Entity Framework 4: auto relacionamento
10, fevereiro, 2010
Pessoal vamos ver como construir um auto relacionamento no Entity Framework 4 + POCOs.
1-Classes
1: public class Category
2: {
3: public virtual int CategoryId { get; set; }
4: public String Name { get; set; }
5: public virtual Category Parent { get; set; }
6:
7: }
Classe de categoria que possui uma auto-referencia
Pronto! todo o resto do código não é necessário.
2-Configuração
1: public class CategoryConfiguration : EntityConfiguration<Category>
2: {
3: public CategoryConfiguration()
4: {
5: Property(p => p.CategoryId).IsIdentity();
6: }
7: }
3-DataContext
1: public class DataContext
2: {
3:
4: public static Model FactoryDataContext()
5: {
6: String connection = @"Data Source=.\SQLEXPRESS;Initial Catalog=EFv4SelfReference;Integrated Security=SSPI;";
7: var builder = new ContextBuilder<Model>();
8: builder.Configurations.Add(new CategoryConfiguration());
9: return builder.Create(new SqlConnection(connection));
10: }
11:
12: public static void CreateDataBase()
13: {
14:
15: var ctx = FactoryDataContext();
16: if (ctx.DatabaseExists())
17: ctx.DeleteDatabase();
18: ctx.CreateDatabase();
19:
20: }
21:
22: }
4-Model
1: public class Model : ObjectContext
2: {
3: public Model(EntityConnection entityConnection)
4: : base(entityConnection)
5: {
6: DefaultContainerName = "Model";
7: }
8: public IObjectSet<Category> Categories
9: {
10: get { return base.CreateObjectSet<Category>(); }
11: }
12: }
5-Exemplo
1: class Program
2: {
3: static void Main(string[] args)
4: {
5: DataContext.CreateDataBase();
6: Category category1 = new Category();
7: category1.Parent = null;
8: category1.Name = "cat1";
9: category1.Parent = new Category() { Name = "Parent1" };
10:
11: Model model = DataContext.FactoryDataContext();
12: model.Categories.AddObject(category1);
13: model.SaveChanges();
14:
15: foreach (var category in model.Categories)
16: {
17: Console.WriteLine("Category Name:" + category.Name + "\n");
18: if (category.Parent != null)
19: Console.WriteLine("Parent Name:" + category.Parent.Name + "\n");
20: else
21: Console.WriteLine("Parent Name: --");
22:
23: Console.WriteLine("\n\n");
24:
25:
26: }
27:
28: Console.ReadKey();
29: }
30:
31:
32: }