try
{
int Number = Convert.ToInt32(Console.ReadLine());
}
catch ( OverflowException )
{
Console.WriteLine("Number to big");
}
TellLastNumber(Number);
It says the 'Number' does not exist in the current context.
How can I make the int 'Number' used everywhere in the main()?

How can I make the int 'Number' used everywhere in the main()?
Just move declaration of variable Number to the scope of main() and it will be available from that point to the end of the function.
Console.Write("Write a number: ");
int Number = 0;
try
{
Number = Convert.ToInt32(Console.ReadLine());
}
catch ( OverflowException )
{
Console.WriteLine("Number to big");
}
TellLastNumber(Number);

To get rid of the error you have to define the Number outside of the try block and assign it some default value.
int Number = 0;
try
{
int Number = Convert.ToInt32(Console.ReadLine());
}
catch ( OverflowException )
{
Console.WriteLine("Number to big");
}
TellLastNumber(Number);
But more importantly use int.TryParse, that will not raise an exception if the number passed to it is not an int.
int Number;
if (!int.TryParse(Console.ReadLine(), out Number))
{
Console.WriteLine("Invalid number");
}
TellLastNumber(Number);
You are getting the error, because compiler can't see Number outside the scope of try.

Returning a value from a static void to a static void, that make use of public variables - some guidance please

Just so everyone knows I have literally just started writing C#, and this is practice.
I found a GuessTheNumberGame code on the internet and have been trying to improve the basic game so that feedback is given, and the user can change the numbers.
I had the program working but wanted to put the 'NumberChange' module separate from the 'Code' Method.
I have made a Main() Method inside of my 'GuessTheNumberGame' with executes the 'Code' method.
The thing is when I go to change the number range the 'NumberChange' module won't change the values of 'Public Static int from' or 'Public static int to'; and because of this the range of the numbers remains the same.
Code below:
using System;
namespace GuessThatNumber
{
class GuessTheNumberGame
{
static void Main()
{
Code(from, to, new_range);
}
public static int new_range = 0;
public static int from = 1;
public static int to = 10;
static void Code(int from, int to, int new_range)
{
//int from = 1; // The range the user will guess from.
//int to = 10; //The range the user will guess to.
int guessedNumber; //This will hold the value that the user guessed.
int Counter = 0; //Counter is used to count the number of guesses the user makes.
int selection = 0; //This value is for the selection at the start of the program
//int new_range = 0;
bool exit = false;
while (exit == false)
{
Console.WriteLine("What would you like to do?");
Console.WriteLine("1: Alter the range of guessed numbers? The range is currently from {0} to {1}.", from, to);
Console.WriteLine("2: Try to guess the number?");
Console.WriteLine("3: Exit the program?");
Console.WriteLine("Please enter a number:");
if (int.TryParse(Console.ReadLine(), out selection))
{
if (selection == 2)
{
int randomNumber = new Random().Next(from, to); //Generates a random number between the (from, to) variables.
Console.Write("The number is between {0} and {1}. ", from, to);
while (true)
{
Console.Write("Make a guess: ");
if (int.TryParse(Console.ReadLine(), out guessedNumber))
{
if (guessedNumber == randomNumber)
{
Console.WriteLine("You guessed the right number!");
if (Counter < 2)
{
Console.WriteLine("You guessed the number in only 1 turn! Amazing!");
Console.WriteLine(" ");
}
else
{
Console.WriteLine("You guessed " + Counter + " times.");
Console.WriteLine(" ");
}
break;
}
else
{
Console.WriteLine("Your guess was too {0}.", (guessedNumber > randomNumber) ? "high" : "low");
Counter = Counter + 1;
}
}
else
{
Console.WriteLine("Input was not an integer.");
}
}
//Console.WriteLine();
//Console.WriteLine("Press any key to exit.");
//Console.ReadKey();
}
else if (selection == 1)
{
NumberChange(from, to, new_range);
}
else
{
exit = true;
}
}
}
}
static int NumberChange(int from, int to, int new_range)
{
Console.WriteLine("Please enter the number that the guess will start from.");
int.TryParse(Console.ReadLine(), out new_range);
from = new_range;
Console.WriteLine("Now enter the number that the guess will go to.");
int.TryParse(Console.ReadLine(), out new_range);
to = new_range;
return new_range;
}
}
}

Please read about passing parameters by reference in C#.
So far, your parameters are passed by value. That means that upon calling Code() in the beginning of your program, the current values of public static int from and public static int to are copied into the parameters from and to.
The same happens when you invoke NumberChange(): The values of the parameters (local variables) from and to are copied into the parameters of the NumberChange() method with the same names, but if those values are modified within NumberChange, the new values don't ever get back from there; you have just modified the local variables from and to that only exist within the respective method.
Instead, you could declare your parameters using the ref keyword:
static int NumberChange(ref int from, ref int to, int new_range)
This means that you will have to invoke your method using the ref keyword for the respective arguments, too:
NumberChange(ref from, ref to, new_range);
Also, note two issues about your NumberChange() method:
You pass in a new_range argument, but you do not use it. In fact, it is overridden in your call to TryParse(). Therefore, you could simply declare int new_range as a local variable rather than passing it as a parameter.
You return a value from that method, but you do not use that value. Therefore, you could declare your method as void and drop the return statement.
Lastly, if you want your public static int from and public static int to variables to be changed by Code(), add the ref keyword analogously to NumberChange(). However, this is not really useful with your current code, as the program ends right after leaving Code() and the new values wouldn't be used at all.

You are using static variables, then passing them into a method that has access to them already. Passing them in essentially overrides the static versions with the local ones.
Change your method to this:
private static void NumberChange()
{
int new_range;
Console.WriteLine("Please enter the number that the guess will start from.");
int.TryParse(Console.ReadLine(), out new_range);
from = new_range;
Console.WriteLine("Now enter the number that the guess will go to.");
int.TryParse(Console.ReadLine(), out new_range);
to = new_range;
}
static void Code()
{
}
And delete this line:
public static int new_range = 0;

If you pass your variables by reference. Then the function your passing them can change them.
something like this
static int NumberChange(ref int from, ref int to, ref int new_range)
{
//Your code here
}
Adn the same for your Code method