Validate file extension

Question

5.00/5 (2 votes)

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I have to upload the file which has the extension .fnm
Here is how I am validating:

VB

If String.Compare(System.IO.Path.GetExtension(fuUpload.FileName), ".fnm", True) <> 0

And its working fine. It only uploads the file having the extension .fnm.

The problem is that when someone manipulates the file extension like changes .txt or .doc to .fnm, it bypasses the validation and gets uploaded.

Is there any way to validate file type other than its extension? Or any other method to validate. Please suggest.

Posted 8-Oct-13 3:16am

ujju.1

Updated 25-May-16 2:33am

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phil.o 8-Oct-13 9:18am

What is the formal description of the .fnm file format?

3 solutions

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Eduard Keilholz · Answer 1 · 2013-10-08T03:20:00

Solution 1

There are a couple of ways, first you can read the mime type, but only well known file types will be recognized. In this case, I think the best way would be to open and read the file and validate to file's content before handling it. That's to only way to be sure.

Posted 8-Oct-13 3:20am

Eduard Keilholz

manvendra patel · Answer 2 · 2013-10-08T03:27:00

Solution 2

http://stackoverflow.com/questions/300406/validating-an-uploaded-files-contenttype-in-asp-net[^]

try this link

Posted 8-Oct-13 3:27am

manvendra patel

MuhammadUSman1 · Answer 3 · 2013-10-08T19:36:00

Solution 3

Please check following links

Asp.net file upload control

file upload HTML control

Posted 8-Oct-13 19:36pm

MuhammadUSman1