Check the Server File Type in ASP. NET

Public static bool isallowextensin (system. Web. UI. htmlcontrols. htmlinputfile hifile) // check the file type
{
System. io. filestream FS = new system. io. filestream (hifile. postedfile. filename, system. io. filemode. open, system. io. fileaccess. read); // create a file stream object
System. Io. binaryreader r = new system. Io. binaryreader (FS); // create a file reader object
String fileclass = ""; // read two bytes from the current file stream to determine the file type
Byte buffer;
Try
{
Buffer = R. readbyte (); // read the next byte from the current stream
Fileclass = buffer. tostring ();
Buffer = R. readbyte ();
Fileclass + = buffer. tostring ();
}
Catch {}
R. Close (); // close the reader object
FS. Close (); // close the file stream
If (fileclass = "255216" | fileclass = "7173" | fileclass = "6677" | fileclass = "13780") // The 255216 is JPG; 7173 is GIF, 6677 is BMP, 13780 is PNG, 7790 is exe, and 8297 is RAR
Return true;
Else
Return false;
}