C#•4y ago

System.FormatException 'Input string was not in a correct format.' - Correct format is entered

https://github.com/AbdulRaheemNazir/MiniApps/blob/main/Main
I have uploaded my code here to display a menu page which it does succesfully.

I click option 2 and option 3 and option 4 and have no Issue

However when I click option 1 the program ends displaying the question and doesn't allow me to input and gives me the error in the screenshot. However I'm unsure what is causing this error to occur

Any assistance would be great

Thank you

GitHub

MiniApps/Main at main · AbdulRaheemNazir/MiniApps

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TheBoxyBear•10/28/22, 2:42 PM

Can't find the issue right now, but in the meantime you should rewrite the ReadLine to avoid crashing when the input is incorrect

TheBoxyBear•10/28/22, 2:42 PM

$tryparse

TTheBoxyBear $tryparse

MODiX•10/28/22, 2:42 PM

The TryParse pattern is considered best practice of parsing data from a string:

a TryParse method returns
```
true
```
```
true
```
or
```
false
```
```
false
```
to inform you if it succeeded or not, so you can use it directly in a condition,
since C# 7 you can declare a variable that will be used as an
```
out
```
```
out
```
argument inline in an argument list,
it forces you to check if the
```
out
```
```
out
```
argument contains valid data afterwards,

Avoid: Convert.ToInt32 — it's a bad choice for parsing an

int

int

. It exists only for backwards compatibility reasons and should be considered last resort.

return Convert.ToInt32(null); //returns 0. null should not be considered as 0 ever
return Convert.ToInt32("asdf"); //throws FormatException

return Convert.ToInt32(null); //returns 0. null should not be considered as 0 ever
return Convert.ToInt32("asdf"); //throws FormatException

(Note: Convert does contain useful conversion methods:

To/FromBase64String

To/FromBase64String

To/FromHexString

To/FromHexString

ToString(X value, int toBase)

ToString(X value, int toBase)

ToX(string? value, int fromBase)

ToX(string? value, int fromBase)

)

Avoid: int.Parse — you have to use a

try

try

catch

catch

statement to handle invalid input, which is a less clean solution.

var number = int.Parse("abc"); //throws FormatException
var number = int.Parse(""); //throws FormatException

var number = int.Parse("abc"); //throws FormatException
var number = int.Parse(""); //throws FormatException

Use int.TryParse https://docs.microsoft.com/en-us/dotnet/api/system.int32.tryparse?view=net-5.0#System_Int32_TryParse_System_String_System_Int32__

if (int.TryParse(someInput, out var result))
{
  Console.WriteLine($"Thanks for giving me the following number: {result}!");
}
else
{
  Console.WriteLine("You didn't give me a valid number :c");
}

if (int.TryParse(someInput, out var result))
{
  Console.WriteLine($"Thanks for giving me the following number: {result}!");
}
else
{
  Console.WriteLine("You didn't give me a valid number :c");
}

Int32.TryParse Method (System)

Converts the string representation of a number to its 32-bit signed integer equivalent. A return value indicates whether the operation succeeded.