Hello i'm trying to create a calculator game but it loops only 2 times and (idk why)not til the user finds the result with input. And i'll later see how to make a random generator of numbers instead of writing them by myself in the code. Ty for helping.
Yassine
using System;
namespace G
{
class Program
{
static void Main(string[] args)
{
Calcul(2, 2);
}
static void Calcul(int nombre1, int nombre2)
{
int result = nombre1 + nombre2;
Console.WriteLine("Combien font " + nombre1 + " + " + nombre2);
int supposed = int.Parse(Console.ReadLine());
if(result != supposed)
{
Console.WriteLine("Try again!");
supposed = int.Parse(Console.ReadLine());
}
else
{
Console.Clear();
Console.WriteLine("Correct!");
}
}
}
}
You can change your if statement to a while loop whose condition is that the input does not match the result. We can also use int.TryParse with Console.ReadLine to handle cases where the user doesn't enter a valid number. This works by taking an out parameter that gets set to the parsed value if it's successful, and it returns a bool that indicates success. Perfect for a loop condition!
Then you can put the "success" message after the body of the while loop (because the only way to exit the loop is to get the correct answer). It would look something like:
static void Calcul(int nombre1, int nombre2)
{
int result = nombre1 + nombre2;
int input;
Console.Write($"Combien font {nombre1} + {nombre2} = ");
while (!int.TryParse(Console.ReadLine(), out input) || input != result)
{
Console.WriteLine("Incorrect, please try again.");
Console.Write($"Combien font {nombre1} + {nombre2} = ");
}
Console.WriteLine("Correct! Press any key to exit.");
Console.ReadKey();
}
Related
This question already has answers here:
check for valid number input - console application
(5 answers)
Allow To Only Input A Number - C#
(1 answer)
Closed 2 years ago.
I have just started a table programme. I am just a trainee learning C# from internet, so I am not so good in this.
I just wanted the programme to run according to the user. I want that if the user hits enter simply, the programme should not crash. That is I just wanted to know how to prevent null enter. This is the code is used:
The "______" which used if for writing a line
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace tables
{
class Program
{
static void Main(string[] args)
{
goto found;
found:
Console.WriteLine("");
string textToEnter = "MULTIPLATION TABLES";
Console.WriteLine(String.Format("{0," + ((Console.WindowWidth / 2) + (textToEnter.Length / 2)) + "}", textToEnter));
Console.WriteLine("");
Console.WriteLine("________________________________________________________________________________");
Console.WriteLine("");
int num, j, i;
Console.Write("enter the number of which table u need ? :- ");
num = Convert.ToInt32( Console.ReadLine());
while (num == 0)
{
Console.WriteLine("please enter a valid input");
Console.Write("enter the number of which table u need ? :- ");
num = Convert.ToInt32(Console.ReadLine());
}
Console.Write("enter the number till which the table need to be ? :- ");
j = Convert.ToInt32(Console.ReadLine());
while (j == 0)
{
Console.WriteLine("please enter a valid input");
Console.Write("enter the number till which the table need to be ? :- ");
j = Convert.ToInt32(Console.ReadLine());
}
i = Convert.ToInt32(j);
for (j=1; ; j++)
{
if (j > i)
{
break;
}
Console.WriteLine(num + " * " + j + " = " + num * j);
}
string str;
Console.Write("do you want to continue? (y/n) :- " );
str= Console.ReadLine();
foreach (char ch in str)
{
if (ch == 'y')
{
goto found;
}
else if (ch=='n' )
{
Console.WriteLine("");
Console.WriteLine("THANK YOU FOR USING MY PRODUCT");
}
else
{
Console.WriteLine("please enter a valid input");
}
}
Console.ReadKey();
}
}
}
As suggested in the comments, I'd use int.TryParse(), but inside a do...while() loop. Use a separate flag (boolean) to track whether the user should keep trying again:
bool invalid;
int num, j, i;
do
{
invalid = true;
Console.Write("enter the number of which table u need ? :- ");
String response = Console.ReadLine();
if (int.TryParse(response, out num))
{
invalid = false;
}
else
{
Console.WriteLine("Invalid input. Please try again.");
}
} while (invalid);
// ...repeat the above do...while() block for "j" and "i"...
When you're accepting user input, it's important to perform validation on it. You can't assume that the user will always enter correctly formatted data that your program will be able to work with. As you discovered, a user who hits enter will give you an empty string (""), which can't be parsed to anything.
C# has several ways of attempting parsing. The first, which you're using, is Convert.ToInt32(), which throws an exception if the input it receives is not, in fact, a number. You have to catch the exception with a try/catch block, like so:
try
{
num = Convert.ToInt32(Console.ReadLine());
}
catch(FormatException ex)
{
Console.WriteLine("You didn't enter a proper number!");
}
However, in general, exceptions should be, well, exceptional. They should only be relied upon when rare failures occur, because unwinding the call stack can be expensive.
I would argue that C# has a better method for you to use in this instance: Int32.TryParse()
You can see the documentation here.
TryParse takes two parameters, the thing you're trying to parse (convert), and then a number to store the value in. It returns true or false, indicating if it succeeded or failed in converting the number.
You might use it like this:
var success = Int32.TryParse(Console.ReadLine(), num);
if (success)
{
// do something with 'num' -- it has a valid value now.
}
else
{
// Warn the user, perhaps prompt them to try again
Console.WriteLine("That wasn't a valid number!");
}
You can use a methode to get a safe int value:
private static int ReadIntValue(string psMessage)
{
int lnInt;
string lsValue = string.Empty;
do
{
Console.Write(psMessage);
lsValue = Console.ReadLine();
} while (!int.TryParse(lsValue, out lnInt));
return lnInt;
}
And then use this:
num = ReadIntValue("enter the number of which table u need ? :- ");
Basically I'm trying to not let the user input string instead of an integer; but on line of code:
else if (Convert.ToString(result) == "")
I get an error.
Full code:
class Program
{
static void Main(string[] args)
{
Console.ForegroundColor = ConsoleColor.Red;
int calcKelvin = 273;
int calcFahren = 32;
int result = Convert.ToInt32(Console.ReadLine());
if (result == 0)
{
Console.WriteLine("Check it up on google!");
Console.Title = "I'M USELESS CONSOLE, YOU CAN NOW EXIT || I'M USELESS CONSOLE, YOU CAN NOW EXIT || I'M USELESS CONSOLE, YOU CAN NOW EXIT ||";
}
else if (Convert.ToString(result) == "")
{
Console.Write("Error, you can not convert a text");
}
else
{
Console.WriteLine("Kelvin = " + calcKelvin * result);
Console.WriteLine("Fahrenheit = " + calcFahren * result);
}
}
}
The safest way to get a number from a string is to use the TryParse method, because this method returns two values! The actual return type is a bool which indicates whether or not the string was successfully converted, and the other is an out parameter, which is of the type that we're converting to, and which gets set to the converted value (or is set to the default value of the type if the conversion fails).
For temperatures, we often deal with decimal numbers, so a double is probably a good type to store the result. So, we'll use double.TryParse.
Now, since we don't necessarily want to just quit if the user makes a mistake, we should probably do our conversion in a loop, so if it fails, we just ask the user to try again. And since this code will be used in other places as well, we can make a helper method that takes in a prompt that we display to the user, and returns the strongly-typed user response:
private static double GetDoubleFromUser(string prompt = null)
{
double result;
do
{
Console.Write(prompt);
} while (!double.TryParse(Console.ReadLine(), out result));
return result;
}
With this method, we can now just declare a double and assign it to the return value of the method above, like:
double userInput = GetDoubleFromUser("Enter a temperature: ");
Another thing we can correct in the code are the formulas used to do the conversions. A quick check online shows us that we add a number for kelvin and we do multiplication, division, and addition for Fahrenheit. We can calculate these values on the fly once we have the Celsius temperature from the user:
private static void Main()
{
double celcius = GetDoubleFromUser("Enter a Celcius temperature: ");
double fahrenheit = celcius * 9 / 5 + 32;
double kelvin = celcius + 273.15;
Console.WriteLine("Kelvin = " + kelvin);
Console.WriteLine("Fahrenheit = " + fahrenheit);
GetKeyFromUser("Done! Press any key to exit...");
}
Output
Convert.ToInt32 throws an exception if the input string is not a number. To fix that, you can use int.TryParse instead.
Example:
using System;
class Program
{
static void Main(string[] args)
{
Console.ForegroundColor = ConsoleColor.Red;
int calcKelvin = 273;
int calcFahren = 32;
int result;
bool isNum=int.TryParse(Console.ReadLine(),out result);
if (!isNum)
{
Console.Write("Error, you can not convert a text");
}
else if (result == 0)
{
Console.WriteLine("Check it up on google!");
Console.Title = "I'M USELESS CONSOLE, YOU CAN NOW EXIT || I'M USELESS CONSOLE, YOU CAN NOW EXIT || I'M USELESS CONSOLE, YOU CAN NOW EXIT ||";
}
else {
Console.WriteLine("Kelvin = " + calcKelvin * result);
Console.WriteLine("Fahrenheit = " + calcFahren * result);
}
}
}
I wrote a basic number guessing game from C#. It seems to return the 3rd option ("Wrong choice! Please try again.") every time no matter what var c is chosen by the user. I was trying with characters (s instead of 1 and w instead of 2 etc with c as a string) but it gave the same results. Not sure where it's going bad.
using System;
namespace Challanges
{
class Program
{
static int guess = 500;
static int low = 1;
static int high = 1000;
static bool cont = false;
static void Guess() //guesses and adjusts variables according to input.
{
int c;
Console.WriteLine("Is your number greater or less than: " + guess + Environment.NewLine + "If it is less than, press 1; if it is greater, press 2." + Environment.NewLine + "If it is your number, press 3.");
c = Convert.ToInt32(Console.Read());
if (c == 1)
{
high = 500;
guess = low + high / 2;
}
else if (c == 2)
{
low = 500;
guess = low + high / 2;
}
else if (c == 3)
{
Console.WriteLine("Congratulations!! We found your number!");
cont = true;
}
else
{
Console.WriteLine("Wrong choice! Please try again.");
Console.ReadKey();
}
}
static void Main(string[] args)
{
Console.WriteLine("Hello World!" + Environment.NewLine + "Let's play a guessing game. Think of a number between 1 and 1000." + Environment.NewLine + "Type your number :)");
int x = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("Your number is: " + x + Environment.NewLine + "Too easy?");
Console.ReadKey();
Console.WriteLine("Think of a number");
if(cont == false)
{
Guess();
} else
{
Console.ReadKey();
}
}
}
}
As mentioned in the comments before, Console.Read() returns a character code. The character code for the number 1 is 49, thus your conditions fail and the else block is executed.
What you wanted to do was use Console.ReadLine()which returns a string instead of character codes. If you cast that string into an Int32 you should be able to evaluate your conditions correctly.
I can't figure out after searching and searching (you know how it goes) why this code doesn't work.
I just want it to work like this
if (Nummer == "") {
Console.WriteLine("0");
}
That's it, and it doesn't work. I have been searching for an hour and a half. Can't understand why there is a simple basic explanation. I only found how to fix it with a string or something, then I tried to convert it and it still didn't work. Can someone help me please?
I appreciate your patience for my limited knowledge. Thanks for your time
static void Main(string[] args)
{
bool herhaal = true;
do
{
Console.Write("Geef een getal : ");
int Nummer = Convert.ToInt16(Console.ReadLine());
if (Console.ReadLine() == "" && Console.ReadLine() == null)
{
Console.WriteLine("0");
}
double kw = Math.Pow(Nummer, 2);
Console.WriteLine("Kwadraat van {0} is: {1}", Nummer, kw + Environment.NewLine);
} while (herhaal);
}
static void Main(string[] args)
{
int Nummer;
bool herhaal = true;
do
{
Console.Write("Geef een getal : ");
//only read from the Console ONCE per loop iteration, and always read to a string first
string input = Console.ReadLine();
//TryParse better than Convert for converting strings to integers
if (!int.TryParse(input, out Nummer))
{
Console.WriteLine("0");
}
else //only do the second part if the conversion worked
{
double kw = Math.Pow(Nummer, 2);
Console.WriteLine("Kwadraat van {0} is: {1}\n", Nummer, kw);
}
} while (herhaal);
}
To do this from a WinForms app, as attempted in the comments:
private void button1_Click(object sender, EventArgs e)
{
double aantalgroep;
if (!double.TryParse(textBox1.Text, out aantalgroep))
{
textBox1.Text = "0";
}
else
{
double kw = Math.Pow(aantalgroep, 2);
textBox1.Text = String.Format("Kwadraat van {0} is: {1}", aantalgroep, kw);
}
}
The Console.ReadLine() method 'reads' one line of user input, and stores in whatever the variable you assign it to. Here's more info.
So, your following line of code reads the number you inputs and stores in Nummer.
int Nummer = Convert.ToInt16(Console.ReadLine());
But then you go on and do two more Console.ReadLine() method calls in your if statement, so what the if statement really does is try to read from the console two more times, and see if the first read is "" and if the second read is null, which is not your desired behavior.
What you want to do is read once, and compare whatever you read. Going by your code it looks like you want to output the square of the number entered by the user, so you probably should check for more than just Nummer == "", since if the user entered an alphabet character, that would also result in an error. So using int.TryPrase() is a better option for you.
static void Main(string[] args)
{
bool herhaal = true;
do
{
Console.Write("Geef een getal : ");
string Nummer = Console.ReadLine();
if (int.TryParse(Nummer, out int result))
{
double kw = Math.Pow(result, 2);
Console.WriteLine("Kwadraat van {0} is: {1}", Nummer, kw + Environment.NewLine);
herhaal = false;
}
else
{
Console.WriteLine("0");
}
} while (herhaal);
Console.ReadLine();
}
According to the C# Documentation, Console.ReadLine does the following
Reads the next line of characters from the standard input stream.
This means that every time you call Console.ReadLine, a new line will be read from the console. From what I can see in your code, this isn't the behavior that you want. To fix your problem, you should store the result of Console.ReadLine in a variable and use that variable instead of the ReadLine method.
Couldn't find any other answer on the site that covers this. If else is run and an error message is displayed, is it possible to restart the program by looping back to the start instead of restarting the console?
class Program
{
static void Main(string[] args)
{
int User;
int Array;
StreamWriter outfile = new StreamWriter("C://log.txt");
Console.WriteLine("Input an number between 1 and 100");
User = Convert.ToInt32(Console.ReadLine());
if (User < 101 && User > 0)
{
for (Array = 1; Array <= User; Array++)
{
Console.WriteLine(Array + ", " + Array * 10 * Array);
outfile.WriteLine(Array + ", " + Array * 10 * Array);
}
{
Console.WriteLine("Press Enter To Exit The Console");
outfile.Close();
Console.ReadLine();
}
}
else
{
Console.WriteLine("Sorry you input an invalid number. ");
Console.ReadLine();
}
}
}
Sorry! To be more clear I need to make the Program start again if the user inputs an invalid number
Thanks for the help!
You can do this instead
User = Convert.ToInt32(Console.ReadLine());
while (User >= 101 || User <= 0)
{
Console.WriteLine("Sorry you input an invalid number. ");
User = Convert.ToInt32(Console.ReadLine());
}
An easy way of doing this is placing your code inside a while loop, so that the code keeps repeating. The only way to exit the loop would be for the condition you just set in the if clause to be true. So something along the lines of:
class Program
{
static void Main(string[] args)
{
int User;
int Array;
bool isUserWrong = true; //This is a flag that we will use to control the flow of the loop
StreamWriter outfile = new StreamWriter("C://log.txt");
while(isUserWrong)
{
Console.WriteLine("Input an number between 1 and 100");
User = Convert.ToInt32(Console.ReadLine());
if (User < 101 && User > 0)
{
for (Array = 1; Array <= User; Array++)
{
Console.WriteLine(Array + ", " + Array * 10 * Array);
outfile.WriteLine(Array + ", " + Array * 10 * Array);
}
isUserWrong = false; // We signal that we may now leave the loop
}
else
{
Console.WriteLine("Sorry you input an invalid number. ");
Console.ReadLine();
//Note that here we keep the value of the flag 'true' so the loop continues
}
}
Console.WriteLine("Press Enter To Exit The Console");
outfile.Close();
Console.ReadLine();
}
}