DataTable is empty in release mode, but not in debug mode although I initialized it

Question

My code works in debug mode, but in release mode I get a System NullReference Exception for the MTable in line 6 and I don't know the reason. In debug mode I have access to the data.

Dim myregex As Regex = New Regex("A[1-6]|A[A-M]") 
Dim MTable As New DataTable
Dim dvr As New System.Windows.Forms.DataGridViewRow

If datasetB.Tables.Contains("BLA") Then

    MTable = datasetB.Tables("BLA").Select().
Where(Function(r) myregex.IsMatch(r.Item("Data"))).ToArray().CopyToDataTable

    MTable.Columns.Add(New DataColumn("textt", GetType(String)))
    MTable.Columns.Add(New DataColumn("texttt", GetType(String)))
    MTable.Columns.Add(New DataColumn("textttt", GetType(String)))
    MTable.Columns.Add(New DataColumn("texttttt", GetType(String)))

    ErrorsDgV.DataSource = MTable

    For Each dvr In Me.ErrorsDgV.Rows

            If dvr.Cells(5).Value IsNot Nothing Then

                'do some things

            End If

        Next
    Else
        MsgBox("didn't work")
    End If

Thanks in advance!

We can't tell which is line 6. Also, you don't need that `.Select()` in there. Additionally you should use [`Option Strict On`](https://stackoverflow.com/a/29985039/1115360) because correcting the problems it points out can often fix the code. — Andrew Morton, Aug 14 '19 at 12:46
Line 6 is the sixth line of the code that I inserted above :) and I can't use `.Where` without `.Select()` — , Aug 14 '19 at 13:05
Possible duplicate of [What is a NullReferenceException, and how do I fix it?](https://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it) — TnTinMn, Aug 14 '19 at 13:59
@ezma well you *can* use `Where` without `Select`. I have never used the empty empty select myself. What if you tried `MTable = datasetB.Tables("BLA").Rows.OfType(Of DataRow).Where(Function(r) myregex.IsMatch(r.Item("Data"))).ToArray().CopyToDataTable` which doesn't convert to an Array? — djv, Aug 14 '19 at 14:45
Where is `datasetB` declared & loaded? Can you show that code? — HardCode, Aug 14 '19 at 16:41
`Dim datasetB As New DataSet` is declared in another `private sub`. Here I load the lines of the file to `StringToAdd = Tools.ExtractFields(line, Ln, Filee)` and add `StringToAdd` to the dataset then: `datasetB.Tables(Trim(StringToAdd(2))).Rows.Add() datasetB.Tables(Trim(StringToAdd(2))).Rows(datasetB.Tables(Trim(StringToAdd(2))).Rows.Count - 1).ItemArray = StringToAdd` — , Aug 15 '19 at 08:00

score 0 · Accepted Answer · answered Aug 15 '19 at 13:36

I opened the Compiler Settings in Visual Studio and selected Release in Configuration. Then I clicked on Advanced Compiler Settings. There I unchecked the Optimize Code Button. This way the code runs as in the debug mode.

DataTable is empty in release mode, but not in debug mode although I initialized it

1 Answers1