How to find the extension of a file in C

Question

In my web application  asp net c   I am uploading video file in a page but I want to upload only flv videos  How can I restrict when I upload other extension videos

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In addition  if you have a FileInfo fi  you can simply do   string ext   fi Extension    and it ll hold the extension of the file  note  it will include the    so a result of the above could be   jpg  txt  and so on

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Path GetExtension  string myFilePath     C  MyFile txt   string ext   Path GetExtension myFilePath      ext would be   txt

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You will not be able to restrict the file type that the user uploads at the client side      You ll only be able to do this at the server side   If a user uploads an incorrect file you will only be able to recognise that once the file is uploaded uploaded   There is no reliable and safe way to stop a user uploading whatever file format they want       yes  you can do all kinds of clever stuff to detect the file extension before starting the upload  but don t rely on it   Someone will get around it and upload whatever they like sooner or later

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You may simply read the stream of a file   using  var target   new MemoryStream          postedFile InputStream CopyTo target       var array   target ToArray        First 5 6 indexes will tell you the file type  In case of FLV its 70  76  86  1  5   private static readonly byte   FLV     70  76  86  1  5    bool isAllowed   array Take 5  SequenceEqual FLV     if isAllowed equals true then its FLV   OR   Read the content of a file  var contentArray   target GetBuffer    var content   Encoding ASCII GetString contentArray     First two three letters will tell you the file type  In case of FLV its  FLV         content StartsWith  FLV

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string FileExtn   System IO Path GetExtension fpdDocument PostedFile FileName     The above method works fine with the firefox and IE   i am able to view all types of files like zip txt xls xlsx doc docx jpg png  but when i try to find the extension of file from googlechrome   i failed

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private string GetExtension string attachment name        var index point   attachment name IndexOf  quot   quot     1      return attachment name Substring index point

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EndsWith    Found an alternate solution over at DotNetPerls that I liked better because it doesn t require you to specify a path  Here s an example where I populated an array with the help of a custom method              This custom method takes a path             and adds all files and folder names to the  files  array         string   files   Utilities FileList  C                     Then for each array item            foreach  string f in files                           Here is the important line I used to ommit  DLL files              if   f EndsWith   dll   StringComparison Ordinal                      then populated a listBox with the array contents                 myListBox Items Add f

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At the server you can check the MIME type  lookup flv mime type here or on google   You should be checking that the mime type is  video x-flv   If you were using a FileUpload in C  for instance  you could do  FileUpload PostedFile ContentType     video x-flv

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I m not sure if this is what you want but   Directory GetFiles   c  mydir      flv      Or   Path GetExtension   c  test flv

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This solution also helps in cases of more than one extension like  Avishay student DB                   FileInfo FileInf   new FileInfo filePath                   string strExtention   FileInf Name Replace System IO Path GetFileNameWithoutExtension FileInf Name

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It is worth to mention how to remove the extension also in parallel with getting the extension   var name   Path GetFileNameWithoutExtension fileFullName      Get the name only  var extension   Path GetExtension fileFullName      Get the extension only

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You can check  flv signature  You can download specification here   http   www adobe com devnet flv   See  The FLV header  chapter

[c#] How to find the extension of a file in C#?

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