How do I resolve index was out of range. Must be non-negative and less than the size of the collection. Error

Question

1.00/5 (1 vote)

See more:

I am getting following exceptions in my code

Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index

I could not understand why it is throwing that exception.

Flow of program is something like this :

I have collection of number say 1 to 200.
for each number in collections, it goes and run the below code. till 120, it did not throw the exception but for 121, its throwing the exception.
and it does randomly, if run the program again, I might get same exception for 123.

What could be the reason? Is it something related with database connection? Is there any problem in my code? if so then should not it be throwing for the first iteration? I did not understand. Please help me out.

What I have tried:

public DataTable GetGrade(DataTable dtReportTbl)
       {
           dtReportTbl.Columns.Add("Salary_Grade", typeof(System.String));
           dtReportTbl.Columns.Add("InsertedDate", typeof(DateTime));
           string query = "select Grade from student_grade where myTable in ('JMS','JSM') and  student_Num in ({StudentNums}) order by student_Num";

           try
           {
               using (OracleConnection con = new OracleConnection(connectionString))
               {
                   List<string> storeNums = new List<string>();


                   foreach (DataRow row in dtReportTbl.Rows)
                   {
                       storeNums.Add(row["store"].ToString());
                   }

                   var cmd = new OracleCommand(query, con);

                   // extension method to get StudentNums as to achieve cmd.Parameters.Add(new OracleParameter("pStudentNums", studentNum)
                   cmd.AddArrayParametersOra(storeNums, "StudentNums");

                   var rdr = cmd.ExecuteReader();
                   List<string> salGradelist = new List<string>();
                   while (rdr.Read())
                   {
                       salGradelist.Add(rdr["Grade"].ToString());
                   }

                   int i = 0;
                   foreach (DataRow row in dtReportTbl.Rows)
                   {
                       row["Grade"] = salGradelist[i];
                       row["RecordInsertedDate"] = DateTime.Today;
                       i++;
                   }
               }
           }
           catch (Exception ex)
           {
               throw;
           }

           return dtReportTbl;
       }

Posted 4-Aug-17 4:12am

gaurav.s23

Updated 4-Aug-17 12:59pm

v2

Add a Solution

3 solutions

Solution 4

Quote:
I could not understand why it is throwing that exception.

Do not do programs relying on expectations, make your program check if expectations are met. When your program fail, use the debugger to inspect variables and check which is the unexpected condition.

There is a tool that allow you to see what your code is doing, its name is debugger. It is also a great learning tool because it show you reality and you can see which expectation match reality.
When you don't understand what your code is doing or why it does what it does, the answer is debugger.
Use the debugger to see what your code is doing. Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute.

Debugger - Wikipedia, the free encyclopedia[^]

Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]
Basic Debugging with Visual Studio 2010 - YouTube[^]
Debugging C# Code in Visual Studio - YouTube[^]
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't find bugs, it just help you to. When the code don't do what is expected, you are close to a bug.

Posted 4-Aug-17 12:59pm

Patrice T

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)

OriginalGriff · Accepted Answer · 2017-08-04T04:18:00

To find out, you need to look at the data in your app while it is running - and we can;t do that!
So, its going to be up to you.
Put a breakpoint on the first line in the method, 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!

Richard Deeming · Accepted Answer · 2017-08-04T04:25:00

The most likely cause is that the number of rows returned from your query is not the same as the number of elements in your array.

int i = 0;
foreach (DataRow row in dtReportTbl.Rows)
{
    ... = salGradelist[i]; // <-- Exception here
    ...
    i++;
}

If the query returns fewer rows than the number of elements in your array, then your code will just ignore the later elements.

But if it returns more rows, then the variable i is going to go beyond the end of your array, and you'll get the "index out of bounds" exception.

You'll need to debug your code and your query to find out why the number of rows returned doesn't match the number of elements in your array.

How do I resolve index was out of range. Must be non-negative and less than the size of the collection. Error

3 solutions

Solution 1

Solution 2

Solution 4

Add your solution here

Preview 0