如何在MVC3（实体框架）中创建存储库类？

Question

I created a project using MVC3 - Entity Framework . I like to use Repository Pattern together with it. I am new to repository pattern. Do I need to create ONE EACH Repository for each Model Class (classes which represent each table in the database) and within each repository do I have to write all the functions which will Insert, Update, Delete and Fetch record ?

Answer 1

You can create common repository which will have common methods, all other repositories will be it's children:

public class MyModelRepository : GenericRepository<MyModel>
{
   // extend
}

var MyModelRepository = new MyModelRepository();

See this , or google for "Generic Repository" :). If your don't need extended functionality for some model repository, then you can even not create repository class, instead do something like this:

var MyModelRepository = new GenericRepository<MyModel>();

Answer 2

Have an interface that represents the common operations between each repository. Ie Insert, Update, Delete and Fetch:

 public interface IRepository<T>
    {
        void Insert(T entity);
        void Delete(T entity);
        void Update(T entity);
        void Fetch(T entity);
    }

 public class Repository<T> : IRepository<T> 
   /// your implementation
 }

Then in each model you could define the repository to suit the context, for instance:

  var repository1 = new Repository<ModelType>(dataContext);
  repository1.Insert(obj);

  var repository2 = new Repository<DifferentModelType>(dataContext);
  repository2.Fetch(objects);

http://www.remondo.net/repository-pattern-example-csharp/

Answer 3

No you don't. You can implement a GenericRepository for all your classes and then override it if you need to add functions. First i am gonna show you the unit of work. Through this class you can access all the repositories. I have added to this example one generic and one overrided:

public class UnitOfWork
{
    FBDbContext context = new FBDbContext();

    public FBDbContext Context { get { return context;  } }

    private BlockRepository BlockRepository;        
    private GenericRepository<Category> CategoryRepository;                     

    #region RepositoryClasses
    public IBlockRepository blockRepository
    {
        get
        {
            if (this.BlockRepository == null)
                this.BlockRepository = new BlockRepository(context);
            return BlockRepository;
        }
    }        
    public IGenericRepository<Category> categoryRepository
    {
        get
        {
            if (this.CategoryRepository == null)
                this.CategoryRepository = new GenericRepository<Category>(context);
            return CategoryRepository;
        }
    }        
#endregion

    public void Save()
    {
        context.SaveChanges();
    }

}

Then you have the generic repository:

public class GenericRepository<TEntity>
{
    internal FBDbContext context;
    internal DbSet<TEntity> dbSet;

    public GenericRepository(FBDbContext context)
    {
        this.context = context;
        this.dbSet = context.Set<TEntity>();
    }

    public virtual TEntity Create()
    {
        return Activator.CreateInstance<TEntity>();
    }

    public IQueryable<TEntity> GetAll()
    {
        return dbSet;
    }
    //And all the functions you want in all your model classes...
}

and an example when you want to override the generic repository:

public class BlockRepository : GenericRepository<Block>
{
    public BlockRepository(FBDbContext context) : base(context) { }

    public IEnumerable<Block> GetByCategory(Category category)
    {
        return context.Blocks.Where(r => r.CategoryId == category.Id);
    }        
}