[RESOLVED] Error "Argument 'Prompt' cannot be converted to type 'String'"

[gkarofilakis]

hi ti all
i have the following code

  Private Sub FillDGV_AllUnCompited_Lipantika()
        Dim Order_Row1 As DataRow
        Dim date1 As Date
        Dim Condition, supplier, DAs, TPs, temp As String
        Condition = ""
        supplier = ""
        DAs = ""
        TPs = ""
        temp = ""
        Try
            OrdersDataSet.Clear()
            ServisNote_connection.Open()
            cmdstr = "SELECT * FROM Lipantika_Orders WHERE Complited = 'FALSE' ORDER BY EkdosiDate DESC"
            OrdersTableAdapter = New SqlDataAdapter(cmdstr, ServisNote_connection)
            OrdersTableAdapter.Fill(OrdersDataSet, "Orders")
            ServisNote_connection.Close()
        Catch ex As Exception
            ServisNote_connection.Close()
            MsgBox(ex.Message)
        End Try
        If OrdersDataSet.Tables("Orders").Rows.Count = 0 Then
            MessageBox.Show("Δεν υπάρχει καμία μη ολοκληρωμένη παραγγελία λιπαντικών καταχωρημένη", "Ενημέρωση!", MessageBoxButtons.OK, MessageBoxIcon.Information)
            chkAllUncomplited.CheckState = CheckState.Unchecked
            Exit Sub
        End If
        For i = 0 To OrdersDataSet.Tables("Orders").Rows.Count - 1
            Order_Row1 = OrdersDataSet.Tables("Orders").Rows(i)
            date1 = Order_Row1.Item(3)
            'If Order_Row.Item(15) = True Then
            Condition = "ΝΑΙ"
            'Else
            '    Condition = "ΟΧΙ"
            'End If
            'MsgBox(OrdersDataSet.Tables("Orders").Rows(i).Item(9))
            'Try
            MsgBox(OrdersDataSet.Tables("Orders").Rows(i).Item(9))
            'Catch ex As Exception
            '    MessageBox.Show(ex.ToString)
            'End Try
            If Order_Row1.Item(9) <> "-" Then
                Try
                    DADataSet.Clear()
                    ServisNote_connection.Open()
                    cmdstr = "SELECT * FROM Deltia_Apostolis"
                    DATableAdapter = New SqlDataAdapter(cmdstr, ServisNote_connection)
                    DATableAdapter.Fill(DADataSet, "DAs")
                    ServisNote_connection.Close()
                Catch ex As Exception
                    ServisNote_connection.Close()
                    MsgBox(ex.Message)
                End Try
                temp = Order_Row1.Item(9)
                If temp.Contains(",") = False Then
                    DACount = 1
                    ReDim DAIDs(DACount - 1)
                    ReDim DANumbers(DACount - 1)
                    DAIDs(0) = temp
                    For j = 0 To DADataSet.Tables("DAs").Rows.Count - 1
                        If DADataSet.Tables("DAs").Rows(j).Item(0) = temp Then
                            DANumbers(0) = DADataSet.Tables("DAs").Rows(j).Item(3)
                        End If
                    Next
                Else
                    Call Find_DAs(temp, DADataSet, DAs)
                End If
                For j = 0 To DACount - 1
                    If j = 0 Then
                        DAs = DANumbers(j)
                    Else
                        DAs = DAs + "," + DANumbers(j)
                    End If
                Next
            Else
                DAs = "-"
            End If
            If Order_Row1.Item(10) <> "-" Then
                Try
                    InvoiceDataSet.Clear()
                    ServisNote_connection.Open()
                    cmdstr = "SELECT * FROM Invoices"
                    InvoiceTableAdapter = New SqlDataAdapter(cmdstr, ServisNote_connection)
                    InvoiceTableAdapter.Fill(InvoiceDataSet, "Invoices")
                    ServisNote_connection.Close()
                Catch ex As Exception
                    ServisNote_connection.Close()
                    MsgBox(ex.Message)
                End Try
                temp = Order_Row1.Item(10)
                If temp.Contains(",") = False Then
                    TPCount = 1
                    ReDim TPIDs(TPCount - 1)
                    ReDim TPNumbers(TPCount - 1)
                    TPIDs(0) = temp
                    For j = 0 To InvoiceDataSet.Tables("Invoices").Rows.Count - 1
                        If InvoiceDataSet.Tables("Invoices").Rows(j).Item(0) = temp Then
                            TPNumbers(0) = InvoiceDataSet.Tables("Invoices").Rows(j).Item(4)
                        End If
                    Next
                Else
                    Call Find_TPs(temp, InvoiceDataSet, TPs)
                End If
                For j = 0 To TPCount - 1
                    If j = 0 Then
                        TPs = TPNumbers(j)
                    Else
                        TPs = TPs + "," + TPNumbers(j)
                    End If
                Next
            Else
                TPs = "-"
            End If
            For j = 0 To SuppliersDataSet.Tables("Suppliers").Rows.Count - 1
                If SuppliersDataSet.Tables("Suppliers").Rows(j).Item(0) = Order_Row1.Item(1) Then
                    supplier = SuppliersDataSet.Tables("Suppliers").Rows(j).Item(1)
                End If
            Next
            Dim row As String() = New String() {Order_Row1.Item(0), Order_Row1.Item(2), date1.ToString("dd-MM-yyyy"), Condition, supplier, DAs, TPs}
            DataGridView1.Rows.Add(row)
        Next
        For i = 0 To DataGridView1.Rows.Count - 1
            If DataGridView1.Rows(i).Cells(3).Value = "ΝΑΙ" Then
                DataGridView1.Rows(i).DefaultCellStyle = New DataGridViewCellStyle With {.BackColor = Color.GreenYellow}
            End If
        Next
    End Sub

the Design of the table "Lipantika_Orders" (means lubricants orders) in my SQL Database is the following



and the selected 2 records of that table



As you see the column 9 named "Related_DA" is type nvarchar(MAX) and have the value of "-" in both 2 records.

When i run my code, at line MsgBox(OrdersDataSet.Tables("Orders").Rows(i).Item(9))
i receive the error message "Argument 'Prompt' cannot be converted to type 'String'"

and if remove that line, at the line If Order_Row1.Item(9) <> "-" Then
i receive the error message "Operator '<>' is not defined for type 'DBNull' and string "-" "

can any one help me why i receive those errors ?

I have no idea, and i google it for 2 hours without any results

Thanks in advance.

[Shaggy Hiker]

Do you really care about the first error? Perhaps not, in the end, so let's focus on the second error. The message in that case tells you the problem, since <> is not defined for DBNull. I suppose it COULD be, since it's pretty clear to us, but it isn't. Therefore, you have to check for DBNull explicitly before you do the comparison. There are a couple ways to do that. What I use is IsDBNull(), so it would look like:

If IsDBNull(Order_Row1.Item(9)) = False AndAlso Order_Row1.Item(9).ToString <> "-" Then

There is also the IsNullOrEmpty method in String, but that may not be any more efficient.

Also, you should turn Option Strict ON for the project and fix all the issues. You're doing some odd things with conversions in there. You seem to be taking a DataAdapter and putting it into a variable that looks like it is supposed to hold a TableAdapter. If these are strongly typed datasets, then you have at least one further means of checking for DBNull values. You also don't need to be opening and closing the connection with the DataAdapter, as it will do what it needs to do, and leave the connection in the same state that it found it.

[gkarofilakis]

Thanks for the responce Shaggy Hiker!
I did the check for DBNull. There is no null value
for the item(9) (Order_Row1.Item(9)).
You ca see that in the second picture i send...

[gkarofilakis]

Again.
I wrote the statement as you say, and the problem is solved.
So thank you very much for your suggestion you make.
I also take in consideration all other you say about
option statement STRICT, and for opening and closing the connection.
Thank you again!