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• Why use Entity Framework over Linq2SQL if...

  - by Refracted Paladin

  To be clear, I am not asking for a side by side comparision which has already been asked Ad Nauseum here on SO. I am also Not asking if Linq2Sql is dead as I don't care. What I am asking is this.... I am building internal apps only for a non-profit organization. I am the only developer on staff. We ALWAYS use SQL Server as our Database backend. I design and build the Databases as well. I have used L2S successfully a couple of times already. Taking all this into consideration can someone offer me a compelling reason that I should use EF instead of L2S? I was at Code Camp this weekend and after an hour long demonstration on EF, all of which I could have done in L2S, I asked this same question. The speakers answer was, "L2S is dead..." Very well then! NOT! (see here) I understand EF is what MS WANTS us to use in the future(see here) and that it offers many more customization options. What I can't figure out is if any of that should, or does, matter for me in this environment. One particular issue we have here is that I inherited the Core App which was built on 4 different SQL Data bases. L2S has great difficulty with this but when I asked the aforementioned speaker if EF would help me in this regard he said "No!"

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• Entity Framework: Attached Entities not Saving

  - by blog

  Hello: I can't figure out why calling SaveChanges() on the following code results in no changes to the objects I attached: // delete existing user roles before re-attaching if (accountUser.AccountRoles.Count > 0) { foreach (AccountRole role in accountUser.AccountRoles.ToList()) { accountUser.AccountRoles.Remove(role); } } // get roles to add List<int> roleIDs = new List<int>(); foreach (UserRole r in this.AccountRoles) { roleIDs.Add(r.RoleID); } var roleEntities = from roles in db.AccountRoles where roleIDs.Contains(roles.id) select roles; accountUser.AccountRoles.Attach(roleEntities); db.SaveChanges(); In the debugger, I see that the correct roleEntities are being loaded, and that they are valid objects. However, if I use SQL Profiler I see no UPDATE or INSERT queries coming in, and as a result none of my attached objects are being saved.

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• Entity comments are removed upon saving of updated model

  - by Adam Asham

  In my entities, I tend to add comments for the properties but as I update the model and save it, all the comments are removed. How can I stop this behavior?

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• Entity Framework with SQL Server 2000 (APPLY Operator) issue

  - by How Lun

  Hello, I have a simple Linq query below: var seq = (from n in GetObjects() select n.SomeKey) .Distinct() .Count(); This query works find with SQL Server 2005 and above. But, this start to give headache when I hooked the EF to SQL Server 2000. Because EF is using APPLY operator which only SQL Server 2005 and above can be supported. I do not know why the hell EF is using APPLy operator instead of sub queries. My current work around is: var seq = (from n in GetObjects() select n.SomeKey) .Distinct() .ToList() .Count(); But, I can forsee more problems to come. The above query is just a simple one. Did anyone come across such issue? And how you guys work around it? Or is there a way to force EF not to use APPLY operator? Any help will be very much appreciated. How Lun.

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• Entity framework Update fails when object is linked to a missing child

  - by McKay

  I’m having trouble updating an objects child when the object has a reference to a nonexising child record. eg. Tables Car and CarColor have a relationship. Car.CarColorId CarColor.CarColorId If I load the car with its color record like so this var result = from x in database.Car.Include("CarColor") where x.CarId = 5 select x; I'll get back the Car object and it’s Color object. Now suppose that some time ago a CarColor had been deleted but the Car record in question still contains the CarColorId value. So when I run the query the Color object is null because the CarColor record didn’t exist. My problem here is that when I attach another Color object that does exist I get a Store update, insert error when saving. Car.Color = newColor Database.SaveChanges(); It’s like the context is trying to delete the nonexisting color. How can I get around this?

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• Saving a modified object from ASP.NET MVC View Using Entity-Franework 4

  - by Dani

  I retrieve an object graph from DB using EF4. The context is closed as soon as the data retrieve and the data passes to the controller, and then to the view. in the view the data is modified, and then the controller gets it back. From the controller I run Repository.Update(MyEmp); and in my repository the code goes: using (var context = new mydb()) { if (myEmp.ID != 0) // Checking if it's modified or new { context.Emp.Attach(MyEmp); int result = context.SaveChanges(); return myEmp.ID; } } The problem - once attached, the object entityState goes to unchanged, and not modified, and of course - nothing is saved to the database. What am I doing wrong ?

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• How to retrieve base class only (entity framework)?

  - by Juvaly

  Hi All, I've been scratching my head here for a while now... I have a Consumer class and a BillableConsumer class that inherits Consumer. They are both a part of the Consumers set. The problem is that this following query: Consumer consumer = (from c in _ctx.Consumers where c.ID = id select c).First(); returns a BillableConsumer instance! Just the same as this query: BillableConsumer bconsumer = (from c in _ctx.Consumers.OfType<BillableConsumer>() where c.ID = id select c).First(); How can I return an instance of just the base class? (these are separate tables in the data store).

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• Entity Framework 4 and 0:1, 0:1 relationships

  - by Eric J.

  I'm using the Model First approach with EF 4 and hit a snag with two tables, Participant (singular because pre-existing from another app) and ActiveParticipants. A Participant may or may not be associated with exactly one ActiveParticipant and vice versa. When I create an association, everything seems to go well on the surface, but then I get a runtime error complaining that Participant does not contain the column ActiveParticipant_Id. It does contain a column ActiveParticipantId (no underscore). When I view the diagram as XML, there's a line like this: <Property Name="ActiveParticipant_Id" Type="uniqueidentifier" Nullable="true" /> Why is it adding an underscore? Is there anything special I need to do for 0:1, 0:1 relationships?

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• Left Join with Entity Framework

  - by sanfra1983

  hi, someone can tell me how to do this query in EF1: select a.idAnimali, a.titolo, a.commenti, a.ordine, a.idcatanimali, table1.nomefoto FROM tabanimali as a LEFT JOIN (SELECT idanimali, nomefoto tabfotoanimali FROM LIMIT 1) AS Table1 On a.idAnimali = table1.idanimali WHERE a.idcatanimali = idcatanimale Thanks

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• Does Entity Framework saves related classes automatically?

  - by herbatnic

  Let's assume that we have such classes public class A{ string someField { get; set; } public virtual B B {get; set; } } public class B { int someIntField {get; set; } [ForeignKey("Id")] [Required] public virtual A A { get; set; } } In code I create new instances for both of them and making relation like: A a = new A () { someField = "abcd"}; B b = new B () { someIntField = 42 }; A.B = b; B.A = a; Should I using DBContext to save both classes like that: using (var db = new myDbContext()) { myDbContext.As.Add(A); myDbContext.Bs.Add(B); myDBContext.SaveChanges(); } Or saving it like that: using (var db = new myDbContext()) { myDbContext.As.Add(A); myDbContext.SaveChanges(); } is enough to store related objects into database?

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• What is the difference between these two statements (asp.net/c#/entity framework)

  - by user318573

  IEnumerable<Department> myQuery = (from D in myContext.Departments orderby D.DeptName select D); var myQuery = (from D in myContext.Departments orderby D.DeptName select D); What is the difference between these two statements above? In my little asp.net/C#/ EF4.0 app I can write them either way, and as far as how I want to use them, they both work, but there has to be a reason why I would choose one over the other?

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• multiple join query in entity framework

  - by gvLearner

  I have following tables tasks id | name | proj_id 1 | task1 | 1 2 | task2 | 1 3 | task3 | 1 projects id | name 1 | sample proj1 2 | demo project budget_versions id | version_name| proj_id 1 | 50 | 1 budgets id | cost | budget_version_id | task_id 1 | 3000 | 1 | 2 2 | 5000 | 1 | 1 I need to join these tables to get a result as below task_id | task_name | project_id | budget_version | budget_id | cost 1 | task1 | 1 | 1 | 2 |5000 2 | task2 | 1 | 1 | 1 |3000 3 | task3 | 1 | NULL | NULL |NULL select tsk.id,tsk.name, tsk.project_id, bgtver.id, bgt.id, bgt.cost from TASK tsk left outer join BUDGET_VERSIONS bgtver on tsk.project_id= bgtver.project_id left outer join BUDGETS bgt on bgtver.id = bgt.budget_version_id and tsk.id = bgt.task_id where bgtver.id = 1

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• Argument exception after trying to use TryGetObjectByKey

  - by Rickjaah

  Hi, EDIT: Somethings wrong.... I have to use objectContext.Frontpages.ToArray() before I can use TryGetObjectByEntityKey(). Any ideas anyone? I'm trying to retrieve an object from my database using entity (framework 4) When I use the following code it gives an ArgumentException: An item with the same key has already been added. if (databaseContext.TryGetObjectByKey(entityKey, out result)) { return (result != null && result is TEntityObject) ? result as TEntityObject : null; } else { return null; } When I check the objectContext, I see the entities, but only if I enumerate the specific list of entities manually using VS2010, it works. What am I missing? Do I have to do something else before i can get the item from the database? I searched google, but could not find any results, the same for the msdn library EDIT: Still working on this.... It's a weird problem. I retrieve a value, but get an error that says a duplicate item exists. STACKTRACE: [ArgumentException: An item with the same key has already been added.] System.ThrowHelper.ThrowArgumentException(ExceptionResource resource) +52 System.Collections.Generic.Dictionary2.Insert(TKey key, TValue value, Boolean add) +9549131 System.Data.Metadata.Edm.ObjectItemAttributeAssemblyLoader.LoadRelationshipTypes() +661 System.Data.Metadata.Edm.ObjectItemAttributeAssemblyLoader.LoadTypesFromAssembly() +17 System.Data.Metadata.Edm.ObjectItemAssemblyLoader.Load() +25 System.Data.Metadata.Edm.ObjectItemAttributeAssemblyLoader.Load() +4 System.Data.Metadata.Edm.AssemblyCache.LoadAssembly(Assembly assembly, Boolean loadReferencedAssemblies, ObjectItemLoadingSessionData loadingData) +160 System.Data.Metadata.Edm.AssemblyCache.LoadAssembly(Assembly assembly, Boolean loadReferencedAssemblies, KnownAssembliesSet knownAssemblies, EdmItemCollection edmItemCollection, Action1 logLoadMessage, Object& loaderCookie, Dictionary2& typesInLoading, List1& errors) +166 System.Data.Metadata.Edm.ObjectItemCollection.LoadAssemblyFromCache(ObjectItemCollection objectItemCollection, Assembly assembly, Boolean loadReferencedAssemblies, EdmItemCollection edmItemCollection, Action`1 logLoadMessage) +316 System.Data.Metadata.Edm.MetadataWorkspace.ImplicitLoadAssemblyForType(Type type, Assembly callingAssembly) +306 System.Data.Metadata.Edm.MetadataWorkspace.ImplicitLoadFromEntityType(EntityType type, Assembly callingAssembly) +109 System.Data.Objects.ObjectContext.TryGetObjectByKey(EntityKey key, Object& value) +288 EDIT: Lazy loading is set to true. EDIT: Somethings wrong.... I have to use objectContext.Frontpages.ToArray() before I can use TryGetObjectByEntityKey(). Any ideas anyone?

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• Best practice for structuring a new large ASP.NET MVC2 plus EF4 VS2010 solution?

  - by Nick

  Hi, we are building a new web application using Microsoft ASP.NET MVC2 and Entity Framework 4. Although I am sure there is not one right answer to my question, we are struggling to agree a VS2010 solution structure. The application will use SQL Server 2008 with a possible future Azure cloud version. We are using EF4 with T4 POCOs (model-first) and accessing a number of third-party web-services. We will also be connecting to a number of external messaging systems. UI is based on standard ASP.NET (MVC) with jQuery. In future we may deliver a Silverlight/WPF version - as well as mobile. So put simply, we start with a VS2010 blank solution - then what? I have suggested 4 folders Data (the EF edmx file etc), Domain (entities, repositories), Services (web-services access), Presentation (web ui etc). However under Presentation, creating the ASP.NET MVC2 project obviously creates it's own Models folder etc and it just doesn't seem to fit too well in this proposed structure. I'm also missing a business layer (or does this sit in the domain?). Again I am sure there is no one right way to do it, but I'd really appreciate your views on this. Thanks

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• EF4 and multiple abstract levels

  - by Cedric

  I need to use inheritance with EF4 and the TPH model created from DB. I created a new projet to test simples classes. There is my class model: There is my table in SQL SERVER 2008 : VEHICLE ID : int PK Owner : varchar(50) Consumption : float FirstCirculationDate : date Type : varchar(50) Discriminator : varchar(10) I added a condition in my EDMX on the Discriminator field to differentiate the Scooter, Car, Motorbike and Bike entities. MotorizedVehicle and Vehicle are Abstract. But when I compile, this error appears : Error 3032: Problem in mapping fragments starting at lines 78, 85:EntityTypes EF4InheritanceModel.Scooter, EF4InheritanceModel.Motorbike, EF4InheritanceModel.Car, EF4InheritanceModel.Bike are being mapped to the same rows in table Vehicle. Mapping conditions can be used to distinguish the rows that these types are mapped to. Edit : To Ladislav : I try it and error change to become it for all of my entities : Error 3034: Problem in mapping fragments starting at lines 72, 86:An entity is mapped to different rows within the same table. Ensure these two mapping fragments do not map two groups of entities with overlapping keys to two distinct groups of rows. To Henk (with Ladislay suggestion) : There are all of mappings details : What's wrong ? Thanks

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• Maintaining state and data context between requests in ASP.NET + EF4

  - by Nick

  I have a EF4/ASP.NET web application that is structured to use POCOs and generic repositories, based essentially on this excellent article. The application is relatively sophisticated with one page that involves selection and linking of multiple entities to build up a complex user profile. This requires access to multiple entity types (20 or so) and associated repositories across multiple posts. When a repository is first accessed it uses the existing data context if exists, else it creates a new context. The problem is that if the lifetime of the context is only per-request (as suggested in the article) then you have to deal with multiple contexts and the complexity around detaching and attaching entities from contexts. My solution is to share the context between posts by creating a single View Model that includes all required repositories (initialised to share the same context) plus any associated data and store this model in a Session variable, retrieving from Session on subsequent page requests. Therefore maintaining the same context across all posts until the profile is saved. This works fine BUT I am concerned that I don't actually know exactly what is stored in the model session variable or more importantly the size of the Session variable. So two questions I suppose: firstly should I look for a better solution to handle the shared context across posts issue (any suggestions welcome)? And secondly what is actually stored in the Session when it includes a repository plus context? Any help appreciated!

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• Mapping composite foreign keys in a many-many relationship, with overlapping components.

  - by Kirk Broadhurst

  I have a Page table and a View table. There is a many-many relationship between these two via a PageView table. Unfortunately all of these tables need to have composite keys (for business reasons). Page has a primary key of (PageCode, Version), View has a primary key of (ViewCode, Version). PageView obviously enough has PageCode, ViewCode, and Version. The FK to Page is (PageCode, Version) and the FK to View is (ViewCode, Version) Makes sense and works, but when I try to map this in Entity framework I get Error 3021: Problem in mapping fragments...: Each of the following columns in table PageView is mapped to multiple conceptual side properties: PageView.Version is mapped to (PageView_Association.View.Version, PageView_Association.Page.Version) So clearly enough, EF is having a complain about the Version column being a common component of the two foreign keys. Obviously I could create a PageVersion and ViewVersion column in the join table, but that kind of defeats the point of the constraint, i.e. the Page and View must have the same Version value. Has anyone encountered this, and is there anything I can do get around it? Thanks!

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• Review: ComponentOne Studio for Entity Framework

  - by Tim Murphy

  While I have always been a fan of libraries that improve coding efficiency and reduce code redundancy I have mostly been using ones that were in the public domain.  As part of the Geeks With Blogs Influencers program a got my hands on ComponentOne’s Studio for Entity Framework.  Below are my thought after working with the product for several weeks. My coding preference has always been maintainable code that is reusable across an enterprises protfolio.  Because of this my focus in reviewing this product is less on the RAD components and more on its benefits for layered applications using code first Entity Framework. Before we get into the pros and cons here is a summary of the main feature listed for SEF. Unified Data Context Virtual Data Access More Powerful Data Binding Pros The first thing that I found to my liking is the C1DataSource. It basically manages a cache for your Entity Model context.  Under RAD conditions this is setup automatically when you drop the object on a your design surface.  If you are like me and want to abstract you data management into a library it takes a little more work, but it is still acceptable and gains the same benefits. The second feature that I found beneficial is the definition of views with improved sorting and filtering.  Again the ease of use of these features is greater on the RAD side but no capabilities are missing when manipulating object in code. Linq has become my friend over the last couple of years and it was great to see that ComponentOne had ensured that it remained a first class citizen in their design.  When you look into this product yourself I would suggest taking a dive into LiveLinq which allow the joining of different data source types. As I went through discovering the features of this framework I appreciated the number of examples that they supplied for different uses.  Besides showing how to use SEF with WinForms, WPF and Silverlight they also showed how to accomplish tasks both RAD, code only and MVVM approaches. Cons The only area that I would really like to see improvement is in there level of detail in their documentation.  Specifically I would like to have seen some of the supporting code explained, such as what some supporting object did, in the examples instead of having to go to the programmer’s reference. I did find some times where currently existing projects had some trouble determining scope that the RAD controls were allowed, but I expect this is something that is in part end user related. Summary Overall I found the Studio for Entity Framework capable and well thought out.  If you are already using the Entity Framework this product will fit into your environment with little effort in return for greater flexibility and greater robustness in your solutions. Whether the $895 list price for a standard version works for you will depend on your return on investment. Smaller companies with only a small number of projects may not be able to stomach it, you get a full featured product that is supported by a well established company.  The more projects and the more code you have the greater your return on investment will be. Personally I intend to apply this product to some production systems and will probably have some tips and tricks in the future. del.icio.us Tags: ComponentOne,Studio for Entity Framework,Geeks With Blogs,Influencers,Product Reviews

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• Présentation de Zkoss, un framework RIA pure Java qui demande à être connu

  Zkoss, un framework RIA pure Java qui demande à être connu 1.Introduction Ce mini-article a pour intention de vous faire découvrir un framework RIA encore peu connu mais si puissant..Zkoss est un framework pur java permettant de faire des applications RIA comparables à Silverlight, Flex, IcesFaces, RichFaces, OpenFaces... Vous allez sûrement me dire qu'il s'agit d'un framework parmi tant d'autres... Cet exact, mais celui-ci apporte de gros avantages par rapport à ceux précités...Vous pouvez découvrir cette démo en ligne ici. 2.Avantages 2.1 Rapidité de conception La rapidité de prise ...

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• Entitiy Framework: "Update Database from Model" instead of "Generate Database from Model"

  - by David

  Hey everyone, I have created a Entity Framework 4 model with Visual Studio 2010 and generated a database from it. Now I found myself adding new properties (with default values), changing documentation of columns, changing names of columns, changing types of columns several times. All tasks that do not require much "extra work" in order not to be possible to be achieved automatically (in my humble opinion). Everytime I did "Generate Database from Model" and lost of course the table data. Is there a way just to update the database's architecture so to say - leaving the table data untouched? Maybe with some user interaction especially when changing types etc.? Or would this functionality be simply too difficult to be realized to work in a reliable way? Thanks in advance! Cheers, David

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• Create a many to many relationship in Entity Framework skipping extra data in the link table.

  - by Paul Smith

  I would like to model the following many to many relationship. Table A ID Field1 Field2 Table B ID Field1 Field2 LinkTable A_ID B_ID Field_I_want_to_ignore As I understand it, if LinkTable.Field_I_want_to_ignore was not present, the Entity Model Designer would automatically create a Many to Many relationship between entity A and entity B. However, because this field exists in the database the designer won't do it for me. I can delete the Field_I_want_to_ignore from the LinkTable Entity that the designer created for me, but how do I eliminate the LinkTable entity altogether and create the many to many relationship I want? I'm not averse to digging through the XML, just at the moment I can't see how to achieve what I want.

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• Entities Framework 4 doing a bulk delete

  - by Adan

  I wish to know if there is a good way to do a bulk delete or delete multiple rows using the Entities Framework 4. I can't seam to find a DeleteAll command. The only one that is available is DeleteObject() which only takes one entity, I would like to perform a delete on a list of entities.Is there a better way than to loop trough the list? I did see an article that used ExecuteStoreQuery and created some sql that would perform the delete. Is there a better way than to perform any of these two options Please advice what is the best way to perform this action.

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• Mapping one to one foreign key relationships in Entity Framework 4.0?

  - by John K.

  Hello all, I'm sure I'm missing something very simple, but let's say I have two entities, Employee and EmployeeType. Employee type would contain values like 'Full time', 'Contractor', 'Intern', etc. An Employee entity would contain one, and only one EmployeeType value. So I am designing a new .edmx model using the Model-First approach and generating my actual sql server data schema from the model. I want to add an integer type foreign key id into my Employee entity, EmployeeTypeId, which will map to the primary key of the EmployeeType entity. So I've gone ahead and done that in my Employee entity. Where I'm stuck is how, though the Entity Framework designer, to enforce the 1:1 referential constraint on that EmployeeTypeId property? Or does the EF handle that automatically behind the scenes? thanks in advance, John

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• How to load entities into readonly collections using the entity framework

  - by Anton P

  I have a POCO domain model which is wired up to the entity framework using the new ObjectContext class. public class Product { private ICollection<Photo> _photos; public Product() { _photos = new Collection<Photo>(); } public int Id { get; set; } public string Name { get; set; } public virtual IEnumerable<Photo> Photos { get { return _photos; } } public void AddPhoto(Photo photo) { //Some biz logic //... _photos.Add(photo); } } In the above example i have set the Photos collection type to IEnumerable as this will make it read only. The only way to add/remove photos is through the public methods. The problem with this is that the Entity Framework cannot load the Photo entities into the IEnumerable collection as it's not of type ICollection. By changing the type to ICollection will allow callers to call the Add mentod on the collection itself which is not good. What are my options?

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• How to install Zend Framework on Windows

  - by sombe

  "installing Zend Framework is so easy!!!!" yeah right... Ok I'm working with a beginner's book and the ONE thing that is not excessively detailed is the most important part: Installing the darn thing. After browsing the quickstart guide for hours, all it said was: "download Zend [...] add the include directory (bla bla) and YOU'RE DONE!" right, i'm done using Zend. Ok, not really, not yet anyway. I beg of you people, I wanna go to bed, please tell me how (in simple 6th grade detail) to install the framework. I've got the unzipped folder in my htdocs directory, and I placed zf.bat+zf.php in the htdocs root. What's next? thank you so much. EDIT: Thanks guys for all the answers. Unfortunately I haven't been able to work with this or find a good enough resource to explain it to me in plain english. It seems that this framework adheres more so to programmers than to beginners. I've since yesterday read a little on CakePHP and found that it was incredibly easy to install and tune. As oppose to Zend Framework, where I had to dig in my "environment variables", configure "httpd.conf" and almost tie the knot between my computer driver cables to just get it running, CakePHP has already allowed me to put together a nice newbie application. In conclusion, I very much appreciate all of your help. I hope someone else venturing on ZF will be more successful with it. Thanks!

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