FileUpload in UpdatePanel

I have a problem with uploading file to server. I have panels of information on my page. Each panel specify a step of information. And on the last panel, I have a FileUpload control to enable user attach a file. All panels are placed inside UpdatePanel.

But, I am not receiving posted file on the server. I tried doing full postback on 开发者_Go百科last step by registering my Save button as PostbackTrigger like below. But, this is not doing the work.

I debugged the page many times & tried several ways to solve this. I found that, if I place my FileUpload control in a panel that is initially hidden & get visible in later step, FileUpload doesn't work. On the other hand, I tried placing FileUpload out side all step panels but inside UpdatePanel, it works. How?

Friends, I want to show FileUpload control on the last Panel. Please guide me.

Regards, Akif

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This is not a limitation of ASP.NET or UpdatePanel. It is a limitation of AJAX which doesn't allow you to upload files. That's why placing the upload control outside the UpdatePanel works as you are performing a full postback. You could use some technique such as hidden iframes, jquery plugins, flash, etc...