How to add role to user in default database created by mvc

Question

How can I convert this: 

 

RoleManager<IdentityRole> roleManager = new RoleManager<IdentityRole>(new RoleStore<IdentityRole>(new IdentityDbContext()));

UserManager<ApplicationUser> userManager = new UserManager<ApplicationUser>(new UserStore<ApplicationUser>(new ApplicationDbContext()));

roleManager.Create(new IdentityRole(RoleName));

ApplicationUser user = userManager.FindByEmail(UserName);

userManager.AddToRole(user.Id, RoleName);

 

to two dropdown lists and one button?

 

I want add role to user in default database. Thx 

 

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