i have used the repo pattern in my web forms application in the following way
UI Layer:
it contains the code behind files in which the controls are being binded and user actions like insert update etc are catered for
the UI Layer calls the
Repository Layer:
it contains the repository classes inheriting the GenericRepo:IGeneric
and the
Data Layer:
it contains the EF generated domain classes
the layers are strict for the time being that is the UI layer calls the Repo layer and it in turns call the data layer to fetch the data.
Problem:
now the problem im facing is that if for example i need a list of products on the Products.aspx page i need to do some thing like
IProductRepo pr = new ProductRepo();
IList<Products> lstProducts = pr.GetAll();
i dont want to add the reference of Data Layer to the UI layer in order to access the domain entities i.e generated by the EF
what are my options? please guide me to the right path
regards.
In my opinion you're missing a layer. I would built it like this:
UI |
----- |
**Domain** | Domain classes
----- |
DAL (Repository) |
This way your logic is in a separate layer and your DAL is completely hidden from your logic and domain model.
Another way you could solve this problem is by using Dependency Injection. That way you can define some interfaces and only keep references to interfaces. With a dependency container you can ten tie those references to real types.
My preferred DI container is for example Ninject
Related
I am trying to use Entity Framework 4.0 for an asp .net application. As of now, it will be old style code behind files and without unit testing but in the future I may use MVP and unit testing but as of now, it is not a concern for me. I am using Database First approach. Here is a model ( I could not post image as I need reputation to post image)
Table: Application (ApplicationID, Name, Hidden)
Table: User (UserID, ApplicationID, Username, IsActive)
Table: Role (RoleID, ApplicationID, Name)
Table: UserRole (UserRoleID, RoleID, UserID)
I have been reading a lot about Entity Framework and how to use it but still could not get a very basic idea about some stuff. Where do I write a code like this for Application, User, Role, UserRole etc?
public List<Application> GetAllUnhiddenApplications()
{
List<Application> applist = null;
using (CustomAppsPortalEntities ctx = new CustomAppsPortalEntities())
{
applist = (from app in ctx.Applications
where app.Hidden == false
orderby app.Name
select app).ToList();
}
return applist;
}
I have separated Context and Entities in separate projects Project.Data and Project.Entities respectively. My question is if above code belongs to BLL (class name ApplicationBLL) or DLL (ApplicationDLL)? From past 2 days, I have been searching lots of SO questions, blogs, tutorials and different people have different approach. Here is my dilemma.
If I put the code in Data layer, then in the business layer, I have to create a "pass through" function like ApplicationBLL.GetAllUnhiddenApplications which will return ApplidationDLL.GetAllUnhiddenApplications. I have to repeat it for all the queries and basically whole BLL will eventually become "pass through" layer for DLL. Can you give me a concrete example of what Business layer will be used for in reference to above schema?
If I put the code in Business layer, then linq will exist in Business layer which eventually will be converted to SQL by Entity Framework so it is like exposing query logic to Business Layer.
Our Environment
Our environment is fast paced and want to complete this project as soon as possible with the moderately proper approach where there is a separate layer but in the future when we find time, we may refactor the code and make it really robust but it is not a concern as of now but if the time permits, we want to implement best practices right now versus refactoring code in the future.
The above code would typically be in the BL layer. Using linq in your BL layer is fine because your linq queries are still data persistence ignorant. From linq queries perspective, it's querying objects from entity framework.
What you might be missing is a "repository pattern" and "unit of work patter". The repository pattern acts as an interface to entity framework. It allows you to interact with EF objects like in-memory collections. Typically I keep all repositories in one project and reference accordingly. To give you an example, Microsoft Spain provides a n-tierd example,
http://microsoftnlayerapp.codeplex.com/
It's very over engineered, but I believe it will give you what your looking for.
Many people argue that EF IS the DLL.
Typically, I set my projects up something like this...
D ---> Presentation Layers (MVC, WCF, WinForms, etc)
A |
T V
A ---> Business Logic Layer
|
M V
O ---> Entity Layer / DLL
D
E
L
The Data Models project is really just a collection of POCO's that can be used in any of the other projects.
The Entity Layer is your EDMX file and Context.
It should be fine to access the context in the Entity/DLL layer, since .Net has abstracted everything out for you.
If you think about it, the whole reason to abstract out a DLL layer is so that you can change databases without having to change the BLL. With EF, you can change a database in 1 step and everything should still work.... as long as your schema stays the same.
I am using ViewModel in asp.net mvc 3.
In my case I have a controller which initiate a ViewModel connected to a View.
If no variable DateForLookUp is appended in the URL the controller initialize the ViewModel with DateTime.UctNow, otherwise it use the variable.
I need create to link on the View. When a user click the link I must take the DateForLookUp value and adding or subtract one day.
My question:
Where is appropriate to place this logic, ServiceLayer, the ViewModel, the Controller or the View?
VIEW
#Html.ActionLink("Next Day", "Daily")
#Html.ActionLink("Previous Day", "Daily")
CONTROLLER
public ActionResult Daily(string dateForLookUp)
{
DateTime dateTimeForLookUp;
if (string.IsNullOrWhiteSpace(dateForLookUp))
dateTimeForLookUp = DateTime.UtcNow;
else
dateTimeForLookUp = DateTime.Parse(dateForLookUp);
var eventsInDate = eventAggregateService.FindAllForDate(dateTimeForLookUp);
EventsAggregateDailyListViewModel eventDailyVM = new EventsAggregateDailyListViewModel();
eventDailyVM = new EventsAggregateDailyListViewModelBuilder().Build(eventDailyVM, dateTimeForLookUp);
return View(eventDailyVM);
}
In my opinion (and in practice), I would place any and all logic in the service layer.
I break my MVC apps into several different projects to keep all layers nicely separated:
AppName.Configuration: to handle any configuration of the app (i.e. pulling in web.config/app settings, resource files, etc.)
AppName.Data: this is the data layer where all DB access is performed (no business logic). The DBML/EDMX lives here, my repository class(es) live here as well.
AppName.Models: this is where all of my ViewModels are defined for MVC, as well as other model objects needed throughout the application.
AppName.Services: This is my business layer, everything must pass through here to get to the data layer or to the presentation/web layer. ViewModels are constructed from the database objects, data validation happens here, etc.
AppName.Web: this would be the MVC application.
AppName.Data.Test: Unit tests for Data app
AppName.Services.Test: Unit tests for the services
AppName.Web.Test: Unit tests for the MVC controllers
AppName.Web.UI.Test: Unit tests for the web user interfaces (using WATIN)
I also have a set of classes packaged up into NuGet packages that I can add to my app if/when needed, namely (for this example):
CompanyName.Data: Common library for data layer logic
CompanyName.MVC: Common library for ASP.NET MVC integration
CompanyName.Utilities: Common library for miscellaneous utilities
My controllers do nothing except get the ViewModels from the service layer to send to the views and then receive the data upon post from the views and send it off to the services layer for validation, processing, saving back to the repository, other business logic, etc.
I have a 3-tier web application wit ha bunch of simple forms. One to list records, one to edit a single record, etc. The works.
I have a DataLayer where my EDMX is.
I have an App Layer where my POCOs are.
I haev a BusinessLayer with all my controller classes, etc. (not MVC!)
I have a UI layer where my web UI is.
The EDMX has many, many tables wit ha lot of navigation properties.
Of course, when I fetch the data in one of my controllers, e.g. GetCustomerById(int id), I create the Object context and close it when I'm done.
However, the ObjectContext is out of scope when I try to access the navigation properties in the UI layer.
Should I do (using MyContext = new MyContext()) {... } in the web layer?? that does not seem right.
Should I create another set of POCOs that I populate from the entities' data from the BizLayer?
What happens when I want to save data entered in a web form? Would I call a BizLayer controller e.g. SaveCustomer()?
My question is, how do you design the web UI layer if I want to be able to properly access the navigation properties of an entity?
Note:
EDMX is set to LazyLoading.
You want to use lazy loading in UI but it means that UI defines lifetime of your ObjectContext. There are many ways to achieve this without exposing the context to UI. You can for example use this simple approach:
You mentioned some controller which uses context and disposes it. So make your controller disposable and instead of disposing context in every method use single context for whole lifetime of the controller. Dispose the context in controller's Dispose method.
Instantiate your controller per request. So for example you can create instance of controller in Page.Load and dispose it in Page.Unload.
Use your controller and entities as you want. Whole processing of the request (between Load and Unload) will be in scope of single living context.
Anyway you should not need lazy loading in Web application too much. In your form you usually know exactly what entities you need so you should request them directly with eager loading.
In web application, i am created one new project in that i added class library, like business layer, datalayer, but when i am accessing the business class in datalayer, class object is created but, when i am accessing the fileds of that class like example :
EmpBL objEmb= new EmpBL();
objEmb is not coming in intellesence, even i am not accessing the fileds of business class can you help me out please.
right click on your data layer project, select Add Reference and select Project tab - then add reference to your .Business project.
However, you can now have circular references, i.e. you can't reference each other. And normally, Business Objects project references Data Access project, not the other way around. Although any architecture is possible, and sometimes BOL project is just storage classes, and they don't know anything about DAL - a third project brings them together. Not sure about your exact architecture.
I was going through Unity 2.0 to check if it has an effective use in our new application. My application is a Windows Forms application and uses a traditional bar menu (at the top), currently.
My UIs (Windows Forms) more or less support Dependency Injection pattern since they all work with a class (Presentation Model Class) supplied to them via the constructor. The form then binds to the properties of the supplied P Model class and calls methods on the P Model class to perform its duties. Pretty simple and straightforward.
How P Model reacts to the UI actions and responds to them by co-ordinating with the Domain Class (Business Logic/Model) is irrelevant here and thus not mentioned.
The object creation sequence to show up one UI from menu then goes like this -
Create Business Model instance
Create Presentation Model instance with Business Model instance passed to P Model constructor.
Create UI instance with Presentation Model instance passed to UI constructor.
My present solution:
To show an UI in the method above from my menu I would have to refer all assemblies (Business, PModel, UI) from my Menu class. Considering I have split the modules into a number of physical assemblies, that would be a dificult task to add references to about 60 different assemblies. Also the approach is not very scalable since I would certainly need to release more modules and with this approach I would have to change the source code every time I release a new module.
So primarily to avoid the reference of so many assemblies from my Menu class (assembly) I did as below -
Stored all the dependency described above in a database table (SQL Server), e.g.
ModuleShortCode | BModelAssembly | BModelFullTypeName | PModelAssembly | PModelFullTypeName | UIAssembly | UIFullTypeName
Now used a static class named "Launcher" with a method "Launch" as below -
Launcher.Launch("Discount");
Launcher.Launch("Customers");
The Launcher internally uses data from the dependency table and uses Activator.CreateInstance() to create each of the objects and uses the instance as constructor parameter to the next object being created, till the UI is built. The UI is then shown as a modal dialog. The code inside Launcher is somewhat like -
Form frm = ResolveForm("Discount");
frm.ShowDialog();`
The ResolveForm does the trick of building the chain of objects.
Can Unity help me here?
Now when I did that I did not have enough information on Unity and now that I have studied Unity I think I have been doing more or less the same thing. So I tried to replace my code with Unity.
However, as soon as I started I hit a block. If I try to resolve UI forms in my Menu as
Form customers = myUnityContainer.Resolve<Customers>();
or
Form customers = myUnityContainer.Resolve(typeof(Customers));
Then either way, I need to refer to my UI assembly from my Menu assembly since the target Type "Customers" need to be known for Unity to resolve it. So I am back to same place since I would have to refer all UI assemblies from the Menu assembly. I understand that with Unity I would have to refer fewer assemblies (only UI assemblies) but those references are needed which defeats my objectives below -
Create the chain of objects dynamically without any assembly reference from Menu assembly. This is to avoid Menu source code changing every time I release a new module. My Menu also is built dynamically from a table.
Be able to supply new modules just by supplying the new assemblies and inserting the new Dependency row in the table by a database patch.
At this stage, I have a feeling that I have to do it the way I was doing, i.e. Activator.CreateInstance() to fulfil all my objectives. I need to verify whether the community thinks the same way as me or have a better suggestion to solve the problem.
The post is really long and I sincerely thank you if you come til this point. Waiting for your valuable suggestions.
Rajarshi
As I can see from this code
Form customers = myUnityContainer.Resolve<Customers>();
all your code need to know about the customer - is that it's a Form class. So if you use xml configuration for unity you can do the following:
<type type="Form" mapTo="Customer" name="Customer">
</type>
And then you'll be able to resolve it like this:
Form customers = myUnityContainer.Resolve<Form>("Customer");
and there is no need to refference your UI assembly. Offcourse it should be presented in the bin directory or GAC. In this case if you'll develop new Assembly - all you need is to change config and put in in bin or gac.
If you want to make unity configuration from db then you'll have to add referrence to your ui, becouse you'll have to call Register("Customer").