Asp.net C# delete controller query is not working

Question

Hello Team,

this my query isn't working, userId reference CreatedBy Column 

public ActionResult DeleteUser(int UserId)
{
    try
    {
        ASPNETMASTERPOSTEntities db = new ASPNETMASTERPOSTEntities();
        var user = db.tblUsers.Find(UserId);
        user.IsActive = false;

        db.Entry(user).State = EntityState.Modified;
        db.SaveChanges();

        return Json(true, JsonRequestBehavior.AllowGet);
    }
    catch (Exception)
    {
        return Json(false, JsonRequestBehavior.AllowGet);
    }
}