小巧玲瓏multimapping和左的連接

Question

鑑於這種測試：

public class Author 
    { 
     public int AuthorId { get; set; } 
     public List<Book> Books { get; set; } = new List<Book>(); 
    } 
    public class Book 
    { 
     public int BookId { get; set; }    
    } 
    [Fact] 
    public async Task DapperCollapseLeftJoin() 
    { 
     var sql = @"  select 1 as AuthorId, 1 as BookId 
        union select 1 as AuthorId, 2 as BookId 
        union select 2 as AuthorId, 3 as BookId 
        union select 2 as AuthorId, 4 as BookId"; 
     var authorsWithBooks = 
      (await AC.OpenConnection.QueryAsync<Author, Book, Author>(sql, 
       (author, book) => { author.Books.Add(book); return author; }, 
       splitOn: "AuthorId, BookId")).ToList(); 

     // fails because we're getting 4 author+book rows 
     Assert.Equal(2, authorsWithBooks.Count); 
    } 

爲精緻小巧的文件說multimapping地圖行至多個對象並沒有提及實際上倒塌的物體（會發生左/內部聯接那裏像什麼重複最左列值）。

有沒有一種巧妙的方式來實現這一點？

Answer 1

目前還沒有內置機制來進行這種展平，但在測試套件here中有一個示例。這不是非常漂亮，這是我想像作出更好的支持，但它從來沒有達到的事情清單的頂部。