Unable to find overflow exception cause

Question

1.00/5 (2 votes)

See more:

I have written the following code to the exercise question given at the end of the book from which I'm learning C#.. However, my code gives me an error and I'm not able to find the reason. Can someone please review the code and mention the problem area

///summary
            ///Write a program, which creates an array containing all Latin letters.
            ///The user inputs a word from the console and as result the program
            ///prints to the console the indices of the characters matching array
            static void Main()
            {
            char ch = 'A';
            char[] alph = new char[26];
            for (int row = 0; row < 26; row++)
            {
                alph[row] = ch;
                ch++;
            }
            for (int row = 0; row < 26; row++)
            {
                Console.Write(alph[row] + " ");
            }
            Console.WriteLine();
            Console.Write("Enter word: ");
            string word = Console.ReadLine();
            string wordUpper = word.ToUpper();
            int wrdIdx = 0;
            for (int i = 0; true; i++)
            {
                if (wordUpper[wrdIdx] == alph[i]) //If below if is removed then this gives as error. Same error of overflow
                {
                    Console.Write(i + " ");
                    wrdIdx++;
                    i = 0;
                    if (wordUpper[wrdIdx] == wordUpper.Length - 1) //This line is giving error if i remove it then the error shows above in the IF statement.
                        break;
                }
            }
            }

This is the output and error message that I get:

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Enter word: Mohit
12 14 7 8 19
Unhandled Exception: System.IndexOutOfRangeException: Index was outside the bounds of the array.
   at System.String.get_Chars(Int32 index)
   at Revision.Program.Main(String[] args) in C:\Users\mohit\source\Revision\Revision\Program.cs:line 632

What I have tried:

Tried to debug the code. But as I'm a beginner so not able to understand whats going on in the debugger.

I request to please provide a very basic answer without using anything external from what I have written. As i dont know much about other functionalities provided by the various classes and methods. Please try to correct only the current code.

Please also excuse me for my English.

Thanks in advance.

Posted 9-Oct-18 20:26pm

Mohit Tomar

Updated 11-Oct-18 5:22am

Add a Solution

3 solutions

Solution 2

Unhandled Exception: System.IndexOutOfRangeException: Index was outside the bounds of the array.
   at System.String.get_Chars(Int32 index)

That isn't a "overflow exception" - it's an "array index exception"which is different.
What it's saying is that i is greater that 25, or wrdIdx exceeds the word length. Why? because your loop is only exited if everything matches and it reaches the break statement.
We can't run your code under the same conditions you do, so it's going to be up to you.
Fortunately, you have a tool available to you which will help you find out what is going on: the debugger.

Put a breakpoint on the first line in the function, and run your code through the debugger. Then look at your code, and at your data and work out what should happen manually. Then single step each line checking that what you expected to happen is exactly what did. When it isn't, that's when you have a problem, and you can back-track (or run it again and look more closely) to find out why.

Sorry, but we can't do that for you - time for you to learn a new (and very, very useful) skill: debugging!

Posted 9-Oct-18 20:51pm

OriginalGriff

Comments

Mohit Tomar 10-Oct-18 3:53am

Is there any beginner friendly Debugging tutorial that I can refer to?? Actually, its been only one month since I started with C# so my knowledge is very very limited.

OriginalGriff 10-Oct-18 4:01am

Loads, and loads:
https://www.google.co.uk/search?q=visual+studio+debugger&oq=visual+studio+debugger&aqs=chrome..69i57j0l5.6712j0j7&sourceid=chrome&ie=UTF-8
Here is the MS one:
https://tutorials.visualstudio.com/vs-get-started/debugging

Mohit Tomar 11-Oct-18 7:18am

However I was wondering, shouldn't the loop break when it reaches at -----if (wordUpper[wrdIdx] == wordUpper.Length - 1) ----- because at this time the value of both the wordUpper[wrdIdx] and wordUpper.Length - 1 becomes same.

OriginalGriff 11-Oct-18 7:29am

Yes but that's nested inside another if, so both conditions have to be true. So unless the first condition matches then there is a good possibility of just running on and on until you get an array index problem.
Relying on your data to be valid every time is a dangerous route...

Mohit Tomar 13-Oct-18 0:23am

Thanks.. :-)

OriginalGriff 13-Oct-18 2:19am

You're welcome!

Solution 1

An error message: System.IndexOutOfRangeException: Index was outside the bounds of the array is corelated with an array. An array index starts from zero to the count of elements minus 1. So, the first element in array has an index 0, second - 1, third - 2, ... tenth - 9, etc.

Look at your for loops to resolve your issue.

Posted 9-Oct-18 20:44pm

Maciej Los

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Richard Deeming · Accepted Answer · 2018-10-11T05:23:00

if (wordUpper[wrdIdx] == wordUpper.Length - 1)

wordUpper[wrdIdx] returns a char representing the character at the specified index.

wordUpper.Length - 1 returns an int - a number one less than the length of the string.

In order to compare them, the char will be converted to its Unicode code-point. (Since you're only working with non-accented letters, this is the same as its ASCII[^] value.)

Given the upper-case input string "MOHIT", the numeric value of wordUpper[wrdIdx] will be: 77, 79, 72, 73 and 84. Obviously, none of those values are equal to wordUpper.Length - 1, so your loop never terminates. Once wrdIdx moves past the end of your string, you get the IndexOutOfRangeException when you try to access the next character.

One simple fix would be to use a nested loop:

C#

foreach (char c in wordUpper)
{
    for (int i = 0; i < alph.Length; i++)
    {
        if (c == alph[i])
        {
            Console.Write(i + " ");
            break;
        }
    }
}