在 WCF 数据服务中保存外键，但不保存整个对象
我正在使用 Silverlight 4、Entity Framework 4 和 WCF 数据服务。 假设我有一个 Playlist 对象。该播放列表对象具有属性和外键，外键由显示对象的 0 到 1 导航属性表示。数据库中有一个 Display_Id 列。
我试图保存播放列表并直接设置 display_id，而不从数据库加载整个显示对象（我从查询字符串中获取显示 id）。 我已经尝试过：
playlist.Display = new Display() { Id = 3136 };
// this SetLink throws an exception that the Display is not yet tracked
context.SetLink(playlist.Display, "Display", playlist);
// or i've tried, but get an error: Entities in 'EDM.Displays' participate in the //'DisplayX' relationship. 0 related 'X' were found. 1 'X' is expected
context.AddToDisplays(playlist.Display);
context.SetLink(playlist, "Display", playlist.Display);
我需要更改我的 EDM 还是有办法在客户端执行此操作？
I'm using Silverlight 4, Entity Framework 4 and WCF Data Services.
Say I have a Playlist object. That Playlist object has properties and a Foreign Key represented by a 0 to 1 navigation property to a Display Object. In the database there is a Display_Id column.
I'm trying to save the playlist and setting the display_id directly, without loading a whole display object from the database (I get the display id from the query string).
I've tried :
playlist.Display = new Display() { Id = 3136 };
// this SetLink throws an exception that the Display is not yet tracked
context.SetLink(playlist.Display, "Display", playlist);
// or i've tried, but get an error: Entities in 'EDM.Displays' participate in the //'DisplayX' relationship. 0 related 'X' were found. 1 'X' is expected
context.AddToDisplays(playlist.Display);
context.SetLink(playlist, "Display", playlist.Display);
Do I need to change my EDM or is there a way to do this on the client side?
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首先你需要将对象附加到ObjectSet
，它将在本地执行而无需调用数据库，然后你可以根据需要工作
还有另一种方法：对象播放列表包含对象DysplayReference，其属性EntityKey如果为null则创建它，否则只需替换key在 EntityKeyValues 中
first of all You need to attach object to ObjectSet
it would executed locally without calling database, and then you can work as you need
there is another way: object playlist contains object DysplayReference with property EntityKey if it's null then create it, else just replace key in EntityKeyValues