Convert Class Error

Curwen Arthurs

4y1.9k.NET

Hi. I am trying to convert a user input string to an int but getting this error.

Unhandled exception. System.FormatException: Input string was not in a correct format.
at System.Number.ThrowOverflowOrFormatException(ParsingStatus status, TypeCode type)
at System.Convert.ToInt32(String value)
at csharpfundamentals.Practice.Main(String[] args)

// Code snippet

Console.WriteLine("Enter a number: ");

string user_input = Console.ReadLine();

int number = Convert.ToInt32(user_input);

5 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vishal Yelve4y ago
int.TryParse(user_input, out number);
Sachin Singh4y ago
It may be something like, you are entering "ABC" and then trying to convert it into an integer.

Any user input through the keyboard is considered as a string, but only that string can be converted into integers that the compiler can parse into integers without any custom calculation.
for example, any number can be converted into an int or long or decimal but an alphabet or word, or sentence can't be.

so, the first test that the input is actually parsable or not.
int num;

if(int.tryParse(Console.ReadLine(), out num))

{
Console.WriteLine("input {0} is an integer",num) ;
}
else
{
Console.WriteLine("Sorry! input is not an integer") ;
}
Uttam Kumar4y ago
Conversion issue. Better go through the article below. It’ll help you understand the safest conversion technique https://www.c-sharpcorner.com/article/safest-way-to-convert-string-to-int-in-c-sharp/
Jaydeep Patil4y ago
You need to handle exceptions using a try-catch block and validate the user input properly so that will not break your code
Jignesh Kumar4y ago
Hello Curwen,

Please try this one will help you out,

Console.WriteLine("Enter a number: ");
string user_input = Console.ReadLine();
if(!string.IsNullOrEmpty(user_input))
{
int num;
bool isNumeric = int.TryParse(user_input, out num);

if(isNumeric)
{
int number = Convert.ToInt32(user_input);
}
else
{
// Show validation message : string is not valid integer
}