How to check uplaod file is executable file or not in c#

Question

Hi i am try to check .exe file change extension .jpg and uplaod then upload this file but this file is how to check this is executable file or not in if change the extension in c# please help me thanks in advance

sudipta sanyal · Answer

Hi Please Try ------------------------------------------ public static bool IsExeFile(byte[] FileContent) { var twoBytes = SubByteArray(FileContent 0 2); return ((Encoding.UTF8.GetString(twoBytes) == MZ)||(Encoding.UTF8.GetString(twoBytes) == ZM)); } private static byte[] SubByteArray(byte[] data int index int length) { byte[] result = new byte[length]; Array.Copy(data index result 0 length); return result; } -------------------- Do mark as correct answer if it resolves your issue.

sudipta sanyal · Answer

Hi @Rafnas Many times we fall in a situation where we have implemented detection of file type based on file extension. It’s pretty easy to do that on both client as well as server side. But does it guarantees that file uploaded is not actually an exe file. Well anyone can rename an test.exe to test.txt and upload it to your web application which may lead to dangerous results & even security threst. For this we must validate the file in deeper.

sudipta sanyal · Answer

Hi @Maharudra @Rafnas was already answered the solution Please go throw his post

Maharudra Gadekar · Answer

Hi Sudipta sanyal please help me.....if i am upload txt file changing extesion in jpg then what is the extension to check same process of xlsxxlscsv docx pngjpggifjpegziprar file help me thanks in advance

sudipta sanyal · Answer

Hi @Rafnas You right I do not understand why he needs this requirement which may damage the system.

Rafnas T P · Answer

HI@sudipta you are right. then dont change the extension. if you know this is an .exe file then why you wanted to change the extension. here he wanted to just change the extension if this is an .exe file so that mean he wanted to upload .exe file as .jpg but I dont know why he is wanted to do like this even he can upload .exe file directly. so according to his requirement he can do like below if he is not worrying about as you said the issue. string path= FullFilepath ; string fileExtension = System.IO.Path.GetExtension(FullFilepath); if( fileExtension ==.exe) { path = System.IO.Path.ChangeExtension(fileLocation .jpeg); }

Amit Kumar · Answer

Hi Dear I agree with Sudipta Sanyal's code is running fine.

Rafnas T P · Answer

to get the file extension use deolw code string fileExtension = System.IO.Path.GetExtension(FullFilepath); to change the file extension directly you can use deolw code string dest = System.IO.Path.ChangeExtension(fileLocation .jpeg);