FileUpload.FileName behavior when there is a semi-colon or opening bracket in the file name

Question

I have a FileUpload control, and there are certain restrictions on the file name, certain characters that shouldn't be allowed. The following code works for most characters, but for some reason not others:

if (FileUpload1.HasFile)
{
    if (FileUpload1.FileName.Contains('#') ||
        FileUpload1.FileName.Contains('&') ||
        FileUpload1.FileName.Contains(';') ||
        FileUpload1.FileName.Contains('{') ||
        FileUpload1.FileName.Contains('}') ||
        FileUpload1.FileName.Contains('+'))
    {
        //error: bad character detected
    }
}

I could probably do this another (better) way, with a regular expression, but first I really want to know why the above doesn't work.

The following characters are detected in the FileName:

# & } +

The following characters are not detected in the FileName:

; {

Why?

Edit: examples of file names that I've tried.

• Final+Version.pdf //+ detected

• Final;Version.pdf //; NOT detected

• WhyHello{there.pdf //{ NOT detected

• Policies}20120303.pdf //} detected

As mentioned in the comments below, there is no problem with these characters on strings, so maybe it's a problem with the value of "FileName" or the way the FileUploader handles the file name?

Edit 2: Breakpoint step through shows that, using Policies{20120303.pdf as an example, the value of FileName is Policies.pdf. So this is not a problem with .Contains() anymore, but with FileUpload and FileName.

So the new question is, how can I handle this? I don't want files with these characters to go through, and I don't want the submitted files to be named differently from what the user named them. So if someone tries to submit 'Policies{20120303.pdf', I need one of two results:

1. invalid name is detected, procedure aborted
2. submit the file with the complete and original name, Policies{20120303.pdf

Edit 3: If I submit a file with the following name: foo;bar{baz.txt, the value of FileUpload.FileName is "foo.txt"

Edit 4: Thanks to some helpful comments below, I tried using a different browser (Chrome), and it works just fine! The file name stays intact, even with foo;bar{baz.txt. I use Opera, and it wasn't working. I guess that narrows it down quite a lot to a browser specific issue. I don't think there's gonna be any way to make this work properly in Opera, unless someone has any ideas?

Answer 1

I used the following code in my program to check the filename:

filename = txtFileName.Text;
if (filename == "" || (filename.IndexOfAny(System.IO.Path.GetInvalidFileNameChars()) != -1))
{
// Ask for a new file name, or whatever else you need to do.
}

In my case, however, I'm checking the user provided string before setting the file name in the file object. I think that would probably solve your problem as well.

I'm guessing that somewhere there's a function that alters the string before you get to the point of verifying it.