Writing an Antivirus in C#

If you do not have the knowledge to program in C++ or C# and the understanding on how to scan for patterns in files and analyzes how a program behave. Then do not try :-)

Try
http://codemink.com/how-to-make-antivirus-using-c-programming-language/[^]
http://itsecuritylab.eu/index.php/2010/09/03/writing-crypter-bypassing-antivirus-how-to-for-beginners/[^]
http://blog.emsisoft.com/2011/05/24/how-many-viruses-are-made-by-anti-virus-companies/[^]

You're not making a driver in C#. It would be easier to learn C/C++ and use the Driver SDK than it would to rewrite sections of the SDK in C# so you can make a driver in C#.

An application like this is not just a simple C# app and hoping that you can use a couple of events to trigger your code.

FAR, FAR from it.

The FileSystemWatcher watches the FILE SYSTEM, not the files in it. Since reading a file does not change the file system, there's nothing for the FileSystemWatcher to notify you of.

In order to write this, you need an in-depth knowledge of Windows internals and NTFS. I suggest start reading these:

Windows Internals - Part 1[^]
Windows Internals - Part 2[^]
Inside Windows Debugging[^] - because you're not going to be able to get away from using WinDbg.
Advanced Windows Debugging[^] - you ARE going to be doing kernel-level debugging for a project like this.