MVC :: Are Repositories Automatically Disposed Of In C#?
Dec 6, 2010
Could someone explain what happens to the Repositories that are created when they are no longer needed? Are they automatically disposed of, or should we dispose of them manually?
Using EF4 as the DAL, to keep the program efficient I have been building repositories for the Model that abstract the data needed for specific views or actions. I have also used the Iinterface for the methods and call them in the Controller to pass them to the View. At some point the program needs to pass a behavior or request that requires the creation of a new repository and the process may repeat itself over and over again. What happens to the repositories that created for previous views, but are no longer needed? Should the dispose be written into each repository, or does garbage collection take care of this? How should this handled?
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Apr 13, 2010
I've been reading up on MVC 2 and the recommended patterns, so far I've come to the conclusion (amongst much hair pulling and total confusion) that:
Model - Is just a basic data container Repository - Provides data access Service - Provides business logic and acts as an API to the Controller
The Controller talks to the Service, the Service talks to the Repository and Model. So for example, if I wanted to display a blog post page with its comments, I might do:
post = PostService.Get(id);
comments = PostService.GetComments(post); Or, would I do:
post = PostService.Get(id);
comments = post.Comments;
If so, where is this being set, from the repository? the problem there being its not lazy loaded.. that's not a huge problem but then say I wanted to list 10 posts with the first 2 comments for each, id have to load the posts then loop and load the comments which becomes messy.All of the example's use "InMemory" repository's for testing and say that including db stuff would be out of scope. But this leaves me with many blanks, so for a start can anyone comment on the above?
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Jun 16, 2010
I don't know if it's IIS, ASP.NET or IIS7 related. I take a chance here, if you think I'm in the wrong forum, just tell me which one I should post to.
I have made the smallest demo project to illustrate my problem. You can download the sources
Here
Visual Studio 2008, .NET 3.5, IIS7, Windows 7 Ultimate 32 bits. The IIS Website is configured
ONLY for Windows Authentication in an Integreated pipeline app pool (DefaultAppPool).
Here's the problem. I have an Asp.NET MVC 2 application. In an action, I start a thread. The View returns.
The thread is doing it's job... but it needs to access Thread.CurrentPrincipal.Identity.Name
BANG
The worker process of IIS7 stops. I have a window that says: "Visual Studio Just-In-Time Debugger An unhandled exception ('System.Object.DisposedException') occured in w3wp.exe [5524]"
I checked with the debugger and the Thread.CurrentPrincipal.Identity is valid, but the Name property is disposed.
If I put a long wait in the action before it returns the view, then the Thread can do it's job and the Identity.Name is not disposed. So I think the Name gets disposed when the view is returned.
For the sake of the discussion, here's the code that the thread runs (but you can also download the demo project. The link is on top of this post):
[Code]....
Here's the code that starts the thread
[Code]....
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Aug 17, 2010
I would like to start a debate on traditional repositories versus one built on the UnitOfWork pattern. In a traditional repository, we wrap inserts, updates and deletes in a transaction, but selects don't really need them. In addition, nhibernate configuration is typically done once per application due to BuildSessionFactory being rather expensive. We often have several repositories of this type (one per aggregate chain). We also need to have projected, ahead of time, exactly what kinds of queries we'll need in order to build the interfaces and concretes correctly. In a single UnitOfWork repository we have the ability to manage both the current session and transaction, perform several operations, and then commit any changes all at once. In such a repository we may opt to put our configuration in the constructor since (typically speaking) no more than one Action is called per request anyway, initializing it in the application doesn't seem like much of an overall gain in speed. I must admit, I'm very temped to use the UnitOfWork pattern, as the following code looks really nice to me:
Csharp Code:
using (IUnitOfWork worker = new UnitOfWork()){// session and transaction are now both set
// save changes to three itemsworker.SaveOrUpdate(item1);worker.SaveOrUpdate(item2);worker.SaveOrUpdate(item3);
// grab a fourth var item4 = worker.Criteria<Foo>().Add(Expression.Eq("title", title)).UniqueResult<Foo>();
// delete the fourthworker.Delete(item4);
// all pending operations are commited or rolled back as a single unit (if one fails, all are rolled back), and then disposed, along with the session}
My proposed UnitOfWork class is rather simple. It implements IDisposable where I use a try-catch-finally in Dispose() to attempt a tx.Commit(), doing a tx.Rollback on failure, and a cleaning everything up in the finally clause. It also exposes common things like SaveOrUpdate, Delete, GetAll, Get, and even a Critera<T>() for custom on-the-spot queries. So what are your thoughts on this? I'd really like to hear about your experience with this pattern.
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May 1, 2010
In a typical business application, a session is started and persisted across several pages. It is commited only when the transaction is complete. A good example of this is a tax preparation application. Once the session is started, it is persisted through session, cookies, or both. Nothing is written to file, or database, until the entire profile is complete and the refund/return is calculated. In such an ennvironment, is makes a great deal of sense to work with the structure imposed by domain driven design, and using a single repository to simple commit the session. However, there are times when this doesn't translate correctly, even when domain driven design is used.
An example of this is my forum project. While the entities themselves are good targets for domain driven design, I am not sure about the repositories. The basic structure is that a Category has many Forums, a Forum has many Threads, and a Thread has many posts. There are other things in there, but that's enough to describe what I want to get across. If a user has navigated to /Thread/Edit/42, and they have rights to edit it, all I am concerned about is fetching that record and displaying it. On postback, all I want is to be able to save it..................
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Mar 9, 2011
Assuming my application did not warrant a full blown DDD setup, would Repositories still be useful? I like the way they shield from implementation details (such as use of Entity Framework) underneath. However Repositories tend to be tied to Aggregate Roots (the concept is still a holy grail to me) by definition.
I suppose the question could also be put as such: if I have a typical 3-tier application, with a business layer facade consisting of "logical grouping" classes based on functionality (rather than aggregate roots as in DDD) such as TradingManager and ContactsManager, would it make sense to also create "logical grouping" repositories. Or perhaps a Data Access Object, which I believe is like a Repository without the aggregate root requirement. Of course I will still have a Model (EF POCOs) that will be passed up and down between the layers.
Also, is what I just described would be considered as a Transaction Script approach? It's certainly not DDD, and not Active Record. I'm not even sure if Active Record exists with EF4 like it does with Nhibernate.
I am trying to understand how others structure n-layered applications when they do not follow DDD.
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I understand I could use another using statement for the SQLCommand however if prefer to do it like I have with the Try/Finally block. My understanding is the Finally block executes last and does the cleanup.
[Code]....
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[Code]....
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[Code]....
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[Code]....
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[code]....
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