在实体框架中定义一对一关系

Question

I have a relationship that I'm not sure how to define, I'm quite new to SQL so I might have it wrong.

I have an Account which looks like this:

public class Account
{
    public int Id { get; set; }
    public string Username { get; set; }
    public LiveCurrencyInfo CurrencyInfo { get; set; }
}

And LiveCurrencyInfo:

public class LiveCurrencyInfo
{
    public int Id { get; set; }
    public decimal USD { get; set; }
}

Account needs to have a link to a single LiveCurrencyInfo entity.

LiveCurrencyInfo exists as a completely separate entity which doesn't depend on anything else - as it's defined.

Is this a 1..0 relationship?

I tried defining it like this but the syntax is wrong:

protected override void OnModelCreating(DbModelBuilder mb)
{
    mb.Entity<Account>()
        .HasRequired(l => l.CurrencyInfo)
        .Map(m =>                        //Can't call .Map here
        {
            m.MapLeftKey("AccountId");
            m.MapRightKey("LiveCurrencyInfoId");
            m.ToTable("UserAccountLiveCurrencyMapping");
        });
}

Edit

I think the tables would look like the following:

Accounts         LiveCurrencyInfo         UserAccountLiveCurrencyMapping

Id | Username    Id | USD                 AccountId | LiveCurrencyInfoId
---+---------    ---+------               ----------+-------------------
20 | User_1      39 | 1.0                 20        | 39

Answer 1

Is this a 1..0 relationship?

First you need to define the relationship ends (from -> to). But no, there is no such relationship at all.

According to your explanation, the relationship from LiveCurrencyInfo to Account is 1 -> 0..1 . Hence by EF terms LiveCurrencyInfo is the principal end and Account is the dependent end. Since as I understand both entities should have independent PKs, then Account would need FK column referencing LiveCurrencyInfo PK.

The fluent setup is as follows (in order to make Map and other relationship fluent APIs available, you need first to complete the relationship ends definition started by HasXyz with the appropriate WithXyz ):

mb.Entity<Account>()
    .HasRequired(e => e.CurrencyInfo)
    .WithOptional()
    .Map(m => m.MapKey("LiveCurrencyInfoId"));