How to verify file exists with asp:FileUpload

bryanp10 · Mar 30, 2007

How do I do a client-side check to see that a file exists before
attempting to upload it? I am trying to avoid the "Access denied"
error I get on form submission if an invalid name is entered in the
textbox.

This page does it beautifully:
http://msconline.maconstate.edu/tutorials/ASPNET2/ASPNET09/aspnet09-11.aspx

But how???

Seems like an obvious feature to discuss, but NOTHING I've seen online
explains how to do.

Ben Rush · Mar 30, 2007

I'm afraid I don't know what you mean. I created a very simple aspx page
using an upload control from ASP.net and it seemed to work exactly as the
one hosted on the page to which you're linking.

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:FileUpload ID="FileUpload1" runat="server" />
<asp:Button ID="Button1" runat="server" OnClick="Button1_Click"
Text="Button" /></div>
</form>
</body>
</html>

Perhaps I am missing something fundamental in your question? If I type some
garbage into the upload text box and click to upload, the behavior is the
same as this other one.

bryanp10 · Mar 30, 2007

Interesting... so with this little code you just posted, when you
insert a file name like:

c:\missingfile.txt (valid file name, but doesn't actually exist)

You see a little message popup that says "The file missingfile.txt
does not exist" and it doesn't post back? Because I'm certainly not
seeing that. Did you check the link I posted?

What I see is that the page posts back and the file size posted is 0
bytes. If I use an invalid file name (no path, bad chars) it simply
doesn't post back, but there is no feedback.

Obviously there is something wrong in my app because I'm getting an
"access denied" javascript error that I am not sure how to catch or
account for when submit() is called.

bryanp10 · Mar 30, 2007

Sheeeeit. I just realized what is going on. The behavior is browser-
specific... duh! IE does not provide any feedback and will postback
even if the file doesn't exist. If it's an invalid filename it will
simply not post back. Opera, on the other hand, pops up a message that
says the file doesn't exist in both cases and does not post back.

To this day, it amazes me that Microsoft was able to capture so much
of the browser market.

kwendex · Mar 30, 2007

Sheeeeit. I just realized what is going on. The behavior is browser-

specific... duh! IE does not provide any feedback and will postback
even if the file doesn't exist. If it's an invalid filename it will
simply not post back. Opera, on the other hand, pops up a message that
says the file doesn't exist in both cases and does not post back.

Yup. That sort of thing is very browser based.

To this day, it amazes me that Microsoft was able to capture so much
of the browser market.

It came preinstalled on the most widely-used operating system on the
planet. Makes sense to me

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How to verify file exists with asp:FileUpload

bryanp10

Ben Rush

bryanp10

bryanp10

kwendex

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