我的DbContext如何处理？(How is my DbContext being disposed?)

 我将单片ASP.NET MVC应用程序拆分为N层应用程序时遇到了很大困难。 在下面的示例中，在第一次调用_messageRepo.Create（）期间，抛出一个异常，说DbContext因为它已被释放而无法使用。 
 
 我无法看到这是怎么回事，并且试图打破Dispose（）方法实际上并没有导致应用程序在调试期间中断。 
 
 基本结构如下： 
 
 
 
 控制器注入他们使用的每个服务的实例//即：public MyController（IMessageService messageService） 
 
 
 服务包含任何所需的存储库实例（即： _messageRepository ） 
 
 
 存储库使用MyContext的实例，这是DbContext的子类 
 
 
 只要需要，就会重建这些实例，如下例所示 
using(var context = new MyContext())
{
    _messageRepo = new MessageRepository(context);
    _idRepo = new IdentityRepository(context);

    var status = _messageRepo.GetStatus(Int32.Parse(message.To));
    message.To = status.Header.From.Name;
    message.ToHash = Obfuscate.SaltAndHash(message.To);
    message.Subject = "RE:" + status.Header.Subject;

    var toUser = _idRepo.Get(message.To);
    var fromUser = _idRepo.Get(_userName);
    var rawMessage = new Message()
    {
        Content = message.Content,
        Attachments = GetAttachments(message.AttachmentIds)
    };
    var header = new MessageHeader()
    {
        To = toUser,
        From = fromUser,
        Subject = message.Subject
    };
    _messageRepo.Create(new MessageStatus()
    {
        CreatedAt = DateTime.Now,
        IsRead = false,
        IsSpam = false,
        IsTrash = false,
        Message = rawMessage,
        Header = header,
        Owner = header.To
    });
    _messageRepo.Create(new MessageStatus()
    {
        CreatedAt = DateTime.Now,
        IsRead = false,
        IsSpam = false,
        IsTrash = false,
        Message = rawMessage,
        Header = header,
        Owner = header.From
    });
    context.Commit();
    Email.SendNewMessageNotification(fromUser.Email, toUser.Email);
}
 
 
 存储库方法是LINQ单行程序，它使用代码第一种方法通过Entity Framework从数据库中检索模型。 
 
 这种方法有问题吗？ 我最初确实有MyContext实现IUnitOfWork，但我删除了它，直到我得到这个不太复杂的方法功能。 
 
 另外，我正在使用IoC框架（AutoFac）来加载这些接口实现的实例。 如果这是问题，那么我需要更改我的逻辑以适应AutoFac？ 
 
//in Global.asax.cs
builder.RegisterType<PonosContext>().As<PonosContext>().InstancePerHttpRequest();

//Example repo constructor
public MessageRepository(PonosContext context)
{
    _db = context;
}

I am having a great deal of difficulty in splitting my monolithic ASP.NET MVC application into an N-tier app. In the following example, during the first call to _messageRepo.Create() an exception is thrown saying that the DbContext cannot be used since it was already disposed. 
 
I cannot see how that is happening, and attempting to break on the Dispose() method doesn't actually cause the application to break during debugging.
 
The basic structure is as follows:
 
 
 
Controllers are injected with instances of each service they use //ie: public MyController(IMessageService messageService)
 
 
Services contain any needed instances of repositories (ie: _messageRepository)
 
 
Repositories utilize an instance of MyContext, a sub-class of DbContext
 
 
These instances are reconstructed whenever needed as in the following example 
 
using(var context = new MyContext())
{
    _messageRepo = new MessageRepository(context);
    _idRepo = new IdentityRepository(context);

    var status = _messageRepo.GetStatus(Int32.Parse(message.To));
    message.To = status.Header.From.Name;
    message.ToHash = Obfuscate.SaltAndHash(message.To);
    message.Subject = "RE:" + status.Header.Subject;

    var toUser = _idRepo.Get(message.To);
    var fromUser = _idRepo.Get(_userName);
    var rawMessage = new Message()
    {
        Content = message.Content,
        Attachments = GetAttachments(message.AttachmentIds)
    };
    var header = new MessageHeader()
    {
        To = toUser,
        From = fromUser,
        Subject = message.Subject
    };
    _messageRepo.Create(new MessageStatus()
    {
        CreatedAt = DateTime.Now,
        IsRead = false,
        IsSpam = false,
        IsTrash = false,
        Message = rawMessage,
        Header = header,
        Owner = header.To
    });
    _messageRepo.Create(new MessageStatus()
    {
        CreatedAt = DateTime.Now,
        IsRead = false,
        IsSpam = false,
        IsTrash = false,
        Message = rawMessage,
        Header = header,
        Owner = header.From
    });
    context.Commit();
    Email.SendNewMessageNotification(fromUser.Email, toUser.Email);
}
 
 
The repository methods are LINQ one-liners that retrieve models from a database through Entity Framework using the code first approach.
 
Is there something wrong with this approach? I did have MyContext implement IUnitOfWork at first, but I removed that until I get this less complicated method functional.
 
Additionally, I am using an IoC framwork (AutoFac) to load instances of these interface implementations. If this is the problem, then what do I need to change about my logic to accomodate AutoFac?
 
//in Global.asax.cs
builder.RegisterType<PonosContext>().As<PonosContext>().InstancePerHttpRequest();

//Example repo constructor
public MessageRepository(PonosContext context)
{
    _db = context;
}

原文：https://stackoverflow.com/questions/9484913