I have a byte array filled from a file uploaded. But, in another part of the code, I need to know this file type uploaded from the byte[] so I can render the correct content-type to browser!
Thanks!!
Most likely the '?' is the ternary operator. Its grammar is: RESULT = (COND) ? ( STATEMEN IF TRUE) : (STATEMENT IF FALSE) It is a nice shorthand for the typical if-else statement: if (COND) { RESULT = (STATEMENT IF TRUE); } else { RESULT = (STATEMENT IF FALSE);
C operators are one of the features in C which has symbols that can be used to perform mathematical, relational, bitwise, conditional, or logical manipulations. The C programming language has a lot of built-in operators to perform various tasks as per the need of the program.
|= just assigns the bitwise OR of a variable with another to the one on the LHS.
As mentioned, MIME magic is the only way to do this. Many platforms provide up-to-date and robust MIME magic files and code to do this efficiently. The only way to do this in .NET without any 3rd party code is to use FindMimeFromData
from urlmon.dll. Here's how:
public static int MimeSampleSize = 256; public static string DefaultMimeType = "application/octet-stream"; [DllImport(@"urlmon.dll", CharSet = CharSet.Auto)] private extern static uint FindMimeFromData( uint pBC, [MarshalAs(UnmanagedType.LPStr)] string pwzUrl, [MarshalAs(UnmanagedType.LPArray)] byte[] pBuffer, uint cbSize, [MarshalAs(UnmanagedType.LPStr)] string pwzMimeProposed, uint dwMimeFlags, out uint ppwzMimeOut, uint dwReserverd ); public static string GetMimeFromBytes(byte[] data) { try { uint mimeType; FindMimeFromData(0, null, data, (uint)MimeSampleSize, null, 0, out mimeType, 0); var mimePointer = new IntPtr(mimeType); var mime = Marshal.PtrToStringUni(mimePointer); Marshal.FreeCoTaskMem(mimePointer); return mime ?? DefaultMimeType; } catch { return DefaultMimeType; } }
This uses the Internet Explorer MIME detector. This is the same code used by IE to send a MIME type along with uploaded files. You can see the list of MIME types supported by urlmon.dll. One thing to watch out for is image/pjpeg
and image/x-png
which are non-standard. In my code I replace these with image/jpeg
and image/png
.
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With