[LinqToSql - Mapeamento entre entidades] Como fazer o mapeamento entre entidades com #linq

MapeamentoEntreEntidades.cs

No LinqToSql, para mapear um relacionamento entre entidades, vamos usar o exemplo do relacionamento Category e SubCategory.

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1 - A subcategory que contém a chave estrangeira, deve conter um objeto "EntityRef<ProductCategory>" privado para ser armazenado a referência e um "Association" public, cujos Get e Set do Association apontam para o EntityRef.
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private EntityRef<ProductCategory> _ProductCategory;

        [Association(Storage = "_ProductCategory", ThisKey = "ProductCategoryID", IsForeignKey = true)]
        public ProductCategory ProductCategory
        {
            get { return this._ProductCategory.Entity; }
            set { this._ProductCategory.Entity = value; }
        }
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2 - A Category precisa informar um EntitySet que é a coleção de SubCategory
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	[Association(OtherKey = "ProductCategoryID")]
        public EntitySet<ProductSubcategory> ProductSubcategories { get; set; }