EF4模型通过使用LINQ to实体

Question

使用我试图做一些同样的事情一个大EF4模型结果的外键引用，可在LINQ2SQL使用单独的dbml的完成。一个基本的问题，我遇到了，这很可能代表了我一个非常缺乏基本的LINQ to实体的知识，就是你怎么使用结果的引用来查找引用表中的对象？

例如，我有4个表即都通过外键连接在一起。

从概念上讲，我可以跳过所有使用foreach对结果引用的表，但它看起来很笨拙，下面的代码如何使用linq来代替？

  //Get book 
      var book= db.books.SingleOrDefault(d => d.bookId == 286); 

      //If no book, return 
      if (book == null) return null; 

      //Get the shelf associated with this book 
      List<shelf> slist = new List<shelf>(); 

      foreach (reading r in book.readings) 
      { 
       foreach (event re in r.events) 
       { 
        slist.Add(re); 
       } 
      } 
      List<event> bookevents = slist.Distinct().ToList(); 

      //Get the customers associated with the events 
      List<int> clist = new List<int>(); 

      foreach (event eb in bookevents) 
      { 
       var cust = db.customers.Where(c => c.customerID == eb.inID || c.customerID == eb.outID).ToList(); 
       clist.AddRange(cust.Select(c => c.customerID)); 
      } 

      //Return the list of customers 
      return clist; 

编辑： 我得到了它下降到3步，万一这张贴其他人遇到类似的问题。我欢迎对如何做到这一点更优雅

 //Get book 
     var book= db.books.SingleOrDefault(d => d.bookId == 286); 

     //If no book, return 
     if (book == null) return null; 

     //Get the bookevents associated with this book 
     var bookevents = (from reading in book.readings 
        select reading.events).SelectMany(e => e).Distinct(); 

     //Get the customers associated with the events 
     var clist = (from be in bookevents 
        from c in db.customers 
        where c.customerID == be.inID || c.customerID == be.outID 
        select c.customerID).ToList(); 

     //Return the list of customers 
     return clist; 

Answer 1

试试这个任何意见：

var distinctEvents = (from event in db.events 
       join reading in db.readings on event.readingID equals reading.readingID 
       where reading.bookID == 286 
       select event).Distinct(); 
       // if you want to see this bookID is present in Book table, you should add a join statement like "join book in db.books on reading.bookID == book.bookID" 
var custIdList = from c in db.customers 
       from event in distinctsEvents 
       where c.customerID == event.inID || c.customerID == be.outID 
       select c.customerID; 

return custIdList.ToList();