Configure more than one dbcontext in EF 7

I created a web starter application with VS 2015 ctp, and I would like to add an in-memory store to do some test, but when I try to read the data, I get this message

The data stores 'SqlServerDataStore' 'InMemoryDataStore' are available. A context can only be configured to use a single data store. Configure a data store by overriding OnConfiguring in your DbContext class or in the AddDbContext method when setting up services.

How can I do to create a second datastore? Now I have this row in the ConfigureService method

AddEntityFramework(Configuration)
  .AddSqlServer()
  .AddDbContext<ApplicationDbContext>()
  .AddInMemoryStore()
  .AddDbContext<WorkModel>( options => { options.UseInMemoryStore(persist: true); });

Edit: Looks like the scenario is not clear. I have the identy sql server dbcontext, and I want to add a second dbcontext, totally separated, that I want to run in memory. I'm looking how configure two different dbcontext, in this case using two different datastores.

The first one is the Identity ApplicationDbContext, and another is something like this:

public class WorkModel : DbContext
{

    public DbSet<Cliente> Clienti { get; set; }
    public DbSet<Commessa> Commesse { get; set; }

    protected override void OnModelCreating(ModelBuilder builder) {
        builder.Entity<Cliente>().Key(cli => cli.ClienteId);
        builder.Entity<Commessa>().Key(cli => cli.CommessaId);
    }
}

Or whatever custom dbcontext do you like