存储库模式以及域模型与实体框架之间的映射

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问题描述

我的存储库处理丰富的域模型并为其提供持久性。我不想将贫乏的Entity Framework数据实体暴露给我的业务层，因此我需要在它们之间进行映射的方法。

My repositories deal with and provide persistence for a rich domain model. I do not want to expose the anemic, Entity Framework data entity to my business layers, so I need some way of mapping between them.

在大多数情况下，构建域数据实体中的模型实例需要使用参数化的构造函数和方法（因为它很丰富）。它不像属性/字段匹配那么简单。可以将AutoMapper用于相反的情况（映射到数据实体），但不能用于创建域模型。

In most cases, constructing a domain model instance from a data entity requires the use of parameterised constructors and methods (since it is rich). It is not as simple as a property/field match. AutoMapper could be used for the opposite situation (mapping to data entities) but not when creating domain models.

以下是我的存储库模式的核心。

Below is the core of my repository pattern.

EntityFrameworkRepository 类可使用两种通用类型：

The EntityFrameworkRepository class works with two generic types:

TDomainModel ：富域模型

TEntityModel ：实体框架数据实体

TDomainModel: The rich domain model
TEntityModel: The Entity Framework data entity

定义了两种抽象方法：

ToDataEntity（TDomainModel）：转换为数据实体（用于 Add（）和 Update（）方法）

ToDomainModel（TEntityModel） ：构造域模型（用于 Find（）方法）。

ToDataEntity(TDomainModel): To convert to data entities (for Add() and Update() methods)
ToDomainModel(TEntityModel): To construct domain models (for the Find() method).

这些方法的具体实现将定义相关存储库所需的映射。

Concrete implementations of these methods would define the mapping required for the repository in question.

public interface IRepository<T> where T : DomainModel
{
    T Find(int id);
    void Add(T item);
    void Update(T item);
}

public abstract class EntityFrameworkRepository<TDomainModel, TEntityModel> : IRepository<TDomainModel>
    where TDomainModel : DomainModel
    where TEntityModel : EntityModel
{
    public EntityFrameworkRepository(IUnitOfWork unitOfWork)
    {
        // ...
    }

    public virtual TDomainModel Find(int id)
    {
        var entity = context.Set<TEntityModel>().Find(id);

        return ToDomainModel(entity);
    }

    public virtual void Add(TDomainModel item)
    {
        context.Set<TEntityModel>().Add(ToDataEntity(item));
    }

    public virtual void Update(TDomainModel item)
    {
        var entity = ToDataEntity(item);

        DbEntityEntry dbEntityEntry = context.Entry<TEntityModel>(entity);

        if (dbEntityEntry.State == EntityState.Detached)
        {
            context.Set<TEntityModel>().Attach(entity);

            dbEntityEntry.State = EntityState.Modified;
        }
    }

    protected abstract TEntityModel ToDataEntity(TDomainModel domainModel);
    protected abstract TDomainModel ToDomainModel(TEntityModel dataEntity);
}

以下是存储库实现的基本示例：

public interface ICompanyRepository : IRepository<Company>
{
    // Any specific methods could be included here
}

public class CompanyRepository : EntityFrameworkRepository<Company, CompanyTableEntity>, ICompanyRepository
{
    protected CompanyTableEntity ToDataEntity(Company domainModel)
    {
        return new CompanyTable()
        {
            Name = domainModel.Name,
            City = domainModel.City
            IsActive = domainModel.IsActive
        };
    }

    protected Company ToDomainModel(CompanyTableEntity dataEntity)
    {
        return new Company(dataEntity.Name, dataEntity.IsActive)
        {
            City = dataEntity.City
        }
    }
}

问题：

一个公司可能由许多部门组成。如果要在获取 Company 时急切地从 CompanyRepository 加载它们，那么我在哪里定义部门和 DepartmentDataEntity ？

A Company might be composed of many Departments. If I want to eagerly load these from the CompanyRepository when fetching a Company then where would I define the mapping between a Department and a DepartmentDataEntity?

我可以提供更多映射 CompanyRepository 中的方法，但这很快就会变得混乱。

I could provide more mapping methods in the CompanyRepository, but this will soon get messy. There would soon be duplicated mapping methods across the system.

什么是更好的解决上述问题的方法？

What is a better approach to the above problem?

TEntityModel

存储库模式以及域模型与实体框架之间的映射

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