如何使用 fluent API 在两个表之间配置不同多重性的导航属性

Question

我是 Entity Framework 的新手，我正在尝试在 Code-First 项目中配置两个导航属性。

第一个属性是employee_pay_period(s) 的集合。每个employee_salary 有多个employee_pay_period(s)，每个employee_pay_period 有一个employee_salary。

employee_pay_period.employee_salary_id 是外键。

第二个属性employee_salary.employee_current_pay_period 有点棘手。它是一个指向当前employee_pay_period 的属性。因此，导航属性从一个employee_salary 到一个employee_pay_period。数据库中没有与第二个属性关联的外键，每个employee_salary 必须包含一个employee_current_pay_period。

如何使用 fluent API 正确映射这些属性。

public class employee_salary
{
    public employee_salary()
    {
        employee_pay_period = new HashSet<employee_pay_period>();
    }

    [Key]
    public int employee_salary_id { get; set; }

    public int? employee_current_pay_period_id { get; set; }

    public virtual employee_pay_period employee_current_pay_period { get; set; }

    public virtual ICollection<employee_pay_period> employee_pay_period { get; set; }

}



public partial class employee_pay_period
{

    [Key]
    public int employee_pay_period_id { get; set; }

    public int employee_salary_id { get; set; }

    public virtual employee_salary employee_salary { get; set; }
}

Answer 1

如果我理解正确，您希望 employee_salary 和 employee_pay_period 之间分别存在一对多的关系，而且 employee_salary 和当前 employee_pay_period 之间也是一对一关系

在OnModelCreating(ModelBuilder builder) 函数中是这样的（假设您已经设置了 fluentApi 上下文配置类的其余部分）：

builder.Entity<employee_salary>(e =>
{
    e.HasMany(s => s.employee_pay_period) // salary has many pay periods
        .WithOne(p => p.employee_salary) // pay period has one salary
        .HasForeignKey(p => p.employee_salary_id) // foreign key on pay period linking to a single salary id
        .OnDelete(DeleteBehavior.Restrict); // Or whatever the desired delete behaviour should be

    e.HasOne(s => s.employee_current_pay_period) // salary has one current pay period
        .WithOne(p => p.employee_salary) // pay period has one salary
        .HasForeignKey<employee_salary>(s => s.employee_current_pay_period_id) // foreign key on salary linking to a single current pay period id
        .OnDelete(DeleteBehavior.Restrict); // Or whatever the desired delete behaviour should be
}