Question

I was trying to update a field called ‘instock'( type is double in database), where the itemcode is a value (type is long integer in access database). But when I try to update them, I get a error which says ‘Invalid index 2 for this oledbparamterCollection with count=2. Can anyone help me please?

 strSQL = "UPDATE tblitem set instock = ? where itemcode= ? "
    Using cn As New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + Application.StartupPath + "\\POS.mdb"), _
           cmd As New OleDbCommand(strSQL, cn)

        cmd.Parameters.Add("?", OleDbType.Double)
        cmd.Parameters.Add("?", OleDbType.integer)
        cn.Open()
        For Each ls As ListViewItem In ListItems.Items
            If Not (ls.SubItems(1).Tag(0) = "n") Then

                cmd.Parameters(1).Value = (ls.SubItems(1).Tag - ls.SubItems(1).Text)
                cmd.Parameters(2).Value = ls.Tag
                cmd.ExecuteNonQuery()
            End If
        Next ls
        cn.Close()
    End Using

Thanks , + I get this error ‘no default member found for the type double’ while exucating this command:

 strSQL = "UPDATE tblitem set instock = ? where itemcode= ? "
            Using cn As New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + Application.StartupPath + "\\POS.mdb"), _
                   cmd As New OleDbCommand(strSQL, cn)

                cmd.Parameters.Add("?", OleDbType.Double)
                cmd.Parameters.Add("?", OleDbType.Double)
                cn.Open()
                For Each ls As ListViewItem In SalesListItems.Items
                    If Not (ls.SubItems(1).Tag(0) = "n") Then

                        cmd.Parameters(0).Value = (CDbl(ls.SubItems(1).Tag) + CDbl(ls.SubItems(1).Text))
                        cmd.Parameters(1).Value = Integer.Parse(ls.Tag)
                        cmd.ExecuteNonQuery()
                    End If
                Next ls
                cn.Close()
            End Using

Answer 1

Indices are 0-based in the .NET class library, including ADO.NET¹

Parameters(1) means “the 2nd parameter” and Parameters(2) means “the 3rd parameter” (which is invalid here).

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¹ This isn’t true for all collections, but it is the most prevalent convention used these days. For instance, collections in the Outlook Object Model, which is COM exposed to .NET, indices are still 1-based ..