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asp.net FileUpload event after choice is made and before submit for upload

Answer 1

+2 A:

The problem is that there's no way to find out the size of file on the client side without posting back. You could use Ajax, but that would mean uploading the file first anyway.

This can only be done using an ActiveX control of some kind. I would recommend using something like the Silverlight FileUploader because it gets the size of the file before posting back and even has a nice progress indicator.

UPDATE: If you want to trigger a postback or Ajax Request after the user clicks browse, the client side event is "onchange". Here's an example of how to use the onchange event.

<asp:FileUpload runat="server" 
    onchange="alert('you selected the file: '+ this.value)" />

You could have the onchange, trigger an ajax to upload the file first and then update a label showing the size of the file. The problem with this is that if it is a large file, it defeats the purpose of letting the user know before hand that it will take a long time.

Here's another recommendation: There's a jQuery plugin that uses flash to determine the size of the file before uploading and it's very easy to use. Check it out at jQuery Uploadify

Jose Basilio 2009-05-06 18:11:26

I was wondering if there would be an event associated with the FileUpload "choosing process" (i.e. clicking "Browse" and making a selection that populates the textbox portion of the FileUpload control. Then perhaps such an event could submit the form a first time using Javascript. A second submit would occur when the Upload Button was clicked. Do you know of such an event and if yes, would it have access to the FileUpload1.PostedFile.ContentLength property?

John Galt 2009-05-06 18:26:51

Thanks for these good ideas. I have already looked into the Silverlight control.In Visual Studio 2005, there is no onchange event for <asp:FileUpload>. I have not checked if VS2008 supports that.

John Galt 2009-05-06 19:00:24

I see what you mean..ignore the lack of this in the intellisense / object model of the control. Here is the generated HTML:<input type="file" name="FileUpload1" id="FileUpload1" onchange="alert('you selected the file: '+e.value)" but the alert is not firing.

John Galt 2009-05-06 19:26:11

Thanks Jose. I came up with something close to this: <script type="text/javascript">function submitform(){document.form1.submit();} </script> <asp:FileUpload ID="FileUpload1" runat="server" Width="848px" onchange="submitform()" />and then this works in Page_Load if (Page.IsPostBack) lblFileSize.Text = GetFileSize(FileUpload1.PostedFile.ContentLength);

John Galt 2009-05-06 20:40:09

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asp.net FileUpload event after choice is made and before submit for upload

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