Public Function AddtoLibrary(ByVal UserName As String, ByVal Password As String, ByVal BookIDs As String, ByVal Device As String, ByVal Log As String) As String

    'Logging
    If Log <> "Internal Silent" Then
        Dim st As StackTrace = New StackTrace()
        Dim sf As StackFrame = st.GetFrame(0)
        Dim currentMethodName As MethodBase = sf.GetMethod()
        Logging(Log, Device, UserName, currentMethodName.Name)
    End If

    'Database Connection Variables
    Dim ConnectionString As String = ConfigurationManager.ConnectionStrings("CnnStr").ConnectionString
    Dim Cnn As New SqlClient.SqlConnection
    Dim Comm As New SqlClient.SqlCommand
    Dim DA As SqlClient.SqlDataAdapter
    Dim DS As DataSet
    Dim Trans As Data.SqlClient.SqlTransaction

    If Trim(UserName) = "" Or Trim(Password) = "" Or Trim(BookIDs) = "" Or Trim(Device) = "" Or Trim(Log) = "" Then
        Return Nothing
    End If

    Try
        If Cnn.State = ConnectionState.Open Then Cnn.Close()
        Cnn.ConnectionString = ConnectionString
        Cnn.Open()
        DS = New DataSet()
        DA = New SqlClient.SqlDataAdapter("SELECT ID From Users WHERE UserName = '" & Replace(UserName, "'", "") & "' AND Password = '" & Password & "'", Cnn)
        DA.Fill(DS, "Table")
        If DS.Tables("Table").Rows.Count <> 0 Then

            Dim UserID As Integer = DS.Tables("Table").Rows(0).Item("ID")
            If Device = "-1" Then
                Return "DEVICE"
            End If

            Trans = Cnn.BeginTransaction(IsolationLevel.ReadCommitted)
            For i = 0 To BookIDs.Split(";").GetUpperBound(0) - 1
                If Mid(BookIDs.Split(";").GetValue(i).ToString, 1, 2) <> "SB" Then
                    DS = New DataSet()
                    DA = New SqlClient.SqlDataAdapter("SELECT Price,Discount From Books WHERE ID = " & BookIDs.Split(";").GetValue(i).ToString, Cnn)
                    DA.Fill(DS, "Table")   // <<<<<<<<<<< HERE I GOT THE EXCEPTION
                    If DS.Tables("Table").Rows.Count <> 0 Then
                        If DS.Tables("Table").Rows(0).Item("Price") = 0 Or DS.Tables("Table").Rows(0).Item("Discount") = 100 Then
                            Comm = New SqlClient.SqlCommand("INSERT INTO Invoices (ID,BookID,UserID,Price,OurShare,PublisherShare,Discount,DiscountType,PaymentDate,PaymentTime,SaleOrderID,SaleReferenceID) VALUES (" & Gen_InvoiceID() & "," & BookIDs.Split(";").GetValue(i).ToString & "," & UserID & ",0,0,0,0,''," & Get_Shamsi() & ",'" & Get_Time() & "','" & 0 & "','" & 0 & "')", Cnn, Trans)
                            Comm.ExecuteNonQuery()
                        End If
                    End If

                    Dim BookID As Integer = BookIDs.Split(";").GetValue(i).ToString
                    Dim TotalDownload As Integer = 0
                    DS = New DataSet()
                    DA = New SqlClient.SqlDataAdapter("SELECT DownloadDeviceNumbers FROM Books WHERE ID = " & BookID, Cnn)
                    DA.Fill(DS, "Table")
                    If DS.Tables("Table").Rows.Count <> 0 Then
                        TotalDownload = DS.Tables("Table").Rows(0).Item("DownloadDeviceNumbers")
                    Else
                        Return Nothing
                    End If
                    Dim DS1 As New DataSet()
                    Dim DA1 As New SqlClient.SqlDataAdapter("SELECT DISTINCT([DeviceID]) FROM [ketabchinDB].[dbo].[UserActivations] WHERE BookID = " & BookID & " AND UserID = " & UserID & " AND DeviceID = '" & Device & "'", Cnn)
                    DA1.Fill(DS1, "Table")
                    If DS1.Tables("Table").Rows.Count = 0 Then
                        Comm = New SqlClient.SqlCommand("INSERT INTO UserActivations (UserID,BookID,DeviceID,Date,Time) VALUES (" & UserID & "," & BookID & ",'" & Device & "'," & Get_Shamsi() & ",'" & Get_Time() & "')", Cnn)
                        Comm.ExecuteNonQuery()
                    End If

                Else
                    DS = New DataSet()
                    DA = New SqlClient.SqlDataAdapter("SELECT SampleBookPath From Books WHERE ID = " & BookIDs.Split(";").GetValue(i).ToString.Replace("SB", ""), Cnn)
                    DA.Fill(DS, "Table")
                    If DS.Tables("Table").Rows.Count <> 0 Then
                        If Trim(DS.Tables("Table").Rows(0).Item("SampleBookPath")) <> "" Then
                            Comm = New SqlClient.SqlCommand("DELETE FROM SampleInvoices WHERE BookID = " & BookIDs.Split(";").GetValue(i).ToString.Replace("SB", "") & " AND UserID = " & UserID, Cnn, Trans)
                            Comm.ExecuteNonQuery()
                            Dim DS1 As New DataSet()
                            Dim DA1 As New SqlClient.SqlDataAdapter("SELECT BookID From Invoices WHERE UserID = " & UserID & " AND BookID = " & BookIDs.Split(";").GetValue(i).ToString.Replace("SB", ""), Cnn)
                            DA1.Fill(DS1, "Table")
                            If DS1.Tables("Table").Rows.Count = 0 Then
                                Comm = New SqlClient.SqlCommand("INSERT INTO SampleInvoices (ID,BookID,UserID,Date,Time) VALUES (" & Gen_InvoiceID() & "," & BookIDs.Split(";").GetValue(i).ToString.Replace("SB", "") & "," & UserID & "," & Get_Shamsi() & ",'" & Get_Time() & "')", Cnn, Trans)
                                Comm.ExecuteNonQuery()
                            End If
                        End If
                    End If

                End If
            Next
            Trans.Commit()
            Return "SUCCESS"

        End If
        Return "WRONG"
    Catch ex As Exception
        SaveError(ex)
        Return ex.Message
    Finally
        Cnn.Close()
    End Try

End Function