public override void CreateRole(string roleName)
 {
     if (string.IsNullOrEmpty(roleName))
     {
         throw CreateArgumentNullOrEmptyException("roleName");
     }
     using (WebApp4Context context = new WebApp4Context())
     {
         dynamic role = context.Role.FirstOrDefault(Rl => Rl.RoleName == roleName);
         if (role != null)
         {
             throw new InvalidOperationException(string.Format("Role exists: {0}", roleName));
         }
         Role NewRole = new Role
         {
             //Id = Guid.NewGuid(),
             RoleName = roleName
         };
         NewRole.GenerateNewIdentity();
         context.Role.Add(NewRole);
         context.SaveChanges();
     }
 }