在调试此线程中的问题时：InvalidCastException when querying nested collection with LINQ我发现我的 Category EntitySet 的填充方式有问题。选择一个类别并抛出此异常以查看发生了什么后，我得到了这个：
throw new Exception("CID: " + cat.CategoryID +
" LCID: " + cat.LocalizedCategories.First().LocalizedCategoryID +
" CID from LC: " + cat.LocalizedCategories.First().Category.CategoryID);
CID：352 LCID：352 来自 LC 的 CID：191
我做错了什么导致 CategoryID 具有不同的值，具体取决于我对它的 LINQ 方式？它应该是 191，并且与 LocalizedCategoryID 的值不同。
这是我用来获取类别的代码：
int categoryId = 352; // In reality this comes from a parameter and is supposed
// to be 191 to get the Category.
var cat = categoriesRepository.Categories.First(c => c.CategoryID == categoryId);
这是我的域对象，去掉了一些不相关的东西：
[Table(Name = "products")]
public class Product
{
[HiddenInput(DisplayValue = false)]
[Column(Name = "id", IsPrimaryKey = true, IsDbGenerated = true, AutoSync = AutoSync.OnInsert)]
public int ProductID { get; set; }
[Required(ErrorMessage = "Please enter a product name")]
[Column]
public string Name { get; set; }
[Required(ErrorMessage = "Please enter a description")]
[DataType(DataType.MultilineText)]
[Column(Name = "info")]
public string Description { get; set; }
private EntitySet<Category> _Categories = new EntitySet<Category>();
[System.Data.Linq.Mapping.Association(Storage = "_Categories", OtherKey = "CategoryID")]
public ICollection<Category> Categories
{
get { return _Categories; }
set { _Categories.Assign(value); }
}
}
[Table(Name = "products_types")]
public class Category
{
[HiddenInput(DisplayValue = false)]
[Column(Name = "id", IsPrimaryKey = true, IsDbGenerated = true, AutoSync = AutoSync.OnInsert)]
public int CategoryID { get; set; }
public string NameByCountryId(int countryId)
{
return _LocalizedCategories.Single(lc => lc.CountryID == countryId).Name;
}
private EntitySet<LocalizedCategory> _LocalizedCategories = new EntitySet<LocalizedCategory>();
[System.Data.Linq.Mapping.Association(Storage = "_LocalizedCategories", OtherKey = "LocalizedCategoryID")]
public ICollection<LocalizedCategory> LocalizedCategories
{
get { return _LocalizedCategories; }
set { _LocalizedCategories.Assign(value); }
}
private EntitySet<Product> _Products = new EntitySet<Product>();
[System.Data.Linq.Mapping.Association(Storage = "_Products", OtherKey = "ProductID")]
public ICollection<Product> Products
{
get { return _Products; }
set { _Products.Assign(value); }
}
}
[Table(Name = "products_types_localized")]
public class LocalizedCategory
{
[HiddenInput(DisplayValue = false)]
[Column(Name = "id", IsPrimaryKey = true, IsDbGenerated = true, AutoSync = AutoSync.OnInsert)]
public int LocalizedCategoryID { get; set; }
[Column(Name = "products_types_id")]
private int CategoryID;
private EntityRef<Category> _Category = new EntityRef<Category>();
[System.Data.Linq.Mapping.Association(Storage = "_Category", ThisKey = "CategoryID")]
public Category Category
{
get { return _Category.Entity; }
set { _Category.Entity = value; }
}
[Column(Name = "country_id")]
public int CountryID { get; set; }
[Column]
public string Name { get; set; }
}