.Net Core MVC 网站开发（Ninesky） 2.3、项目架构调整(续)-使用配置文件动态注入

上次实现了依赖注入，但是web项目必须要引用业务逻辑层和数据存储层的实现，项目解耦并不完全；另一方面，要同时注入业务逻辑层和数据访问层，注入的服务直接写在Startup中显得非常臃肿。理想的方式是，web项目近引用接口而不引用实现，在配置文件中进行配置实现程序集合类，注入业务逻辑层而不必注入数据访问层。

一、数据访问层

在项目中摒弃数据访问层或者使用EntityFramework作为数据访问层。

在项目中数据访问层主要实现数据的存储，仔细看一下EntityFramework发现DbContext的功能完全实现了查、增、删、改等各种操作，并且有缓存等功能，本身就实现了仓储模式，并且比自己封装的数据存储层的功能还强大，干脆在项目中用EntityFramework作为数据存储层。删除掉Ninesky.InterfaceDataLibrary项目和Ninesky.DataLibrary项目。

注：项目结构调整的确实太频繁了，以后一段时间内绝不再调整了。

二、实现业务逻辑层。

添加业务逻辑层接口项目Ninesky.InterfaceBase

1、添加接口基类接口InterfaceBaseService，添加基本的查、增、删、改方法

using Ninesky.Models;
using System;
using System.Linq;
using System.Linq.Expressions;

namespace Ninesky.InterfaceBase
{
    /// <summary>
    ///  服务基础接口
    /// </summary>
    public interface InterfaceBaseService<T> where T:class
    {

        /// <summary>
        /// 添加
        /// </summary>
        /// <param name="entity">实体</param>
        /// <param name="isSave">是否立即保存</param>
        /// <returns>添加的记录数</returns>
        int Add(T entity, bool isSave = true);

        /// <summary>
        /// 添加[批量]
        /// </summary>
        /// <param name="entities">实体</param>
        /// <param name="isSave">是否立即保存</param>
        /// <returns>添加的记录数</returns>
        int AddRange(T[] entities, bool isSave = true);

        /// <summary>
        /// 查询记录数
        /// </summary>
        /// <param name="predicate">查询条件</param>
        /// <returns>记录数</returns>
        int Count(Expression<Func<T, bool>> predicate);

        /// <summary>
        /// 查询是否存在
        /// </summary>
        /// <param name="predicate">查询条件</param>
        /// <returns>是否存在</returns>
        bool Exists(Expression<Func<T, bool>> predicate);

        /// <summary>
        /// 查找
        /// </summary>
        /// <param name="Id">主键</param>
        /// <returns></returns>
        T Find(int Id);

        /// <summary>
        /// 查找
        /// </summary>
        /// <param name="keyValues">主键</param>
        /// <returns></returns>
        T Find(object[] keyValues);


        /// <summary>
        /// 查找
        /// </summary>
        /// <param name="predicate">查询条件</param>
        /// <returns></returns>
        T Find(Expression<Func<T, bool>> predicate);


        IQueryable<T> FindList<TKey>(int number, Expression<Func<T, bool>> predicate);

        /// <summary>
        /// 查询
        /// </summary>
        /// <typeparam name="TKey">排序属性</typeparam>
        /// <param name="number">显示数量[小于等于0-不启用]</param>
        /// <param name="predicate">查询条件</param>
        /// <param name="keySelector">排序</param>
        /// <param name="isAsc">正序</param>
        /// <returns></returns>
        IQueryable<T> FindList<TKey>(int number, Expression<Func<T, bool>> predicate, Expression<Func<T, TKey>> keySelector, bool isAsc);

        /// <summary>
        /// 查询[分页]
        /// </summary>
        /// <typeparam name="TKey">排序属性</typeparam>
        /// <param name="predicate">查询条件</param>
        /// <param name="keySelector">排序</param>
        /// <param name="isAsc">是否正序</param>
        /// <param name="paging">分页数据</param>
        /// <returns></returns>
        Paging<T> FindList<TKey>(Expression<Func<T, bool>> predicate, Expression<Func<T, TKey>> keySelector, bool isAsc, Paging<T> paging);

        /// <summary>
        /// 查询[分页]
        /// </summary>
        /// <typeparam name="TKey">排序属性</typeparam>
        /// <param name="predicate">查询条件</param>
        /// <param name="keySelector">排序</param>
        /// <param name="isAsc">是否正序</param>
        /// <param name="pageIndex">当前页</param>
        /// <param name="pageSize">每页记录数</param>
        /// <returns></returns>
        Paging<T> FindList<TKey>(Expression<Func<T, bool>> predicate, Expression<Func<T, TKey>> keySelector, bool isAsc, int pageIndex, int pageSize);

        /// <summary>
        /// 删除
        /// </summary>
        /// <param name="entity">实体</param>
        /// <param name="isSave">是否立即保存</param>
        /// <returns>是否删除成功</returns>
        bool Remove(T entity, bool isSave = true);

        /// <summary>
        /// 删除[批量]
        /// </summary>
        /// <param name="entities">实体数组</param>
        /// <param name="isSave">是否立即保存</param>
        /// <returns>成功删除的记录数</returns>
        int RemoveRange(T[] entities, bool isSave = true);


        /// <summary>
        ///  保存到数据库
        /// </summary>
        /// <returns>更改的记录数</returns>
        int SaveChanges();

        /// <summary>
        /// 更新
        /// </summary>
        /// <param name="entity">实体</param>
        /// <param name="isSave">是否立即保存</param>
        /// <returns>是否保存成功</returns>
        bool Update(T entity, bool isSave = true);

        /// <summary>
        /// 更新[批量]
        /// </summary>
        /// <param name="entities">实体数组</param>
        /// <param name="isSave">是否立即保存</param>
        /// <returns>更新成功的记录数</returns>
        int UpdateRange(T[] entities, bool isSave = true);

    }
}

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2、在Ninesky.Base中添加，接口InterfaceBaseService的实现类BaseService.cs

using Microsoft.EntityFrameworkCore;
using Ninesky.InterfaceBase;
using Ninesky.Models;
using System;
using System.Linq;
using System.Linq.Expressions;

namespace Ninesky.Base
{
    /// <summary>
    /// 服务基类
    /// </summary>
    public class BaseService<T>:InterfaceBaseService<T> where T:class
    {
        protected DbContext _dbContext;
        public BaseService(DbContext dbContext)
        {
            _dbContext = dbContext;
        }

        public virtual int Add(T entity, bool isSave = true)
        {
            _dbContext.Set<T>().Add(entity);
            if (isSave) return _dbContext.SaveChanges();
            else return 0;
        }

        public virtual int AddRange(T[] entities, bool isSave = true)
        {
            _dbContext.Set<T>().AddRange(entities);
            if (isSave) return _dbContext.SaveChanges();
            else return 0;
        }

        /// <summary>
        /// 查询记录数
        /// </summary>
        /// <param name="predicate">查询条件</param>
        /// <returns>记录数</returns>
        public virtual int Count(Expression<Func<T, bool>> predicate)
        {
            return _dbContext.Set<T>().Count(predicate);
        }

        /// <summary>
        /// 查询是否存在
        /// </summary>
        /// <param name="predicate">查询条件</param>
        /// <returns>是否存在</returns>
        public virtual bool Exists(Expression<Func<T, bool>> predicate)
        {
            return Count(predicate) > 0;
        }

        /// <summary>
        /// 查找
        /// </summary>
        /// <param name="Id">主键</param>
        /// <returns></returns>
        public virtual T Find(int Id)
        {
            return _dbContext.Set<T>().Find(Id);
        }

        public virtual T Find(object[] keyValues)
        {
            return _dbContext.Set<T>().Find(keyValues);
        }

        public virtual T Find(Expression<Func<T, bool>> predicate)
        {
            return _dbContext.Set<T>().SingleOrDefault(predicate);
        }

        public virtual IQueryable<T> FindList<TKey>(int number, Expression<Func<T, bool>> predicate)
        {
            var entityList = _dbContext.Set<T>().Where(predicate);
            if (number > 0) return entityList.Take(number);
            else return entityList;
        }

        public virtual IQueryable<T> FindList<TKey>(int number, Expression<Func<T, bool>> predicate, Expression<Func<T, TKey>> keySelector, bool isAsc)
        {
            var entityList = _dbContext.Set<T>().Where(predicate);
            if (isAsc) entityList = entityList.OrderBy(keySelector);
            else entityList.OrderByDescending(keySelector);
            if (number > 0) return entityList.Take(number);
            else return entityList;
        }


        public virtual Paging<T> FindList<TKey>(Expression<Func<T, bool>> predicate, Expression<Func<T, TKey>> keySelector, bool isAsc, Paging<T> paging)
        {
            var entityList = _dbContext.Set<T>().Where(predicate);
            paging.Total = entityList.Count();
            if (isAsc) entityList = entityList.OrderBy(keySelector);
            else entityList.OrderByDescending(keySelector);
            paging.Entities = entityList.Skip((paging.PageIndex - 1) * paging.PageSize).Take(paging.PageSize).ToList();
            return paging;
        }

        public virtual Paging<T> FindList<TKey>(Expression<Func<T, bool>> predicate, Expression<Func<T, TKey>> keySelector, bool isAsc, int pageIndex, int pageSize)
        {
            Paging<T> paging = new Paging<T> { PageIndex = pageIndex, PageSize = pageSize };
            return FindList(predicate, keySelector, isAsc, paging);
        }

        /// <summary>
        /// 删除
        /// </summary>
        /// <param name="entity">实体</param>
        /// <param name="isSave">是否立即保存</param>
        /// <returns>是否删除成功</returns>
        public virtual bool Remove(T entity, bool isSave = true)
        {
            _dbContext.Set<T>().Remove(entity);
            if (isSave) return _dbContext.SaveChanges() > 0;
            else return false;
        }

        /// <summary>
        /// 删除[批量]
        /// </summary>
        /// <param name="entities">实体数组</param>
        /// <param name="isSave">是否立即保存</param>
        /// <returns>成功删除的记录数</returns>
        public virtual int RemoveRange(T[] entities, bool isSave = true)
        {
            _dbContext.Set<T>().RemoveRange(entities);
            if (isSave) return _dbContext.SaveChanges();
            else return 0;
        }


        public virtual int SaveChanges()
        {
            return _dbContext.SaveChanges();
        }

        /// <summary>
        /// 更新
        /// </summary>
        /// <param name="entity">实体</param>
        /// <param name="isSave">是否立即保存</param>
        /// <returns>是否保存成功</returns>
        public virtual bool Update(T entity, bool isSave = true)
        {
            _dbContext.Set<T>().Update(entity);
            if (isSave) return _dbContext.SaveChanges() > 0;
            else return false;
        }

        /// <summary>
        /// 更新[批量]
        /// </summary>
        /// <param name="entities">实体数组</param>
        /// <param name="isSave">是否立即保存</param>
        /// <returns>更新成功的记录数</returns>
        public virtual int UpdateRange(T[] entities, bool isSave = true)
        {
            _dbContext.Set<T>().UpdateRange(entities);
            if (isSave) return _dbContext.SaveChanges();
            else return 0;
        }
    }
}

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3、在Ninesky.InterfaceBase项目中添加栏目接口InterfaceCategoryService.cs，新增了一个Findtree的方法

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Ninesky.Models;

namespace Ninesky.InterfaceBase
{
    /// <summary>
    /// 栏目服务接口
    /// </summary>
    public interface InterfaceCategoryService:InterfaceBaseService<Category>
    {
        /// <summary>
        /// 查找树形菜单
        /// </summary>
        /// <param name="categoryType">栏目类型，可以为空</param>
        /// <returns></returns>
        List<Category> FindTree(CategoryType? categoryType);
    }
}

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4、在Ninesky.Base中添加栏目接口的实现类CategoryService.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;
using Ninesky.Models;
using Ninesky.InterfaceBase;

namespace Ninesky.Base
{
    /// <summary>
    /// 栏目服务类
    /// </summary>
    public class CategoryService:BaseService<Category>,InterfaceCategoryService
    {
        public CategoryService(DbContext dbContext):base(dbContext)
        {
        }
        /// <summary>
        /// 查找
        /// </summary>
        /// <param name="Id">栏目ID</param>
        /// <returns></returns>
        public override Category Find(int Id)
        {
            return _dbContext.Set<Category>().Include("General").Include("Page").Include("Link").SingleOrDefault(c => c.CategoryId == Id);
        }

        /// <summary>
        /// 查找树形菜单
        /// </summary>
        /// <param name="categoryType">栏目类型，可以为空</param>
        /// <returns></returns>
        public List<Category> FindTree(CategoryType? categoryType)
        {
            var categories = _dbContext.Set<Category>().AsQueryable();
            //根据栏目类型分类处理
            switch (categoryType)
            {
                case null:
                    break;
                case CategoryType.General:
                    categories = categories.Where(c => c.Type == categoryType);
                    break;
                    //默认-Page或Link类型
                default:
                    //Id数组-含本栏目及父栏目
                    List<int> idArray = new List<int>();
                    //查找栏目id及父栏目路径
                    var categoryArray = categories.Where(c => c.Type == categoryType).Select(c => new { CategoryId = c.CategoryId, ParentPath = c.ParentPath });
                    if(categoryArray != null)
                    {
                        //添加栏目ID到
                        idArray.AddRange(categoryArray.Select(c => c.CategoryId));
                        foreach (var parentPath in categoryArray.Select(c=>c.ParentPath))
                        {
                            var parentIdArray = parentPath.Split(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries);
                            if (parentIdArray != null)
                            {
                                int parseId = 0;
                                foreach(var parentId in parentIdArray)
                                {
                                    if (int.TryParse(parentId, out parseId)) idArray.Add(parseId);
                                }
                            }
                        }
                    }
                    categories = categories.Where(c => idArray.Contains(c.CategoryId));
                    break;
            }
            return categories.OrderBy(c => c.ParentPath).ThenBy(C => C.Order).ToList();
        }
    }
}

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三、实现dll动态加载和注入

要在web项目中对实现类进行解耦和注入，那么项目只能对接口进行依赖，解除对实现的依赖，然后在配置文件中配置实现的程序集和注入的服务，在Startup类中读取配置文件并加载程序集，然后实现接口的注入。

1、解除实现类依赖

在Web项目中添加对Ninesky.InterfaceBase项目的引用，解除对Ninesky.Base项目的引用。

2、实现注入的配置文件

首先在Models项目中实现注入服务类型配置项ServiceItem

using Microsoft.Extensions.DependencyInjection;
using Newtonsoft.Json;
using Newtonsoft.Json.Converters;

namespace Ninesky.Models
{
    /// <summary>
    /// 注入服务配置
    /// </summary>
    public class ServiceItem
    {
        /// <summary>
        /// 服务类型[含命名空间]
        /// </summary>
        public string ServiceType { get; set; }

        /// <summary>
        /// 实现类类型[含命名空间]
        /// </summary>
        public string ImplementationType { get; set; }

        /// <summary>
        /// 生命周期
        /// </summary>
        [JsonConverter(typeof(StringEnumConverter))]
        public ServiceLifetime LifeTime { get; set; }
    }
}

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然后在Models项目中实现注入需要加载的程序集配置项 AssemblyItem

using System.Collections.Generic;

namespace Ninesky.Models
{
    /// <summary>
    /// 程序集注入项目
    /// </summary>
    public class AssemblyItem
    {
        /// <summary>
        ///  服务的程序集名称[不含后缀]
        /// </summary>
        public string ServiceAssembly { get; set; }
        /// <summary>
        /// 实现程序集名称[含后缀.dll]
        /// </summary>
        public string ImplementationAssembly { get; set; }

        /// <summary>
        /// 注入服务集合
        /// </summary>
        public List<ServiceItem> DICollections { get; set; }
    }
}

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添加配置文件

在Web项目中添加配置文件service.json

{
  "AssemblyCollections": [
    {
      "ServiceAssembly": "Ninesky.InterfaceBase",
      "ImplementationAssembly": "Ninesky.Base.dll",
      "DICollections": [
        {
          "ServiceType": "Ninesky.InterfaceBase.InterfaceCategoryService",
          "ImplementationType": "Ninesky.Base.CategoryService",
          "LifeTime": "Scoped"
        }
      ]
    }
  ]
}

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可以看到配置文件的键值对于AssemblyItem类和ServiceItem类对应。集合的服务程序集为Ninesky.InterfaceBase，实现程序集为Ninesky.Base.dll，注入的服务为Ninesky.InterfaceBase.InterfaceCategoryService，实现类是Ninesky.Base.CategoryService。

读取配置文件并绑定到类型

在Startup只需要一行到即可绑定配置到类型。读取配置文件并绑定的详细操作见《Asp.Net Core自定义配置并绑定》

var assemblyCollections =  new ConfigurationBuilder().SetBasePath(Directory.GetCurrentDirectory()).AddJsonFile("service.json").Build().GetSection("AssemblyCollections").Get<List<AssemblyItem>>();

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3、进行注入

在assemblyCollections变量加载了配置文件后使用如下代码即可实现注入

            foreach(var assembly in assemblyCollections)
            {
                var serviceAssembly = Assembly.Load(new AssemblyName(assembly.ServiceAssembly));
                var implementationAssembly = AssemblyLoadContext.Default.LoadFromAssemblyPath(AppContext.BaseDirectory + "//" + assembly.ImplementationAssembly);
                foreach(var service in assembly.DICollections)
                {
                    services.Add(new ServiceDescriptor(serviceAssembly.GetType(service.ServiceType), implementationAssembly.GetType(service.ImplementationType), service.LifeTime));
                }
            }

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代码中可以看到加载接口程序集使用的方法是Assembly.Load(new AssemblyName(assembly.ServiceAssembly))，这是因为项目引用了接口程序集的项目，加载程序集的时候只需要提供程序集的名称就可以。

加载实现类所在程序集的时候使用的是AssemblyLoadContext.Default.LoadFromAssemblyPath(AppContext.BaseDirectory + "//" + assembly.ImplementationAssembly)。在.Net Core中Assembly没有了LoadFrom方法，仅有一个Load方法加载已引用的程序集。多方搜索资料才找到AssemblyLoadContext中有一个方法可以不需要引用项目可以动态加载Dll，但必须包含Dll的完整路径。

到这里就完整实现了解耦，现在项目结构看起来是这样子