Unity DI 使用 PerRequestLifetimeManager 注入 DbContext

Question

我有以下代码用 Unity 初始化实例：

IUnityContainer container = new UnityContainer();
container.RegisterType<DbContext, VotingSystemContext>(new PerRequestLifetimeManager(), new InjectionConstructor());
container.RegisterType(typeof(IGenericRepository<>), typeof(GenericRepository<>));
container.RegisterType<IUnitOfWork, UnitOfWork>(new PerRequestLifetimeManager());    
container.RegisterTypes(
    AllClasses.FromAssemblies(
        Assembly.GetAssembly(typeof(IUserService)),
        Assembly.GetAssembly(typeof(UserService))),
    WithMappings.FromMatchingInterface,
    WithName.Default, WithLifetime.PerResolve);
DependencyResolver.SetResolver(new Unity.Mvc4.UnityDependencyResolver(container));
GlobalConfiguration.Configuration.DependencyResolver = new Unity.WebApi.UnityDependencyResolver(container);

我使用PerRequestLifetimeManager，所以我按照MSDN 上的建议在上面的代码末尾添加了新行：

DynamicModuleUtility.RegisterModule(typeof(UnityPerRequestHttpModule));

但是在我放置之后。加载页面（仅静态 html）时，我将 ajax 请求发送到我的 WebApi 控制器，该控制器调用 GenericReposirory Get() 引发错误的方法：The operation cannot be completed because the DbContext has been disposed.
如果没有这行代码，一切正常，但如果不设置它，上下文可能不会被处理。
我的UnitOfWork 班级：

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

   //GenericRepository properties

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

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

附：我使用最新版本的 Unity 3.5.1404。
提前致谢。

编辑：

Repository的Get()方法：

public sealed class GenericRepository<TEntity> : IGenericRepository<TEntity> where TEntity : BaseEntity
{
    public GenericRepository(VotingSystemContext context)
    {
        _context = context;
        _dbSet = context.Set<TEntity>();
    }

    private readonly DbSet<TEntity> _dbSet;
    private readonly VotingSystemContext _context;

    public IEnumerable<TEntity> Get(Expression<Func<TEntity, bool>> filter = null,
        Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> orderBy = null,
        string includeProperties = "", int? page = null, int? pageSize = null)
    {
        IQueryable<TEntity> query = _dbSet;
        if (filter != null)
        {
            query = query.Where(filter);
        }
        List<string> properties = includeProperties.Split(new[] { ',' }, StringSplitOptions.RemoveEmptyEntries).ToList();
        properties.ForEach(property =>
            {
                query = query.Include(property);
            });
        if (orderBy != null)
        {
            query = orderBy(query);
        }
        if (page != null && pageSize != null)
        {
            query = query.Skip((page.Value - 1) * pageSize.Value).Take(pageSize.Value);
        }
        return query;
    }
    // other methods like Delete, Update and GetById
    }
}

ApiController 的Get() 方法：

public IEnumerable<VotingModel> Get(int page = 1, int size = 10)
{
    //get all themes
    List<Theme> themes = _themeService.GetAll(page, size);
    //convert themes to VotingModel (same model as Theme just without converting system throw an error about serializing object and also add new filed UserName).
    List<VotingModel> model = themes.Select(t =>
        {
            MembershipUser membershipUser = Membership.GetUser(t.UserId ?? -1);
            return t.ToVotingModel(membershipUser != null ? membershipUser.UserName : string.Empty);
        }).ToList();
    return model;
}

服务GetAll()方法：

public List<Theme> GetAll(int page = 1, int pageSize = 10)
{
    return UnitOfWork.ThemeRepository.Get(null, null, "Comments", page, pageSize).ToList();
}

Answer 1

所以我会有这样的依赖结构：

• UnitOfWork - 获取 DbContext
• 存储库 - 获取 UnitofWork
• 服务 - 获取存储库
• ApiController - 获取服务

并且您会坚持使用 Unity 来处理每个人的生命周期。但问题是，您希望服务具有请求范围，就像其他服务（UoW 和 Repos）一样。您可能以这种方式设置了服务生命周期，但我不知道 Unity 在我的脑海中。我可以看到您确实为 UofW 和 repos 设置了请求生命周期。

最大的区别在于UnitOfWork 不依赖于存储库，而是相反。因此，存储库基类通过具有 DbContext. 的 UnitOfWork 获取其 DbSet<T> 您将在 UnitOfWork 上有一些方法，该方法将返回 IDbSet<T>，就像您在 DbContext. 上调用它一样UnitOfWork 是 DbContext 的包装器，它本身非常类似于工作单元。

public sealed class GenericRepository<T> : IRepository<T> where T : BaseEntity
{
    private readonly IDbSet<T> _dbSet;
    private readonly IUoW _uoW;

    public GenericRepository(IUoW unitOfWork)
    {
        _uoW = unitOfWork;
        _dbSet = _uoW.Set<T>();
    }

    public IEnumerable<TEntity> Get(Expression<Func<TEntity, bool>> filter = null,
    Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> orderBy = null,
    string includeProperties = "", int? page = null, int? pageSize = null)
    {
        IQueryable<TEntity> query = _dbSet;
        if (filter != null)
        {
            query = query.Where(filter);
        }
        List<string> properties = includeProperties.Split(new[] { ',' }, StringSplitOptions.RemoveEmptyEntries).ToList();
        properties.ForEach(property =>
            {
                query = query.Include(property);
            });
        if (orderBy != null)
        {
            query = orderBy(query);
        }
        if (page != null && pageSize != null)
        {
            query = query.Skip((page.Value - 1) * pageSize.Value).Take(pageSize.Value);
        }
        return query;
    }
// other methods like Delete, Update and GetById
}

UnitOfWork 与此类似，但将DbContext 作为依赖项（您可能已经有了它但省略了构造函数）：

public class UnitOfWork : IUnitOfWork
{
   private readonly VotingSystemContext _context;
   private bool _disposed;

   public UnitOfWork(DbContext context)
   {
       _context = context;
   }

   public IDbSet<T> Set<T>()
   {
       return _context.Set<T>();
   ]
}

该服务将注入存储库：

public class ThemeService
{
    private IRepository<Theme> ThemeRepository { get; set; }

    public ThemeService(IRepository<Theme> themeRepo)
    {
        ThemeRepository = themeRepo;
    }

    public List<Theme> GetAll(int page = 1, int pageSize = 10)
    {
        return ThemeRepository.Get(null, null, "Comments", page, pageSize).ToList();
    }

    // etc.
}

ApiController 将注入所需的服务，在本例中为 ThemeService：

public class ApiController ThemeController
{
    private ThemeService _themeService;

    public ThemeController(ThemeService service) // along with any other needed services
    {
        _themeService = service;
    }

    public IEnumerable<VotingModel> Get(int page = 1, int size = 10)
    {
        //get all themes
        List<Theme> themes = _themeService.GetAll(page, size);
        //convert themes to VotingModel (same model as Theme just without converting system throw an error about serializing object and also add new filed UserName).
        List<VotingModel> model = themes.Select(t =>
            {
                MembershipUser membershipUser = Membership.GetUser(t.UserId ?? -1);
                return t.ToVotingModel(membershipUser != null ? membershipUser.UserName : string.Empty);
            }).ToList();
        return model;
}

最终的想法是 Unity 容器处理所有依赖项的生命周期，UnitOfWork 不必尝试管理存储库。你的线路

DynamicModuleUtility.RegisterModule(typeof(UnityPerRequestHttpModule));

会留下来，DbContext 会被 Unity 处理掉，你不必自己打电话给Dispose()。

Answer 2

尝试改用 Microsoft.Practices.Unity.HierarchicalLifetimeManager，这样：

container.RegisterType<DbContext, VotingSystemContext>(new HierarchicalLifetimeManager(), new InjectionConstructor());

Microsoft.Practices.Unity.HierarchicalLifetimeManager 提供：

1. 每次请求后调用 Dispose()
2. 每个请求使用相同的 DbContext 实例

点赞文章：https://jasenhk.wordpress.com/2013/06/11/unit-of-work-and-repository-pattern-with-unity-dependency-injection/