We Keep Coding

Trying to convert from hexadecimal to decimal and binary but shows an error if i input letter after f

I created this code in c# to convert a hexadecimal number entered by the user to decimal and binary which the code does but I want the code to run so that if the user enters a letter that is not between a-f, a message box shows up with a message telling the user their input is invalid but instead of doing this, the code gives me an error. Can anyone help me out?
bool valid = false;
string hexadecimalnum = HexadecimalTxt.Text;
Checking if the number inputed by the user is in between 0-9 and a-f (lowercase or uppercase)
if(Regex.IsMatch(hexadecimalnum, "\[^-9A-F\]+$") || Regex.IsMatch(hexadecimalnum, "\[^-9a- f\]+$"))
{
// if the hex value is in between 0-9 and a-f then the condition is true
valid = true;
}
since the condition is true convert the hex number to binary and decimal
if(valid)
{
DecimalTxt.Text = Convert.ToInt32(hexadecimalnum, 16).ToString();
int temp = Convert.ToInt32(hexadecimalnum, 16);
BinaryTxt.Text = Convert.ToString(temp, 2);
}
// the condition is not true so print out a invalid number message
else
{
MessageBox.Show("Invalid - please enter a hexadecimal value in this box");
}

So, after some testing and googling, I think it's your regex pattern.
Another answer here worked: Validate hexadecimal string using regular expression
I tested the match and it worked fine.
"^(0x|0X)?[a-fA-F0-9]+$"
if you don't want the 0x, go with: "^[a-fA-F0-9]+$"
I find that using an online tester like http://regexstorm.net/tester helps.

try this solution:
if (Regex.IsMatch(s, #"\A\b[0-9a-fA-F]+\b\Z"))
{
int temp = int.Parse(hexadecimalnum, System.Globalization.NumberStyles.HexNumber);
DecimalTxt.Text= temp.ToString();
BinaryTxt.Text = Convert.ToString(temp, 2);
}
else
{
MessageBox.Show("Invalid - please enter a hexadecimal value in this box");
}
or you can use TryPrase() Int64_TryParse to check if string is valid
long temp ;
if(long.TryParse(hexadecimalnum, System.Globalization.NumberStyles.HexNumber, null, out temp))
{
DecimalTxt.Text= temp.ToString();
BinaryTxt.Text = Convert.ToString(temp, 2);
}

Why is my code outputting strings multiple times in my if statement?

My code outputs the same string multiple times. For example, typing in 40 results in "Nope! Your answer is too high. Try again." twice, and it displays "your answer is too low" twice.
while (numberguess != 40.5)
{
numberguess = Console.Read();
if (numberguess < 40.5)
{
Console.WriteLine("Nope! Your answer is too low. Try again.");
}
else if (numberguess > 40.5)
{
Console.WriteLine("Nope! Your answer is too high. Try again.");
}
else if (numberguess == 40.5)
{
Console.WriteLine("Correct! Wow, I didn't really think you would figure it out!");
break;
}
}
I expect only one string to show up when typing in a number, and I want it to correspond to whether it is lower or higher than a particular number.

There are several problems with this single line:
numberguess = Console.Read();
First this returns an int, so it will never return 40.5. Also this reads one character at a time, including the ones input by the enter key, so when you type 40 and press Enter it reads '4', then '0' then '\r' and finally '\n' (converting those chars to int). That's why it displays four messages.
Instead you have to read everything typed before the Enter with Console.ReadLine() and then convert this (string) to a double. So in the end you have to do this:
numberguess = double.Parse(Console.ReadLine());

Console.Read() reads a single character as an int. If you're trying to get what the user typed before they hit enter, read the current line, and then parse an integer from it.
int.Parse(Console.ReadLine());

C# Ask user another input

I am creating a soundDex application and I need to ask the user for a second name after they have inputted the first one. I also want "error no input" if the user does not input a second name. How would I do this within my soundDex?
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace SoundDexFinal
{
class Program
{
static void Main(string[] args)
{
string input = null;
bool good = false;
Console.WriteLine("SoundDex is a phonetic algorithm which allows a user to encode words which sound the same into digits."
+ "The program allows the user essentially to enter two names and get an encoded value.");
while (!good) // while the boolean is true
{
Console.WriteLine("Please enter a name -> "); // asks user for an input
input = Console.ReadLine();
// Make sure the user entered something
good = !string.IsNullOrEmpty(input); // if user enters a string which is null or empty
if (!good) // if boolean is true
Console.WriteLine("Error! No input."); // displays an error to the user
}
soundex soundex = new soundex(); // sets new instance variable and assigns from the method
Console.WriteLine(soundex.GetSoundex(input)); // gets the method prior to whatever the user enters
Console.ReadLine(); // reads the users input
}
class soundex
{
public string GetSoundex(string value)
{
value = value.ToUpper(); // capitalises the string
StringBuilder soundex = new StringBuilder(); // Stringbuilder holds the soundex code or digits
foreach (char ch in value) // gets the individual chars via a foreach which loops through the chars
{
if (char.IsLetter(ch))
AddChar(soundex, ch); // When a letter is found this will then add a char
} // soundex in (parameter) is for adding the soundex code or digits
return soundex.ToString(); //return the value which is then converted into a .String()
}
private void AddChar(StringBuilder soundex, char character) //encodes letter as soundex char and this then gets appended to the code
{
string code = GetSoundexValue(character);
if (soundex.Length == 0 || code != soundex[soundex.Length - 1].ToString())
soundex.Append(code);
}
private string GetSoundexValue(char ch)
{
string chString = ch.ToString();
if ("BFPV".Contains(chString)) // converts this string into a value returned as '1'
return "1";
else if ("CGJKQSXZ".Contains(chString)) // converts this string into a value returned as '2'
return "2";
else if ("DT".Contains(chString)) // converts this string into a value returned as '3'
return "3";
else if ("L".Contains(chString)) // converts this string into a value returned as '4'
return "4";
else if ("MN".Contains(chString)) // converts this string into a value returned as '5'
return "5";
else if ("R".Contains(chString)) // converts this string into a value returned as '6'
return "6";
else
return ""; // if it can't do any of these conversions then return nothing
}
}
}
}

I admit, I am not entirely clear on what part precisely you're having trouble with. But the specific goal is stated clearly enough, and you've provided a sufficient code example, so…
The basic problem is "how do I require the user to input the same kind of data more than once?" The basic answer is the same as for any programming problem that involves having to repeat an action: generalize that action into a subroutine (i.e. "method" in C# parlance) that will perform that action, and call the subroutine every time you need to perform the action.
For example:
class Program
{
static void Main(string[] args)
{
string input1, input2;
Console.WriteLine("SoundDex is a phonetic algorithm which allows a user to encode words which sound the same into digits."
+ "The program allows the user essentially to enter two names and get an encoded value.");
input1 = GetValidInput("Please enter a name -> ");
input2 = GetValidInput("Please enter a second name -> ");
soundex soundex = new soundex(); // sets new instance variable and assigns from the method
Console.WriteLine(soundex.GetSoundex(input1)); // gets the method prior to whatever the user enters
// do whatever you want with input2 as well
Console.ReadLine(); // reads the users input
}
static string GetValidInput(string prompt)
{
while (true)
{
string input;
Console.WriteLine(prompt); // asks user for an input
input = Console.ReadLine();
// Make sure the user entered something
if (!string.IsNullOrEmpty(input))
{
return input;
}
Console.WriteLine("Error! No input."); // displays an error to the user
}
}
}

C# if statement readline must equal number [duplicate]

This question already has answers here:
How can I validate console input as integers?
(10 answers)
Closed 8 years ago.
I can't figure out what to put in brackets to make my program check if the input was number. I would like to return an error if not, and restart the process. Any suggestions?
bool running = true;
Console.Write("Enter the number of victims so we can predict the next murder, Sherlock: ");
while (running)
{
victimCount = int.Parse(Console.ReadLine());
if (/*I want victimCount only to be accepted if it's a number*/)
{
Console.Write("\nThat's an invalid entry. Enter a correct number!: ");
}
else
{
running = false;
}
}

I want victimCount only to be accepted if it's a number
You can use int.TryParse method instead. It returns boolean value that your value is a valid int or not.
string s = Console.ReadLine();
int victimCount;
if(Int32.TryParse(s, out victimCount))
{
// Your value is a valid int.
}
else
{
// Your value is not a valid int.
}
Int32.TryParse method uses NumberStyles.Integer by default. That means your string can have;
Leading CurrentCulture's sign. (PositiveSign or NegativeSign)
Leading white spaces.
Trailing white spaces
as a number stye.

Try this:
int victimcount;
bool is Num = int.TryParse(Console.ReadLine(), out victimcount);
If `isNum` is true then the input is an integer. Use this for your check. At the same time, if the parse succeeds, the parsed value gets assigned to the `victimcount` variable (0 is assigned if it fails).

Validating User Input and Type

I have designed an input validation loop in C#, and I would like it to be able to check for the correct input format. I'm not sure, but I think my designed loop is not checking the type of input, just what char is entered. I know I could use a try-catch block, but shouldn't you only use exceptions for exceptional situations? This is not an exceptional situation, because I expect that the user would enter an incorrect value.
Question:
Is there a way I could redesign this loop so that it checks for valid input type as well?
Code:
do
{
Console.Write("Do you wish to enter another complex number?: (Y or N)");
response = char.Parse(Console.ReadLine());
response = char.ToUpper(response);
if (response != 'Y' && response != 'N')
Console.WriteLine("You must respond Y or N!");
} while (response != 'Y' && response != 'N');

Well Console.Readline():
Reads the next line of characters from the standard input stream.
So your data will be of type System.String.
The only other checking you could do is to check that the returned string is of length 1, so you know you have input of the right format. You don't really need the char.Parse as the elements of a string are of type char.

I don't know what your original asigment is, but the example you provided can be simplyfied by just comparing strings, ie:
response = Console.ReadLine();
if (response.ToUpper() == "Y") {...}
If you want to see if the input can be cast to the type you need (for example char), you can allways do (for every value type):
char input;
bool IsValid = char.TryParse(Console.ReadLine().ToUpper(), out input);
if (IsValid)
{
Console.WriteLine("You entered the following char: " + input);
}
Hope this helps.

Another helpful check in such a situation
Checks for a null string , "" (Empty string) and trims extra white space I.E s string like this " " become this ""
if(String.IsNullOrEmpty(response.Trim() && response != 'Y' && response != 'N'))
{
Console.WriteLine("You must respond Y or N!"); }
And for the most part it is easier to use strings over char in most simple input validation situations.