Linq返回IEnumerable <T>

我希望返回可枚舉項目以綁定嵌套網格。頂部網格顯示書名，嵌套網格顯示該書的作者列表。Linq返回IEnumerable <T>

作者收集

static public Author[] Authors = 
{ 
    new Author {FirstName="Johnny", LastName="Good"}, 
    new Author {FirstName="Graziella", LastName="Simplegame"}, 
    new Author {FirstName="Octavio", LastName="Prince"}, 
    new Author {FirstName="Jeremy", LastName="Legrand"} 
}

藏書

static public Book[] Books = 
{ 
    new Book 
    { 
     Title="Funny Stories", 
     Publisher=Publishers[0], 
     Authors=new[]{Authors[0], Authors[1]}, 
     PageCount=101, 
     Price=25.55M, 
     PublicationDate=new DateTime(2004, 11, 10), 
     Isbn="0-000-77777-2", 
     Subject=Subjects[0] 
    }, 
    new Book 
    { 
     Title="LINQ rules", 
     Publisher=Publishers[1], 
     Authors=new[]{Authors[2]}, 
     PageCount=300, 
     Price=12M, 
     PublicationDate=new DateTime(2007, 9, 2), 
     Isbn="0-111-77777-2", 
     Subject=Subjects[0] 
    }, 

    new Book 
    { 
     Title="C# on Rails", 
     Publisher=Publishers[1], 
     Authors=new[]{Authors[2]}, 
     PageCount=256, 
     Price=35.5M, 
     PublicationDate=new DateTime(2007, 4, 1), 
     Isbn="0-222-77777-2", 
     Subject=Subjects[0] 
    }, 
    new Book 
    { 
     Title="All your base are belong to us", 
     Publisher=Publishers[1], 
     Authors=new[]{Authors[3]}, 
     PageCount=1205, 
     Price=35.5M, 
     PublicationDate=new DateTime(2006, 5, 5), 
     Isbn="0-333-77777-2", 
     Subject=Subjects[2] 
    }, 
    new Book 
    { 
     Title="Bonjour mon Amour", 
     Publisher=Publishers[0], 
     Authors=new[]{Authors[1], Authors[0]}, 
     PageCount=50, 
     Price=29M, 
     PublicationDate=new DateTime(1973, 2, 18), 
     Isbn="2-444-77777-2", 
     Subject=Subjects[1] 
    } 
};

1）如何編寫可以返回以下查詢可枚舉的方法？

（ofcourse我的實現是錯誤的）

public IEnumerable<Book> GetBook() 
{ 
    IEnumerable<Book> booklist 
    = from book in SampleData.Books 
      select new Book 
      { 
      Title = book.Title, 
      Authors = 
         from author in SampleData.Authors 
         where book.Authors == author 
         select new Author 
         { 
         FirstName = author.FirstName 
         } 
      }; 
    return booklist; 
}

2）我收到輸出（嵌套的BulletedList未充滿作者的名字）。

我懷疑問題出在

where book.Authors == author (checking Types with == operator).

HTML代碼

<asp:GridView ID="GridView2" runat="server" AutoGenerateColumns="False"> 
    <Columns> 
      <asp:TemplateField HeaderText="Author List"> 
       <ItemTemplate> 
         <asp:BulletedList ID="BulletedList1" runat="server" 
         DataSource='<%# Eval("Authors") %>'> 
         </asp:BulletedList> 
       </ItemTemplate> 
      </asp:TemplateField> 
      <asp:BoundField DataField="Title" HeaderText="Title" 
      SortExpression="Title" /> 
     </Columns> 
</asp:GridView>

如何提高編碼，以獲得正確的結果？

來源

2009-12-15 Dilson

相反的：

where book.Authors == author

你應該這樣做：

where book.Authors.Contains(author)

顯然==不起作用，因爲您將一位作者與作者集進行比較。您想檢查本書的作者集合是否包含指定的作者。

來源

2009-12-15 19:01:33

而不是使用Eval（「Authors」），使用Eval（「Authors.FirstName」）。

此外，您不需要書籍和作者之間的聯接。您可以從書對象中選擇.Authors屬性。（我認爲作者實際上是一個錯字，它應該是「作者」在這種情況下？）

來源

2009-12-15 18:58:54

Linq返回IEnumerable <T>

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