How to Show all Roles in Web Forms Application?

Hello, I am making a form to show all Roles in the AspNetRoles table. I see how it is done in AspnetIdentitySample but not getting it work on Web Forms App. Here is how i am doing..

private ApplicationDbContext context; private UserManager manager; public RoleManager roleManager; public ApplicationUser currentUser; public UserManager<ApplicationUser> UserManager { get; private set; } public RoleManager<IdentityRole> RoleManager { get; private set; } protected string SuccessMessage { get; private set; } public RolesList() { context = new ApplicationDbContext(); manager = new UserManager<ApplicationUser>(new UserStore<ApplicationUser>(context)); roleManager = new RoleManager<IdentityRole>(new RoleStore<IdentityRole>(context)); } public RolesList(UserManager<Applicati ...