我在 C# 中遇到 System.ArgumentOutOfRangeException 错误？

Question

I'm working on a school assignment where I have to convert a 8 bit binary number to decimal. This is my code;

         private void btnCalculate_Click(object sender, EventArgs e)
        {
            string invoer = txtBoxInput.Text;

            // binair naar decimaal
            if (rdBtnBinair.Checked == true)
            {
                int invoerlengte = invoer.Length;
                double nieuwgetal = 0;
                for (int i = 0; i <= invoerlengte; i++)
                {
                    if (int.Parse(invoer.Substring(i, 1)) == 1)
                    {
                        nieuwgetal += Math.Pow(2,(i+1));
                    }
                }
                txtBoxOutput.Text = nieuwgetal.ToString();

In C#. Error im getting: System.ArgumentOutOfRangeException: Index and length must refer to a location within the string.

Think my code should be good, don't see whats wrong. Regards

Answer 1

You probably want to change this:

for (int i = 0; i <= invoerlengte; i++)

to this:

for (int i = 0; i < invoerlengte; i++)

Because when i is equal to invoer.Length then the next line of code will be looking for the next character after the end of the string, which is out of range:

invoer.Substring(i, 1)

Answer 2

Its because your foreach loops one iteration too much, because you use <= instead of '<'.

In these cases its always good to check what happens when. You can do this with a debugger, or plain old Console.WriteLine (or debug.log w/e)

online sample: https://dotnetfiddle.net/UyE2rw

    public static void Main()
    {
        var invoer = "12345";
        int invoerlengte = invoer.Length;
                double nieuwgetal = 0;
                for (int i = 0; i <= invoerlengte; i++)
                {
                    Console.WriteLine("i: " + i + ", substring: " + invoer.Substring(i, 1));

                    if (int.Parse(invoer.Substring(i, 1)) == 1)
                    {
                        nieuwgetal += Math.Pow(2,(i+1));
                    }
                }

    }

outputs:

i: 0, substring: 1
i: 1, substring: 2
i: 2, substring: 3
i: 3, substring: 4
i: 4, substring: 5
Run-time exception (line 13): Index and length must refer to a location within the string.
Parameter name: length

Stack Trace:

[System.ArgumentOutOfRangeException: Index and length must refer to a location within the string.
Parameter name: length]
   at System.String.Substring(Int32 startIndex, Int32 length)
   at MyApp.Main() :line 13

and be mindful - indexes start at 0, counting at 1. So substring(0,1) is a char at index 0, but is the first element (char) in the string array.

item1 is at index0, item2 is at index1 etc.

De groetjes!

Answer 3

private void btnCalculate_Click(object sender, EventArgs e)
        {
            string invoer = txtBoxInput.Text;
            int invoerlengte = invoer.Length;
            double nieuwgetal = 0;
            if (rdBtnBinair.Checked == true)
            {
                for (int i = 1; i <= invoerlengte; i++)
                {
                    if (int.Parse(invoer.Substring(invoerlengte - (1 * i), 1)) == 1)
                    {
                        nieuwgetal += Math.Pow(2, (i - 1));
                    }
                }
            }

            txtBoxOutput.Text = nieuwgetal.ToString();

        }

This is the solution and it works now. Bye!