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How to accept the user response either as an int, or a char or a string. C#

int number;
do
{
DisplayMenu();
number = Convert.ToInt32(Console.ReadLine()); //here need int, string, and char
if (number < 0 || number > 6)
{
Console.WriteLine("An error occured!");
break;
}
} while (number != 0);
static void DisplayMenu()
{
Console.WriteLine("Main Menu");
Console.WriteLine("1) Calculate Sum ");
Console.WriteLine("2) Calculate Average");
Console.WriteLine("3) Display Numbers");
Console.WriteLine("4) Display Poem");
Console.WriteLine("5) Create Numbers Array");
Console.WriteLine("0) To Exit");
Console.WriteLine();
Console.WriteLine("Enter the number that corresponds to your choice: ");
}
I need to take the user input in integer, string, and character. Moreover, this code should then still work properly.
I was searching on other boards but there is no such thing I could find.

Reading your code, it appears that you are asking the user to enter a single digit from 0-5 to select the next function. One straightforward way of doing this is to substitute the ReadKey() method and switch on the result. As a bonus, the menu will execute immediately without having to wait for the [Enter] key.
// Loop until a valid int is received.
bool exit = false;
while (!exit)
{
DisplayMenu();
switch (Console.ReadKey().Key)
{
case ConsoleKey.D0: exit = true; break;
case ConsoleKey.D1: calculateSum(); break;
case ConsoleKey.D2: calculateAverage(); break;
case ConsoleKey.D3: displayNumbers(); break;
case ConsoleKey.D4: displayPoem(); break;
case ConsoleKey.D5: createNumbersArray(); break;
default:
Console.Clear();
Console.WriteLine("Please enter a number 0-5");
Thread.Sleep(1000);
break;
}
}

A problem with getting/printing answers in a C# calculator

I'm trying to make simple projects for learning C# and have tried to make a simple console calculator. I have only found this current error when getting to the getting/printing the answer bit when test-running my program, so I have no idea if there are any other errors/things that will or may not work or run properly/as intended. So if there are any of those, please let me know and if you want to you can fix them yourself. It only recognized the error when it reached that specific line of code, and otherwise will run the program until it reaches the error.
Code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Calculator
{
class Program
{
static void Main(string[] args)
{
string num1;
string num2;
string condition;
string answer;
Console.WriteLine("Calculator");
Console.WriteLine("For division, use /. For multiplication, use *.\n");
while (true)
{
Console.WriteLine("Enter a number: "); // gets first number to add in problem
num1 = Console.ReadLine();
Console.WriteLine("Enter a condition: "); // gets condition to add in problem
condition = Console.ReadLine();
Console.WriteLine("Enter your second number: "); // gets second number to add in problem
num2 = Console.ReadLine();
Console.WriteLine("Calculating..");
// converting strings to int and working out answer
Convert.ToInt32(num1);
Convert.ToInt32(num2);
// error is from here on (not sure if the Convert.ToInt32() code above causes errors)
answer = num1 + condition + num2;
Convert.ToInt32(answer);
Console.WriteLine(answer);
// sets values to null after getting & printing answer (probably unnessessary)
answer = null;
num1 = null;
num2 = null;
condition = null;
}
}
}
}

When facing problems like this one - the routine is too complex to be tested:
if there are any other errors/things that will or may not work"
split routine into smaller ones: start extracting methods.
// Get integer value from user
public static int ReadInteger(string title) {
while (true) {
if (!string.IsNullOrEmpty(title))
Console.WriteLine(title);
if (int.TryParse(Console.ReadLine(), out int result))
return result;
Console.WriteLine("Sorry, not a valid integer value, please, try again.");
}
}
// Get character operator ('+', '-' etc.) from user
public static char ReadOperator(string title, string operators) {
while (true) {
if (!string.IsNullOrEmpty(title))
Console.WriteLine(title);
string input = Console.ReadLine().Trim();
if (input.Length == 1 && operators.Contains(input[0]))
return input[0];
Console.WriteLine("Sorry, not a valid operator, please, try again.");
}
}
Now we are ready to implement Main method:
static void Main(string[] args) {
while (true) {
int num1 = ReadInteger("Enter a number: ");
char op = ReadOperator("Enter a condition: ", "+-*/");
int num2 = ReadInteger("Enter your second number: ");
//TODO: I've skipped error handling (zero division, overflow)
int answer =
op == '+' ? num1 + num2 :
op == '-' ? num1 - num2 :
op == '*' ? num1 * num2 :
op == '/' ? num1 / num2 : 0;
Console.WriteLine($"{num1} {op} {num2} = {answer}");
//TODO: it's a right place here to ask user if (s)he wants to continue
Console.WriteLine();
}
}

You receive input (condition) as a string
cant do this : answer = num1 + condition + num2 because those variables are
string
you have to check that with switch , for example :
int num1 = 0, num2 = 0, answer = 0;
string condition;
Console.WriteLine("Calculator");
Console.WriteLine("For division, use /. For multiplication, use *.\n");
while (true)
{
Console.WriteLine("Enter a number: "); // gets first number to add in problem
num1 = int.Parse(Console.ReadLine());
Console.WriteLine("Enter a condition: "); // gets condition to add in problem
condition = Console.ReadLine();
Console.WriteLine("Enter your second number: "); // gets second number to add in problem
num2 = int.Parse(Console.ReadLine());
Console.WriteLine("Calculating..");
// converting strings to int and working out answer
Convert.ToInt32(num1);
Convert.ToInt32(num2);
// error is from here on (not sure if the Convert.ToInt32() code above causes errors)
switch (condition)
{
case "/":
answer = num1 / num2;
break;
case "*":
answer = num1 * num2;
break;
case "+":
answer = num1 + num2;
break;
case "-":
answer = num1 - num2;
break;
default:
Console.WriteLine("error : unknown operator");
break;
}
Console.WriteLine(answer);
// sets values to null after getting & printing answer (probably unnessessary)
}

You can't do this line because all the variables are strings and not the real values (e.g: num1 & num2 should ints/doubles... and condition should be a real operator).
answer = num1 + condition + num2;
Also, you can't do it because let's assume the user inputs the multiplication sign, and then the string of "*" is not equal to the sign of *.
Instead, you can do some switch-case statements to check the value of the condition variable. Also, you need to make sure num1 & num2 are numbers (you can parse/try-parse them to a number (int/double...)). You will also have to parse them to another variables as they are strings.
switch (condition)
{
case '*':
answer = numX * numY;
break;
case "/":
// Validate that numY is not 0 to avoid [DivideByZeroException][1]
answer = numX / numY;
break;
...
}
Note, it is just one way to do it and I just gave you a small example that might help you to continue.
I would also offer you to make a default case (in case that the input of the user is not something you expect, in this case, you may ask him again to write an input because the current input is invalid).

Need help Improving Basic C# Calculator [closed]

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Closed 3 years ago.
Improve this question
I made this Basic C# Calculator to reflect on what I've learned these past few days. I'm an absolute beginner and I wanted to get suggestions on improving and shortening it.
I've tried to add switch statements and multiple methods, but it has been really hard grasping them.
using System;
namespace lol
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Hi! What is your name?");
string name = Console.ReadLine();
Console.WriteLine(name + " What do you wanna do?");
Console.WriteLine("Type \"+\" for addition");
Console.WriteLine("Type \"-\" for Subraction");
Console.WriteLine("Type \"*\" for Multiplication");
Console.WriteLine("Type \"/\" for division");
string operation = Console.ReadLine();
Console.Write("Now, Give me number one: ");
double num1 = Convert.ToDouble(Console.ReadLine());
Console.Write("Now give me number two: ");
double num2 = Convert.ToDouble(Console.ReadLine());
if (operation == "+")
{
Console.WriteLine(num1 + num2);
}
else if (operation == "-")
{
Console.WriteLine(num1 - num2);
}
else if (operation == "*")
{
Console.WriteLine(num1 * num2);
}
else
{
Console.WriteLine(num1 / num2);
}
}
}
}

If it better for your eyes, you can write like that:
static class Program
{
static void Main(string[] args)
{
Console.WriteLine("Hi! What is your name?");
string name = Console.ReadLine();
Console.WriteLine(name + " What do you wanna do?");
string[] operations = new string[] { "\"+\" for addition", "\"-\" for subtraction", "\"*\" for multiplication", "\"/\" for divsion" };
foreach (string operation in operations) { Console.WriteLine("Type " + operation); }
string cmd = Console.ReadLine();
Console.Write("Now, Give me number one: ");
double num1 = Convert.ToDouble(Console.ReadLine());
Console.Write("Now give me number two: ");
double num2 = Convert.ToDouble(Console.ReadLine());
switch (cmd)
{
case "+": Console.WriteLine(num1 + num2); break;
case "-": Console.WriteLine(num1 - num2); break;
case "*": Console.WriteLine(num1 * num2); break;
case "/": Console.WriteLine(num1 / num2); break;
}
}
}

Using enums and checking if the user input is valid. I also added a loop that checks if the user wants to input equations.
References:
double.TryParse
Enum
Switch Case
You can try it here: https://dotnetfiddle.net/aIwX5P
using System;
public class Program
{
enum eOperator
{
opAdd = 0,
opSub = 1,
opDiv = 2,
opMul = 3,
opInvalid = int.MinValue + 1,
opQuit = int.MinValue
}
public static void Main()
{
double a = 0.0, b = 0.0;
eOperator op = eOperator.opQuit;
string input = String.Empty;
Console.WriteLine("Calculator");
Console.WriteLine("Enter 'quit' at any time to exit.");
// repeat until the user wants to quit.
do // while(op != eOperator.opQuit)
{
Console.Write("a = ");
input = Console.ReadLine().ToLower().Trim();
if (double.TryParse(input, out a))
{
// input is a valid double and was stored in a
Console.Write("Operator: ");
input = Console.ReadLine().ToLower().Trim();
switch (input)
{
case "+":
op = eOperator.opAdd;
break;
case "-":
op = eOperator.opSub;
break;
case "*":
op = eOperator.opMul;
break;
case "/":
op = eOperator.opDiv;
break;
case "quit":
op = eOperator.opQuit;
break;
default:
op = eOperator.opInvalid; // can't be left as quit
Console.WriteLine("Invalid entry. +, -, *, / or quit for operator.");
break;
}
if (op != eOperator.opQuit && op != eOperator.opInvalid)
{
// user didn't choose to quit or type something invalid
Console.Write("b = ");
input = Console.ReadLine().ToLower().Trim();
if (double.TryParse(input, out b))
{
// input is a valid double and was parsed into b
double result = a; // we use the operator on a, so we might as well just store a into the result right away.
// do the operation on result.
switch (op)
{
case eOperator.opAdd:
result += b;
break;
case eOperator.opSub:
result -= b;
break;
case eOperator.opMul:
result *= b;
break;
case eOperator.opDiv:
// Div by 0 check. without this, this still works since double has +/- inf values.
if (b != 0.0) // comparing double with = and != is usually bad idea, but 0.0 is saved without rounding errors.
{
result /= b;
}
else
{
Console.WriteLine("Div by 0");
op = eOperator.opInvalid;
}
break;
default:
// this if branch checked for the other two operators. since we never chanced op after that check, this exception should never happen.
// it is still a good idea to include it to find errors in your logic, should they have occurred.
throw new Exception("This shouldn't happen.");
}
if (op != eOperator.opInvalid)
{
Console.WriteLine("Result: " + result.ToString());
}
// the only invalid operation is div by 0 for now. the message was sent to the user in that case, so no else is needed at this point.
// alternatively you can store an error message into a string, and when op = opInvalid, then display that error message here centralized.
// this would be a good idea if multiple things can go wrong.
}
else if (input == "quit")
{
// input for b was an invalid number, but input was 'quit'
op = eOperator.opQuit;
}
else
{
// input for b was an invalid number and also not 'quit', display error message
Console.WriteLine("Invalid entry. Type a number or Quit");
}
}
}
else if (input == "quit")
{
// input for a was invalid number, but 'quit'
op = eOperator.opQuit;
}
else
{
// input for a was invalid number and also not 'quit'
Console.WriteLine("Invalid entry. Type a number or Quit");
}
// repeat until the user wants to quit.
}while(op != eOperator.opQuit);
Console.WriteLine("Bye");
}
}

Pseudocode for switch statement in c#

How do I write the pseudocode for a switch (case) statement in C#?
switch (option)
{
case 1:
Console.Write("Enter First Number: ");
num1 = Convert.ToDouble(Console.ReadLine());
Console.Write("Enter Second Number: ");
num2 = Convert.ToDouble(Console.ReadLine());
result = num1 + num2;
Console.WriteLine(result);
break;
case 2:
Console.Write("Enter First Number: ");
num1 = Convert.ToDouble(Console.ReadLine());
Console.Write("Enter Second Number: ");
num2 = Convert.ToDouble(Console.ReadLine());
result = num1 - num2;
Console.WriteLine(result);
break;
case 3:
Console.Write("Enter First Number: ");
num1 = Convert.ToDouble(Console.ReadLine());
Console.Write("Enter Second Number: ");
num2 = Convert.ToDouble(Console.ReadLine());
result = num1 * num2;
Console.WriteLine(result);
break;
default:
Console.WriteLine("\n Next time follow instructions. You can only choose numbers 1 - 4");
break;
}

So, if I was going to write this, I'd start with an enumerated type for the operations:
public enum ArithmeticOperation
{
Add,
Subtract,
Multiply,
Divide,
}
I'd write a little helper function:
private static string ShowEnumOptions<T>() where T : struct
{
if (!typeof(T).IsEnum)
{
throw new ArgumentException($"Type: {typeof(T).ToString()} must be an enumerated type");
}
var options = Enum.GetNames(typeof(T));
return string.Join("/", options);
}
(the newest version of C# (which I don't use yet) allows a System.Enum constraint on a generic type parameter which would simplify this)
Then I'd write my main program to look like this:
static void Main(string[] args)
{
while (true)
{
ArithmeticOperation operation = default(ArithmeticOperation);
var goodOperation = false;
while (!goodOperation)
{
Console.Write(
$"Enter operation (one of [{ShowEnumOptions<ArithmeticOperation>()}] or \"Quit\"): ");
var response = Console.ReadLine();
if (string.Equals(response, "Quit", StringComparison.InvariantCultureIgnoreCase))
{
return; //quit the app
}
if (Enum.TryParse<ArithmeticOperation>(response, true, out operation))
{
goodOperation = true;
}
}
double value1 = 0.0;
double value2 = 0.0; //initialize them to keep the compiler happy
var goodDouble = false;
while (!goodDouble)
{
Console.Write("Enter the first number: ");
var response = Console.ReadLine();
if (double.TryParse(response, out value1))
{
goodDouble = true;
}
}
goodDouble = false;
while (!goodDouble)
{
Console.Write("Enter the second number: ");
var response = Console.ReadLine();
if (double.TryParse(response, out value2))
{
goodDouble = true;
}
}
//ok, got an operation and two numbers
double result = 0.0;
switch (operation)
{
case ArithmeticOperation.Add:
result = value1 + value2;
break;
case ArithmeticOperation.Subtract:
result = value1 - value2;
break;
case ArithmeticOperation.Multiply:
result = value1 * value2;
break;
case ArithmeticOperation.Divide:
if (value2 == 0.0)
{
Console.WriteLine("Division by zero is invalid");
result = double.NaN; //NaN means "not a number"
break;
}
result = value1 / value2;
break;
}
Console.WriteLine($"Result is {result}");
}
}
Note that I check all input for validity. Always assume your users will enter bad data. Also note that I check my double for equality with zero. Checking for floating point equality is usually a bad idea, but it's the right thing to do here.
Then, as pseudo code, all I'd write would be:
// Get the operation (one of add/subtract/multiply or divide) - or allow the user to quit
// Get each of value1 and value2 as doubles
// Based on the operation, calculate the result (pay attention to division by zero)
// Show the result
// Loop back and let the user try again (or quit)

Pseudocode is basically writing what you're trying to do in comments. What your professor was probably trying to teach you is to make a bunch of comments to plan out the structure of your code, and then write your code. What you have above is already functional code. At the risk of answering your homework question, I'd say it goes something like this:
switch(option)
{
case 1:
//do something
break;
case 2:
//do something else
break;
default:
//what to do if none of the cases are met
break;
}

I don't know what you mean with pseudocode but this code is less repetitive:
double result = 0;
Console.Write("Enter First Number: ");
double num1 = Convert.ToDouble(Console.ReadLine());
Console.Write("Enter Second Number: ");
double num2 = Convert.ToDouble(Console.ReadLine());
Console.WriteLine("Enter a number from 1 to 3");
string input = Console.ReadLine();
switch (input) {
case "1" :
result = num1 + num2;
break;
case "2":
result = num1 - num2;
break;
case "3":
result = num1 * num2;
break;
default:
Console.WriteLine("\n Next time follow instructions. You can only choose numbers 1 - 4");
break;
}
Console.WriteLine("Result = " + result);

System.FormatException in C#

I keep getting a FormatException in each of the cases on the line where I try to assign the value for the sale variable. Anyone know what I am doing wrong? I am supposed to make this console program as homework to learn about loops, but I am finding out more about other things. It is supposed to keep a running tab of salesperson's commission based a a 10% commission of each sale. Anyways, here is the code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace TubSales
{
class Program
{
static void Main(string[] args)
{
char initial;
const double COMM_INT = 0.10;
double sale, aComm = 0, bComm = 0, eComm = 0;
Console.Write("Enter 'A' for Andrea, 'B' for Brittany,\n'E' for Eric, or 'Z' to quit >> ");
initial = Convert.ToChar(Console.Read());
while (initial != 'z' && initial != 'Z')
{
switch (initial)
{
case 'a':
case 'A':
Console.Write("Enter the sales for Andrea >> ");
sale = Convert.ToDouble(Console.ReadLine());
aComm = aComm + COMM_INT * sale;
break;
case 'b':
case 'B':
Console.Write("Enter the sales for Brittany >> ");
sale = Convert.ToDouble(Console.ReadLine());
bComm = bComm + COMM_INT * sale;
break;
case 'e':
case 'E':
Console.Write("Enter the sales for Eric >> ");
sale = Convert.ToDouble(Console.ReadLine());
eComm = eComm + COMM_INT * sale;
break;
default:
Console.WriteLine("You did not enter a valid initial");
break;
}
Console.Write("Enter 'A' for Andrea, 'B' for Brittany, or 'E' for Eric >> ");
initial = (char)Console.Read();
}
Console.WriteLine("Andrea had {0}, Brittany had {1}, and Eric had {2} in commissions.", aComm.ToString("C"), bComm.ToString("C"), eComm.ToString("C"));
Console.Write("Press any key to exit... ");
Console.ReadKey();
}
}
}

I keep getting a FormatException in each of the cases on the line where I try to assign the value for the sale variable. Anyone know what I am doing wrong?
The Convert.ToDouble method will raise a FormatException if the string (returned from Console.ReadLine()) is not a valid number.
Typically, if you want to parse user input, it's a better idea to use Double.TryParse instead, as this lets you determine whether the input was a valid number without catching the exception.
This would normally look something like:
Console.Write("Enter the sales for Andrea >> ");
while (!double.TryParse(Console.ReadLine(), out sale))
{
Console.WriteLine("Value entered was not a valid number.");
Console.Write("Enter the sales for Andrea >> ");
}
// Once you get here, "sale" will be set appropriately

While Reed's answers is great, it's not the problem here.
What really happens is the same situation as this one
Console.Read only read the "Second part of the carriage return" and returns "". This is why the Convert fails.
replace
initial = Convert.ToChar(Console.Read());
with
initial = Convert.ToChar(Console.ReadLine());

Replace
initial = Convert.ToChar(Console.Read());
with
initial = Convert.ToChar(Console.ReadLine().FirstOrDefault());