在实体框架中使用多对多关系出现错误

Question

我有两个名为Buttons和Tiles的表，它们具有如下的多对多关系:

Buttons            *-----------
    ButtonID                  |
    Title                     |
                              |
Tiles              *-----------
    TileID
    Title

现在我试着像这样查询它:

b = new ObservableCollection<Buttons>(from x in db.Buttons
                                      where x.Tile == SelectedTileObj
                                      select x);

但是我得到如下所述的错误:

Unable to create a constant value of type 'Data.Tiles'.
Only primitive types or enumeration types are supported in this context.

Answer 1

假设TileID是主键，您可以采用另一种方法:

• 选择你感兴趣的贴图(有正确的id)

• 使用导航属性，获得与上述磁贴相关联的按钮

  var tiles = db.Tiles.Where(t => t.TileId == SelectedTileObj.TileId);
// t.Buttons should be the navigation property for retrieving associated buttons
var buttons = tiles.SelectMany(t => t.Buttons);
var b = new ObservableCollection<Buttons>(b);