如何实现资源库的FindAll（）方法？ [英] How to Implement Repository FindAll() Method?

问题描述

我有以下Repository模式。要求是查找所有帐户的主人的名字是Lijo。所以，我需要编写一个函数findAll。如何写这个功能呢？

约束是：

1）客户端BankAccountService不应该DBML_Project使用类。

2）我们不应该用GETALL方法reti​​reve帐户的完整列表，然后做一个过滤器。

注：我面对这个问题，当工作在这个问题<一href="http://stackoverflow.com/questions/11257484/polymorphism-is-orm-entity-a-domain-entity-or-data-entity">Polymorphism:是ORM实体域实体或实体的数据？

code

 命名空间ApplicationService_Bank
{
公共类BankAccountService
{
    RepositoryLayer.ILijosBankRepository accountRepository =新RepositoryLayer.LijosSimpleBankRepository（）;

    公共无效FreezeAllAccountsForUser（用户名字符串）
    {
        //不宜使用汇编DBML_Project。

        IEnumerable的＆LT; D​​omainEntitiesForBank.IBankAccount＆GT; accountsForUserWithNameLIJO = NULL;
        // accountsForUserWithNameLIJO = accountRepository.FindAll（P =＆GT; p.BankUser.Name ==Lijo）;
    }

}

}


命名空间RepositoryLayer
{
公共接口ILijosBankRepository
{
    名单＆LT; D​​omainEntitiesForBank.IBankAccount＆GT; GETALL（）;
    IEnumerable的＆LT; D​​BML_Project.BankAccount＆GT;的FindAll（System.Func＆LT; D​​BML_Project.BankAccount，布尔＆GT; predicate）;
    无效的SubmitChanges（）;
        }

公共类LijosSimpleBankRepository：ILijosBankRepository
{

    私人IBankAccountFactory bankFactory =新MySimpleBankAccountFactory（）;
    公共System.Data.Linq.DataContext上下文
    {
        得到;
        组;
    }

    公共虚拟目录＆LT; D​​omainEntitiesForBank.IBankAccount＆GT; GETALL（）
    {

        名单＆LT; D​​BML_Project.BankAccount＆GT; allItems = Context.GetTable＆LT; D​​BML_Project.BankAccount＆GT;（）了ToList（）;
        名单＆LT; D​​omainEntitiesForBank.IBankAccount＆GT; bankAccounts =新的名单，其中，DomainEntitiesForBank.IBankAccount＆GT;（）;
        的foreach（DBML_Project.BankAccount ACC在allItems）
        {
            DomainEntitiesForBank.IBankAccount theAccount = bankFactory.CreateAccount（acc.AccountType，acc.BankAccountID，acc.Status，acc.OpenedDate，acc.AccountOwnerID）;
            bankAccounts.Add（theAccount）;
        }
        返回bankAccounts;
    }


    公开的IEnumerable＆LT; D​​BML_Project.BankAccount＆GT;的FindAll（System.Func＆LT; D​​BML_Project.BankAccount，布尔＆GT; predicate）
    {
        //哪里
        VAR的结果= Context.GetTable＆LT; D​​BML_Project.BankAccount＆GT;（）式（predicate）。
        返回结果;
    }

    公共虚拟无效的SubmitChanges（）
    {
        Context.SubmitChanges（）;
    }

}

}
 

阅读：

1. <一个href="http://stackoverflow.com/questions/2876616/returning-ienumerablet-vs-iqueryablet/2876655#2876655">Returning IEnumerable的＆LT; T＆GT; VS IQueryable的＆LT; T＆GT;

2. <一个href="http://stackoverflow.com/questions/1507286/how-to-design-repository-pattern-to-be-easy-switch-to-another-orm-later?rq=1">how设计Repository模式很容易切换到另一个ORM以后呢？

解决方案

一个简单的方法是只建立手工查询：

 公共类SearchCriteria
{
    公共字符串名称{;组; }
    // ...更多
}

公开的IEnumerable＆LT;实体＆GT;的FindAll（SearchCriteria标准）
{
    IQueryable的＆LT;实体＆GT;实体= _datasource.Entities; //替换为L2S相当于

    如果（criteria.Name！= NULL）
        实体= entities.Where（E =＆GT; e.Name == criteria.Name）;

    // ...更多

    返回实体;
}
 

如果你不想直接返回生成的对象，映射到之前你一件事返回：

 返回地图（实体）; // IEnumerable的＆LT; CustomObject＆GT;地图（IEnumerable的＆LT;实体＆GT;实体）
 

I have the following Repository Pattern. Requirement is to "Find All accounts whose owner’s name is Lijo". So, I need to write a FindAll function. How to write this function?

Constraints are:

1) The client "BankAccountService" should not use classes from 'DBML_Project'.

2) We should NOT use GetAll method to retireve complete list of accounts and then do a filter.

Note: I confronted this problem while working on the question Polymorphism: Is ORM entity a Domain Entity or Data Entity?

CODE

namespace ApplicationService_Bank
{
public class BankAccountService
{
    RepositoryLayer.ILijosBankRepository accountRepository = new RepositoryLayer.LijosSimpleBankRepository();

    public void FreezeAllAccountsForUser(string userName)
    {
        //Should not use assembly 'DBML_Project'.

        IEnumerable<DomainEntitiesForBank.IBankAccount> accountsForUserWithNameLIJO = null;
        //accountsForUserWithNameLIJO = accountRepository.FindAll(p => p.BankUser.Name == "Lijo");
    }

}

}


namespace RepositoryLayer
{
public interface ILijosBankRepository
{
    List<DomainEntitiesForBank.IBankAccount> GetAll();
    IEnumerable<DBML_Project.BankAccount> FindAll(System.Func<DBML_Project.BankAccount, bool> predicate);
    void SubmitChanges();
        }

public class LijosSimpleBankRepository : ILijosBankRepository
{

    private IBankAccountFactory bankFactory = new MySimpleBankAccountFactory();
    public System.Data.Linq.DataContext Context
    {
        get;
        set;
    }

    public virtual List<DomainEntitiesForBank.IBankAccount> GetAll()
    {

        List<DBML_Project.BankAccount> allItems = Context.GetTable<DBML_Project.BankAccount>().ToList();
        List<DomainEntitiesForBank.IBankAccount> bankAccounts = new List<DomainEntitiesForBank.IBankAccount>();
        foreach (DBML_Project.BankAccount acc in allItems)
        {
            DomainEntitiesForBank.IBankAccount theAccount = bankFactory.CreateAccount(acc.AccountType, acc.BankAccountID, acc.Status, acc.OpenedDate, acc.AccountOwnerID);
            bankAccounts.Add(theAccount);
        }
        return bankAccounts;
    }


    public IEnumerable<DBML_Project.BankAccount> FindAll(System.Func<DBML_Project.BankAccount, bool> predicate)
    {
        //Where
        var results = Context.GetTable<DBML_Project.BankAccount>().Where(predicate);
        return results;
    }

    public virtual void SubmitChanges()
    {
        Context.SubmitChanges();
    }

}

}

READING:

1. Returning IEnumerable<T> vs IQueryable<T>

2. how to design Repository pattern to be easy switch to another ORM later?

解决方案

A simple approach is to just build the query by hand:

public class SearchCriteria
{
    public string Name { get; set; }
    // ...more
}

public IEnumerable<Entity> FindAll(SearchCriteria criteria)
{
    IQueryable<Entity> entities = _datasource.Entities; // replace with your L2S equivalent

    if (criteria.Name != null)
        entities = entities.Where(e => e.Name == criteria.Name);

    // ...more

    return entities;
}

If you don't want to return the generated objects directly, map to something else before you return:

return Map(entities); // IEnumerable<CustomObject> Map(IEnumerable<Entity> entities)

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