EF4 Code First tying to Membership Role's User

Playing with code first, and want to keep track of a user's state related to certain items. To contrive an example, let's say I've got

public class Currency
{ 
    public decimal Value {get;set开发者_运维知识库;}
    public string OldDude {get;set;}
}

public class UsersCurrencyAmount
{
    virtual public Currency {get;set;} //type of currency in my man-purse
    int quantity {get;set;}
    //how do I refer to MembershipUser here?
}

Do I use MembershipUser directly through some magic, or do I make something like a

public class User
{
    int UserId {get;}
    string UserName {get;}
}

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You shouldn't create a dependency from your domain model to the .NET Membership. You should have a User class in your domain. At a higher level in your application you could use the membership model (most likely through an abstraction) to implement authorization needs.