The following example demonstrates how to create a FileUpload control. . You can use the ContentType property to get the MIME content type of the file. tLength); int length = ; string fileName = ng(); string type = File. ContentType. = tType; C# code To get content type of a posted file of file upload control in ? 01 Wednesday.
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Content type is basically determined by the client, but mostly client may not send content type, in that case checking extension is only best way to verify type of file. Or you should check both. We did face problem with some mac clients that did not send content type. Content type is bad idea because if user does not have corresponding software installed, os will send wrong content type. The best way to do that is using the FileOpenDialog component to let the user postddfile a file neatly, while adding filters to the component eg.
You need to maintain a black list of content type as you know what types needs to be blocked rather than the types which needs to be allowed even though later is a much secure practice. I would recommend you to run through some antivirus webservice or scan before acepting the files something like http: When they upload the file do they need to be available immediately? What I have done in the past is to place them in a pending folder on the server, then at a given interval although it could be a called function following upload I run a small process that read the first few bytes of data.
Executables often start with the charcaters “MZ”. Have a look in a hex editor TextPad will work for example. This is of course you final port of call, your safety net, first steps is to limit by suffix as you are doing although this is no real guarantee of file contents.
Note that some of those files you wish to omit are just text files: So, MIME Types or reading the start of the data will not help – so best way is to either ban these extensions altogether or rename the extensions rileuploadcontrol.
They can do not harm as text files with. Have you checked this answer Using. NET, how can you find the mime type of a file based on the file signature not the extension?
[Solved] Fileupload image types validation C# – CodeProject
Getting the mime type from the file is possible by server side and black list the ones you don’t want. Posedfile using a reg expression to filter the file type in Open file dialog is somewhat unreliable since any user can type for example. I would use the file extension as the first line of defense,then content type, then file signature. Try using a nested if statement three levels deep to insure the file fileuploadclntrol all filejploadcontrol way through.
That will save you some code, especially if the acceptance list is not finite and or small. Think about the guy who may have to make changes to your code later You should absolutely not accept all file types – this is a huge security hole.
Fileupload image types validation C# asp.net
I would fire you for doing something like that. I suspect your problem may be user error. Can you verify that the ‘mac’ user does not have the file open while he is trying to upload? There is no reason that an upload from mac should behave differently than from pc.
FileName ; if Finfo. Apple user may use OpenOffice, or some other softwares to upload. In case of absence of both, you will have to check few initial bytes of file to check its type. The only improvement I can think of is: Ramesh 9, 2 37 Wolf 1, 9 Now assign Bounty to yourself. Carlos Ferreira 2 Why not just do reverse logic on the file extensions that are prohibited?
For example, lets say a few years later one of the accepted file types becomes unacceptable. I have personally had to search through thousands of lines of code in order to make fixes like this, trust me. Accepting all file types is hardly a fire-able offense.
A good manager would take the opportunity to teach their growing developers or maybe assign a senior developer to do a code review. Or maybe instruct the developer to do some research online at StackOverflow to learn best practices!
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