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Adding an error message before restarting loop in c#

I am trying to add an error message that says "Please enter a non-zero or non-negative number" before my loop asks the user for input again. Here is what I have right now. Any text I try seems to only appear when the user inputs the correct number. Here is what I have right now.
using System;
public class Program
{
public static void Main()
{
double length;
bool isInteger = false;
do
{
Console.WriteLine("Please Enter Length: ");
isInteger = double.TryParse(Console.ReadLine(), out length);
}
while (!(isInteger && length >= 0));
Console.WriteLine();
Console.WriteLine("You have input: " + length);
Console.WriteLine();
{
double width;
bool isInteger2 = false;
do
{
Console.WriteLine("Please Enter Width: ");
isInteger2 = double.TryParse(Console.ReadLine(), out width);
}
while (!(isInteger2 && width >= 0));
Console.WriteLine();
Console.WriteLine("You have input: " + width);
Console.WriteLine();
{
double height;
bool isInteger3 = false;
do
{
Console.WriteLine("Please Enter Height: ");
isInteger3 = double.TryParse(Console.ReadLine(), out height);
}
while (!(isInteger3 && height >= 0));
Console.WriteLine();
Console.WriteLine("You have input " + height);
Console.WriteLine();
}
}
}
}

You can use a pattern like this:
double length;
bool success;
do
{
Console.WriteLine("Please Enter Length: ");
success = double.TryParse(Console.ReadLine(), out length) && (length > 0);
if (!success)
{
Console.WriteLine("Please enter a non-zero or non-negative number");
}
}
while (!success);

If open to using a open source NuGet package Spectre.Console
internal partial class Program
{
static void Main(string[] args)
{
double length = GetDouble("Please Enter Length:");
double width = GetDouble("Please Enter Width:");
double height = GetDouble("Please Enter Height:");
Console.WriteLine();
Console.WriteLine($"Length {length} Width {width} Height {height}");
Console.ReadLine();
}
public static double GetDouble(string title) =>
AnsiConsole.Prompt(
new TextPrompt<double>(title)
.PromptStyle("white")
.Validate(input => input switch
{
< 1 => ValidationResult.Error("[cyan]1 is min value[/]"),
_ => ValidationResult.Success(),
}));
}

I am having trouble evaluating the height in c#, when i introduce a number smaller than 1.5 still says come in

using System;
namespace Tarea_C_
{
class Program
{
static void Main(string[] args)
{
Console.Write("Write your age: ");
int age = Convert.ToInt32(Console.ReadLine());
if (age >= 18){
Console.Write("Write your height: ");
float height = float.Parse(Console.ReadLine());
if (height > 1.5 ){
Console.WriteLine("Come in");
}
else{
Console.WriteLine("Stay out");
}
}
else{
Console.Write("Stay out");
}
}
}
}

How can I make my C# calculator run as intended

I have a C# calculator I'm trying to get to run however I keep running into problems, particularly with my last function and currently get stuck in an infinite validation loop, how can I make this work as intended which is to take two numbers and based on user input get the answer for their equation.
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Hello User what is your name?");
string name = Console.ReadLine();
Console.WriteLine("Hello " + name + " Please enter in a number");
Console.ReadLine();
Console.WriteLine("Please enter a Math Operator: +, -, *, / ");
string beta = IsValidSymbol();
string equation = Console.ReadLine();
string useint1 = Console.ReadLine();
string useint2 = Console.ReadLine();
Console.WriteLine("Please enter another number");
Console.WriteLine(MathSymbols(equation,useint1,useint2));
}
public static double Validation()
{
string numbString = Console.ReadLine();
double numbVerify;
while (!double.TryParse(numbString, out numbVerify))
{
Console.WriteLine("please only enter in numbers and do not leave blank");
numbString = Console.ReadLine();
}
return numbVerify;
}
private static string IsValidSymbol()
{
string mathValidation = Console.ReadLine();
while ((String.IsNullOrEmpty(mathValidation)))
{
Console.WriteLine("Please, do not leave the sentence field empty!");
Console.WriteLine("Enter a Math Operator: +, -, *, / ");
mathValidation = Console.ReadLine();
}
return mathValidation;
}
private static double MathSymbols(string e, string useint1,string useint2)
{
useint1 = Console.ReadLine();
useint2 = Console.ReadLine();
double result;
double userinput1;
double userinput2;
while (!double.TryParse(useint1, out userinput1))
{
Console.WriteLine("please type in a number");
useint1 = Console.ReadLine();
}
while (!double.TryParse(useint2, out userinput2))
{
Console.WriteLine("please type in a number");
useint1 = Console.ReadLine();
}
if (e == "+")
{
result = userinput1 + userinput2;
}
else if (e == "-")
{
result = userinput1 - userinput2;
}
else if (e == "*")
{
result = (userinput1 * userinput2);
}
else if (e == "/")
{
result = (userinput1 / userinput2);
}
result = 0;
return result;
}
}
}

In many places you had an unnecessary call to Console.ReadLine and overriding variables. Also you didn't use your method Validation (think about renaming it to GetValidNumber).
I corrected your code to work for valid input. You still need additional validations and refactoring in your code, good luck!
using System;
namespace CalculatorExample
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Hello User what is your name?");
string name = Console.ReadLine();
Console.WriteLine("Hello " + name + " Please enter in a number");
double useint1 = Validation();
Console.WriteLine("Please enter a Math Operator: +, -, *, / ");
string equation = IsValidSymbol();
Console.WriteLine($"You equation symbol: {equation}");
Console.WriteLine("Please enter another number");
double useint2 = Validation();
double result = MathSymbols(equation, useint1, useint2);
Console.WriteLine($"Result: {result}");
Console.ReadKey();
}
public static double Validation()
{
string numbString = Console.ReadLine();
double numbVerify;
while (!double.TryParse(numbString, out numbVerify))
{
Console.WriteLine("please only enter in numbers and do not leave blank");
numbString = Console.ReadLine();
}
return numbVerify;
}
private static string IsValidSymbol()
{
string mathValidation = Console.ReadLine();
while ((String.IsNullOrEmpty(mathValidation)))
{
Console.WriteLine("Please, do not leave the sentence field empty!");
Console.WriteLine("Enter a Math Operator: +, -, *, / ");
mathValidation = Console.ReadLine();
}
return mathValidation;
}
private static double MathSymbols(string equation, double useint1, double useint2)
{
if (equation == "+")
return useint1 + useint2;
if (equation == "-")
return useint1 - useint2;
if (equation == "*")
return useint1 * useint2;
if (equation == "/")
return useint1 / useint2;
throw new InvalidOperationException($"Unrecognized equation symbol: {equation}");
}
}
}

Return to Start/Top in C # console application

I am trying to go back to start in c# console program, and i am somehow able to do it, but the problem is that i am not able to do it using the Y/N statement. mean if i type the Y (yes) from keyboard then the program start from it's starting (beginning) point if i type N then it will terminate the program.
My Console code is:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace simple_calculation
{
class Program
{
static void Main(string[] args)
{
bool bktop = true;
string option;
while (bktop)
{
Console.WriteLine("Please enter the values");
int val = int.Parse(Console.ReadLine());
int val1 = int.Parse(Console.ReadLine());
int res = val + val1;
int red = val / val1;
Console.WriteLine("Please enter the operator");
string oper=Console.ReadLine();
if (oper == "+")
{
Console.WriteLine("sum is:" + res);
}
else if (oper == "/")
{
Console.WriteLine("division is:" + red);
}
else
{
Console.WriteLine("do you want to continue? enter Y/N");
option = Console.ReadLine();
if(option=="Y")
{
bktop = false;
}
else
{
bktop = true;
}
}
Console.ReadLine();
}
}
}
}
What I want: i want that when the program reaches to the else condition then there is a text appear in the console "do you want to continue? enter Y/N" if the user enter Y then the program start again and if the user enter N then the program will terminate.
Any help will be appreciated.

class Program
{
static void Main(string[] args)
{
// Change 1
bool bktop = true;
string option;
while (bktop)
{
bktop = true;
Console.WriteLine("Please enter the values");
int val = int.Parse(Console.ReadLine());
int val1 = int.Parse(Console.ReadLine());
int res = val + val1;
int red = val / val1;
Console.WriteLine("Please enter the operator");
string oper = Console.ReadLine();
if (oper == "+")
{
Console.WriteLine("sum is:" + res);
}
else if (oper == "/")
{
Console.WriteLine("division is:" + red);
}
else
{
Console.WriteLine("do you want to continue? enter Y/N");
option = Console.ReadLine();
// Change 2
if (option.ToUpper() != "Y")
{
bktop = false;
}
}
}
}
}

simple temperature conversion questions

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConTempConversion_LeeMichelle
{
class Program
{
static void Main(string[] args)
{
double fTemp;
double cTemp;
double convertC;
double convertF;
Console.WriteLine("Welcome to the temperature conversion application");
Console.WriteLine("_________________________________________________");
Console.WriteLine("1. Fahrenheit to Celsius");
Console.WriteLine("2. Celsius to Fahrenheit");
Console.WriteLine("3. Exit");
Console.Write("Enter choice: ");
Console.ReadKey();
int ichoice = 0;
do
{
if (ichoice == 1)
{
Console.WriteLine("Enter Fahrenheit temperature: ");
fTemp = int.Parse(Console.ReadLine());
convertC = ConvertCelcius(fTemp);
Console.WriteLine(fTemp + "Fahrenheit is " + convertC + "Celsius");
Console.WriteLine("Welcome to the temperature conversion application");
Console.WriteLine("_________________________________________________");
Console.ReadKey();
}
if (ichoice == 2)
{
Console.WriteLine("Enter Celsius temperature: ");
cTemp = int.Parse(Console.ReadLine());
convertF = ConvertFahrenheit(cTemp);
Console.WriteLine(cTemp + "Celsius is " + convertF + "Fahrenheit");
Console.WriteLine("Welcome to the temperature conversion application");
Console.WriteLine("____________________________________________________");
Console.ReadKey();
}
if (ichoice == 3)
{
Console.WriteLine("Thank you for using the temperature conversion application. Please come again.");
}
else
{
Console.WriteLine("Invalid choice. Please choose again!");
}
}
while (ichoice > 3);
Console.ReadKey();
}
static double ConvertCelcius(double c){
double f;
return f= 9.0 / 5.0 * c + 32;
}
static double ConvertFahrenheit(double f) {
double c;
return c = 5.0 / 9.0 * (f - 32);
}
}
}
so suppose the user has three options from 1 - 3. After option 3, there will be an error alert. my problem is why this code gives me an infinity loop? what did I do wrong? can I put break after each if statment?
Please help, thank you!

You're creating a do...while loop without anything to ever exit it. When the loop begins, ichoice is already set in stone. So you'll always be stuck in that loop!

You are never assigning a value to ichoice If I were you, I would try something like this:
int ichoice = 0;
int.TryParse(Console.ReadKey().ToString(), out ichoice );
do
{
if (ichoice == 1)
{
Console.WriteLine("Enter Fahrenheit temperature: ");
fTemp = int.Parse(Console.ReadLine());
convertC = ConvertCelcius(fTemp);
Console.WriteLine(fTemp + "Fahrenheit is " + convertC + "Celsius");
Console.WriteLine("Welcome to the temperature conversion application");
Console.WriteLine("_________________________________________________");
int.TryParse(Console.ReadKey().ToString(), out ichoice );
Add the int.TryParse(Console.ReadKey().ToString(), out ichoice ); everywhere you have Console.Readline(). What this is doing is getting the user input and converting it to an integer (if it's not an integer, then the value is 0).
Also add this:
if (ichoice == 3)
{
Console.WriteLine("Thank you for using the temperature conversion application. Please come again.");
break;
}
else
{
Console.WriteLine("Invalid choice. Please choose again!");
int.TryParse(Console.ReadKey().ToString(), out ichoice );
}
Finally, remove this (I'm not quite sure what it was for...)
while (ichoice > 3);
Console.ReadKey();

When you need to do some prep work before your condition, the most straightforward way involves combining your loop with a separate structure.
This is the format to use when your loop condition is at the beginning of the loop:
prep work
while (condition) // if false then loop body will never run
{
loop body
}
This is the format to use when the loop condition is at the end of the loop:
prep work
do
{
loop body
}
while (condition); // loop body will always execute at least once
In this case, you have some prep work to do before each iteration--you want to get the key press from the user each time. For this, I recommend the following from Code Complete:
while (true) // loop termination condition is inside the loop
{
prep work
if (condition)
{
break;
}
loop body
}
In your case, it would look something like:
Console.Write("Enter choice: ");
while (true) // loop termination condition is inside the loop
{
Console.ReadKey();
if (ichoice == 3)
{
Console.WriteLine(...);
break;
}
...
}
Also, consider changing most of your ifs into else ifs; otherwise, you're repeatedly checking the condition even when you've gone through one case.

you should assign a value to iChoice. and set your while to read a terminating character. like:
namespace YourNameSpace
{
static void Main(string[] args)
{
double fTemp;
double cTemp;
double convertC;
double convertF;
int iChoice;
Console.WriteLine("Welcome to the temperature conversion application");
Console.WriteLine("_________________________________________________");
Console.WriteLine("1. Fahrenheit to Celsius");
Console.WriteLine("2. Celsius to Fahrenheit");
Console.Write("Enter choice(0 to exit): ");
iChoice = Console.Read();
do{
switch(iChoice)
{
case 1:
Console.WriteLine("Enter Fahrenheit temperature: ");
fTemp = int.Parse(Console.ReadLine());
convertC = ConvertCelcius(fTemp);
Console.WriteLine(fTemp + "Fahrenheit is " + convertC + "Celsius");
case 2:
Console.WriteLine("Enter Celsius temperature: ");
cTemp = int.Parse(Console.ReadLine());
convertF = ConvertFahrenheit(cTemp);
Console.WriteLine(cTemp + "Celsius is " + convertF + "Fahrenheit");
}
Console.WriteLine("Welcome to the temperature conversion application");
Console.WriteLine("_________________________________________________");
Console.WriteLine("1. Fahrenheit to Celsius");
Console.WriteLine("2. Celsius to Fahrenheit");
Console.Write("Enter choice(0 to exit): ");
iChoice = Console.Read();
}while(iChoice != 0);
}
static double ConvertCelcius(double c){
double f;
return f= 9.0 / 5.0 * c + 32;
}
static double ConvertFahrenheit(double f) {
double c;
return c = 5.0 / 9.0 * (f - 32);
}
}

Each time you call Console.ReadKey you should store returning value.You are receiving input from user but you didn't store it anywhere.
First you can create a function to get ichoice, and force user to enter the correct value:
static void GetChoice(ref int ichoice)
{
string input = Console.ReadLine();
Console.Write("Enter choice: ");
bool result = int.TryParse(input, out ichoice);
if (!result)
{
while (!result && ichoice > 3)
{
Console.WriteLine("Invalid value.Try again:");
input = Console.ReadLine();
result = int.TryParse(input, out ichoice);
}
}
}
Then use this function whenever you need to make a choice.
Here is the working version or your program:
double fTemp;
double cTemp;
double convertC;
double convertF;
Console.WriteLine("Welcome to the temperature conversion application");
Console.WriteLine("_________________________________________________");
Console.WriteLine("1. Fahrenheit to Celsius");
Console.WriteLine("2. Celsius to Fahrenheit");
Console.WriteLine("3. Exit");
int ichoice = 0;
GetChoice(ref ichoice);
do
{
if (ichoice == 1)
{
Console.WriteLine("Enter Fahrenheit temperature: ");
fTemp = int.Parse(Console.ReadLine());
convertC = ConvertCelcius(fTemp);
Console.WriteLine(fTemp + "Fahrenheit is " + convertC + "Celsius");
Console.WriteLine("Welcome to the temperature conversion application");
Console.WriteLine("_________________________________________________");
GetChoice(ref ichoice);
}
if (ichoice == 2)
{
Console.WriteLine("Enter Celsius temperature: ");
cTemp = int.Parse(Console.ReadLine());
Console.WriteLine(cTemp + "Celsius is " + cTemp + "Fahrenheit");
Console.WriteLine("Welcome to the temperature conversion application");
Console.WriteLine("____________________________________________________");
GetChoice(ref ichoice);
}
if (ichoice == 3)
{
Console.WriteLine("Thank you for using the temperature conversion application. Please come again.");
}
else
{
Console.WriteLine("Invalid choice. Please choose again!");
}
}
while (ichoice < 3);
}
static double ConvertCelcius(double c)
{
double f;
return f = 9.0 / 5.0 * c + 32;
}
static double ConvertFahrenheit(double f)
{
double c;
return c = 5.0 / 9.0 * (f - 32);
}
And here is the full code: http://pastebin.com/bkegSAFL