Unity DI使用PerRequestLifetimeManager注入DbContext

Question

我有以下代码可使用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所以我遵循了MSDN上的建议，并在上面的代码末尾添加了新行：

DynamicModuleUtility.RegisterModule(typeof(UnityPerRequestHttpModule));

但是在我放置它之后。 加载页面（仅静态html）时，我向WebApi constroller发送ajax请求，该WebApi constroller调用该类的GenericReposirory Get()方法， The operation cannot be completed because the DbContext has been disposed.方法抛出错误： The operation cannot be completed because the DbContext has been disposed.
如果没有这行代码，一切都会正常，但是如果没有设置它，上下文可能就不会被处理。
我的UnitOfWork类：

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);
   }
}

PS我使用最新版本的Unity 3.5.1404 。
提前致谢。

编辑：

存储库的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

因此，我将具有如下所示的依赖结构：

• UnitOfWork-获取DbContext
• 存储库-获取工作单位
• 服务-获取存储库
• ApiController-获取服务

并且您会坚持使用Unity来处理每个生命周期。 事实是，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寿命，但我不知道Unity是我的头等大事。 我可以看到您确实为UofW和repos设置了请求生存期。

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> DbContext. 您在UnitOfWork上有一些方法可以返回IDbSet<T>就像在DbContext.上调用它DbContext. UnitOfWork是DbContext的包装， DbContext本身就是类似Work of Unit的包装。

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会类似，但是将DbContext作为依赖项（您可能已经有了它，但是省略了构造函数）：

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容器可以处理所有依赖项的生命周期，而UnitOfWork不必尝试管理存储库。 你的线

DynamicModuleUtility.RegisterModule(typeof(UnityPerRequestHttpModule));

会保留，而DbContext会被Unity处理，而您不必自己对其调用Dispose() 。

Answer 2

尝试改为使用Microsoft.Practices.Unity.HierarchicalLifetimeManager，方法是：

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

Microsoft.Practices.Unity.HierarchicalLifetimeManager提供：

1. 在每个请求之后进行Dispose（）调用
2. 每个请求相同的DbContext实例

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