How to read empty data

[mosipenko]

I used to have a problem with DBNull, but now my issue is:

System.InvalidO perationExcepti on: Invalid attempt to read when no data
is present

Here's my code behind:

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArg s) Handles Me.Load
Dim connectionStrin g As String = "Data Source=server;I nitial
Catalog=databas e; User ID=user;Passwor d=password;"
Dim connection As SqlClient.SqlCo nnection
Dim command As SqlClient.SqlCo mmand
Dim reader As SqlClient.SqlDa taReader
Dim strID As String
strID = Request.QuerySt ring("cidL")
Try
connection = New SqlClient.SqlCo nnection(connec tionString)
command = New SqlClient.SqlCo mmand()
command.Command Text = "select top 10 a.cid, a.title,
dbo.GetImagePat hNoDT(a.cid) as ImagePath, Body as DisplayText from
Article a inner join Schedule s on s.cid = a.cid inner join
ContentIndex x on x.cid = a.cid inner join contentcategory cc on cc.cid
= a.cid where cc.catid = 185 and GetDate() between s.startdt and
s.enddt and (x.ownerpid = 'HT8071') order by updateddt desc"
command.Connect ion = connection
connection.Open ()
reader = command.Execute Reader()
DataList1.DataS ource = reader
DataList1.DataB ind()
Finally
'If Not connection Is Nothing Then
'connection.Dis pose()
'End If
'If Not command Is Nothing Then
'command.Dispos e()
'End If
If reader("ImagePa th") IsNot System.DBNull.V alue Then
Session("Image" ) = reader("ImagePa th")
Else
Session("Image" ) = "logo.jpg"
End If
End Try

End Sub

And on my page, this is the code to display all the stuff from the db:

<asp:DataList ID="DataList1" runat="server" DataKeyField="c id">
<ItemTemplate >
cid:
<asp:Label ID="cidLabel" runat="server" Text='<%#
Eval("cid") %>' value="cidL"></asp:Label><br />
title:
<asp:Label ID="titleLabel " runat="server" Text='<%#
Eval("title") %>'></asp:Label><br />
ImagePath:
<asp:Label ID="ImagePathLa bel" runat="server" Text='<%#
Eval("ImagePath ") %>'></asp:Label><br />
<asp:TemplateCo lumn>
<ItemTemplate >
<img src='\SuperNova \content\images \<%#
System.IO.Path. GetFileName(Ses sion("Image"))% >' width="150px">

</ItemTemplate>
</asp:TemplateCol umn>
DisplayText:
<asp:Label ID="DisplayText Label" runat="server"
Text='<%# Eval("DisplayTe xt") %>'>
</asp:Label><br />
<br />
</ItemTemplate>
</asp:DataList>
Some of the articles don't have images. The article text and image are
stored in 2 tables, so if the article doesn't have an image, there's no
record in the image table. It's no problem just displaying the path,
which will just be blank if there's no image. The problem is when I'm
trying to display the actual image.

[Marina Levit [MVP]]

In your Finally block you are trying to read something from the datareader.
At this point, your datalist has been bound to it, and the datareader is
past the last row in the resultset - meaning, you can't get anything out of
it, since the entire result has been read by the datalist binding.

So you can't do what you are doing there.

In general, this error happens when you try to get data out of a datareader,
but it is not pointing to a row in the result set - either because no rows
were returned from the query, the datareader has not been positioned to the
first row in the result, or the reader is past the last record (which is
your case here).

<mo*******@hotm ail.com> wrote in message
news:11******** *************@t 31g2000cwb.goog legroups.com...

I used to have a problem with DBNull, but now my issue is:

System.InvalidO perationExcepti on: Invalid attempt to read when no data
is present

Here's my code behind:

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArg s) Handles Me.Load
Dim connectionStrin g As String = "Data Source=server;I nitial
Catalog=databas e; User ID=user;Passwor d=password;"
Dim connection As SqlClient.SqlCo nnection
Dim command As SqlClient.SqlCo mmand
Dim reader As SqlClient.SqlDa taReader
Dim strID As String
strID = Request.QuerySt ring("cidL")
Try
connection = New SqlClient.SqlCo nnection(connec tionString)
command = New SqlClient.SqlCo mmand()
command.Command Text = "select top 10 a.cid, a.title,
dbo.GetImagePat hNoDT(a.cid) as ImagePath, Body as DisplayText from
Article a inner join Schedule s on s.cid = a.cid inner join
ContentIndex x on x.cid = a.cid inner join contentcategory cc on cc.cid
= a.cid where cc.catid = 185 and GetDate() between s.startdt and
s.enddt and (x.ownerpid = 'HT8071') order by updateddt desc"
command.Connect ion = connection
connection.Open ()
reader = command.Execute Reader()
DataList1.DataS ource = reader
DataList1.DataB ind()
Finally
'If Not connection Is Nothing Then
'connection.Dis pose()
'End If
'If Not command Is Nothing Then
'command.Dispos e()
'End If
If reader("ImagePa th") IsNot System.DBNull.V alue Then
Session("Image" ) = reader("ImagePa th")
Else
Session("Image" ) = "logo.jpg"
End If
End Try

End Sub

And on my page, this is the code to display all the stuff from the db:

<asp:DataList ID="DataList1" runat="server" DataKeyField="c id">
<ItemTemplate >
cid:
<asp:Label ID="cidLabel" runat="server" Text='<%#
Eval("cid") %>' value="cidL"></asp:Label><br />
title:
<asp:Label ID="titleLabel " runat="server" Text='<%#
Eval("title") %>'></asp:Label><br />
ImagePath:
<asp:Label ID="ImagePathLa bel" runat="server" Text='<%#
Eval("ImagePath ") %>'></asp:Label><br />
<asp:TemplateCo lumn>
<ItemTemplate >
<img src='\SuperNova \content\images \<%#
System.IO.Path. GetFileName(Ses sion("Image"))% >' width="150px">

</ItemTemplate>
</asp:TemplateCol umn>
DisplayText:
<asp:Label ID="DisplayText Label" runat="server"
Text='<%# Eval("DisplayTe xt") %>'>
</asp:Label><br />
<br />
</ItemTemplate>
</asp:DataList>
Some of the articles don't have images. The article text and image are
stored in 2 tables, so if the article doesn't have an image, there's no
record in the image table. It's no problem just displaying the path,
which will just be blank if there's no image. The problem is when I'm
trying to display the actual image.

[mosipenko]

So what's a better way of doing it? I'm still new to asp.net

[Mark Rae]

<mo*******@hotm ail.com> wrote in message
news:11******** **************@ t31g2000cwb.goo glegroups.com.. .

So what's a better way of doing it? I'm still new to asp.net

What are you actually trying to achieve in your Finally clause...?

[Marina Levit [MVP]]

This is really more of an ADO.NET problem, not realy related to web
programming.

I have no idea what it is you are trying to do, so it's hard to say.

I am not sure why your are trying to put an Image from session into your
datalist. First off, the binding occurrs *before* you even try to set your
session variable - so first time around, the binding would all happen before
the session variable is set, so no image.

Second of all, if your query is returning the image paths - why not use what
you get from your data? Presumably you are trying to get an image path from
the last row - then make that the image for every row in the list. Why?

<mo*******@hotm ail.com> wrote in message
news:11******** **************@ t31g2000cwb.goo glegroups.com.. .

So what's a better way of doing it? I'm still new to asp.net

[mosipenko]

That is the way that someone had suggested (on a different post) that I
get my data. What I am trying to do is pull all the articles from the
database that are for a specific category. Then, on the webpage,
display the text and images (if any) for those articles. The articles
are in one table, and if they have an image, it's in a different table.
The article text and imagepath displays fine. The problem I have is
with displaying the actual image (the <img
src='\SuperNova \content\images \<%#
System.IO.Path. GetFileName(Ses sion("Image"))% >' width="150px"> part on
my aspx page). If there is an image it displays, if there is no image I
get an error.

[Mark Rae]

<mo*******@hotm ail.com> wrote in message
news:11******** **************@ g10g2000cwb.goo glegroups.com.. .

<snip>

are in one table, and if they have an image, it's in a different table.
<snip>
src='\SuperNova \content\images \<%#
System.IO.Path. GetFileName(Ses sion("Image"))% >' width="150px">

But this is querying a Session variable, not a record in your DataReader...

???

[mosipenko]

I originally had it as Eval("ImagePath ") but I changed it for the If
statement to the Session variable based on what the person who
suggested that code told me to do.

My original code for the images was this:

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArg s) Handles Me.Load
Dim connStr As String = "Data Source=server;I nitial
Catalog=databas e; User ID=user;Passwor d=password;"

Dim connObj As SqlClient.SqlCo nnection = New
SqlClient.SqlCo nnection

Dim connCmd As New SqlClient.SqlCo mmand

Dim strID As String
strID = Request.QuerySt ring("cidL")

Dim selectstr As String = "Select ImagePath from Image where
cid='" + strID + "'"
Dim dataread As SqlClient.SqlDa taReader

Dim unameexists As Boolean

connObj.Connect ionString = connStr

connObj.Open()

connCmd.Command Text = selectstr

connCmd.Connect ion = connObj

dataread = connCmd.Execute Reader()

DataList1.DataB ind()

dataread.Close( )

End Sub

[Marina Levit [MVP]]

1 problem here, is that you are never closing your connection. You need to
do that.

What was the problem with this code, and how was using a session variable
supposd to solve that problem?

What did the other person actually tell you to do? And how did he/she say
that suggestion would make it work?

<mo*******@hotm ail.com> wrote in message
news:11******** *************@j 33g2000cwa.goog legroups.com...

I originally had it as Eval("ImagePath ") but I changed it for the If
statement to the Session variable based on what the person who
suggested that code told me to do.

My original code for the images was this:

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArg s) Handles Me.Load
Dim connStr As String = "Data Source=server;I nitial
Catalog=databas e; User ID=user;Passwor d=password;"

Dim connObj As SqlClient.SqlCo nnection = New
SqlClient.SqlCo nnection

Dim connCmd As New SqlClient.SqlCo mmand

Dim strID As String
strID = Request.QuerySt ring("cidL")

Dim selectstr As String = "Select ImagePath from Image where
cid='" + strID + "'"
Dim dataread As SqlClient.SqlDa taReader

Dim unameexists As Boolean

connObj.Connect ionString = connStr

connObj.Open()

connCmd.Command Text = selectstr

connCmd.Connect ion = connObj

dataread = connCmd.Execute Reader()

DataList1.DataB ind()

dataread.Close( )

End Sub

[mosipenko]

The problem with my original code (the one without the Try...Finally)
was that I get a DBNull to String conversion error. The other person
said I needed to use a Try...Finally to stop it, and gave me that other
code that I posted at the top. All they had in the If statement was
that if the reader was nothing then dispose of it. But what I needed to
do was if the field ImagePath was DBNull, then to replace it with a
different image (the logo.jpg). The other person suggested using the
Session variable in the If statement to do that.