Asp.Net Design Pattern Studynotes -- Part1

let's start with an exampleto entry amazing OO world !

let's saynow we need to implement a small feature which need :

an entityclass: Product

businesslogic : List<Product>GetProductBy(Function<Product,bool> where);

Service : List<Product> GetProductBy(Function<Product,bool>where);

1st Version

Entity：

[csharp]

public classProduct{}

Logic：

[csharp]

public classProductRepositoryV1
    {

       public List<Product>GetProductBy(Func<Product,bool> where )
       {
           var products = newList<Product>();
           returnproducts.Where(where).ToList();
       }
    }

service：

[csharp]

classProductServiceV1
    {
        private ProductRepositoryV1 _productRespository;
        private List<Product>_cacheProduct ;

        public ProductServiceV1()
        {
            _productRespository = newProductRepositoryV1(); //1.instant
            _cacheProduct = newList<Product>();
        }

        public List<Product>GetProductListBy(Func<Product,bool> where)
        {
            var productInCache =_cacheProduct.Where(where);//3.in couple with BL
            if (!productInCache.Any())
            {
                var products =_productRespository.GetProductBy(where);
               _cacheProduct.AddRange(products); //2.also care about how to cache
                return products;
            }
            return productInCache.ToList();
        }

    }

But we cansee the deficiencies :

For 1stVersion (Original Version):

1.productServiceis in couple with ProductRepository .once productRespository changed method signature, service have to change code.

solution: depend onabstract but not on concrete implementation

2.code is untestable .which need data base ready , but if data base can not connect ,meaning can not be tested.

solution: decoupleservice from business class

3.do multiple things .

a. cache thedata ,b. provice service .c. instance the repository object .

solution : do only one thing .

ok, nowlet's fix it !

2nd version :

Entity: same with above .

business:

[csharp]

interface IProductRespository//added interface fordependency inversion
    {
        List<Product>GetProductBy(Func<Product, bool> where);
    }
class ProductRespositoryV2:IProductRespository
    {
        public List<Product>GetProductBy(Func<Product, bool> where)
        {
            var products = newList<Product>();
            returnproducts.Where(where).ToList();
        }
    }

补充：Web开发 , ASP.Net ,