CODEWITHSUNDEEP
c#.net
Karol2137
Karol2137

Reputation: 3

How to print an error message if input is not a number?

I wonder how to print an error message if user's input is not a number.

Console.WriteLine("Water amount in ml:");
        int waterAmount = Convert.ToInt32(Console.ReadLine());

Most answers from other posts don't work, because waterAmount is a Int32, not a string. Also, sorry if my English is weak, it's not my native language

Upvotes: 0

Views: 1973

Answers (4)

Nicholas
Nicholas

Reputation: 87

I see you did not accept the other answers. Maybe you want to make the user try again after he did not input a number. You can do that with a while loop, or easier, using the goto keyword. You simply put a tag before everything is happening (in my case, waterAmountInput), and if the input was not a number, you write your error message and go to the beginning again. Here is the code:

        int waterAmount;

        waterAmountInput:
        Console.Write("Water amount in ml: ");
        try
        {
            waterAmount = Convert.ToInt32(Console.ReadLine());
        }
        catch
        {
            Console.WriteLine("The water amount needs to be a number!");
            goto waterAmountInput;
        }

Upvotes: 1

Vaibhav
Vaibhav

Reputation: 1166

You will need to use TryParse before presuming it to be a number. After Console.WriteLine you can capture and parse the input and if TryParse returns false, you can display an error message.

Note: if the conversion succeeds the numeric value is available in the waterAmt local variable.

Console.WriteLine("Water amount in ml:");
var input = Console.ReadLine();
if(!int.TryParse(input, out int waterAmt))
      Console.WriteLine("Input is not a number");

Upvotes: 0

Yellowsink
Yellowsink

Reputation: 189

You can try using C#'s TryParse() functions. These attempt to convert values, but if they fail they return false rather than erroring.

I would suggest trying this code:

Console.WriteLine("Water amount in ml:");
string input = Console.ReadLine();

if (Int32.TryParse(input, out var value))
    // Do something here. The converted int is stored in "value".
else
    Console.WriteLine("Please enter a number");

Upvotes: 1

Mahdi Aslami Khavari
Mahdi Aslami Khavari

Reputation: 1985

You should use TryParse function:

Console.WriteLine("Water amount in ml:");
int waterAmount = 0;
if (int.TryParse(Console.ReadLine(), waterAmount)) {

} else {
    Console.WriteLine("Error Message");
}

Upvotes: 0

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