如何使用Entity Framework为我的存储库实现事务？

Question

我试图在我的应用程序中使用存储库设计模式有两个原因

1. 如果我决定不在某个时候使用Entity Framework,我喜欢将我的应用程序与Entity分离

2. 我希望能够重用与模型交互的逻辑

我成功设置并使用了存储库模式.但是,我有一个复杂性来处理哪个是交易.

我希望能够使用事务,以便我可以对存储库进行多次调用,然后提交或回滚.

这是我的存储库界面

using System;
using System.Collections.Generic;
using System.Linq.Expressions;

namespace Support.Repositories.Contracts
{
    public interface IRepository<TModel> where TModel : class
    {
        // Get records by it's primary key
        TModel Get(int id);

        // Get all records
        IEnumerable<TModel> GetAll();

        // Get all records matching a lambda expression
        IEnumerable<TModel> Find(Expression<Func<TModel, bool>> predicate);

        // Get the a single matching record or null
        TModel SingleOrDefault(Expression<Func<TModel, bool>> predicate);

        // Add single record
        void Add(TModel entity);

        // Add multiple records
        void AddRange(IEnumerable<TModel> entities);

        // Remove records
        void Remove(TModel entity);

        // remove multiple records
        void RemoveRange(IEnumerable<TModel> entities);
    }
}

然后我像这样为Entity Framework创建一个实现

using Support.Repositories.Contracts;
using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Linq.Expressions;

namespace Support.Repositories
{
    public class EntityRepository<TEntity> : IRepository<TEntity>
        where TEntity : class
    {
        protected readonly DbContext Context;
        protected readonly DbSet<TEntity> DbSet;

        public EntityRepository(DbContext context)
        {
            Context = context;
            DbSet = context.Set<TEntity>();
        }

        public TEntity Get(int id)
        {
            return DbSet.Find(id);
        }

        public IEnumerable<TEntity> GetAll()
        {
            return DbSet.ToList();
        }

        public IEnumerable<TEntity> Find(Expression<Func<TEntity, bool>> predicate)
        {
            return DbSet.Where(predicate);
        }

        public TEntity SingleOrDefault(Expression<Func<TEntity, bool>> predicate)
        {
            return DbSet.SingleOrDefault(predicate);
        }

        public void Add(TEntity entity)
        {
            DbSet.Add(entity);
        }

        public void AddRange(IEnumerable<TEntity> entities)
        {
            DbSet.AddRange(entities);
        }

        public void Remove(TEntity entity)
        {
            DbSet.Remove(entity);
        }

        public void RemoveRange(IEnumerable<TEntity> entities)
        {
            DbSet.RemoveRange(entities);
        }

    }
}

现在,我创建了一个IUnitOfWork与存储库交互的方式

using System;

namespace App.Repositories.Contracts
{
    public interface IUnitOfWork : IDisposable
    {
        IUserRepository Users { get; }
        IAddressRepository Addresses { get;  }
    }
}

然后我为Entity Framework实现了这样的接口,如下所示:

using App.Contexts;
using App.Repositories.Contracts;
using App.Repositories.Entity;

namespace App.Repositories
{
    public class UnitOfWork : IUnitOfWork
    {
        private readonly AppContext _context;
        public IUserRepository  Users { get; private set; }
        public IAddressRepository Addresses { get; private set; }

        public UnitOfWork(AppContext context)
        {
            _context = context;

            Users = new UserRepository(_context);
            Addresses = new AddressRepository(_context);
        }

        public UnitOfWork() : this(new AppContext())
        {
        }

        public int Save()
        {
            return _context.SaveChanges();
        }

        public void Dispose()
        {
            _context.Dispose();
        }
    }
}

我可以像这样使用存储库

using(var repository = new UnitOfWork())
{
     repository.Users.Add(new User(... User One ...))
     repository.Save();

     repository.Addresses(new Address(... Address For User One ...))
     repository.Save();

     repository.Users.Add(new User(... User Two...))
     repository.Save();

     repository.Addresses(new Address(... Address For User Two...))
     repository.Save();
}

现在,我希望能够使用数据库事务,所以只有在一切都很好的情况下才能提交回滚.

我的第一个想法是添加一个叫BeginTransaction()我UnitOfWork班级的新方法.但是我的代码只会与Entity Framework结合.

现在,我正在考虑创建一个提供的新接口BeginTransaction(),Commit()以及Rollback()允许我为任何ORM编写实现的方法.

即

namespace Support.Contracts
{
    public IRepositoryDatabase
    {
        SomethingToReturn BeginTransaction();

        void Commit();
        void Rollback();
    }
}

问题是如何IRepositoryDatabase绑定到我的UnitOfWork以便我能正确实现？什么BeginTransaction()需要返回？

Answer 1

我想我找到了做到这一点的方法.(我希望我以正确的方式做到了)

这就是我所做的,我希望这可以帮助那些想要做同样事情的人.

我创建了一个新的界面

using System;

    namespace Support.Repositories.Contracts
    {
        public interface IDatabaseTransaction : IDisposable
        {
            void Commit();

            void Rollback();
        }
    }

然后我IDatabaseTransaction像这样为Entity框架实现了

using Support.Repositories.Contracts;
using System.Data.Entity;

namespace Support.Entity.Repositories
{
    public class EntityDatabaseTransaction : IDatabaseTransaction
    {
        private DbContextTransaction _transaction;

        public EntityDatabaseTransaction(DbContext context)
        {
            _transaction = context.Database.BeginTransaction();
        }

        public void Commit()
        {
            _transaction.Commit();
        }

        public void Rollback()
        {
            _transaction.Rollback();
        }

        public void Dispose()
        {
            _transaction.Dispose();
        }
    }
}

然后,我添加了一个新的方法调用BeginTransaction()我的IUnitOfWork合同,就像这样

using System;

namespace App.Repositories.Contracts
{
    public interface IUnitOfWork : IDisposable
    {
        IDatabaseTransaction BeginTrainsaction();
        IUserRepository Users { get; }
        IAddressRepository Addresses { get;  }
    }
}

最后,以下是我UnitOfwork对Entity的实现

using App.Contexts;
using App.Repositories.Contracts;
using App.Repositories.Entity;
using Support.Repositories;


namespace App.Repositories
{
    public class UnitOfWork : IUnitOfWork
    {
        private readonly AppContext _context;
        public IUserRepository  Users { get; private set; }
        public IAddressRepository Addresses { get; private set; }

        public UnitOfWork(AppContext context)
        {
            _context = context;

            Users = new UserRepository(_context);
            Addresses = new AddressRepository(_context);
        }

        public UnitOfWork() : this(new AppContext())
        {
        }

        public int Save()
        {
            return _context.SaveChanges();
        }

        public void Dispose()
        {
            _context.Dispose();
        }

        public IDatabaseTransaction BeginTransaction()
        {
            return new EntityDatabaseTransaction(_context);
        }
    }
}

以下是我如何从控制器中使用UnitOfWork实现

using(var unitOfWork = new UnitOfWork())
using(var transaction = new unitOfWork.BeginTransaction())
{
     try
     {
         repository.Users.Add(new User(... User One ...))
         repository.Save();

         repository.Addresses(new Address(... Address For User One ...))
         repository.Save();

         repository.Users.Add(new User(... User Two...))
         repository.Save();

         repository.Addresses(new Address(... Address For User Two...))
         repository.Save();
         transaction.Commit();
     } 
     catch(Exception)
     {
          transaction.Rollback();
     }

}

Answer 2

在EF Core中，虽然 UnitOfWork 模式是在内部实现的，但您可以简单地使用IDbContextTransaction接口，如下所示（假设您使用依赖注入）：

public interface IUnitOfWork 
{
    int SaveChanges();
    Task<int> SaveChangesAsync();
    IDbContextTransaction BeginTransaction();
    Task<IDbContextTransaction> BeginTransactionAsync();
    
    IUserRepository Users { get; }
    IAddressRepository Addresses { get;  }
}

和实施：

public class UnitOfWork : IUnitOfWork, IDisposable
{
    private bool _disposed;
    private readonly AppDbContext _context;

    public UnitOfWork(AppDbContext context, 
                 IUserRepository userRepositpry, IAddressRepository addressRepository)
    {
        _context = context;
        Users = userRepositpry;
        Addresses = addressRepository;
    }

    public IUserRepository Users { get; }
    public IAddressRepository Addresses { get; }

    public int SaveChanges()
    {
        return _context.SaveChanges();
    }

    public async Task<int> SaveChangesAsync()
    {
        return await _context.SaveChangesAsync();
    }

    public IDbContextTransaction BeginTransaction()
    {
        return _context.Database.BeginTransaction();
    }

    public async Task<IDbContextTransaction> BeginTransactionAsync()
    {
        return await _context.Database.BeginTransactionAsync();
    }

    protected void Dispose(bool disposing)
    {
        if (!this._disposed)
        {
            if (disposing)
            {
                _context.Dispose();
            }
        }
        this._disposed = true;
    }

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }
}

用法：

 public class FooService
{
    private readonly IUnitOfWork _unitOfWork;
    public FooService(IUnitOfWork unitOfWork)
    {
        _unitOfWork = unitOfWork;
    }

    public void Bar()
    {
        using (var transaction = _unitOfWork.BeginTransaction())
        {
            try
            {
                _unitOfWork.Users.Add(new UserModel("dummy username"));
                _unitOfWork.SaveChanges();
                _unitOfWork.Addresses.Add(new AddressModel("dummy address"));
                _unitOfWork.SaveChanges();

                transaction.Commit();
            }
            catch (Exception)
            {
                transaction.Rollback();
            }
        }
    }
}

Answer 3

虽然 Rufo 爵士的评论是正确的，但您确实说过想要一个独立于 EF 的解决方案，虽然通常从 ORM 中抽象出来是一种矫枉过正，但如果您仍然决定自己处理事务，您可以使用TransactionScope（这显然是实现在BeginTransaction拥有之前控制交易context.Database）。

有关详细信息，请参阅以下文章：https://msdn.microsoft.com/en-us/data/dn456843.aspx

相关的一点是，您可以将所有调用包含在 a 中TransactionScope（这实际上也可以在其他 ORM 中开箱即用）：

using System.Collections.Generic; 
using System.Data.Entity; 
using System.Data.SqlClient; 
using System.Linq; 
using System.Transactions; 

namespace TransactionsExamples 
{ 
    class TransactionsExample 
    { 
        static void UsingTransactionScope() 
        { 
            using (var scope = new TransactionScope(TransactionScopeOption.Required)) 
            { 
                using (var conn = new SqlConnection("...")) 
                { 
                    conn.Open(); 

                    var sqlCommand = new SqlCommand(); 
                    sqlCommand.Connection = conn; 
                    sqlCommand.CommandText = 
                        @"UPDATE Blogs SET Rating = 5" + 
                            " WHERE Name LIKE '%Entity Framework%'"; 
                    sqlCommand.ExecuteNonQuery(); 

                    using (var context = 
                        new BloggingContext(conn, contextOwnsConnection: false)) 
                    { 
                        var query = context.Posts.Where(p => p.Blog.Rating > 5); 
                        foreach (var post in query) 
                        { 
                            post.Title += "[Cool Blog]"; 
                        } 
                        context.SaveChanges(); 
                    } 
                } 

                scope.Complete(); 
            } 
        } 
    } 
}

但需要注意以下注意事项：

该方法仍然存在一些局限性TransactionScope：

• 需要 .NET 4.5.1 或更高版本才能使用异步方法
• 不能在云场景中使用，除非你确定你有且只有一个连接（云场景不支持分布式事务）
• Database.UseTransaction()它不能与前面部分的方法结合使用
• 如果您发出任何 DDL（例如，由于数据库初始化程序）并且未通过 MSDTC 服务启用分布式事务，它将引发异常