可选的实体框架

Question

我有以下模型，我试图在 Request对象上将 Notification属性归为null或通知的ID。

但是，我不太确定如何使用流利的映射将其映射。HasOptional -> WithMany似乎是我可以获得的最接近的，但是我想确保Requests中的NotificationId列是唯一的。通过流利的映射完成此操作的最佳方法是什么？

public class Request
{
    public int RequestId { get; set; }
    public string Description { get; set; }
    public int? NotificationId { get; set; }
    public virtual Notification Notification { get; set; }
}
public class Notification
{
    public int NotificationId { get; set; }
    public string Description { get; set; }
    public DateTime CreateDate { get; set; }
}
public class RequestMap : EntityTypeConfiguration<Request>
{
    public RequestMap()
    {
        HasKey(x => x.RequestId);
        Property(x => x.Description).IsRequired().HasMaxLength(255);
        HasOptional(x => x.Notification)
            .WithWhat?
    }
}

Answer 1

使用hasoptional（x => x.notification）就足够了，您不需要WithMany

您没有很多Request，而Notification

public class Request
{
    public int RequestID { get; set; }
    public string Description { get; set; }
    public int? NotificationId { get; set; }
    public Notification Notification { get; set; }
}
public class Notification
{
    public int NotificationId { get; set; }
    public string Description { get; set; }
    public DateTime CreateDate { get; set; }
}
public class RequestMap : EntityTypeConfiguration<Request>
{
    public RequestMap()
    {
        HasKey(x => x.RequestID);
        Property(x => x.Description).IsRequired().HasMaxLength(255);
        HasOptional(x => x.Notification);
    }
}

和生成的迁移

public partial class initial : DbMigration
{
    public override void Up()
    {
        CreateTable(
            "dbo.Notifications",
            c => new
                {
                    NotificationId = c.Int(nullable: false, identity: true),
                    Description = c.String(),
                    CreateDate = c.DateTime(nullable: false),
                })
            .PrimaryKey(t => t.NotificationId);
        CreateTable(
            "dbo.Requests",
            c => new
                {
                    RequestID = c.Int(nullable: false, identity: true),
                    Description = c.String(nullable: false, maxLength: 255),
                    NotificationId = c.Int(),
                })
            .PrimaryKey(t => t.RequestID)
            .ForeignKey("dbo.Notifications", t => t.NotificationId)
            .Index(t => t.NotificationId);
    }       
    public override void Down()
    {
        DropForeignKey("dbo.Requests", "NotificationId", "dbo.Notifications");
        DropIndex("dbo.Requests", new[] { "NotificationId" });
        DropTable("dbo.Requests");
        DropTable("dbo.Notifications");
    }
}