Question

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：来自LC的352 CID：191

我做错了什么导致CategoryID具有不同的值，具体取决于我LINQ的方式？它应该是191，而不是与LocalizedCategoryID相同的值。

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，其中包含一些不相关的内容：

[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; }
}

Answer 1

这（在Category课程中）看起来很奇怪：

[System.Data.Linq.Mapping.Association(Storage = "_LocalizedCategories",
    OtherKey = "LocalizedCategoryID" )] // ????
public ICollection<LocalizedCategory> LocalizedCategories

Category有一个LocalizedCategory的集合，这意味着在数据库中，表products_types_localized有一个外键CategoryID。那个字段应该是“OtherKey”。这个映射是如何生成的？

为什么我从EntitySet中获取不同的值，具体取决于我的LINQ方式？

1 个答案: