Its known that DTO doesnt have methods.
Since the controller uses the DTO objects , there is a dependency . should we set expectaions on the properties of DTO(mock DTO properties) while testing the controllers.?
thanks
Where a DTO is just holding values, there's no point in mocking it. Mock objects should be used to confirm how an object collaborates with its neighbour. If there's no real behaviour, if the DTO is not providing a service, then don't use a mock.
A DTO is so lightweight that the additional cost of stubbing it out just seems silly. Plus now you need an interface for your DTO or everything has to be marked as virtual...
Can you name at least one thing why not?
I can't.
P.s. i mean - why not to use properties. You got 2 controversial questions in your post.
I agree with Arnis L. You just pass your DTO to your controller during your tests (initialized with the values you need) and there's nothing to test in your DTO (unless you have some logic in your getter/setter but it's not really a good practice for DTO).
Are you thinking of the dto going into the action, or the one(s) coming out?
The one going in will be used directly against a repository, a service or some other collaborator. I would mock those instead and place my expectations there.
Your test code will also have full control on creating the ingoing dto.
If you like to use the outgoing dto, I would just grab that one from the ViewResult and verify it is the expected one. How you do that is up to you: You could mock the repository or talk to your persistence storage of choice.
Don't Mock your DTOs. It's simpler just to create your DTO than to create the Mock and in some situation can get you into a bit of trouble if you mutate their state.
I've written about one such experiences at the link below.
Don't Mock DTOs
Related
I think I understand the concept of services, but I don't seem to be able to find practical, real-life examples of them, except, of course, for the mailer service. The mailer example is great, but it would really help me catch the whole thing if there were other ones. Can anyone provide me with a (short and simple) list of concrete cases where you should use a service ? I'm not asking for code here...
All business logic must be in service. According slide number 46 in How Kris Writes Symfony Apps. Thin model, thin controller, fat service layer.
You should think a Service like not a real "service" ( as the mailer ) but you have thinking about at the dependency Injection design pattern. So if you have an action named 'enrolledStudentAction()' your controller method should be thin and you have to make "the logic" inside a class named StudentManager. The studentManager do the logic in order to find the enrolled users and return the result to the controller. The controller call the method getEntolledStudent by the service container. Decoupling!
I have been reading about entity framework over the past couple of days and have managed to get a fair idea of using it but I still have a couple of questions some of which might seem a bit too basic. For perspective I am using entity framework 4.0 in an asp.net web application.If you can answer any of the questions please go ahead.
What advantage do I get by using POCO templates. I understand that if I wish to get persistence ignorance and keep my Entities clear of any information related to storage POCO entities are the way to go. Also I could switch from Entity framework to say NHibernate with relative ease when using POCO entities? Apart from loose coupling is there any significant reason for me to go towards POCO entities. Also if I do use POCO do I end up losing anything. I still get change tracking and lazy loading with the help of proxies?
Is it normal practice to use the Entities of the EF model as Data transfer Objects or Business Objects. i.e for example I have a separate class library for my entity model.Supposing I am using MVP , where I want a list of Employee's in a company. The presenter would request my business logic functions which would query the entity model for the list of Employee's and return the list of entities to the presenter. In this case my presenter would need to have a reference to the EF model. Is this the correct way? In the case of my asp.net web applciation it shouldnt be a problem but if I am using web services how does this work? Is this the reason to go towards POCO entities?
Supposing The Employee entity has a navigation property to a company table. If I use and wrap the data context in an 'using' block , and try to access the navigation property in the BL I am assuming I would get an exception. Would I also get an exception if I turned off lazyloading and used the 'include' linq query to get the entity? On a previous post someone recommended I use an context per request implying that the context remains active even when I am in the BL. I am assuming I would still need to detach the object and attach it to the context on my next request if I wish to persist any changes I make? or Instead should I just query for the object again with the new context and update it?
This question has more to do with organizing files/best practices and is a followup to a question i posted earlier. When I am using separate files based on entities to organize my data access layer, what is the best practice to organize my queries involving joins between multiple tables. I am still a bit hazy on organization. Have tried searching online but havent had much help.
Terrific question. My first recommendation is to think in patterns. With that said...
You pretty much nailed the advantages of using POCO. There are some distinct advantages to decoupling your business objects (POCO entities) from your data access layer. But the primary reason is like you said the ability to change or modify layers below. However using POCO you are essentially following the Code First (CF) approach. Personally, I consider it Code In Parallel depending upon your software development life cycle. You still have all the bells and whistles that data or model first approach have and some since you can extend the DbContext which is ObjectContext under the hood. I read an article, which I cannot seem to find, that CF is the future of Entity Framework. Lastly the nice thing with POCO is you are able to incorporate validation rules here or else where. You can also provide projections. Lets say you have Date of Birth but you want an Age property as well. That now becomes a no brainer as the Age property is ignored when mapping to the database.
Personally I create my own business objects (POCO) for large projects that tend to have a life of its own where change is a way of life. Another thought is scalability and maintainability. What if down the road I choose to split functionality between applications where, like you mentioned web services, functionality is now delivered from two disparate locations. If you have encapsulated your business objects and DAL within the same code block separation or scalability has now become a bit more complex. However, consider the project. It may be small with very little future change so no need to throw a grenade to kill a fly. At which time data first might be the way to go and let edmx file represent your objects. So don't marry yourself to one technology or one methodology/pattern. Do what makes sense for your time and business.
Using statements are perfectly fine. In fact I've recently been turned on to then wrapping that within a TransactionScope. If an error occurs rollbacks are inherent. Next, something to consider is the UnitOfWork. UnitOfWork pattern encapsulates a snapshot of what needs to be performed where the Data Context is the boundaries from which you work within. For each UnitOfWork you have a subject for which work is to be performed on. For example an Employee. So if you are to save Employee information to keep it simple you would make a call to the BL service or repository (which ever). There you pass in the Employee Id, perform some work under that UnitOfWork where it is either instantiated in the constructor or using Dependency Injections (DI or IoC). Easy starter is StructureMap. There the service makes the necessary calls to your UnitOfWork (DbContext) then returns control back upstream (e.g. UI).
The best way to learn here is to view others code. I'd start with some Microsoft examples. I'd start with Nerd Dinner (http://nerddinner.codeplex.com/) then build off that.
Additional Reading:
Use prototype pattern or not
http://weblogs.asp.net/manavi/archive/2011/05/17/associations-in-ef-4-1-code-first-part-6-many-valued-associations.aspx
[EDIT]
NightHawk457, I'm terribly sorry for not responding to your questions. Hopefully you figured it out but for future readers...
To help everyone visualize, imagine the below Architecture using the Domain Model and Repository as an example. Remember, there are many ways to skin a cat so take this and make it your own and don't forget my Grenade comment above.
Data Layer (Data Access): MyDbContext : DbContext, IUnitOfWork, where IUnitWork contracts the CRUD operations.
Data Repository (Data Access / Business Logic): MyDomainObjectRepository : IMyDomainObjectRepository, which receives IUnitOfWork by Factory class or Dependency Injection. Calls MyDomainObject validation on CRUD operations.
Domain Model (Business Logic): MyDomainObject using [Custom] Validation Attributes. Read this for pros/cons.
MVVM / MVC / WCF (Presentation / Service Layers): What ever additional layers you chose, you now have access to your data which is wrapped nicely in smaller modules who are self encapsulating of their function. The presentation layer (e.g. ViewModel, Controller, Code-Behind, etc.) can then receive an IMyObjectRepository by a Factory class or by Dependency Injection.
Tips:
Pass connection string into MyDbContext so you can reuse MyDbContext.
MySql does not play well with System.Transactions.TransactionScope, example. I don't recall exactly but it was something MySql did not support. This makes Testing a bit difficult since we have created this level of separation.
Create a Test project for each layer and at the minimum test general functionality/rules.
Each Domain Object should extend base object with ID field at minimum. Also do not implement Key attributes here. Domain Object should not describe architecture but rather the specific data as an entity. Even on Code First this can be achieved by the Fluent API.
Think generics when creating MyDbContext. ;) Read Diego's post.
In ASP.NET, the repositories are nice to use with ObjectDataSources.
As you can see, there is clear separation of roles where IUnitOfWork and IMyDomainObjectRepository are the Interfaces which expose the above layers functionality. And as an example, IUnitOfWork could be NHibernate, Entity Framework, LinqToSql or ADO.NET where a change to the factory class or dependency injection registration is all that has to change. FYI, I've heard the Repository called the Service Layer as well. Personally I like the first name to not be confused with Web Services. The next big take away from this structure is realizing the scope for you Database Context (IUnitOfWork). A simple example would be a ASP.NET page where for each page there is one and only one IUnitOfWork for either each repository or for that scope of work. Same holds true for ViewModels, Controllers, etc. So let's say you need to utilize two repositories, EmployeeRepository and HRRepository. You then could share the IUnitOfWork between both or not. To cross page, ViewModel or Controller boundaries, we use the ID for entities where they are then pulled from the DB and work is performed. You could alternatively pass a DTO across boundaries and attach to the context but then you begin losing separation of layers.
To continue, POCO classes do not have to be auto generated. In fact you can create your Entity Classes from scratch and perform the mapping in your extended DbContext class inside the OnModelCreating(DbModelBuilder mb) method. Start here, then here and note the Additional Resources, google Fluent API and read this post by Diego.
As for validation, this is an interesting point because it would be GREAT if all Business Rules could be validated in one location. Well, as we all know that doesn't work real well. So here is my recommendation, keep all data level validation (i.e. required, range, format, etc.) with data annotation as much as possible in the domain object and leave process validation in the Repository with clear roles of the Repository (i.e. if (isEmployee) do this, else that). I say clear, such that you do not want to add an Employee in two different Repositories where validation has to be duplicated. To call the validation, start here. Capture the ValidationResults and send upstream with a MyRepositoryValidationException which contains a collection of validations errors (e.g. Employee is required) which can be presented to the presentation layer. With all that said, don't forget to perform validation at the presentation layer. You don't want post backs to make sure an Employee has a valid Email, for example.
Just remember to balance time and effort with complexity. For something simple, use Data First or Model First with your EDMX file. Then lay a repository on top of that which also contains all the validation rules.
I have few concerns about DTO. I am trying to create 4 level architecture for my asp.net website. I will have DTO, BLL, DAL and Presentation Layer.
Do I need to create DTO for each table? I have almost 100 tables and some of the tables have 70-100 columns.
For complicated query where I join 5-8 tables, How do I approach this? DO I need to get DTO for each table and then run Linq Query on all those DTO List in BLL then return result back to aspx page?
If there are other suggestions, please let me know. Thanks in advance for your help.
You will only need a DTO when you need to pass a simple object, perhaps from the DAL repository (where your DTO = a table, stored procedure result or view result) to a domain / BLL object which might well be an aggregate object providing a logical view of the domain rather than a one to one mapping from the database. It all depends on how you are 'growing' your application.
If you are going to have loads of similar DTO's it can be a good idea to use a tool, like AutoMapper - it will save you a lot of time writing boring mapping code.
Some people insist on having separate DTOs for every single service call you make. Depending on the complexity of the logic, this could potentially lead to much more than 100 different DTOs.
I prefer a generic approach, where you build a DTO model with a 1-1 correspondence between DTOs and domain entities. In this approach, you'll have 100 DTO tables. If you use any tool to automatically create code (Codesmith, T4), creating the DTO layer can be easy.
The other concern, returning compound results can be tackled with a generic DTO container to hold your DTO classes:
http://netpl.blogspot.com/2010/12/generic-dto-model-and-other-silverlight.html
(the section starts at the "Generic DTO Models)
i am using EF4 and StructureMap in an asp.net web application. I am using the repository/unit of work patterns as detailed in this post. In the code, there is a line that delegates the setup of an ObjectContext in global.asax.
EntityUnitOfWorkFactory.SetObjectContext(() => new MyObjectContext());
On the web page code-behind, you can create a generic repository interface like so ...
IRepository<MyPocoObject> ds = ObjectFactory.GetInstance<IRepository<MyPocoObject>>();
My question is what is a good approach to refactoring this code so that I can use more than one ObjectContext and differentiate between them in the code-behind? Basically i have two databases/entity models in my application and need to query them both on the same page.
The Unit of Work is used to manage persistence across multiple repositories, not multiple object contexts.
You're not going to be able to persist changes across multiple contexts using a unit of work, as the UoW is simply implemented as a wrapper for a ObjectContext. Therefore, you'll need two unit of works.
Overall, things are going to get messy. You're going to have two OCs newed up and disposed each HTTP request, not to mention transaction management is going to be a nightmare.
Must you have two ObjectContexts? What is the reasoning for this? If it's for scalability, don't bother; it's going to be too painful for other things like your repository, unit of work and http scope management.
It's hard to provide good advice without seeing how you have your repositories set up.
Try creating wrapper classes for each object context, each implementing IUnitOfWork and a secondary unique interface (IEfSqlContext1, etc which represents one of your models/contexts).
Then you can inject whichever context you want.
As I said though, try and avoid having two EDMX/Contexts. It's more trouble than it's worth.
We're developing a business ASP.NET application. Is it better to pass an entire entity to a method or pass each property of this entity as parameters? What is the best practice?
Case 1. Pass Customer entity to a manager - InsertCustomer(Customer cust)
Case 2. Pass each property as a parameter - InsertCustomer(string name, string address...etc)
P.S. We're using Entity Framework as our data access layer
Pass the entire entity, not only for reasons given in the other answers, but generally methods with long parameter chains are bad. They are prone to error, and tough to work with from a development standpoint (just look at Interop with Office)
In general, if I see I am getting too many parameters (usually more than three), either I have a method trying to do too much, or I explore ways of encapsulating this data in a struct.
You should pass the entire entity as when you update the entity, e.g. add or remove members you do not have to update all your method calls in all your layers. You only need to change your datalayer and the layer where you are consuming the entity. asp.net is Object Oriented and therefore you should orientate your code around your objects
The whole concept of object orientation requires objects to be passed around. If all is happening internally I would go with this.
If this is being posted to a webservice / across a network etc you would need to serialize, and hence may find it better to pass each individual parameter, especially if the receiving framework is different.
Don't forget your Strings etc are all objects too.
I agree with another poster, passing a whole entity "encapsulates" everything so that it can be updated/modified so you have less to worry about.