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How to delete items from a DataTable during an enumeration

Greg McGuffey — Sat, 27 Jan 2007 10:27:43 GMT

I'm trying to enumerate all the rows in a DataTable and if a certain condition is met, delete the current row. .NET doesn't like this:

[codesnippet]
Dim myTable As DataTable
'...fill table, two columns a string and an integer
For Each myRow As DataRow In myTable.Rows
If myRow.Item(1) = 34 Then
myTable.Delete(myRow)
End If
Next
[/codesnippet]

It bombs when the Next statement hits. Is there another way to do this?

RE: How to delete items from a DataTable during an enumeration

Trent L. Taylor — Sat, 27 Jan 2007 10:27:43 GMT

Good. :)

RE: How to delete items from a DataTable during an enumeration

Greg McGuffey — Fri, 26 Jan 2007 20:19:39 GMT

Got it. I think the DataRow.Delete() works because it doesn't remove the item from the collection until you AcceptChanges, which I'm doing after the enum.

RE: How to delete items from a DataTable during an enumeration

Trent L. Taylor — Fri, 26 Jan 2007 17:57:36 GMT

This has nothing to do with data tables, but rather any type of collection in .NET. If you had tried removing items from a collection inside of a loop you would have had the same issue.

RE: How to delete items from a DataTable during an enumeration

Greg McGuffey — Fri, 26 Jan 2007 15:39:30 GMT

Thanks for the help. While implementing what you suggestion, I noticed that the DataRow has a Delete method...then I noticed an AcceptChanges property on the DataTable. I tried this and it works:

[codesnippet]
Dim myTable As DataTable
'...fill table, two columns a string and an integer
For Each myRow As DataRow In myTable.Rows
If myRow.Item(1) = 34 Then
myRow.Delete()
End If
Next
myTable.AcceptChanges
[/codesnippet]

Apparently, the Delete() method of the row just marks it for deletion (thus doesn't whack the enumeration). The AcceptChanges property actually removes the rows.

RE: How to delete items from a DataTable during an enumeration

Trent L. Taylor — Fri, 26 Jan 2007 15:17:09 GMT

It is because you are changing the contents of the value being enumerated. You can't do this. Just create an array or list that has all of the rows that you want to delete inside of the loop. Then create another loop that cycles through the array you created to actually delete the rows.