How can I upload files asynchronously on ASP.NET?

Question

I've been looking for a way to achieve this behavior and I found this sample project.

The trick in this project is that it changes the form target to an iframe created on the fly.

So far so good, I can get the byte[] on the server-side. But I need to change an image preview after the file is uploaded.

How can I get the iframe to update the main page? Would I have to save it on a file on the disk, make a javascript callback to change the image url? Is there another way to do this? What's recommended?

This control suggested by vorrtex actually causes a full page postback, am I missing something or is it the correct behavior?

BrunoLM · Accepted Answer · 2010-09-28 19:20:41Z

1

I recommend you to use AsyncFileUploader and UpdatePanel. You have to save file on the disk but you can use C# for changing imageUrl.

edited Sep 28, 2010 at 19:20

BrunoLM

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answered Sep 28, 2010 at 19:11

vortexwolf

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3 Comments

BrunoLM Over a year ago

Actually the page keeps getting a full postback. Am I missing something?

vortexwolf Over a year ago

It seems that such behaviour is prohibited: weblogs.asp.net/leftslipper/archive/2007/03/30/…. Maybe this is reason why Google uses flash in Gmail.

BrunoLM Over a year ago

I see, so I will have to do the callback on javascript... Thanks for this link it was very clarifying.

SLaks · Accepted Answer · 2010-09-28 19:04:12Z

0

Add a <script> block to the page that gets loaded in the <iframe> that interacts with the parent page and updates whatever you need to.

answered Sep 28, 2010 at 19:04

SLaks

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3 Comments

Valera Kolupaev Over a year ago

AFAIK, it will allow to upload anything, except files.

SLaks Over a year ago

@Valera: Huh? What are you talking about?

Valera Kolupaev Over a year ago

oops, I thought, that you are proposing to implement "async file upload functionality" using <script> and <iframe>, my bad.

dhinesh · Accepted Answer · 2010-11-04 09:49:38Z

0

You can use the project mentioned below to preview the image before uploading. Working sample is also attached.

http://www.dotnetspider.com/resources/40858-Preview-Image-before-uploading-using.aspx

This uses AjaxControlToolKit's AsyncFileUploadControl and HTTPHandler to upload the image.

answered Nov 4, 2010 at 9:49

dhinesh

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