C# - How to handle errors in this code using try-catch block?

Question

I have this code:

else if (number == 5)
        {
            Console.Write("Student's index: ");
            int index1 = int.Parse(Console.ReadLine());
            try
            {
                customDataList.FindStudent(index1); //displays the element that has the specified index
            }
            catch (ArgumentOutOfRangeException)
            {
                Console.WriteLine("Please choose an index from 0 to 9!");
            }
        }

I need to handle errors using try-catch when the user doesn't enter any character or enters a non-integer character. How can that be done?

Why don't use int.TryParse here? See learn.microsoft.com/en-us/dotnet/api/system.int32.tryparse — Dennis
– Dennis, Commented Dec 19, 2018 at 9:09
Not with try/catch. Validate the user-input before trying to find the student, and display an error message if validation fails. Only call FindStudent if the input is valid. — Lennart
– Lennart, Commented Dec 19, 2018 at 9:09
Handle ArgumentNullException and/or FormatException in separate catch blocks. Or, a better approach, follow the ideas on the comments above and use int.TryParse to validated the input before trying to use it. — Lucas Araujo
– Lucas Araujo, Commented Dec 19, 2018 at 9:14

currarpickt · Accepted Answer · 2018-12-19 09:19:37Z

1

Use TryParse to check if the input is an integer or not. Then if it's an integer, do whatever you want with the index.

else if (number == 5)
{
    Console.Write("Student's index: ");
    var success = int.TryParse(Console.ReadLine(), out int index1);
    if (success)
    {
        //next logic here if the input is an integer
        try
        {
            customDataList.FindStudent(index1); //displays the element that has the specified index
        }
        catch (ArgumentOutOfRangeException)
        {
            Console.WriteLine("Please choose an index from 0 to 9!");
        }
    }
    else
    {
        //do something when the input is not an integer
    }
}

answered Dec 19, 2018 at 9:19

currarpickt

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Comments

Ryan · Accepted Answer · 2018-12-19 09:25:30Z

You need to move your int.Parse line inside the try {} block. Only then will it be in the safety net of structured exception handling. You can then add a second catch {} block against a FormatException see Int32.Parse docs for exceptions thrown.

else if (number == 5)
{
    Console.Write("Student's index: ");

    try
    {
        int index1 = int.Parse(Console.ReadLine());
        customDataList.FindStudent(index1); //displays the element that has the specified index
    }
    catch (ArgumentOutOfRangeException)
    {
        Console.WriteLine("Please choose an index from 0 to 9!");
    }
    catch (FormatException)
    {
        Console.WriteLine("Error: Index must be a number.");
    }
}

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