3.  Page_Init  Page_Load  cmdINew_Click  cmdISave_Click  cmdIDelete_Click  cmdISubmit_Click  cmdIClear_Click  gridLineItem_RowEditing  gridLineItem_RowDeleting  UpdateGridLineItem  ShowInvoice  FillProduct  txtPassLookupValues_TextChanged  InitializeSystemVariables Event of Main menu Event of Edit product menu Event of Grid line button Function to process data Function to Initial database connection (Utilities.vb) Function receive data return from frmListOfValue

4.  Query Product from database and fill into textbox

5.  Query Invoice to fill into textbox and  Query InvoiceLineItem to set in variable Collection (row_coll)

6.  Read variable Collection (row_coll) and set to variable DataTable, Datarow before set to GridView (GridLineItem). It has 3 case row_coll is nothing (new page) row_coll.count <= 0 (data in collection is empty) row_coll.count > 0 (have data in collection Note: fist 2 case will set blank data into Datatable

7.  In Page_Load, Button add event onclick to call function OpenListofValue in javascript and pass name of table in parameter.  Function OpenListofValue (javascript) popup form frmListofValue.aspx.  Function MyInitializeListOfValue in frmListofValue.aspx.vb check case and set query string, data field, and header.  After select data in List of Value, Function GetFromListOfValue (javascript) will pass selected value to caller (Default.aspx).  Function GetFromListOfValue (javascript in Default.aspx) pass value to textbox txtPassLookupValues.  Finally, Function txtPassLookupValues_TextChanged will process data.