Pattern For Retrieving Complex Object Graphs With Repository Pattern With Entity Framework
Oct 13, 2010
We have an ASP.NET MVC site that uses Entity Framework abstractions with Repository and UnitOfWork patterns. What I'm wondering is how others have implemented navigation of complex object graphs with these patterns. Let me give an example from one of our controllers:
[code]....
It's a registration process and pretty much everything hangs off the POCO class Person. In this case we're caching the person through the registration process. I've now started implementing the latter part of the registration process which requires access to data deeper in the object graph. Specifically DPA data which hangs off Legal inside Country.
The code above is just mapping out the model information into a simpler format for the ViewModel. My question is do you consider this fairly deep navigation of the graph good practice or would you abstract out the retrieval of the objects further down the graph into repositories?
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Jan 17, 2011
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.
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Dec 8, 2010
i'm new to asp.net MVC, and I'm trying to understand the service/repository pattern and how to best implement it.
I've followed the MVC Music store tutorial, and it suggests that the public partial class ShoppingCart implements an AddToCart method looking like this:
[Code]....
Now if I would like to use the service/repository pattern in a correct way, should I just replace the row "storeDB.AddToCarts(cartItem)" with something like cartService.AddToCarts(cartItem) and then just save the added row by calling cartService.Save() instead of shopDB.Save()? The methods AddToCart(...) and Save() in cartService then calls the repository that does the actual saving.
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Mar 8, 2011
I've been using MVC for the last year and unfortunately I am stuck adding features to an existing web forms site. The site makes heavy use of inline SQL and it is kind of all over the place. Using an ORM is not going to happen either and wouldn't address the problem of keeping queries all in one place.
Can the Repository Pattern and Service layers also work well with classic asp.net web forms?
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Feb 15, 2010
I am building an application using asp.net mvc, DI, IoC, TDD as a bit of a learning exercise.
For my data access I am using the repository pattern. Now I am looking at membership and how this can work with the repository pattern. I am currently using a Linq to Sql repository but don't want to be tied to SQL Server for membership.
Secondly, I am looking to split out membership into a number of services:
AuthenticationService - identify the user
AuthorizationService - what can they do
PersonalizationService - profile
The personalization service will be what really defines a "customer" in my application and each customer will have a unique id/username that ties back to the AuthenticationService - thus, allowing me to use the default ASP.NET Membership provider, roll my own or use something like Open ID.
Is this a good approach? I don't want to reinvent the wheel but would rather these important parts of my application follow the same patterns as the rest.
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Oct 18, 2010
I am sort of using a repository pattern to extract information from a database. I have two classes, report and reportRepository.
The trouble I have is that since reportReposity has to fill in all the details for the report object, all the members in the report have to be publicly accessible.
Is there a way so that I can ensure that only the repository class can access some of the methods of the report class and only it can set some of the properties that other classes cannot, sort of like what friend does in c++. Or is there a completely different way of handling this situation?
I am using C# in ASP.NET 2.0
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Jul 8, 2010
This is possibly the worst kind of religious debate -- a religious debate with practical consequences. But it's one that needs to be had, and I can't seem to fit it in my tiny head. Here are the pros and cons of the pattern as I know them:
Pros:
-Encourages DRY (don't repeat yourself) design in that identical queries are written only once per set of query conditions
-Facilitates unit testing by allowing itself to be abstracted into an interface
-Creates an opportunity for business-level validation
Cons:
-Breaks DRY philosophy in that you're generally repeating your database schema
-In a sense breaks separation of concerns, because the query concerns of the controller and view frequently become the concerns of whoever is maintaining the repository
-Determining what should be a repository and what should be returned as a raw associated ORM entity becomes an ambiguous art
To me it seems like all this stuff should be done at the ORM level, but Entity Framework has much fewer hooks than Linq to Sql does, yet Entity Framework tends to be regarded as being more robust, so it seems that this is by design, and that the designers of EF are in fact encouraging another layer. Are there any tools or anything that I could be using for this? Am I missing something?
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Dec 21, 2010
I am currently using the 3-tier Repository pattern in my application. Actually it's the first time for me to implement a design pattern at all! i used to put all my code in the so called now presentation layer.
i want to implement data validation, for example, password should not be more than 10 characters and have to contain special characters. Should i put this code in the data access layer? but my data access layer contains methods that take the DTO as a parameter for example
[Code]....
and the same is for other CRUD operations (DELETE and UPDATE), so implementing such validation on the DAL would make me duplicate the code in each and every method that accepts the DataObject as a paramter. Same holds for the business logic layer where i am using it as a proxy between the presentation and the data access layers.
Eventually it has to use the same Data Objects as parameters. This only leaves me with one option which is to do the validation on the Data Object part. But i think this is not the essence of the respository pattern which states that the Data object class should only be a "container" class with no behavior.
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Nov 2, 2010
I'm working on adding an HtmlHelper for pagination, but I am unsure where the proper and/or most beneficial place to put certain parts of the pagination code from a performance and maintainability standpoint.
I am unsure if the Skip(), Take() and Count() portions of Linq to SQL data manipulation should live within the repository or the controller.
I am also unsure if their order and where they are used affects performance in any way.
If they live within the repository from my understanding this is how it would work:
1. I would pass the pageIndex and pageSize as arguments to the repository's method that grabs the data from the database.
2. Then grab the full data set from the database.
3. Then store the count of TotalItems of that full data set in a variable.
4. Then apply the Skip() and Take() so the data set retains only the page I need.
5. Display the partial data set as a single page in the view.
If they live in the controller from my understanding this is how it would work:
1. I would grab the full data set from the repository and store it into a variable inside of the controller.
2. Then get the count of TotalItems for the full data set.
3. Then apply the Skip() and Take() so the data set retains only the page I need.
4. Display the partial data set as a single page in the view.
Inside the controller (I realize I will incorrectly get the page count here and not TotalItems):
[code]....
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Feb 4, 2011
I am trying to understand the fundamental differences between the Provider Model and Repository Pattern.
I have used the Provider Model in many many situations and am confident with it when designing applications. However, the more examples I encounter on the internet and asp.net evolution I keep coming across "Repository" Interfaces for classes that look like a Provider Model.
I have dug around a bit but all I can see is that they kinda do the same thing, or closely overlap by enforcing an inheriting class to adhere to a "contract" of implemented / abstracted methods etc...is there more to it?
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Feb 23, 2010
Does anyone have a working pattern for converting a GET-POST-GET pattern to asny?
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Jan 19, 2010
When I first heard about ASP.NET MVC, I was thinking that would mean applications with three parts: model, view, and controller.
Then I read NerdDinner and learned the ways of repositories and view-models. Next, I read this tutorial and soon became sold on the virtues of a service layer. Finally, I read the Fluent Validation documentation, and I'll be darned if I didn't end up writing a bunch of validators.
Tonight, I took a step back and thought about what had become of my project. It seems to have become the victim of the design pattern equivalent of "feature creep". Somehow I'd gone from Model-View-Controller to Model-Repository-Service-Validator-View-ViewModel-Controller. You want loosely coupled and DRY? We got your loosely coupled and DRY right here! But I'm wondering if this could be a case of too much of a good thing.
Am I right to be concerned? Or is this actually not as crazy as it sounds? On one hand, it seems crazy to have so many layers. On the other hand, every layer has a clearly defined purpose that makes sense to me. Have your MVC applications turned into MRSVVVMC apps too? If not, what do they look like? Where's that right balance?
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Jan 28, 2011
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I am creating an authentication service. This service has one of the methods to validate username and password and return a status based on it.
The validation method has bunch of things to check before it can say user is valid. This method has a pseudo code similar to this:
If UserName and Password is correct
If User Account is Locked (due to invalid attempts)
{[code]....
As you can see there are lots of if else statements that I am writing. It looks more like a procedural programming rather than object oriented.How can I fit such kind of code in object oriented pattern?
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Feb 18, 2011
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Feb 20, 2011
I want to be able to update a model and all its collections of child objects in the same view. I have been referred to these examples: http://haacked.com/archive/2008/10/23/model-binding-to-a-list.aspx and http://blog.stevensanderson.com/2010/01/28/editing-a-variable-length-list-aspnet-mvc-2-style/ .
For example, I have an object Consultant, that has a collection of "WorkExperiences". All this is in an Entity Framework model. In the view, the simple properties of the Consultant object is no problem, but the collection I cannot get a textbox to show up for. I tried following the examples in the links above, but it doesn't work. The problem is, in those examples the model is just a list (not an object with a child list property). And also, the model again is an EF model. And for some reason that doesn't seem to work as in those examples.
[Code]....
This stuff with the EditorTemplate works fine in Phil Haack's sample project, which I downloaded to try, but here, with the EF model or whatever the problem is, I don't get any textbox at all. The table in the view is just there as a test, because in the table I do get the rows for WorkExperiences, whether I add an empty WorkExperience object or fill out its properties doesn't matter, the rows show up for each object. But again, no textbox...
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Apr 2, 2010
I have a table in my database with a one to many relationship to another table, which has a relationship to a third table:
[Code].....
This seems to work fine. My question to you good folks: Is there a correct way to do this? I tried following the making a custom model binder per the blog link I posted above but it didn't work (there was an issue with reflection, the code expected certain properties to exist) and I needed to get something going ASAP. PS - I tried to cleanup the code to hide specific information, so beware I may have hosed something up.
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Jun 8, 2010
I am very new to entity, sql, c#, and asp.net so this might be something easily fixed. I am attempting to display all the inactive products stored in my table called products in a datagrid.
var productQuery = from b in solutionContext.Version
where b.Product.Name == search && b.Product.ActiveNumber > b.VersionNumber
select new Product
{
Name = b.Product.Name,
Description = b.Product.Description,
ID = b.ID,
LastNumber = b.Product.LastNumber,
MiddleNumber = b.Product.MiddleNumber,
RSTATE = b.RSTATE,
ActiveNumber = b.Product.ActiveNumber,
LastModified = b.Product.LastModified,
ParentID = b.Product.ParentID,
ProductType = b.Product.ProductType
};
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Aug 20, 2010
When I use classical ADO.NET or (which is interesting) EntityDataSource (e.g. for GridView), then page load within 1 second.But when I use ic codefile code like:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Cty = CType(Request.QueryString("cty"), Integer) ' course type
Page.SetFocus(ddl_FGPhotosOK)
If Not IsPostBack Then ' read course status
Using ctx_sdbEntities As New sdbEntities()
[code]...
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Mar 10, 2010
i have 2 tables without any cascade deletind. i wont to delete parent object with all child objects. i do like this
//get parent object
return _dataContext.Menu.Include("ChildMenu").Include("ParentMenu").Include("Pictures").FirstOrDefault(m => m.MenuId == id);
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var picList = (List<Picture>)menu.Pictures.ToList();
//foreach (var item in menu.Pictures)
for (int i = 0; i < picList.Count; i++)
{
if (File.Exists(HttpContext.Current.Server.MapPath(picList[i].ImgPath)))
{
File.Delete(HttpContext.Current.Server.MapPath(picList[i].ImgPath));
}
if (File.Exists(HttpContext.Current.Server.MapPath(picList[i].ThumbPath)))
{
File.Delete(HttpContext.Current.Server.MapPath(picList[i].ThumbPath));
}
//**what must i do here?**
//menu.Pictures.Remove(picList[i]);
// DataManager dm = new DataManager();
// dm.Picture.Delete(picList[i].Id);
//menu.Pictures.de
//_dataContext.SaveChanges();
//picList[i] = null;
}
//delete parent object
_dataContext.DeleteObject(_dataContext.Menu.Include("ChildMenu").Include("ParentMenu").Include("Pictures").FirstOrDefault(m => m.MenuId == id););
_dataContext.SaveChanges();
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Feb 12, 2010
Tables: Article, Author, Comment (1 article and 1 author can have * comments)In the database is 1 article, 1 author and 1 comment.
The problem is, that code
myBD my_bd = new myBD();
var articles = by_bd.Article;
works OK, I can see that an Author and an Article has 1 comment. But that code
var comm = (from u in my_bd.Comment
where ......
select u);
returns the comment but it has NULL values in property Article and Author. Why ?
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Nov 14, 2010
I'm trying to figure out how to bind an EF4.0 object to my textbox control. I have a call to my business object that returns an entity CFUser that has a FirstName parameter on it of type string. However, after I make the call and bind the object, the codebehind executes which fills the BindUser property with the correct value. However, nothing shows up in the textbox.
my aspx side is
[Code]....
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