ASP Image causes page to load twice

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DBLWizard - 06 Sep 2007 17:53 GMT

Howdy All,

I need some help I can't believe this is bug in Visual Studio 2005 and
hasn't been reported yet, but I have recreated it on two different
machines with the same result. I created a brand new website using VS
2005 and the default.aspx page looks like this:

<%@ Page Language="C#" AutoEventWireup="true"
CodeBehind="WebForm1.aspx.cs" Inherits="Pgi.Hub.WebForm1" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://
www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Image ID="imgTest" runat="server" />
<asp:Label ID="Label1" runat="server" Text="PageCount:"/>
<asp:Label ID="Label2" runat="server" />
</div>
</form>
</body>
</html>

And the Default.aspx.cs page looks like this:

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{

if (Session["Default"] == null)
{
Session["Default"] = 0;
}

Session["Default"] = (int)Session["Default"] + 1;
Label2.Text = Session["Default"].ToString();
}
}

The first time the page loads it displays PageCount:1 if you hit
refresh again it shows PageCount:3. If you put a break point in the
Page_Load it will hit the break point twice each time you load the
page. This seems to be tied to the Image control, because you can
remove the <ASP:Image ...> entry from the page and it only loads
once. Also it seems to be a ghost page because the the second time
through the Label2.Text is set to 2 but the page that displays only
says 1.

I would appreciate any feedback or thoughts on what I'm doing wrong or
if there is some way around this and the best way to report it to
Microsoft if I'm not wrong.

Thanks

dbl

Reply to this Message

George Ter-Saakov - 06 Sep 2007 18:45 GMT

Your code works fine on my machine. IE 7.
What browser are you using?
I suspect the problem is that you have Image control and no source fro image
(src) assigned.
So the generated HTML <img src=""> might trigger the request for the same
page.
Since browser trying to concatenate the src path with the path of the page
and I am not sure what is the rule when src is blank.

George.

> Howdy All,
>
[quoted text clipped - 21 lines]
> </div>
> </form>

> </html>
>
[quoted text clipped - 41 lines]
>
> dbl

Reply to this Message

DBLWizard - 06 Sep 2007 19:21 GMT

I question if "my" code works fine on your system. If you are saying
that you added a ImageUrl property to the Image and then the problem
went away then I can buy that. But I don't think my code as I entered
it above works perfectly on your system unless its something that
Microsoft did differently in IE 7. I am running both IE 6 and Firefox
2.0.0.6 and they both exhibit the behavior.

I just added the ImageUrl property and an image and the problem went
away. It even goes away if you have something in the
ImageUrl(ImageUrl="abcdefg") but it doesn't resolve properly. But if
the is blank ImageUrl="" or the tag is not there the problem does
exist.

I also reduced my page down to:

<%@ Page Language="C#" AutoEventWireup="true"
CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://
www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<img id="Image2" src="" alt=""/>
</div>
</form>
</body>
</html>

And it double loads so its not a Visual Studio bug but it is a bizarre
behavior. So thanks for pointing me in the correct direction.

dbl

> Your code works fine on my machine. IE 7.
> What browser are you using?
[quoted text clipped - 77 lines]
>
> > dbl

Reply to this Message

George Ter-Saakov - 06 Sep 2007 19:48 GMT

Well, you got your answer. It's a browser problem
Browser IE 6 and Firefox does not know what to do with html like
<img src="">
they are "concatenating" empty string with the page's url and comes up with
the same URL. And sends "GET" request for that image.

But I am surprised in that behavior as well.

George.

>I question if "my" code works fine on your system. If you are saying
> that you added a ImageUrl property to the Image and then the problem
[quoted text clipped - 118 lines]
>>
>> > dbl

Reply to this Message

Lit - 06 Sep 2007 19:06 GMT

Your code works fine on my machine.
when I refresh the count goes, 1, 2, 3.....
No loading twice.

create a new page and see may be you have some double subscription to your
events.
what happens if AutoEventWireup="true" is false?

Lit

> Howdy All,
>
[quoted text clipped - 67 lines]
>
> dbl

Reply to this Message

Mark Rae [MVP] - 06 Sep 2007 19:37 GMT

> Your code works fine on my machine.

And on mine.

> when I refresh the count goes, 1, 2, 3.....
> No loading twice.

Same here.

Signature

Mark Rae
ASP.NET MVP
http://www.markrae.net

Reply to this Message

DBLWizard - 06 Sep 2007 20:00 GMT

For everybody that this works fine with are ya'll using IE 7?

And I have decided that it still is a Visual Studio bug becuase if I
turn AutoEventsWireup to false the problem doesn't happen. Yes I know
that none of the events fire but still it is a bug in the event
handlers somewhere in Visual Studio. I don't have time at the moment
to dig into that and see exactly where the problem is as I have
already wasted a day trying to figure out what was causing this in the
first place ... but when I do I will try and add more details to this
post.

Thanks

dbl

> > Your code works fine on my machine.
>
[quoted text clipped - 8 lines]
> Mark Rae
> ASP.NET MVPhttp://www.markrae.net

Reply to this Message

Lit - 06 Sep 2007 20:15 GMT

I have IE 7 here. thanks for testing AutoEventsWireup.

Lit

> For everybody that this works fine with are ya'll using IE 7?
>
[quoted text clipped - 23 lines]
>> Mark Rae
>> ASP.NET MVPhttp://www.markrae.net

Reply to this Message

George Ter-Saakov - 06 Sep 2007 20:44 GMT

I failed to understand reasoning why it's Visual Studio bug.....

If the AutoEventsWireup is false then Page_Load is not wired as an even
handler. Your page is still called twice.
Replace
protected void Page_Load(object sender, EventArgs e)

with

protected override void OnLoad(EventArgs e)

and you will see that. Even with AutoEventsWireup = false.

------------------------------

You just learned today (and we did too)

that having <img src=""> on a page.aspx is the same as having <img
src="page.aspx">

That is all.

I would call it a browser's bug at most. But even that would be a stretch,
cause I am positive that behavior when src is empty is not determined in the
standard (never read it :). But it's first time i come accross when someone
has empty src for image. If you need to make an invisible image just put
transparent gif 1x1 in there.

George.

> For everybody that this works fine with are ya'll using IE 7?
>
[quoted text clipped - 23 lines]
>> Mark Rae
>> ASP.NET MVPhttp://www.markrae.net

Reply to this Message

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ASP Image causes page to load twice

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