Refresh Page

[David]

Hello.

I have such problem:
I have ImageButton on my form which is attached to some image like
"image.jpg", now when I change image file (physically file) with some other
file with the same name my page shows the old image until I click "Refresh"
button of the browser.
So how can I refresh web form from code?
Or may be there is some other way to solve this problem?

Thank you.

 

[David]

No! It's imposable.
Is there any other way?

The image gets cached on client side. You can trick the browser onto
refreshing the image by adding a random number to the image url. For
example
image.jpg?1234

Eliyahu

 

[Eliyahu Goldin]

The image gets cached on client side. You can trick the browser onto
refreshing the image by adding a random number to the image url. For example
image.jpg?1234

Eliyahu

 

[Eliyahu Goldin]

Yes, in the code-behind:

Response.ExpiresAbsolute = DateTime.Now.AddDays (-1);
Response.Cache.SetCacheability (System.Web.HttpCacheability.NoCache);

Response.AppendHeader ("Pragma", "no-cache");


Eliyahu

 

[Joerg Jooss]

Yes, in the code-behind:

Response.ExpiresAbsolute = DateTime.Now.AddDays (-1);
Response.Cache.SetCacheability (System.Web.HttpCacheability.NoCache);

Response.AppendHeader ("Pragma", "no-cache");

This only affects the page itself, but not any referenced resource. In order
to make the image file non-cacheable, put all it and all other non-cacheable
images in a common folder and assign this folder the HTTP headers

Cache-Control: no-cache (*)
Pragma: no-cache

using the IIS admin applet.

(*) Technically, "Cache-Control: must-revalidate" would be the right choice,
but IE handles this incorrectly :-(


Cheers,

 

[William F. Robertson, Jr.]

That is the way it should be done. I read a great article about what
yahoo.com does for their impression ads and image tracking. You will need
to put some value on the end of the src.

<img srg="http:\\site.com\images\bob.jpg?5531234">

This will force the client browser to "redownload" the image, as it doesn't
think it has it downloaded already.

bill

 

[Joerg Jooss]

That is the way it should be done.

Should? No, not really. HTTP 1.1 covers all required cache and expiration
mechanisms. But if you said "must" be done, you're most likely correct.
There are still too many crappy HTTP implementations out there that are
beyond any poor web application developer's control :-(

Cheers,