ASP.NET - Limit file upload available file types

Question

I have added a file upload to my asp.net website. However, I want to limit the file types that user can select. For example, I only the user to select mp3 files. How can I add a filter to the file upload so that it displays only the mp3 files in the folder selected?

 <asp:FileUpload ID="FileUpload1" runat="server" />
 <asp:Button ID="btnAudUpload" Text="Upload" CssClass="btncssUpload" OnClick="btnAudUpload_Click" runat="server" />

Answer 1

Use the accept attribute directly in the tag (it's not really supported by the control, but will be delivered to client anyway)

While you could list file extensions, e.g: ".xls,.xlsx", this is NOT recommended, and some browsers get confused by it.

It's better to use MIME types (browser will map them to appropriate extensions for you):

 Upload MP3: <asp:FileUpload runat="server" accept=""audio/mpeg" />

Use comma-separated list if needed, e.g.:

 Upload Excel files: <asp:FileUpload runat="server" 
                 accept="application/vnd.ms-excel,application/vnd.openxmlformats-officedocument.spreadsheetml.sheet" />

Supported browsers and more info: http://www.w3schools.com/tags/att_input_accept.asp

Common MIME types below (snapshot of http://www.sitepoint.com/web-foundations/mime-types-summary-list/ )

.au audio/basic
.avi video/msvideo, video/avi, video/x-msvideo
.bmp image/bmp
.bz2 application/x-bzip2
.css text/css
.dtd application/xml-dtd
.doc application/msword
.docx application/vnd.openxmlformats-officedocument.wordprocessingml.document
.dotx application/vnd.openxmlformats-officedocument.wordprocessingml.template
.es application/ecmascript
.exe application/octet-stream
.gif image/gif
.gz application/x-gzip
.hqx application/mac-binhex40
.html text/html
.jar application/java-archive
.jpg image/jpeg
.js application/x-javascript
.midi audio/x-midi
.mp3 audio/mpeg
.mpeg video/mpeg
.ogg audio/vorbis, application/ogg
.pdf application/pdf
.pl application/x-perl
.png image/png
.potx application/vnd.openxmlformats-officedocument.presentationml.template
.ppsx application/vnd.openxmlformats-officedocument.presentationml.slideshow
.ppt application/vnd.ms-powerpointtd>
.pptx application/vnd.openxmlformats-officedocument.presentationml.presentation
.ps application/postscript
.qt video/quicktime
.ra audio/x-pn-realaudio, audio/vnd.rn-realaudio
.ram audio/x-pn-realaudio, audio/vnd.rn-realaudio
.rdf application/rdf, application/rdf+xml
.rtf application/rtf
.sgml text/sgml
.sit application/x-stuffit
.sldx application/vnd.openxmlformats-officedocument.presentationml.slide
.svg image/svg+xml
.swf application/x-shockwave-flash
.tar.gz application/x-tar
.tgz application/x-tar
.tiff image/tiff
.tsv text/tab-separated-values
.txt text/plain
.wav audio/wav, audio/x-wav
.xlam application/vnd.ms-excel.addin.macroEnabled.12
.xls application/vnd.ms-excel
.xlsb application/vnd.ms-excel.sheet.binary.macroEnabled.12
.xlsx application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
.xltx application/vnd.openxmlformats-officedocument.spreadsheetml.template
.xml application/xml
.zip application/zip, application/x-compressed-zip

Answer 2

Using RegularExpressionValidator may help you. No serverside code is necessary for the checking of the file extension. Check out this code

<asp:RegularExpressionValidator ID="uplValidator" runat="server" ControlToValidate="FileUpload1"
 ErrorMessage=".mp3, .mp4 & wma formats are allowed" 
 ValidationExpression="(.+\.([Mm][Pp][3])|.+\.([Mm][Pp][4])|.+\.([Ww][Mm][Aa]))"></asp:RegularExpressionValidator>

Remember all you have to do is now add a fileupload control with the id FileUpload1. Done. You can press F5 and see the effect