SitePoint.com

comicghozt · Sep 11, 2006, 09:46

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

HTML Code:

<%@ 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">&nbsp;</td>
  </tr>
  <tr>
    <td height="135">&nbsp;</td>
  </tr>
</table>
</body>
</html>

cart.aspx

HTML Code:

<%@ 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.

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