為什麼要使用泛型倉儲？好處是？前兩章在autofac註入的時候，用的User類作為例子，寫了增刪改查四個介面，也就是倉儲的GRUD。當我們再添加一個實體（比如Student）時，StudentRepository跟UserRepository代碼幾乎一樣的代碼，重覆量很大，為了減少冗餘、提高工作 ...

為什麼要使用泛型倉儲？好處是？

前兩章在autofac註入的時候，用的User類作為例子，寫了增刪改查四個介面，也就是倉儲的GRUD。

當我們再添加一個實體（比如Student）時，StudentRepository跟UserRepository代碼幾乎一樣的代碼，重覆量很大，為了減少冗餘、提高工作效率，使用泛型倉儲最好不過了

好處：

減少代碼冗餘

提高了開發人員的工作效率

提高對資料庫訪問的維護

一、泛型倉儲介面和泛型倉儲實現類

泛型倉儲介面

在類庫項目上右鍵->添加->新建文件夾，命名為Repository，存放泛型倉儲類。在Repository文件夾下麵新建泛型倉儲介面類：IRepository，如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using NetCoreWebApi.Repository.Dto;

namespace NetCoreWebApi.Repository.Repository
{
    public interface IRepository<T> where T : class
    {
        /// <summary>
        /// 添加實體(單個)
        /// </summary>
        /// <param name="entity">實體對象</param>
        int Add(T entity);

        /// <summary>
        /// 批量插入實體(多個)
        /// </summary>
        /// <param name="list">實體列表</param>
        int AddRange(List<T> list);

        /// <summary>
        /// 刪除實體(單個)
        /// </summary>
        /// <param name="entity"></param>
        int Remove(T entity);

        /// <summary>
        /// 批量刪除實體(多個)
        /// </summary>
        /// <param name="list">實體列表</param>
        int RemoveRange(List<T> list);
        /// <summary>
        /// 獲取所有 
        /// </summary>
        /// <returns></returns>
        IQueryable<T> GetAll();
        /// <summary>
        /// 分頁條件查詢
        /// </summary>
        /// <typeparam name="TKey">排序類型</typeparam>
        /// <param name="pageIndex">當前頁</param>
        /// <param name="pageSize">每頁大小</param>
        /// <param name="predicate">條件表達式</param>
        /// <param name="isAsc">是否升序排列</param>
        /// <param name="keySelector">排序表達式</param>
        /// <returns></returns>
        Page<T> SearchFor<TKey>(int pageIndex, int pageSize, Expression<Func<T, bool>> predicate,
            bool isAsc, Expression<Func<T, TKey>> keySelector);
        /// <summary>
        /// 獲取實體（主鍵）
        /// </summary>
        /// <param name="id">主鍵id</param>
        /// <returns></returns>
        T GetModelById(object id);
        /// <summary>
        /// 獲取實體（條件）
        /// </summary>
        /// <param name="predicate">條件表達式</param>
        /// <returns></returns>
        T GetModel(Expression<Func<T, bool>> predicate);
        /// <summary>
        /// 查詢記錄數
        /// </summary>
        /// <param name="predicate">條件表達式</param>
        /// <returns>記錄數</returns>
        int Count(Expression<Func<T, bool>> predicate);
        /// <summary>
        /// 是否存在
        /// </summary>
        /// <param name="anyLambda">查詢表達式</param>
        /// <returns>布爾值</returns>
        bool Exist(Expression<Func<T, bool>> anyLambda);
    }
}

泛型倉儲實現類

在Repository文件夾下麵新建泛型倉儲實現類：Repository，並繼承IRepository，如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using Microsoft.EntityFrameworkCore;
using NetCoreWebApi.Model;
using NetCoreWebApi.Repository.Dto;

namespace NetCoreWebApi.Repository.Repository
{
    public class Repository<T> : IRepository<T> where T : class
    {
        private readonly MyDbContext _dbContext;
        private DbSet<T> _entity;

        /// <summary>
        /// 構造函數
        /// </summary>
        /// <param name="dbContext"></param>
        public Repository(MyDbContext dbContext)
        {
            _dbContext = dbContext;
        }
        private DbSet<T> Entity => _entity ?? (_entity = _dbContext.Set<T>());
        /// <summary>
        /// 添加實體(單個)
        /// </summary>
        /// <param name="entity">實體對象</param>
        public int Add(T entity)
        {
            Entity.Add(entity);
            return _dbContext.SaveChanges();
        }
        /// <summary>
        /// 批量插入實體(多個)
        /// </summary>
        /// <param name="list">實體列表</param>
        public int AddRange(List<T> list)
        {
            Entity.AddRange(list);
            return _dbContext.SaveChanges();
        }

        /// <summary>
        /// 刪除實體(單個)
        /// </summary>
        /// <param name="entity"></param>
        public int Remove(T entity)
        {
            Entity.Remove(entity);
            return _dbContext.SaveChanges();
        }
        /// <summary>
        /// 批量刪除實體(多個)
        /// </summary>
        /// <param name="list">實體列表</param>
        public int RemoveRange(List<T> list)
        {
            Entity.RemoveRange(list);
            return _dbContext.SaveChanges();
        }
        /// <summary>
        /// 獲取所有
        /// </summary>
        /// <returns></returns>
        public IQueryable<T> GetAll()
        {
            return Entity.AsQueryable().AsNoTracking();
        }
        /// <summary>
        /// 條件查詢
        /// </summary>
        /// <typeparam name="TKey">排序類型</typeparam>
        /// <param name="pageIndex">當前頁</param>
        /// <param name="pageSize">每頁大小</param>
        /// <param name="isAsc">是否升序排列</param>
        /// <param name="predicate">條件表達式</param>
        /// <param name="keySelector">排序表達式</param>
        /// <returns></returns>
        public Page<T> SearchFor<TKey>(int pageIndex, int pageSize, Expression<Func<T, bool>> predicate, bool isAsc,
            Expression<Func<T, TKey>> keySelector)
        {
            if (pageIndex <= 0 || pageSize <= 0) throw new Exception("pageIndex或pageSize不能小於等於0");
            var page = new Page<T> { PageIndex = pageIndex, PageSize = pageSize };
            var skip = (pageIndex - 1) * pageSize;
            var able = Entity.AsQueryable().AsNoTracking();
            if (predicate == null)
            {
                var count = Entity.Count();
                var query = isAsc
                    ? able.OrderBy(keySelector).Skip(skip).Take(pageSize)
                    : able.OrderByDescending(keySelector).Skip(skip).Take(pageSize);
                page.TotalRows = count;
                page.LsList = query.ToList();
                page.TotalPages = page.TotalRows / pageSize;
                if (page.TotalRows % pageSize != 0) page.TotalPages++;
            }
            else
            {
                var queryable = able.Where(predicate);
                var count = queryable.Count();
                var query = isAsc
                    ? queryable.OrderBy(keySelector).Skip(skip).Take(pageSize)
                    : queryable.OrderByDescending(keySelector).Skip(skip).Take(pageSize);
                page.TotalRows = count;
                page.LsList = query.ToList();
                page.TotalPages = page.TotalRows / pageSize;
                if (page.TotalRows % pageSize != 0) page.TotalPages++;
            }
            return page;
        }
        /// <summary>
        /// 獲取實體
        /// </summary>
        /// <param name="id">主鍵id</param>
        /// <returns></returns>
        public T GetModelById(object id)
        {
            return Entity.Find(id);
        }

        /// <summary>
        /// 獲取實體（條件）
        /// </summary>
        /// <param name="predicate">條件表達式</param>
        /// <returns></returns>
        public T GetModel(Expression<Func<T, bool>> predicate)
        {
            return Entity.FirstOrDefault(predicate);
        }
        /// <summary>
        /// 查詢記錄數
        /// </summary>
        /// <param name="predicate"></param>
        /// <returns></returns>
        public int Count(Expression<Func<T, bool>> predicate)
        {
            return predicate != null ? Entity.Where(predicate).Count() : Entity.Count();
        }
        /// <summary>
        /// 是否存在
        /// </summary>
        /// <param name="anyLambda"></param>
        /// <returns></returns>
        public bool Exist(Expression<Func<T, bool>> anyLambda)
        {
            return Entity.Any(anyLambda);
        }
    }
}

分頁Page類

using System.Collections.Generic;

namespace NetCoreWebApi.Repository.Dto
{
    public class Page<T>
    {
        /// <summary>
        /// 當前頁
        /// </summary>
        public int PageIndex { get; set; }
        /// <summary>
        /// 總頁數
        /// </summary>
        public int TotalPages { get; set; }
        /// <summary>
        /// 集合總數
        /// </summary>
        public int TotalRows { get; set; }
        /// <summary>
        /// 每頁項數
        /// </summary>
        public int PageSize { get; set; }
        /// <summary>
        /// 集合
        /// </summary>
        public IList<T> LsList { get; set; }
    }
}

二、倉儲的泛型的依賴註入。

修改Startup.cs啟動類中ConfigureServices方法

        public static IContainer ApplicationContainer { get; set; }
        /// <summary>
        /// //負責註入服務
        /// </summary>
        /// <param name="services"></param>
        /// <returns></returns>
        public IServiceProvider ConfigureServices(IServiceCollection services)
        {
            //獲取資料庫連接字元串
            var connectionStr = Configuration.GetConnectionString("SqlServer");
            services.AddDbContext<MyDbContext>
                (options => options.UseSqlServer(connectionStr,
                    e => e.MigrationsAssembly("NetCoreWebApi.Model")));
            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);
            //初始化容器
            var builder = new ContainerBuilder();
            //管道寄居
            builder.Populate(services);
            //註冊業務
            builder.RegisterAssemblyTypes(Assembly.Load("NetCoreWebApi.Repository"), Assembly.Load("NetCoreWebApi.Repository"))
                .Where(t => t.Name.EndsWith("Repository"))
                .AsImplementedInterfaces();
            //註冊倉儲，所有IRepository介面到Repository的映射
            builder.RegisterGeneric(typeof(Repository<>))
                //InstancePerDependency：預設模式，每次調用，都會重新實例化對象；每次請求都創建一個新的對象；
                .As(typeof(IRepository<>)).InstancePerDependency();
            //構造
            ApplicationContainer = builder.Build();
            //將AutoFac反饋到管道中
            return new AutofacServiceProvider(ApplicationContainer);
        }

三、測試

修改業務層---UserRepository

給泛型類指定ThUser，紅色字體是主要更改部分。

using System.Collections.Generic;
using System.Linq;
using NetCoreWebApi.Model.Models;
using NetCoreWebApi.Repository.Interface;
using NetCoreWebApi.Repository.Repository;

namespace NetCoreWebApi.Repository.Implement
{
    /// <summary>
    /// 業務處理
    /// </summary>
    public class UserRepository:IUserRepository
    {
        private readonly IRepository<TbUser> _userRepository;

        /// <summary>
        /// 構造函數
        /// </summary>
        /// <param name="userRepository"></param>
        public UserRepository(IRepository<TbUser> userRepository)
        {
            _userRepository = userRepository;
        }
        /// <summary>
        /// 添加用戶
        /// </summary>
        /// <param name="entity"></param>
        /// <returns></returns>
        public int Add(TbUser entity)
        {
            return _userRepository.Add(entity);
        }
        /// <summary>
        /// 刪除用戶
        /// </summary>
        /// <param name="entity"></param>
        /// <returns></returns>
        public int Remove(TbUser entity)
        {
            return _userRepository.Remove(entity);
        }
        /// <summary>
        /// 查詢用戶
        /// </summary>
        /// <returns></returns>
        public IList<TbUser> GetAll()
        {
            return _userRepository.GetAll().ToList();
        }
    }
}

運行項目執行介面，可以看到跟之前一樣

如果有其他實體只需要改變傳入的T就可以了，不需要再重新創建TEntityRepository

ASP.NET Core 2.2 系列【六】泛型倉儲模式