连接两个表时的C＃实体框架

Question

I have some tables,using Entity Framework

UserTable

• UserID

BookTable

• BookID
• BookName

OwnTable

• UserID
• BookID

now I can use:

uw.ownRepository.GetData().where(v=>v.userid=1).select(o=>o.Book)

to get all the book I own.But If I want to get all the books , and note that whether the user own it or not

I have some solution

1.

select all the book, then for each one select once

stupid solution = ="

2.

    var s = from book in uw.bookRepository.GetData()                    
    join own in uw.ownRepository.GetData() on book.Id equals like.Id into ps
    from o in ps.DefaultIfEmpty()
    select new {bookName =book.name,IsOwn =o==null};

just some pseudocode.

I tried it and works fine.

But I'm wondering if there is another better solution

if I want to select a strong type like

    select new Book{bookName =book.name,bookType=book.bookType, IsOwn =o==null};

in this case , if I have many field in bookTable , i have to assign every field.

Does anybody have some idea?

Answer 1

This is really simple. You want all books so you want to start your lambda express on books entity. In the example here, I have selected an anonymous type. However, you can select your predefined type.

Books.GetData().Select(b=> new {name = b.BookName , DoIOwnThisBook = OwnTable.GetData().Where()})