使用自定義表和字段名稱時如何在EF Core中建立關系模型

Question

我正在嘗試使用EF Core對現有MsSQL Db中的兩個表之間的關系進行建模，但是Db的表具有使用自定義表名和列名的表。

即使我使用屬性或FluentAPI指定關系，EF Core也無法建立關系。

我認為問題是因為我有表和列的非常規名稱，並且EF無法正確設置關系。

這是SQL：

CREATE TABLE paid_authors
(
    paid_author_id varchar(50) NOT NULL,
    [name] varchar(50) NOT NULL
)

CREATE TABLE hardback_books
(
    hardback_book_id uniqueidentifier NOT NULL,
    paid_author_id varchar(50) NOT NULL,
    title varchar(50) NOT NULL
)

INSERT INTO paid_authors VALUES ('duck' ,'Scrooge McDuck')
INSERT INTO hardback_books VALUES (NEWID(), 'duck', 'Duck Tales')

這是C＃建模：

[Table("paid_authors")]
public class PaidAuthor
{        
    [Key]
    [Column("paid_author_id")]
    public string PaidAuthorId { get; set; }

    [Column("name")]
    public string Name { get; set; }

    public virtual List<HardbackBook> HardbackBooks { get; set; }
}

[Table("hardback_books")]
public class HardbackBook
{
    [Key]
    [Column("hardback_book_id")]
    public Guid HardbackBookId { get; set; }

    [Column("title")]
    public string Title { get; set; }

    [ForeignKey("HardbackBooks")] // This could be wrong!
    [Column("paid_author_id")]
    public string PaidAuthorId {get; set;}
}

我的代碼：

foreach(var author in context.PaidAuthors.Take(10))
{
    // This next line makes it work, but it shouldn’t be needed!
    // author.HardbackBooks = context.HardbackBooks.Where(x => x.PaidAuthorId == author.PaidAuthorId).ToList();

    Console.WriteLine(author.PaidAuthorId + " - " + author.Name);
    Console.WriteLine(author.HardbackBooks.Count);
}

當我運行代碼時，我得到System.NullReferenceException和author.HardbackBooks為null。

我已經嘗試過FluentAPI，在父類上指定ForeignKey……但是肯定有些明顯的東西我不見了！ 如果可以在此工作，我很樂意切換到FluentAPI。

不用說，我無法更改Db結構... :-(

Answer 1

您不能將集合Navigation Property保留為空，並且在書上應該具有反向Navigation屬性。 就像是：

[Table("paid_authors")]
public class PaidAuthor
{
    [Key]
    [Column("paid_author_id")]
    public string PaidAuthorId { get; set; }

    [Column("name")]
    public string Name { get; set; }

    public virtual List<HardbackBook> HardbackBooks { get; } = new HashSet<HardbackBook>();
}

[Table("hardback_books")]
public class HardbackBook
{
    [Key]
    [Column("hardback_book_id")]
    public Guid HardbackBookId { get; set; }

    [Column("title")]
    public string Title { get; set; }

    public PaidAuthor PaidAuthor { get; set; }

    [ForeignKey("PaidAuthor")] 
    [Column("paid_author_id")]
    public string PaidAuthorId { get; set; }
}