EF中类EntityTypeConfiguration是一个很有用的类，在nopCommerence中就使用这个类来分文件分文件配置Model映射关系。今天我就来谈谈Repository模式在Entity Framework Code First中使用EntityTypeConfiguration的实现例子。

背景

为了简化我们就只使用两个表：分类表Category，产品类Product。最终项目结构如下：

注意：EfRepPatTest.Entity和EfRepPatTest.Data是类库项目，EfRepPatTest.Implementation是控制台项目。项目EfRepPatTest.Data需要对Entity Framework类库的引用。

BaseEntity.cs

创建一个所有实体的基类BaseEntity，把一些公共的属性封装在里面。

1. public class BaseEntity<T>
2. {
3. public T Id { get; set; }
4. }

这样表示所有实体都有一个字段为Id，类型为泛型这样可以满足所有类型的情况。

IRepository.cs:

下面定义一个泛型的接口IRepository，其中包括一个泛型的增、删、改。

1. public interface IRepository<TEntity> where TEntity:class
2. {
3. IQueryable<TEntity> GetAll();
4. TEntity GetById(object id);
5. void Insert(TEntity entity);
6. void Update(TEntity entity);
7. void Delete(TEntity entity);
8. }

Category.cs:

实体分类类

1. public class Category:BaseEntity<int>
2. {
3. public virtual string Name { get; set; }
4. public List<Product> Products { get; set; }
5. }

Product.cs:

实体产品类

1. public class Product:BaseEntity<long>
2. {
3. public virtual int CategoryId { get; set; }
4. public virtual Category Category { get; set; }
5. public virtual string Name { get; set; }
6. public virtual int MinimumStockLevel { get; set; }
7. }

IDbContext.cs:

接口IDbContext封装一些EF的公共接口方法。

1. public interface IDbContext
2. {
3. IDbSet<TEntity> Set<TEntity>() where TEntity:class;
4. int SaveChanges();
5. void Dispose();
6. }

DataContext.cs:

1. public class DataContext: DbContext,IDbContext
2. {
3. public new IDbSet<TEntity> Set<TEntity>() where TEntity : class
4. {
5. return base.Set<TEntity>();
6. }
7. }

CategoryMap.cs:

分类映射类继承于EntityTypeConfigureation<T>

1. public class CategoryMap:EntityTypeConfiguration<Category>
2. {
3. public CategoryMap()
4. {
5. ToTable("Category");
6. HasKey(c => c.Id).Property(c => c.Id).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
7. Property(c => c.Name).IsRequired().HasMaxLength(50);
8. }
9. }

ProductMap.cs:

产品类映射类继承于EntityTypeConfigureation<T>

1. public class ProductMap:EntityTypeConfiguration<Product>
2. {
3. public ProductMap()
4. {
5. ToTable("Product");
6. HasKey(p => p.Id).Property(p => p.Id).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
7. //CategoryId as foreign key
8. HasRequired(p => p.Category)
9. .WithMany(c=>c.Products)
10. .HasForeignKey(p => p.CategoryId);
11. Property(p => p.Name).IsRequired().HasMaxLength(100);
12. Property(p => p.MinimumStockLevel);
13. }
14. }

在类DataContext中重写OnModelCreating方法依次加上我们新建的EF的Map配置文件，加入以下代码：

1. modelBuilder.Configurations.Add(new CategoryMap());
2. modelBuilder.Configurations.Add(new ProductMap());
3. base.OnModelCreating(modelBuilder);

上面的代码可以优化一下，可以利用反射自动添加EF的Map配置文件，如下：

1. public class DataContext: DbContext,IDbContext
2. {
3. public new IDbSet<TEntity> Set<TEntity>() where TEntity : class
4. {
5. return base.Set<TEntity>();
6. }
7. protected override void OnModelCreating(DbModelBuilder modelBuilder)
8. {
9. var typesToRegister = Assembly.GetExecutingAssembly().GetTypes()
10. .Where(type => !String.IsNullOrEmpty(type.Namespace))
11. .Where(type => type.BaseType != null && type.BaseType.IsGenericType &&
12. type.BaseType.GetGenericTypeDefinition() == typeof(EntityTypeConfiguration<>));
13. foreach (var type in typesToRegister)
14. {
15. dynamicconfigurationInstance = Activator.CreateInstance(type);
16. modelBuilder.Configurations.Add(configurationInstance);
17. }
18. base.OnModelCreating(modelBuilder);
19. }
20. }

这样的好处是以后新加EF的实体Map类，不用修改DataContext。

RepositoryService.cs：

IRepositroy接口的一个具体实现的RepositoryService，数据访问采用EF的IDbContext。

1. public class RepositoryService<TEntity>:IRepository<TEntity> where TEntity:class
2. {
3. private IDbContext Context;
4. private IDbSet<TEntity> Entities
5. {
6. get { return this.Context.Set<TEntity>(); }
7. }
8. public RepositoryService(IDbContext context)
9. {
10. this.Context = context;
11. }
12. public IQueryable<TEntity> GetAll()
13. {
14. return Entities.AsQueryable();
15. }
16. public TEntity GetById(object id)
17. {
18. return Entities.Find(id);
19. }
20. public void Insert(TEntity entity)
21. {
22. Entities.Add(entity);
23. }
24. public void Update(TEntity entity)
25. {
26. if (entity == null)
27. throw new ArgumentNullException("entity");
28. this.Context.SaveChanges();
29. }
30. public void Delete(TEntity entity)
31. {
32. Entities.Remove(entity);
33. }
34. public void Dispose()
35. {
36. Dispose(true);
37. GC.SuppressFinalize(this);
38. }
39. protected virtual void Dispose(bool disposing)
40. {
41. if (disposing)
42. {
43. if (this.Context != null)
44. {
45. this.Context.Dispose();
46. this.Context = null;
47. }
48. }
49. }
50. }

新建一个类DataBaseInitializer为EF Code First数据库访问的初始化类。

1. public class DataBaseInitializer : IDatabaseInitializer<DataContext>
2. {
3. public void InitializeDatabase(DataContext context)
4. {
5. context.Database.CreateIfNotExists();
6. }
7. }

新建一个控制台程序来测试上面的代码Program.cs：

1. class Program
2. {
3. static void Main(string[] args)
4. {
5. var context = new DataContext();
6. var dataBaseInitializer = new DataBaseInitializer();
7. dataBaseInitializer.InitializeDatabase(context);
8. var categoryRepository = new RepositoryService<Category>(context);
9. //Adding category in the category entity
10. var category = new Category()
11. {
12. Name = "Baverage"
13. };
14. var products = new List<Product>();
15. //Adding product in the product entity
16. var product = new Product()
17. {
18. Name = "Soft Drink A",
19. MinimumStockLevel = 50
20. };
21. products.Add(product);
22. product = new Product()
23. {
24. Name = "Soft Drink B",
25. MinimumStockLevel = 30
26. };
27. products.Add(product);
28. category.Products = products;
29. //Insert category and save changes
30. categoryRepository.Insert(category);
31. context.SaveChanges();
32. ///
33. /For the next project we shall add Dependency Injection
34. But now we have add a Service layer for test manually//
35. ///
36. IProductService productRepository = new ProductService();
37. Console.WriteLine("\n");
38. Console.WriteLine("Product List:");
39. Console.WriteLine("-------------------------------------------------");
40. foreach (var product1 in productRepository.GetAll())
41. {
42. Console.WriteLine(string.Format("Product Name : {0}",product1.Name));
43. if (product1.Id == 9)
44. {
45. product1.Name = "Soft Drink AAA";
46. productRepository.Update(product1);
47. }
48. }
49. Console.WriteLine("Press any key to exit");
50. Console.ReadKey();
51. }
52. }

在配置文件添加数据库的链接。

App.config:

1. <?xml version="1.0" encoding="utf-8"?>
2. <configuration>
3. <configSections>
4. <!-- For more information
5. on Entity Framework configuration, visit
6. http://go.microsoft.com/fwlink/?LinkID=237468 -->
7. <section name="entityFramework"
8. type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection,
9. EntityFramework, Version=4.4.0.0, Culture=neutral,
10. PublicKeyToken=b77a5c561934e089"
11. requirePermission="false" />
12. </configSections>
13. <entityFramework>
14. <defaultConnectionFactory type="System.Data.Entity.Infrastructure.SqlConnectionFactory,
15. EntityFramework" />
16. </entityFramework>
17. <connectionStrings>
18. <add name="DataContext"
19. providerName="System.Data.SqlClient"
20. connectionString="Data
21. Source=YourSERVER;Initial Catalog=EfDBExistRepository;Integrated
22. Security=True;MultipleActiveResultSets=True;"/>
23. </connectionStrings>
24. </configuration>

注意：数据库链接结点名为“DataContext”，正好和我们自己写的类“DataContext”名字一样。这样EF框架就可以自动找到这个数据库链接信息。

参考：http://www.codeproject.com/Articles/561584/Repository-Pattern-with-Entity-Framework-using