Using Multiple ObjectContexts In Entity Framework 4 With The Repository/uow Pattern
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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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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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 7, 2011
We have an IVR product that reads a configuration database for callflow information. I am writing a tool for our implementation team that will allow them to add/delete/update the data in the configuration database. Once the tool is in production, the implementer will use only the production release of the tool to modify the configuration database in all four of the IVR regions (Dev, QA, Cert, and Prod). Each region has its own database with identical schemas. The tool has 'tabs' across the top for each region. If a user is currently working in the Dev region and clicks the QA tab, how do I switch my connection from the Dev db server to the QA db server?
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Dec 14, 2010
I have a model that consists of Order, OrderLine, Product.
I want to create an Order and add OrderLines (each OrderLine related to a Product). I create the Order and add new OrderLines to it. Between posts I store the Order entity in Session (or ViewState). Just so you know I have added suppport for binary serialisation which works fine.
The relationship is therefore Order > OrderLine(s) > Product(s).
You might have already guessed what the problem is - that when I SaveChanges() I get the usual 'AcceptChanges cannot continue because the object's key values conflict with another object in the ObjectStateManager.' error.
I have referred to a number of articles online but none seem to handle this case (where I have the relationship across more than two entities) e.g. [URL].
This must be a very common requirement surely? Is there anyone out there doing the same kind of thing with Entity Framework (and without using DTOs etc)?
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Jun 10, 2010
A relative newcomer to .net MVC2 and the entity framework, I am working on a project which requires a single web application, (C# .net 4), to connect to multiple different databases depending on the route of access, (ie subdomain).
No problem with this in principle and all the logic is written to transform the subdomain into an entity connection and pass this through to the Entity Model.
The problem comes with the fact that the different database whilst being largely similar in structure contain 3 or 4 unique tables bespoke to that instance.
To my mind there are two ways to solve this issue, neither of which i am sure will be possible.
1/ Use a separate entity model for each database. -Attempts down this route have through up conflicts where table/sp names are the same across differnt db's, or implicit conversion errors when I try and put the different models in different namespaces. or
2/ Overwrite the classes which refer to the changeable database objects based on the value of a base controller property.
My question is if either of theser routes can ever work in principle or if i should just give up on the EF and connect to the dtabases directlky using ADO. Perhaps there is another way to solve this problem i haven't thought of?
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Jan 21, 2011
So, have a search form where users can enter one or more keywords, these keywords are then held in a List<string> called keywords. Now using Entity Framework have an Organisation entity with a Name field. What I want to do is select those organisations whose name contains all the keywords. I don't care if they are in the right order or not but it just contain all the keywords. Also organsiations is a big table in the database so I don't want to materialise all the organsiation objects on the server and then loop through them. So what I'm looking for (excuse my LINQ naivety here) is equivalent to the non-existent LINQ statement:
[Code]....
I'm sure this must have already been answered but just can't find it.
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Dec 10, 2010
I want to write a query in Entity Framework that has multiple joins. The only problem is the tables arn't related using their primary / foreign keys (its the Umbraco database), as such I can't use .Include and the Navigation properties.
Essentially the query I would like to run is this:
select t.*, n.* from cmsContentType t
inner join cmsContentTypeAllowedContentType a on t.nodeId = a.Id
inner join vicinity.DocumentTypeExtendedProperty x on x.UmbracoDocumentTypeId = t.pk
inner join umbracoNode n on n.id = t.nodeId
I have two EF entities mapped to cmsContentType and umbracoNode as such I would like them to be populated as if I was running the query like
var q = from p in cmsContentType.Include("umbracoNode")
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Feb 24, 2013
I am using Entity Framework 4.0. I want To write a query for multiple row update.
Then how to write Query for multiple row update in Entity Framework.
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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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Oct 7, 2010
i'm trying to use Entity Framework to insert into SQL SERVER 2005, using Visual studio 2008.the following codes are a Button onclick event,I want to insert into DB multiple rows at a time
[Code]....
however this does not work, it seems we can only insert into DB only one row at a time
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Mar 23, 2010
public void saveOptionalCourses( ArrayList coursesAdded, int studentID)
{
StudentOptionalCoursesXRef XRefObject = new StudentOptionalCoursesXRef();
using (var EntityObject = new SchoolProjectEntities2())
{
foreach ( string list in coursesAdded)
{
XRefObject.StudentDetails = EntityObject.StudentDetails.Where(c => c.StudentID == studentID).First();
XRefObject.OptionalCourses = EntityObject.OptionalCourses.Where(c => c.OptionalCourseName == list).FirstOrDefault();
EntityObject.AddToStudentOptionalCoursesXRef(XRefObject);
}
EntityObject.SaveChanges();
}
with this above method and could save only last row that am returning remaining rows are iterated but are not saving on to database
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Mar 9, 2011
I have a repeater like so:
[Code]....
Problem is, I also want to show the viewer the available number of spots in the room. But this requires somehow pull in either the current_occupancy / max_occupancy or in performing a calculation (e.g. max_occupancy - current_occupancy = actual_available) and then returning that with the room.
The end result I'm looking for is to return each room in a button control with text that looks like this:
"Room 1 - 2 Open" "Room 8 - 1 Open" and so on
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Oct 25, 2010
Is there a way to export a EF 4.0 Data Model to EF 3.5?
I looked around and found that we are not able to access EF 4.0 from a ASP.Net 3.5 project here: [URL]
Our project is the 1st to go to .Net 4.0 using Entity Framework and we (the team) were wondering if there was a way for the other projects that "might" need to access our data that are still using the .Net 3.5 framework.
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Apr 8, 2010
I have a question that I'm ashamed to ask, but I'm going to have a go at it anyway. I am creating a generic repository in asp.net mvc. I came across an example on this website which I find to be exactly what I was looking for, but there is one problem. It references an object - Entity - and I don't know what namespace it is in. I typically create my repositories and use Entity Framework but I decided to use a generic repository because I am using the same code in multiple projects over and over again.
Here is the code:
public interface IRepository
{
void Save(ENTITY entity)
where ENTITY : Entity;
void Delete<ENTITY>(ENTITY entity)
where ENTITY : Entity;
[code]....
what namespace Entity is in? As you can tell, a constraint is placed on the code so that it must be an Entity type. I know that there is an Entity in System.Data.Entity, but that isn't what I need. I have had instances before where I was looking for some namespace that took me forever to find, but I have searched and I'm unable to find the appropriate namespace to cast my generic items correctly. I could cast it as a class and be done with it, but it is bugging me that I can't find Entity anywhere.
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Nov 2, 2010
I am new to entity framework , it is really very good , but I want to know what is the difference between using entity framework with stored procedure or without stored procedure , which one the faster and what is the benefits for using stored procedures with entity framework.
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Jun 30, 2010
I have an EDM, it includes the entities extension and history. My goal is to use history to keep track of all the changes made to extension entity. For example, if extension with ID 223 has its property 'Name_Display' changed - I want the history entity to record this.
I'm using ASP.NET with VB.NET. Where in my code do I put the hook to say, "update the history entity" and what should that hook look like?
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Feb 9, 2011
I get an cast exception when i am trying to insert an entity in Entity Framework (using code-first). From this code :
public virtual T Insert(T entity)
{
return Context.Set<T>().Add(entity);
}
The cast exception is like "impossible to cast ...Collection'1(Entity) to type (Entity)" I can't figure out why. I am pretty sure ive done everything right. Post entity
public class Post
{
public long PostId { get; private set; }
public DateTime date { get; set; }
[Required]
public string Subject { get; set; }
public User User { get; set; }
public Category Category { get; set; }
[Required]
public string Body { get; set; }
public virtual ICollection<Tag> Tags { get; private set; }
public Post()
{
Category = new Category();
if (Tags == null)
Tags = new Collection<Tag>();
}................................
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