private void btn_Delete_InvoiceService_Click(object sender, EventArgs e)
        {
            BLInvoice_Service blRT = new BLInvoice_Service();

            blRT.DeleteInvoice_Service(Convert.ToInt32(txt_InvoiceService_ID.Text));
            dgv_InvoiceService.DataSource = blRT.LoadInvoice_Service();
            dgv_InvoiceService_CellClick(null, null);
        }
        private void btn_Save_InvoiceService_Click(object sender, EventArgs e)
        {
            BLInvoice_Service blSP = new BLInvoice_Service();

            if (SaveStatus == 1)
            {
                blSP.CreateInvoice_Service(txt_InvoiceService_InvoiceID.Text, txt_InvoiceService_ServiceID.Text, txt_InvoiceService_Times.Text);
            }
            else if (SaveStatus == 2)
            {
                blSP.UpdateInvoice_Service(Convert.ToInt32(txt_InvoiceService_ID.Text), txt_InvoiceService_InvoiceID.Text, txt_InvoiceService_ServiceID.Text, txt_InvoiceService_Times.Text);
            }
            SaveStatus = 0;
            dgv_InvoiceService.DataSource = blSP.LoadInvoice_Service();
            dgv_InvoiceService_CellClick(null, null);
            btn_Update_InvoiceService.Enabled = true;
            btn_Create_InvoiceService.Enabled = true;
            btn_Save_InvoiceService.Enabled   = false;
        }
        private void btn_InvoiceService_Click(object sender, EventArgs e)
        {
            TabControl_Main.TabPages.Clear();
            TabControl_Main.TabPages.Add(TabPage_Invoice_Service);
            dgv_InvoiceService.AutoResizeColumns();
            BLInvoice_Service dbB = new BLInvoice_Service();
            var data = dbB.LoadInvoice_Service();

            if (data != null)
            {
                dgv_InvoiceService.DataSource = data;
            }
            else
            {
                dgv_InvoiceService.DataSource = null;
            }
            dgv_InvoiceService_CellClick(null, null);
            txt_InvoiceService_ID.Enabled = false;
        }