Collection was modified; enumeration operation might not execute.

Question

0.00/5 (No votes)

See more:

Hello,

I am trying to loop through a DataTable to find each row where the "AccountNo" is equal to a number that is passed in.

I am getting the following error now:

Collection was modified; enumeration operation might not execute.

The code has errored on this loop:

VB

For Each DataRow In dt.Rows

            RowNumber = RowNumber + 1

            If DataRow("AccountNo").ToString() = CustomerIDForHistory Then

                Dim output As String = DataRow.ToString.ElementAt(RowNumber)

                dt.Rows.Add(output)

            End If
        Next

Thanks Glen

Posted 14-Jan-14 23:36pm

Glen Childs

Add a Solution

3 solutions

Solution 1

You can not change the Collection you currently loop through !

so adding a value to dt.Rows, while you run a for each on dt.Rows.. throws that error

greets

Posted 15-Jan-14 0:06am

F. Xaver

Solution 3

The right way and also easiest to parse or loop a dictionary is to get its keys in a List and then loop through the dictionary using this key-list.

C#

List keyList = new List<int>(Dictionary.Keys);foreach (key in keys)
{
  // Now we can perform any modification wh values of dictionary.
  Dictionary[key] = Dictionary[key] - 1;
}</int>

Here is a detail blogpost about this: Example Here

Posted 11-Nov-14 0:46am

open and free

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)

CPallini · Accepted Answer · 2014-01-15T00:16:00

Solution 2

If you really need to add items inside the loop then you should (properly) use another kind of loop (for instance a for, or a while, depending on your needs) to iterate on the items of the DataTable collection, e.g.

C#

// this is most likely what you want to do, that is: NOT iterate on the newly inserted items
int COUNT = dt.Rows.Count;
for (int r = 0; r<COUNT; ++r)
{
  DataRow dr = dr.Rows[r];
  //...
}

Posted 15-Jan-14 0:16am

CPallini

Updated 15-Jan-14 0:18am

v3

Comments

Glen Childs 15-Jan-14 9:52am

Thanks that has solved the error, now I am getting a slightly different error... No default member found for type 'DataColumn'. Errors on the IF statement

Dim COUNT As Integer = dt.Rows.Count

For Each DataColumn In dt.Columns

For r As Integer = 0 To COUNT - 1

If DataColumn("AccountNo") = FrmSearch.txtCustID1.Text Then

Dim output As String = DataColumn.ToString().ElementAt(r)

dtValue.Rows.Add(output)

End If
Next
Next