Question

I have a For Each loop written in Visual Basic that’s trying to modify a table it is iterating through. This is causing the “”Collection was modified; enumeration operation might not execute” exception.

What is frastrating about this is that I’ve tried to make copies of all the objects that I was using and and only removed from the copy but the exception still happened.

I know that this is due to my using a For Each loop instead of a For or While loop but I could not rewrite my code and make it work (I’m more familiar with C#). This is why I decided to ask for help here.

This is my code. How can I rewrite to be able to remove the Row that I wish to remove? Any help and code would be very appreciated!

Dim drAcademicRecord, drSchool As DataRow
For Each drSchool In dsR.Tables("School").Rows
    If drSchool("OrganizationName") = "NA" Then
        For Each drAcademicRecord In dsR.Tables("AcademicRecord").Rows
            If drAcademicRecord("AcademicRecord_Id") = drSchool("AcademicRecord_Id") Then
                dsR.Tables("AcademicRecord").Rows.Remove(drAcademicRecord)  '<-- This is the line causing my exception
            End If
        Next
    End If
Next

Answer 1

You don’t need to use

dsR.Tables("AcademicRecord").Rows.Remove(drAcademicRecord)

Because you have already got drAcademicRecord, so you can directly delete that row by

drAcademicRecord.Delete

e.g.

For Each drSchool As DataRow In dsR.Tables("School").Select("OrganizationName='NA'")
    For Each drAcademicRecord As DataRow In dsR.Tables("AcademicRecord").Select("AcademicRecord_Id=" & drSchool("AcademicRecord_Id"))
        drAcademicRecord.Delete
    Next
Next