Member Avatar for sujimon

Hi,

I am using VS-2005.
In my website I have used the html input control with type=file.

The problem is that when I place this control inside an 'UpdatePanel' the 'PostedFile' property becomes 'Nothing' on postback. So in order to get things working I have removed the 'UpdatePanel' and things are working fine.

However, I am interested to know what kind of workaround is required if I were to use an 'UpdatePanel'? In one of the threads at forums.asp.net I found that we need to set a 'PostBackHandler' for the update panel. I have no idea how to implement this. Does it refer to 'AsyncPostbackTrigger' or 'SyncPostBackTrigger'?

Can someone give an idea how to implement this?

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  • Latest Post Latest Post by toddanglin
Member Avatar for dnanetwork

This is a Major drawback of asp.net which is not capable of providing this piece of functionality.

search on google this is a legendary problem since 2005 came in..!

i.e the reason why ppl switch to Telerik Controls.

Member Avatar for sujimon

Hi Ashish,
I was able to resolve the issue.
I had to set the trigger to 'PostBackTrigger' instead of 'AsyncPostbackTrigger' inside the UpdatePanel for the 'Upload' button.

Member Avatar for toddanglin

In general, you cannot upload files with Ajax. This is simply a limit of HTTP and browsers. The only way to upload files asynchronously are:

  1. By using a browser plug-in (like Silverlight)
  2. By using a hack that "secretly" POSTs the file (IFRAME)

This article well describes the common IFRAME workaround used to enable "async" file uploads in standards-based sites:

http://www.openjs.com/articles/ajax/ajax_file_upload/

If you prefer a tool, you can use things like RadAsyncUpload for ASP.NET to achieve the same effect with less manual code:

http://demos.telerik.com/aspnet-ajax/upload/examples/async/ajaxprocessing/defaultcs.aspx

Hope that helps.

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