private void CloseAllOpenInstance()
        {
            if (orderEntryView != null)
            {
                orderEntryView.Close();
            }

            if (reprintBill != null)
            {
                reprintBill.Close();
            }

            if (inwardEntry != null)
            {
                inwardEntry.Close();
            }

            if (productMaster != null)
            {
                productMaster.Close();
            }

            if (customerMaster != null)
            {
                customerMaster.Close();
            }

            if (supplierMaster != null)
            {
                supplierMaster.Close();
            }

            if (sendEmail != null)
            {
                sendEmail.Close();
            }
        }