|
Subject:
|
Problem with session on Shopping Cart
|
|
Posted By:
|
comicghozt
|
Post Date:
|
9/11/2006 10:56:05 AM
|
Hello again!
I've been trying to put up a shopping cart with a items list page and a second one (cart). When I hit the "buy" button from one item I get this error on "cart.aspx":
"Object reference not set to an instance of an object"
Line 5: Dim ds as DataSet Line 6: ds = CType(Session("myDataSet"), Dataset) Line 7: MyDataGrid.Datasource=ds.Tables("Catalogo").DefaultView Line 8: MyDataGrid.DataBind() Line 9: End Sub
I have no clu where the error may come from so I'm gonna post both entire files code.
item list.aspx
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.OleDB" %>
<%@ Page Language="VB" Debug="true" %>
<html>
<script language="VB" runat="server">
Dim MyConnection As OleDBConnection
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs)
If Not Page.IsPostBack() Then
DataBind()
dlsearchby.items.Add("produto")
End If
End Sub
Private Sub DataBind()
DIM MyConnection As New OleDBConnection("Provider=Microsoft.Jet.OLEDB.4.0;" & "Data Source=C:\Inetpub\wwwroot\DOT\InforJ\db\newBD.mdb")
Dim MyCommand As New OleDBDataAdapter("select * from catalogo where promo LIKE 'p%' order by promo", MyConnection)
Dim DS As New DataSet
If Not (Page.IsPostBack)
MyCommand.Fill(DS)
DS = Nothing
DS = New DataSet()
End If
Session("myDataSet") = DS
MyCommand.Fill (DS, "Catalog")
MyDataList.DataSource = DS.Tables(0).DefaultView
MyDataList.DataBind()
End Sub
Sub doSearch(Source as Object, E as EventArgs)
Dim sSearchby as String
MyDataList.visible="false"
Dim strConn as string = "Provider=Microsoft.Jet.OLEDB.4.0;" & "Data Source=C:\Inetpub\wwwroot\DOT\InforJ\db\newBD.mdb"
Dim MySQL as string = "Select * from Catalogo where " & dlsearchby.selectedItem.text & _
" Like '%" & txtSearch.text & "%' order by ID"
Trace.Warn("sql = " & MySQL)
Dim MyConn as New OleDBConnection(strConn)
Dim objDR as OledbDataReader
Dim Cmd as New OleDBCommand(MySQL, MyConn)
MyConn.Open()
objDR=Cmd.ExecuteReader(system.data.CommandBehavior.CloseConnection)
dlSearch.DataSource = objDR
dlSearch.DataBind()
MyConn.Close
dlSearch.visible="true"
End Sub
Sub doInsert(Source as Object, E as EventArgs)
Dim MySQL as string = "Insert into mailing (mail) values (@mail)"
Dim myConn As OleDbConnection = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;" & _
"Data Source=" & server.mappath("DB\newBD.mdb") & ";" )
Dim Cmd as New OleDbCommand(MySQL, MyConn)
cmd.Parameters.Add(New OleDbParameter("@mail", frmfname.text))
MyConn.Open()
cmd.ExecuteNonQuery
MyConn.Close()
label1.visible="true"
label1.text = "<font size=1>E-mail adicionado."
End Sub
Sub doit(Source as Object, E as EventArgs)
response.Redirect ("page3.aspx")
End Sub
Sub MyDataList_Select(sender As Object, e As EventArgs)
Response.Redirect("detail.aspx?id=@id")
End Sub
</script>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<title>inforJ - produtos informácticos</title>
<!-- ImageReady Preload Script (menu.psd) -->
<script type="text/javascript">
<!--
function newImage(arg) {
if (document.images) {
rslt = new Image();
rslt.src = arg;
return rslt;
}
}
function changeImages() {
if (document.images && (preloadFlag == true)) {
for (var i=0; i<changeImages.arguments.length; i+=2) {
document[changeImages.arguments[i]].src = changeImages.arguments[i+1];
}
}
}
var preloadFlag = false;
function preloadImages() {
if (document.images) {
menu_inicio_over = newImage("images/menu_inicio-over.jpg");
menu_tinteiros_over = newImage("images/menu_tinteiros-over.jpg");
menu_hardware_over = newImage("images/menu_hardware-over.jpg");
menu_software_over = newImage("images/menu_software-over.jpg");
menu_webdesign_over = newImage("images/menu_webdesign-over.jpg");
menu_encomendas_over = newImage("images/menu_encomendas-over.jpg");
menu_contactos_over = newImage("images/menu_contactos-over.jpg");
menu_campanha_over = newImage("images/menu_campanha-over.jpg");
preloadFlag = true;
}
}
// -->
</script>
<!-- End Preload Script -->
</head>
<body bgcolor="#FFFFFF" link="#000000" vlink="#000099" alink="#000099" onload="preloadImages();">
<table width="655" height="659" border="1" align="center" id="main">
<tr>
<td height="77" colspan="3"> <img src="images/pagina/cab.jpg" width="737" height="142" align="absmiddle"></td>
</tr>
<tr>
<td width="158" valign="top" rowspan="2" align="center">
<!-- ImageReady Slices (menu.psd) -->
<table id="Table_01" width="153" height="290" border="0" cellpadding="0" cellspacing="0">
<tr>
<td colspan="3">
<img src="images/menu_01.jpg" width="153" height="24" alt=""></td>
</tr>
<tr>
<td rowspan="9">
<img src="images/menu_02.jpg" width="8" height="266" alt=""></td>
<td>
<a href="default.aspx"
onmouseover="changeImages('menu_inicio', 'images/menu_inicio-over.jpg'); return true;"
onmouseout="changeImages('menu_inicio', 'images/menu_inicio.jpg'); return true;"
onmousedown="changeImages('menu_inicio', 'images/menu_inicio-over.jpg'); return true;"
onmouseup="changeImages('menu_inicio', 'images/menu_inicio-over.jpg'); return true;">
<img name="menu_inicio" src="images/menu_inicio.jpg" width="138" height="30" border="0" alt=""></a></td>
<td rowspan="9">
<img src="images/menu_04.jpg" width="7" height="266" alt=""></td>
</tr>
<tr>
<td>
<a href="tinteiros.aspx"
onmouseover="changeImages('menu_tinteiros', 'images/menu_tinteiros-over.jpg'); return true;"
onmouseout="changeImages('menu_tinteiros', 'images/menu_tinteiros.jpg'); return true;"
onmousedown="changeImages('menu_tinteiros', 'images/menu_tinteiros-over.jpg'); return true;"
onmouseup="changeImages('menu_tinteiros', 'images/menu_tinteiros-over.jpg'); return true;">
<img name="menu_tinteiros" src="images/menu_tinteiros.jpg" width="138" height="30" border="0" alt=""></a></td>
</tr>
<tr>
<td>
<a href="computadores.aspx"
onmouseover="changeImages('menu_hardware', 'images/menu_hardware-over.jpg'); return true;"
onmouseout="changeImages('menu_hardware', 'images/menu_hardware.jpg'); return true;"
onmousedown="changeImages('menu_hardware', 'images/menu_hardware-over.jpg'); return true;"
onmouseup="changeImages('menu_hardware', 'images/menu_hardware-over.jpg'); return true;">
<img name="menu_hardware" src="images/menu_hardware.jpg" width="138" height="30" border="0" alt=""></a></td>
</tr>
<tr>
<td>
<a href="componentes.aspx"
onmouseover="changeImages('menu_software', 'images/menu_software-over.jpg'); return true;"
onmouseout="changeImages('menu_software', 'images/menu_software.jpg'); return true;"
onmousedown="changeImages('menu_software', 'images/menu_software-over.jpg'); return true;"
onmouseup="changeImages('menu_software', 'images/menu_software-over.jpg'); return true;">
<img name="menu_software" src="images/menu_software.jpg" width="138" height="30" border="0" alt=""></a></td>
</tr>
<tr>
<td>
<a href="software.aspx"
onmouseover="changeImages('menu_webdesign', 'images/menu_webdesign-over.jpg'); return true;"
onmouseout="changeImages('menu_webdesign', 'images/menu_webdesign.jpg'); return true;"
onmousedown="changeImages('menu_webdesign', 'images/menu_webdesign-over.jpg'); return true;"
onmouseup="changeImages('menu_webdesign', 'images/menu_webdesign-over.jpg'); return true;">
<img name="menu_webdesign" src="images/menu_webdesign.jpg" width="138" height="30" border="0" alt=""></a></td>
</tr>
<tr>
<td>
<a href="webd.aspx"
onmouseover="changeImages('menu_encomendas', 'images/menu_encomendas-over.jpg'); return true;"
onmouseout="changeImages('menu_encomendas', 'images/menu_encomendas.jpg'); return true;"
onmousedown="changeImages('menu_encomendas', 'images/menu_encomendas-over.jpg'); return true;"
onmouseup="changeImages('menu_encomendas', 'images/menu_encomendas-over.jpg'); return true;">
<img name="menu_encomendas" src="images/menu_encomendas.jpg" width="138" height="30" border="0" alt=""></a></td>
</tr>
<tr>
<td>
<a href="contactos.aspx"
onmouseover="changeImages('menu_contactos', 'images/menu_contactos-over.jpg'); return true;"
onmouseout="changeImages('menu_contactos', 'images/menu_contactos.jpg'); return true;"
onmousedown="changeImages('menu_contactos', 'images/menu_contactos-over.jpg'); return true;"
onmouseup="changeImages('menu_contactos', 'images/menu_contactos-over.jpg'); return true;">
<img name="menu_contactos" src="images/menu_contactos.jpg" width="138" height="30" border="0" alt=""></a></td>
</tr>
<tr>
<td>
<a href="download.aspx"
onmouseover="changeImages('menu_campanha', 'images/menu_campanha-over.jpg'); return true;"
onmouseout="changeImages('menu_campanha', 'images/menu_campanha.jpg'); return true;"
onmousedown="changeImages('menu_campanha', 'images/menu_campanha-over.jpg'); return true;"
onmouseup="changeImages('menu_campanha', 'images/menu_campanha-over.jpg'); return true;">
<img name="menu_campanha" src="images/menu_campanha.jpg" width="138" height="36" border="0" alt=""></a></td>
</tr>
<tr>
<td>
<img src="images/menu_12.jpg" width="138" height="20" alt=""></td>
</tr>
</table>
<!-- End ImageReady Slices -->
<br>
<img src="images/pagina/index2.jpg" width="153" height="73">
</td>
<td width="446" rowspan="4" valign="top" align="center">
<img border="0" src="images/pagina/barraNews.jpg" width="400">
<form runat="server">
<asp:DropDownList id="dlsearchby" runat="server" />
<asp:TextBox id="txtSearch" runat="server" />
<asp:Button id="btnSearch" Text="Search" onclick="doSearch" runat="server" /><br>
<asp:RequiredFieldValidator ID="vldSearch"
ControlToValidate="txtSearch"
Display="Dynamic" runat="server">
You must include search criteria
</asp:RequiredFieldValidator>
<asp:DataList runat="server"
Id="dlSearch"
GridLines="None"
cellpadding="2"
cellspacing="2"
Headerstyle-BackColor="#000000"
HeaderStyle-Forecolor="White"
Headerstyle-Font-Name="Arial"
Headerstyle-Font-Size="8"
OnSelectedIndexChanged="MyDataList_Select"
Font-Name="Arial"
Font-Size="10"
Width="100%">
<HeaderTemplate>
<b><i><font Size="2">Resultados de pesquisa </font></i></b>
<br>
</HeaderTemplate>
<ItemTemplate>
<b><%# Container.DataItem("produto")%></b><br>
<a title="Detalhes de <%# DataBinder.Eval(Container.DataItem, "produto") %>" href="detail.aspx?id=<%# DataBinder.Eval(Container.DataItem, "ID") %>"><%# DataBinder.Eval(Container.DataItem, "produto") %></a>
Categoria: <%# Container.DataItem("categoria")%><br>
ID: <%# Container.DataItem("codigo")%><br>
</ItemTemplate>
</ASP:DataList>
<table border="0" width="100%">
<tr>
<td>
<ASP:DataList id="MyDataList" RepeatColumns="2" RepeatDirection="Horizontal" runat="server">
<ItemTemplate>
<table width="100%" border="0" cellpadding=2 cellspacing=4 style="font: 8pt verdana">
<tr>
<td width="200" valign="top" align="center">
<b><%# DataBinder.Eval(Container.DataItem, "produto") %></b><br>
<IMG alt="foto" align="top" src='<%# DataBinder.Eval(Container.DataItem, "foto") %>' width="100" Border="0"><br>
<%# DataBinder.Eval(Container.DataItem, "categoria") %><br>
<a title="Detalhes de <%# DataBinder.Eval(Container.DataItem, "produto") %>" CommandName="Select" href="detailPC.aspx?id=<%# DataBinder.Eval(Container.DataItem, "ID") %>">Detalhes</a><br>
<b><%# DataBinder.Eval(Container.DataItem, "preco", "{0:c}") %></b><br>
<a title="Comprar <%# DataBinder.Eval(Container.DataItem, "produto") %>" CommandName="Select" onclick="doit" href="cart/page2.aspx?id=<%# DataBinder.Eval(Container.DataItem, "ID") %>"><font color="red">Comprar</font></a>
</td>
</tr>
</table>
</ItemTemplate>
</ASP:DataList>
</td>
</tr>
</table>
</td>
<td width="153" height="136"><img src="images/pagina/pub02.jpg" width="153" height="132">
<br><img src="images/pagina/pub01.jpg" width="153" height="207">
<table border="0">
<tr>
<td align="center"><font size="2">Quero receber<br>novidades</td></tr>
<tr><td align="center"> <asp:textbox columns="10" Text="e-mail" id="frmfname" runat="server" />
<asp:RequiredFieldValidator
runat="server"
id="vldfname"
ControlToValidate="frmfname"
ErrorMessage=""
display="dynamic"
Font-Names="Arial" Font-Size="8">
Inválido
</asp:RequiredFieldValidator>
<asp:RegularExpressionValidator
id="emailRegexVal"
ControlToValidate="frmfname"
ErrorMessage="Email. "
Display="dynamic"
ValidationExpression="^[\w-]+@[\w-]+\.(pt|br|com|net|org|edu|mil)$"
Font-Names="Arial" Font-Size="8" runat="server">
Inválido. Deve ser email@host.domínio.
</asp:RegularExpressionValidator></td>
</tr>
<tr>
<td align="center" colspan="2">
<asp:button id="button1" Text="Inserir" onclick="doInsert" runat="server" />
</td>
</tr>
</table>
<div align="center"><b><i><asp:Label ID="label1" runat="server" /></i></b></div>
</Form>
</td>
</tr>
<tr>
<td height="211"></td>
</tr>
<tr>
<td width="153" rowspan="2"> </td>
</tr>
<tr>
<td height="135"> </td>
</tr>
</table>
</body>
</html>
cart.aspx
<%@ Import Namespace="System.Data" %>
<%@ Page Language="VB" Debug="true" %>
<script language="VB" runat="server">
Sub Page_Load(Source as Object, E as EventArgs)
Dim ds as DataSet
ds = CType(Session("myDataSet"), Dataset)
MyDataGrid.Datasource=ds.Tables("Catalogo").DefaultView
MyDataGrid.DataBind()
End Sub
</script>
<html>
<head>
<title>Page 2</TITLE>
</head>
<body>
<Form id="form1" runat="server">
<div align="center">
<b><i>Employees Table</i></b>
<asp:Datagrid runat="server"
Id="MyDataGrid"
GridLines="Both"
cellpadding="0"
cellspacing="0"
Headerstyle-BackColor="#8080C0"
Headerstyle-Font-Name="Arial"
Headerstyle-Font-Bold="True"
Headerstyle-Font-Size="14"
BackColor="#8080FF"
Font-Name="Arial"
Font-Size="11"
AlternatingItemStyle-BackColor="#DFDFDF"
AlternatingItemStyle-Font-Name="Arial"
AlternatingItemStyle-Font-Size="11"
BorderColor="Black">
</asp:DataGrid>
</Form>
</body>
</html>
I'm sorry for the size, but I really don't know where the error might be... Please help me, I'm getting desperate
Thanx in advance.
|
|
Reply By:
|
Steve McGuire
|
Reply Date:
|
9/11/2006 9:00:48 PM
|
Line 5 should be: Dim ds As New DataSet
You ommitted 'New'!!
Steve
|
|
Reply By:
|
comicghozt
|
Reply Date:
|
9/12/2006 8:40:09 AM
|
Thank you Steve.
That must be one of a few other errors in the code but it didn't stop the error.
Any other suggestions?
|
|
Reply By:
|
Steve McGuire
|
Reply Date:
|
9/12/2006 5:30:39 PM
|
The error you mention is related to you using an object that has not been instantiated.
For example, if you 'Dim ds As DataSet' will 'dimension' the ds variable but the object has not been instantiated (ready for use) until you also include the line 'ds = New DataSet'. You can include both these lines in one statement such as 'Dim ds As New DataSet'.
I quickly scanned through your code and noticed a few places where your code needs to be sorted out...
Set breakpoints and step through your code to see where these errors occur and you may be able to fix them yourself.
Alternatively, post the code without HTML, Javascript and designer code. It will be easier to explain line numbers for error modifications...
Steve
|
|
Reply By:
|
comicghozt
|
Reply Date:
|
9/13/2006 3:18:18 AM
|
Thanx again Steve.
That's exactly what Ive been doing and I came up with an answeer:
I changed my Page_Load to this:
Sub Page_Load(Source as Object, E as EventArgs)
If Session("myDataSet") Is Nothing Then
' Handle session state...
Exit Sub
Else
Dim ds as New DataSet
ds = CType(Session("myDataSet"), Dataset)
MyDataList.Datasource=ds.Tables("Catalog").DefaultView
MyDataList.DataBind()
End If
End Sub
and a few more things and it's working!
Now I've another question:
How do I manage to get only the item I chose? Because I'm passing the Dataset in the session. Do I have to change that in the itemList.aspx or on page2.aspx?
|
|
Reply By:
|
Steve McGuire
|
Reply Date:
|
9/13/2006 1:14:19 PM
|
Item you chose from what?
I don't understand your question...
Steve
|
|
Reply By:
|
comicghozt
|
Reply Date:
|
9/21/2006 9:22:46 AM
|
I only want to put in the cart the item I chose from the list when I'm getting all the items I bound in the items list (when pressing the 'buy' button of any item).
|
|
