C# Console application crashing before if statement can run - c#

static void Main(string[] args)
{
Console.ForegroundColor = ConsoleColor.Green;
Console.WriteLine("1. SHC ");
int UserInput1 = Console.Read();
if (UserInput1 == 1)
{
Console.WriteLine("Mass (kg): ");
int shcmass = Console.Read();
Console.WriteLine("Specific Heat Capactiy (J/Kg/°C): ");
int shcshc = Console.Read();
Console.WriteLine("Temperature Difference (△Ø): ");
int shctemp = Console.Read();
int shcfinal = shcmass * shcshc * shctemp;
Console.WriteLine("Energy: " + shcfinal);
}
This is the code I am using within a small console application. I don't know if I am missing something but every time I run it, the first bit works where it says "1. SHC" and gives time for the user input. But once entered the console application dies and I cannot figure out why.

There's nothing stopping the console application to close, add a Console.ReadLine() at the end of your mainloop. I'd recommend using ReadLine() over reads for other input as well, but it would depend on your needs. If you see from the "Remarks" section of the Console.Read documentation it's preferable to use ReadLine()
e.g.
static void Main(string[] args)
{
Console.ForegroundColor = ConsoleColor.Green;
Console.WriteLine("1. SHC ");
int UserInput1 = int.Parse(Console.ReadLine());
if (UserInput1 == 1)
{
Console.WriteLine("Mass (kg): ");
int shcmass = int.Parse(Console.ReadLine());
Console.WriteLine("Specific Heat Capactiy (J/Kg/°C): ");
int shcshc = int.Parse(Console.ReadLine());
Console.WriteLine("Temperature Difference (△Ø): ");
int shctemp = int.Parse(Console.ReadLine());
int shcfinal = shcmass * shcshc * shctemp;
Console.WriteLine("Energy: " + shcfinal);
}
Console.ReadLine();
}

Console.Read() returns
The next character from the input stream, or negative one (-1) if
there are currently no more characters to be read.
https://msdn.microsoft.com/en-us/library/system.console.read(v=vs.110).aspx
You will need
ch = Convert.ToChar(x);
Excerpt:
class Sample
{
public static void Main()
{
string m1 = "\nType a string of text then press Enter. " +
"Type '+' anywhere in the text to quit:\n";
string m2 = "Character '{0}' is hexadecimal 0x{1:x4}.";
string m3 = "Character is hexadecimal 0x{0:x4}.";
char ch;
int x;
//
Console.WriteLine(m1);
do
{
x = Console.Read();
try
{
ch = Convert.ToChar(x);
if (Char.IsWhiteSpace(ch))
{
Console.WriteLine(m3, x);
if (ch == 0x0a)
Console.WriteLine(m1);
}
else
Console.WriteLine(m2, ch, x);
}
catch (OverflowException e)
{
Console.WriteLine("{0} Value read = {1}.", e.Message, x);
ch = Char.MinValue;
Console.WriteLine(m1);
}
} while (ch != '+');
}
}

I've had similar issues before. When using Console.Read() after Console.WriteLine() you'll end up reading '\r' which is what causes the crash I believe. Try using Console.ReadKey() instead.

Related

C# How can I handle this exception?

I am new to C# and trying to create a GPA calculator using a sentinel controlled loop. To end the loop, I want the user to enter an 'x', but it is throwing an exception. I'm pretty sure it is because 'x' is not a double type, but I am not sure how I can make it work. I was using a number to exit before but it kept being added to the gradeTotal. Any suggestions would be great! Thanks!
Code:
class Program
{
static void Main(string[] args)
{
double gradeTotal = 0;
int[] score = new int[100];
string inValue;
int scoreCnt = 0;
Console.WriteLine("When entering grades, use a 0-4 scale. Remember;
A = 4, B = 3, C = 2, D = 1, F = 0");
Console.WriteLine("Enter grade {0}: ((X to exit)) ", scoreCnt + 1);
inValue = Console.ReadLine();
gradeTotal += double.Parse(inValue);//This may be a problem area
while (inValue != "x")
{
if (int.TryParse(inValue, out score[scoreCnt]) == false)
Console.WriteLine("Invalid data -" + "0 stored in array");
++scoreCnt;
Console.WriteLine("Enter Score{0}: ((X to exit)) ", scoreCnt +
1);
inValue = Console.ReadLine();
gradeTotal += double.Parse(inValue);//This is a problem area
}
Console.WriteLine("The number of scores: " + scoreCnt);
Console.WriteLine("Your GPA is: " + gradeTotal);//Obviously not the
//right calculation, just trying to figure it out
Console.ReadLine();
}
}
Least effort
Instead of
gradeTotal += double.Parse(inValue);//This is a problem area
Try
if (inValue == "X") break;
gradeTotal += double.Parse(inValue);
More robust
double d;
var ok = double.TryParse(inValue, out d);
if (!ok) break;
gradeTotal += d;
You have zero validation on the inValue before trying to parse it. That's the problem. How you resolve this is up to you. Here's a couple suggestions:
wrap the code in a try...catch...
try {
grandTotal += double.Parse(inValue);
} catch (Exception e) {
Console.WriteLine("Invalid input!");
}
Use Regular Expressions to validate user input and return error if not a number
(System.Text.RegularExpressions.Regex)

How do I prevent crashing due to invalid input in C#?

The program I've written is set to only accept positive integers as input. If the user inputs a letter instead, then it crashes. Negative integers don't cause any problems, though it's not 'valid' in regards to how my program functions.
What I want to do is:
Prevent the program from crashing from invalid input.
Display an error message if the input is invalid
Have the program continue where it left off, without affecting the rest of the program.
Also, a part of my program involves division. Is there a way to prevent the user from entering all zeros?
This is in C#
My code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace OverallCalculator
{
class Program
{
static void Main(string[] args)
{
bool shouldContinue;
do
{
Console.WriteLine("Enter Striking Level: ");
string striking = Console.ReadLine();
Console.WriteLine("Enter Grappling Level: ");
string grappling = Console.ReadLine();
Console.WriteLine("Enter Submission Level: ");
string submission = Console.ReadLine();
Console.WriteLine("Enter Durability Level: ");
string durability = Console.ReadLine();
Console.WriteLine("Enter Technical Level: ");
string technical = Console.ReadLine();
Console.WriteLine("Enter Speed Level: ");
string speed = Console.ReadLine();
Console.WriteLine("Enter Hardcore Level: ");
string hardcore = Console.ReadLine();
Console.WriteLine("Enter Charisma Level: ");
string charisma = Console.ReadLine();
int gra = Convert.ToInt32(grappling);
int str = Convert.ToInt32(striking);
int dur = Convert.ToInt32(durability);
int spd = Convert.ToInt32(speed);
int tec = Convert.ToInt32(technical);
int hdc = Convert.ToInt32(hardcore);
int cha = Convert.ToInt32(charisma);
int sub = Convert.ToInt32(submission);
int total = str + gra + sub + dur + tec + spd + cha + hdc;
int overall = total / 8 + 8;
Console.WriteLine("The Overall is " + overall);
Console.WriteLine("Do you wish to continue? y/n? ");
if (Console.ReadLine() == "y")
{
shouldContinue = true;
}
else break;
} while (shouldContinue == true);
}
}
}
Here you go:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace OverallCalculator
{
class Program
{
static void Main(string[] args)
{
bool shouldContinue = true;
while (shouldContinue)
{
int strikingLevel = GetValue("Enter Striking Level: ");
int grapplingLevel = GetValue("Enter Grappling Level: ");
int submissionLevel = GetValue("Enter Submission Level: ");
int durabilityLevel = GetValue("Enter Durability Level: ");
int technicalLevel = GetValue("Enter Technical Level: ");
int speedLevel = GetValue("Enter Speed Level: ");
int hardcoreLevel = GetValue("Enter Hardcore Level: ");
int charismaLevel = GetValue("Enter Charisma Level: ");
int total = strikingLevel + grapplingLevel + durabilityLevel + submissionLevel +
technicalLevel + speedLevel + charismaLevel + hardcoreLevel;
int overall = total / 8 + 8;
Console.WriteLine("\nThe Overall is {0}.", overall);
while (true)
{
Console.WriteLine("Do you wish to continue? y/n? ");
string response = Console.ReadLine();
if (response.Equals("y", StringComparison.CurrentCultureIgnoreCase) ||
response.Equals("yes", StringComparison.CurrentCultureIgnoreCase))
{
shouldContinue = true;
break;
}
else if (response.Equals("n", StringComparison.CurrentCultureIgnoreCase) ||
response.Equals("no", StringComparison.CurrentCultureIgnoreCase))
{
shouldContinue = false;
break;
}
}
}
}
private static int GetValue(string prompt)
{
while (true)
{
Console.WriteLine(prompt);
string input = Console.ReadLine();
int value;
if (int.TryParse(input, out value))
{
if (value <= 0)
Console.WriteLine("Please enter a positive number.");
else
return value;
}
else
{
Console.WriteLine("Please enter a number.");
}
}
}
}
}
int value = 0;
if (!int.TryParse(input, out value))
{
MessageBox.Show("Oops");
} else {
// use the value in the variable "value".
}
static void Main(string[] args)
{
bool validInput = false;
string inputString;
UInt32 validPositiveInteger = 0;
while (!validInput)
{
Console.WriteLine("Please enter a positive 32 bit integer:");
inputString = Console.ReadLine();
if (!UInt32.TryParse(inputString, out validPositiveInteger))
{
Console.WriteLine("Input was not a positive integer.");
}
else if (validPositiveInteger.Equals(0))
{
Console.WriteLine("You cannot enter zero.");
}
else
{
validInput = true;
//Or you could just break
//break;
}
}
Console.WriteLine(String.Format("Positive integer = {0}", validPositiveInteger));
}
Yes... before you do anything calculations, you need to validate the data you are going to use. If any data is incorrect, then you display a messagebox detailing the errors and return focus to the form so the user can fix the errors. Repeat as necessary.
I wrote this one many moons ago when I first learned C#. It is a conversion from a VB function that I got back in VB5 days. The major benefit of the function is that there is no error - an input will just not allow any characters outside of the predefined list.
/***********************************************************************
* bool ValiText(char inChar,
* string valid,
* bool editable,
* bool casesensitive
* Description: Validate Input Characters As They Are Input
* Notes: For each control whose input you wish to validate, just put
* e.Handled = ValiText(e.KeyChar, "0123456789/-" [,true][,true])
* In The KeyPress Event
***********************************************************************/
public bool ValiText(char inChar, string valid, bool editable, bool casesensitive)
{
string inVal = inChar.ToString();
string tst = valid;
/// Editable - Add The Backspace Key
if (editable) tst += ((char)8).ToString();
/// Case InSensitive - Make Them Both The Same Case
if (!casesensitive)
{
tst = tst.ToLower();
inVal = inVal.ToLower();
}
return tst.IndexOf(inVal,0,tst.Length) < 0;
}
public bool ValiText(char inChar, string valid, bool editable)
{
string tst = valid;
/// Editable - Add The Backspace Key
if (editable) tst += ((char)8).ToString();
return tst.IndexOf(inChar.ToString(),0,tst.Length) < 0;
}
public bool ValiText(char inChar, string valid)
{
return valid.IndexOf(inChar.ToString(),0,valid.Length) < 0;
}
Note That This Will Not Work On A Web APP.

C# How do I error check the input ensuring only integers between 1-100 are accepted

I'm creating a program for a college assignment and the task is to create a program that basically creates random times table questions. I have done that, but need to error check the input to only accept integer inputs between 1-100. I can not find anything online only for like java or for text box using OOP.
Here is my code:
static void help()
{
Console.WriteLine("This program is to help children learn how to multiply");
Console.WriteLine("The program will create times table questions from 1-10");
Console.WriteLine("The user will be given 10 random questions to complete");
Console.WriteLine("The user will get a score out of 10 at the end");
Console.WriteLine("If the user gets the answer wrong, the correct answer will be displayed");
Console.WriteLine("");
Console.ReadLine();
Console.Clear();
}
static void Main(string[] args)
{
int Random1 = 0;
int Random2 = 0;
int Answer;
int Count = 0;
int Score = 0;
int input = 0;
String choice;
Console.WriteLine("To begin the Maths test please hit any key");
Console.WriteLine("If you need any help, just, type help");
choice = Console.ReadLine();
if (choice == "help")
{
help();
}
while (Count != 10)
{
Random numbers = new Random();
Random1 = numbers.Next(0, 11);
Count = Count + 1;
Random numbers2 = new Random();
Random2 = numbers.Next(0, 11);
Console.WriteLine(Random1 + "x" + Random2 + "=");
input = int.Parse(Console.ReadLine());
Answer = Random1 * Random2;
if (Answer == input)
{
Console.ForegroundColor = ConsoleColor.Green;
Console.WriteLine("Correct");
Score = Score + 1;
Console.ResetColor();
}
else
{
Console.ForegroundColor = ConsoleColor.Red;
Console.WriteLine("Thats the wrong answer, the correct is " + Answer);
Console.ResetColor();
}
}
if (Score > 5)
{
Console.ForegroundColor = ConsoleColor.Green;
Console.WriteLine("Good job you got more than 5 answers correct! With a score of " + Score + " out of 10");
Console.ResetColor();
Console.ReadLine();
}
else if (Score < 5)
{
Console.ForegroundColor = ConsoleColor.Red;
Console.WriteLine("");
Console.WriteLine("Try again you got less than 5 correct! With a score of " + Score + " out of 10");
Console.ResetColor();
Console.ReadLine();
}
}
}
}
Firstly, I suggest you to use TryParse instead of Parse to prevent unexpected errors because of invalid inputs. So, try something like that;
Random numbers = new Random();
Random1 = numbers.Next(0, 11);
Count = Count + 1;
Random numbers2 = new Random();
Random2 = numbers.Next(0, 11);
Console.WriteLine(Random1 + "x" + Random2 + "=");
//Modified
int input = 0;
while (true)
{
if (!int.TryParse(Console.ReadLine(), out input))
{
Console.WriteLine("Invalid Input. Please enter a valid integer.");
}
else
{
if (input >= 1 && input <= 100)
{
break;
}
Console.WriteLine("Invalid Input. Please enter a integer between 1-100.");
}
}
//Modified
I'd simply use a loop that will keep asking for input until it
matches your requirement:
int MinVal = 1; // No magic numbers! You may consider placing them in a config
int MaxVal = 100; // or as static readonly class members (a bit like "const").
int input = -1;
for(;;) // "empty" for-loop = infinite loop. No problem, we break on condition inside.
{
// attempt getting input from user
bool parseOK = int.TryParse(Console.ReadLine(), out input);
// Exit loop if input is valid.
if( parseOK && input >= MinVal && input <= MaxVal ) break;
Console.WriteLine( "Errormessage telling user what you expect" );
}
You may also consider granting only N trys to get the input right.
A few hints:
do not use "magic numbers". Define constants or put numbers into Properties/Settings. Name them self-explanatory and document why you chose the value they happen to have.
The errormessage should tell the user what an expected valid input is (as opposed to what they typed in) not just that their input was invalid.
Whats about this?
input = int.Parse(Console.ReadLine());
if(input > 1 && input < 100){
// valid
}else{
// invalid
}

How to start over with my code? C# Console [duplicate]

This question already has an answer here:
How to loop a Console App
6 answers
I wanted to try how the if conditional works so I created this code almost by myself. I also had problems with random into int.
Here's my code:
using System;
namespace Bigger_Smaller_Equal
{
class Program
{
static void Main(string[] args)
{
int min = 1;
int max = 100;
Random rnd = new Random();
int gen = rnd.Next(min, max);
Console.WriteLine("My Number is : " + gen + "!");
Console.WriteLine("Tell me your number:");
string typ = Console.ReadLine();
int num = int.Parse(typ);
if (num == gen)
{
Console.WriteLine(num + " is Equal to " + gen);
}
else if (num > gen)
{
Console.WriteLine(num + " Is Bigger than " + gen);
}
else if (num < gen)
{
Console.WriteLine(num + " Is Smaller than " + gen);
}
Console.WriteLine("Press Any Key to exit.");
Console.ReadLine();
}
}
}
How to make the console stop, so it will allow me to enter another number?
Basically:
I write a number it tells me if its smaller bigger or equal to number which was randomly generated
After I press enter instead of closing the console the number will be generated again and I can write new number and so on.
You can use console.ReadKey() insted of using console.ReadLine().
console.ReadLine() wait for input set of character thats why you console window is apperre there after pressing any key.
You can use "do while" or "while" operator.If you dont want to use while(true) , you can use this diffirent way. I mean that when user enter 0 or -1 this system can stop. while()
bool repeat = true;
do
{
Console.WriteLine("Enter value ");
string typ = Console.ReadLine();
int num = int.Parse(typ);
if (num!=0)
// bla bla bla.
else
repeat = false;
}while (repeat);
Here's an example using goto, although it is not recommended for more complex applications as you could end up creating endless loops. Feel free to try it out
static void Main(string[] args)
{
int min = 1;
int max = 100;
Random rnd = new Random();
again:
int gen = rnd.Next(min, max);
Console.WriteLine("My Number is : " + gen + "!");
Console.WriteLine("Tell me your number:");
string typ = Console.ReadLine();
int num = int.Parse(typ);
if (num == gen)
{
Console.WriteLine(num + " is Equal to " + gen);
}
else if (num > gen)
{
Console.WriteLine(num + " Is Bigger than " + gen);
}
else if (num < gen)
{
Console.WriteLine(num + " Is Smaller than " + gen);
}
repeat:
Console.WriteLine("Play again? (Y/N)");
string ans = Console.ReadLine();
switch (ans.ToUpper())
{
case "Y": goto again; break;
case "N": break; //continue
default: goto repeat; break;
}
}

Program skips lines of code

I have a small program that changes values of char arrays. But first you need to tell the program in which array you want to change a value; and write a new value and its position into that same array position.
But when I enter the array number, the program skips the code lines allowing the entry of the new value and its position. Then the program throws a FormatException at the end.
Here's the code:
static void addLetters(char[] messageOne, char[] messageTwo)
{
char Mnumber;
char letter;
string pos;
int position;
Console.Write("- Message #: ");
Mnumber = (char)Console.Read();
if (Mnumber == '1')
{
Console.Write("Letter: ");
letter = (char)Console.Read();
Console.Write("\nPosition: ");
pos = Console.ReadLine();
position = Int32.Parse(pos);
messageOne[position - 1] = letter;
}
if (Mnumber == '2')
{
Console.Write("Letter: ");
letter = (char)Console.Read();
Console.Write("\nPosition: ");
pos = Console.ReadLine();
position = Int32.Parse(pos);
messageTwo[position - 1] = letter;
}
}
static void Main(string[] args)
{
char[] array1 = new char[50];
char[] array2 = new char[50];
for (int i = 0; i < 50; i++)
{
array1[i] = '*';
array2[i] = '*';
}
addLetters(array1, array2);
}
}
P.S. Could you please tell me how I can make this code more 'elegant'?
When reading a single character it's reccommended to use Console.ReadKey().KeyChar. I've modified your code to handle exceptions as well:
static void addLetters(char[] messageOne, char[] messageTwo)
{
char Mnumber;
char letter;
string pos;
int position;
try
{
do
{
Console.Write("- Message #: ");
Mnumber = Console.ReadKey().KeyChar;
Console.WriteLine();
}
while (Mnumber != '1' && Mnumber != '2');
Console.Write("\nLetter: ");
letter = Console.ReadKey().KeyChar;
Console.Write("\nPosition: ");
pos = Console.ReadLine();
position = Int32.Parse(pos);
if (Mnumber == '1')
messageOne[position - 1] = letter;
else
messageTwo[position - 1] = letter;
}
catch (FormatException)
{
Console.WriteLine("Invalid input format, position must be an integer");
}
catch (IndexOutOfRangeException)
{
Console.WriteLine("Position out of array bounds");
}
finally
{
Console.Read();
}
}
Try a single function for both messages, and TryParse() your string to integer conversions
static char ReadChar(string prompt)
{
// Screen Prompt
Console.Write(prompt);
// Read a Character
return Console.ReadKey(false).KeyChar;
}
static int ReadNumber(string prompt)
{
// Screen Prompt
Console.Write(prompt);
int result=-1;
// Reads a number and onverts it into an integer
int.TryParse(Console.ReadLine(), out result);
return result;
}
// Caution, this modifies the contents of `messages`
static void addLetters(params char[][] messages)
{
// Read message index (first=1, second=2, etc)
int Mnumber=ReadNumber("- Message #: ");
// Read letter
char letter=ReadChar("Letter: ");
// Read placement position
int position=ReadNumber("\nPosition: ");
// Get the right message
char[] current_message=messages[Mnumber-1];
// Assigns a letter to the message
current_message[position]=letter;
}
static void Main(string[] args)
{
int n=50; //Store the size instead of hard coding it all over your code
char[] array1=new char[n];
char[] array2=new char[n];
for (int i=0; i<n; i++)
{
array1[i]='*';
array2[i]='*';
}
addLetters(array1, array2);
}

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