小巧玲珑multimapping和左的连接

Question

鉴于这种测试：

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); 
    } 

为精致小巧的文件说multimapping地图行至多个对象并没有提及实际上倒塌的物体（会发生左/内部联接那里像什么重复最左列值）。

有没有一种巧妙的方式来实现这一点？

Answer 1

目前还没有内置机制来进行这种展平，但在测试套件here中有一个示例。这不是非常漂亮，这是我想像作出更好的支持，但它从来没有达到的事情清单的顶部。