I intend to use session variable to capture searching keywords and catagory input by user. I created datatable dTable to store "catagory", "keyword" and "ID" and save it into session variable session("MyCat") when page is firstly loaded.
If it is still within same session time frame, any new input will be automatically added into this datatable and session variable updated as well.
Anyway, my program can not get through as it is captured error in
dim dr as DataRow=dTable.NewRow() in my else statement.
May I know what is wrong with my coding in Sub Submit portion and how this can be implemented efficiently in ASP.NET?

<%@ Page Language="VB" EnableSessionState=true %>
<%@ Register TagPrefix="CityLibrary" TagName="Header_search" Src="..\include/header_search.ascx" %>
<%@ Register TagPrefix="CityLibrary" TagName="bar_empty" Src="..\include/bar_empty.ascx" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.OleDb" %>

<script runat="server">

Sub Submit(Sender As Object, e As EventArgs)
if NOT Page.IsPostBack then
dim dTable as New DataTable("mySearch")
dTable.Columns.Add("catagory", System.Type.getType("System.String"))
dTable.Columns.Add("keyword", System.Type.getType("System.String"))
dTable.Columns.Add("ID", System.Type.getType("System.Int32"))
Dim PrimaryKeyColumns(0) As DataColumn
PrimaryKeyColumns(0)= dTable.Columns("ID")
dTable.PrimaryKey = PrimaryKeyColumns
dim dr as DataRow=dTable.NewRow()
session("myCat")= dTable

dim dTable as New DataTable
dTable= session("myCat")
dim dr as DataRow=dTable.NewRow()
session("myCat")= dTable
end if


dim keyword as String
dim catagory as String
dim objitem as new CityLibrary.libraryItem

keyword = tbtext.Text
catagory = Listbox1.SelectedItem.value

dim objReader as OleDbDataReader
objReader = objitem.GetLibraryItemGeneral(catagory,keyword)
End Sub



<table height="100%" cellspacing=0 cellpadding=0 width="100%">
<CityLibrary:Header_Search runat="server"/>
<tr height="100%">
<CityLibrary:bar_empty runat="server"/>

<td align=left valign="top" width=100% nowrap>
<table height="100%" valign="top" align="left" cellspacing=0 cellpadding=0 width="100%">
<tr height="100%" valign="top">
<td nowrap>
<table cellspacing=0 cellpadding=0 width="100%">
<td valign="top">


<form action="Basicsearchmain.aspx" runat="server">

<h3> Name: <asp:Textbox id="tbText" type=text runat="Server"/><br><br>

UserGroup: <asp:Listbox runat="server" id="listbox1" width="200" rows="1"
<asp:Listitem value="title">Title Keywords</asp:Listitem>
<asp:Listitem value="name">Author Last Name or FIrst Name</asp:Listitem>
<asp:Listitem value="subject">Subject Keywords</asp:Listitem>
<asp:Listitem value="kidstitle"> Kids' Reading Title</asp:Listitem>
<asp:Listitem value="kidssubject">Kids' reading Subject</asp:Listitem>
<asp:Listitem value="periodical">Periodical title</asp:Listitem>
<asp:Listitem value="keywordall">All Keywords</asp:Listitem>

<ASP:Button id="btSubmit" onclick="Submit" text="Lookup" runat="server"/>



The problem is this line of code

dTable= session("myCat")

you are trying to put a session varible datatype to a Datatable datatype (make sense?) but you can't do this implicitly, you must cast it to the datatype you want.

so it should be something like this

dTable = CType(Session("myCat"), DataTable)

Hope this helps

Happy coding :cool: