How to Customize my Create Method in MVC

Hi,
I want to get Max(ID) + 1 from table and wan to update to the table at code behind because my ID is not incremental. My Create method is:
[HttpPost] [ValidateAntiForgeryToken] public ActionResult Create([Bind(Include = "ID,LastName,FirstMidName,EnrollmentDate,CountryID,Account_Code")] Studen ...