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  • what is Entity Framework with POCO

    - by pdiddy
    What is the benefit of using POCO? I don't understand the meaning of Persistence Ignorance, what does this mean? That the poco object can't expose things like Save? I can't wrap my head around this POCO that there's alot of buzz around. What is the difference with the EF generated entities and POCO?

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  • Entity Framework Reusing Connection

    - by LB
    in a using block for a connection to the entities, How am I to reuse the connection when calling another method? so I have: using (SampleEntities entities = new SampleEntities()) { entities.Connection.Open(); SomeMethod(); ... } void SomeMethod() { using (SampleEntities entities = new SampleEntities()) { // I want to be able to use the existing connection before the method call, any ideas? } }

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  • Entity framework not loading relationship even when using include

    - by dilbert789
    I have this code: Category selectedCategory = (from c in DB.Category.Include("SubCategory") join a in DB.Accessory on c.AccCatUID equals a.Category.AccCatUID where a.AccUID == currentAccessory.AccUID select c).FirstOrDefault(); It works fine, selectedCategory gets populated as expected. BUT selectedCategory has a child table 'SubCategory' which does not get loaded even though there is the include there. It is not loaded until I do this: selectedCategory.SubCategory.Load(); Why do I have to call load explicitly in order to load the child table?

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  • How to cache L2E entity without attach/detach?

    - by Eran Betzalel
    The following code will select a key/value table in the DB and will save the result to the cache: using (var db = new TestEntities()) { if(Cache["locName_" + inventoryLocationName] != null) return Cache["locName_" + inventoryLocationName]; var location = db.InventoryLocationsSet.FirstOrDefault( i => i.InventoryLocationName.Equals( inventoryLocationName, StringComparison.CurrentCultureIgnoreCase)); db.Detach(location); // ???? Cache["locName_" + inventoryLocationName] = location; return location; } But it doesn't work well when I'm trying to use the cached object. Of course, the problem is the different ObjectContext, so I use Attach/Detach and then the problem solves but with a codding horror price: db.Attach(locationFromCache); // ???? try { // Use location as foreign key db.SaveChanges(); } finally { db.Detach(locationFromCache); // ???? } So, how can I use cached objects without using attach/detach methods? What happens if more than one user will have to use this cached object? Should I put the whole thing in a CriticalSection?!

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  • Retrive data from two tables in asp.net mvc using ADO.Net Entity Framework

    - by user192972
    Please read my question carefully and reply me. I have two tables as table1 and table2. In table1 i have columns as AddressID(Primary Key),Address1,Address2,City In table2 i have columns as ContactID(Primary Key),AddressID(Foriegn Key),Last Name,First Name. By using join operation i can retrive data from both the tables. I created a Model in my MVC Application.I can see both the tables in enitity editor. In the ViewData folder of my solution explorer i created two class as ContactViewData.cs and SLXRepository.cs In the ContactViewData.cs i have following code public IEnumerable<CONTACT> contacts { get; set; } In the SLXRepository.cs i have following code public IEnumerable<CONTACT> GetContacts() { var contact = ( from c in context.CONTACT join a in context.ADDRESS on c.ADDRESSID equals a.ADDRESSID select new { a.ADDRESS1, a.ADDRESS2, a.CITY, c.FIRSTNAME, c.LASTNAME } ); return contact; } I am getting the error in return type Cannot implicitly convert type 'System.Linq.IQueryable' to 'System.Collections.Generic.IEnumerable'. An explicit conversion exists (are you missing a cast?)

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  • Entity framework memory leak after detaching newly created object

    - by Tom Peplow
    Hi, Here's a test: WeakReference ref1; WeakReference ref2; TestRepositoryEntitiesContainer context; int i = 0; using (context = GetContext<TestRepositoryEntitiesContainer>()) { context.ObjectMaterialized += (o, s) => i++; var item = context.SomeEntities.Where(e => e.SomePropertyToLookupOn == "some property").First(); context.Detach(item); ref1 = new WeakReference(item); var newItem = new SomeEntity {SomePropertyToLookupOn = "another value"}; context.SomeEntities.AddObject(newItem); ref2 = new WeakReference(newItem); context.SaveChanges(); context.SomeEntities.Detach(newItem); newItem = null; item = null; } context = null; GC.Collect(); Assert.IsFalse(ref1.IsAlive); Assert.IsFalse(ref2.IsAlive); First assert passes, second fails... I hope I'm missing something, it is late... But it appears that detaching a fetched item will actually release all handles on the object letting it be collected. However, for new objects something keeps a pointer and creates a memory leak. NB - this is EF 4.0 Anyone seen this before and worked around it? Thanks for your help! Tom

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  • Entity Framework connection metadata extraction

    - by James
    Hi, I am using the EntityFramework POCO adapter and since there are limitations to what microsoft gives access to with regards to the meta data, i am manually extracting the information i need out of the xml. The only problem is i want to get the ssdl, msl, csdl file names to load without having to directly check for the connection string node in app.config. In short where in the ObjectContext/EntityConnection can i get access to these file names? Worst case scenario i need to get the connection name from the EntityConnection object then load this from app.config and parse the string itself and extract the filenames myself. (But i obviously don't want to do that). Thanks

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  • How to apply global filter on Entity Framework?

    - by Hernan
    I have a table in my model named Customers with a field IsActive. Whenever I run a query on Customers, only the active customers should be retrieved. I can include the filter in every query, but that doesn't look very. I would like to be able to override the Customers property at the Object Context lever, but I am not sure if this is possible. Any help would be very appreciated! Thanks

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  • Entity Framework ObjectContext re-usage

    - by verror
    I'm learning EF now and have a question regarding the ObjectContext: Should I create instance of ObjectContext for every query (function) when I access the database? Or it's better to create it once (singleton) and reuse it? Before EF I was using enterprise library data access block and created instance of dataacess for DataAccess function...

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  • entity framework inserting a many-to-many relationship between two existing objects while updating

    - by redbluegreen
    I'm trying to do this: using(var context = new SampleEntities()) { User user = select a user from database; //Update user's properties user.Username = ... user.Website = ... //Add a role Role role = select a role from database //trying to insert into table UserRoles which has columns (UserID, RoleID) user.Roles.Add(role); //Apply property changes context.ApplyPropertyChanges("Users", user); context.SaveChanges(); } However, I get an exception telling me that "The existing object in the ObjectContext is in the Added state" and can't "ApplyPropertyChanges". If "ApplyPropertyChanges()" is removed, it adds a User. What orders should these methods be called? I don't need to do them separately right? Thanks.

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  • ADO.NET Entity Framework: Can I have multiple entity types for the same row.

    - by black_nm
    Hi all, I have a base class Participants inherited by Artist, Author and TextWriter. I have only one table in the data store: Participants { ID, FirstName, LastName, IsArtist, IsAuthor, IsTextWriter, } The idea is to have a class for all the roles that a participant can have. I've managed to create the edmx file but when I try to get an Participant (as Artist) that is also an Author I receive the following error: All objects in the EntitySet 'Participants' must have unique primary keys. However, an instance of type 'Artist' and an instance of type 'Author' both have the same primary key value, 'EntitySet=Participants;ID=1'. Thank you

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  • Entity framework (1): implement 1 foreign key to multiple tables

    - by Michel
    Hi, i've modeled this: i have an import table, and an import steps table import 1 .. N importsteps Now i have a table importparams, which hold key/value pairs to register all kind of info about the import or the importsteps. So i have modeled a FK in SqlServer which points to the PK of the import table and to the PK of the importsteps table (the ID's for both the import as the importsteps table are guids, so i can query the importparams with either the id from import or from importsteps and get the right importparams). Makes sense a bit? But how can i model this in the EF? I can see it's a bit hard for the EF to model this, because one realtion can point to multiple classes, but is there a way? The workaround normally is just to get all importparams where FK is the ID, but as you know the FK is not available in the EF version 1. I hope you can help me out, michel

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  • Fixing up an entity framework query

    - by vdh_ant
    My table structure is as follows: Person 1-M PesonAddress Person 1-M PesonPhone Person 1-M PesonEmail Person 1-M Contract Contract M-M Program Contract M-1 Organization At the end of this query I need a populated object graph where each person has their: PesonAddress's PesonPhone's PesonEmail's PesonPhone's Contract's - and this has its respective Program's Now I had the following query and I thought that it was working great, but it has a couple of problems: from people in ctx.People.Include("PersonAddress") .Include("PersonLandline") .Include("PersonMobile") .Include("PersonEmail") .Include("Contract") .Include("Contract.Program") where people.Contract.Any( contract => (param.OrganizationId == contract.OrganizationId) && contract.Program.Any( contractProgram => (param.ProgramId == contractProgram.ProgramId))) select people; The problem is that it filters the person to the criteria but not the Contracts or the Contract's Programs. It brings back all Contracts that each person has not just the ones that have an OrganizationId of x and the same goes for each of those Contract's Programs respectively. What I want is only the people that have at least one contract with an OrgId of x with and where that contract has a Program with the Id of y... and for the object graph that is returned to have only the contracts that match and programs within that contract that match. I kinda understand why its not working, but I don't know how to change it so it is working... This is my attempt thus far: from people in ctx.People.Include("PersonAddress") .Include("PersonLandline") .Include("PersonMobile") .Include("PersonEmail") .Include("Contract") .Include("Contract.Program") let currentContracts = from contract in people.Contract where (param.OrganizationId == contract.OrganizationId) select contract let currentContractPrograms = from contractProgram in currentContracts let temp = from x in contractProgram.Program where (param.ProgramId == contractProgram.ProgramId) select x where temp.Any() select temp where currentContracts.Any() && currentContractPrograms.Any() select new Person { PersonId = people.PersonId, FirstName = people.FirstName, ..., ...., MiddleName = people.MiddleName, Surname = people.Surname, ..., ...., Gender = people.Gender, DateOfBirth = people.DateOfBirth, ..., ...., Contract = currentContracts, ... }; //This doesn't work But this has several problems (where the Person type is an EF object): I am left to do the mapping by myself, which in this case there is quite a lot to map When ever I try to map a list to a property (i.e. Scholarship = currentScholarships) it says I can't because IEnumerable is trying to be cast to EntityCollection Include doesn't work Hence how do I get this to work. Keeping in mind that I am trying to do this as a compiled query so I think that means anonymous types are out.

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  • Entity Framework v4 examples and tutorials of conceptual model mapping

    - by Rody van Sambeek
    In an application I'm writing I have a fairly complicated Database model. I'd like to use EF4 to map this to a whole lot nicer conceptual model. However all the tutorials I've read are with samples of 2 or 3 tables which all map 1 on 1 to the conceptual model. I'd like to learn how to correctly map the database model to a different conceptual model using VS 2010. However I can't find any good tutorials or (preferabally) instruction video's. Somebody got any tips, links or even books?

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  • Entity-attribute-value model using codeigniter / php

    - by John Stewart
    SO I am trying to create a way to structure my database to be able customize forms. I looked into EAV pattern and here is my db structure: Table form - form_id - form_name - form_added_on - form_modified_at Table: form_fields - field_id - form_id - field_type (TEXT, RADIO etc..) - field_default_value - field_required Table: form_data - data_id - field_id - form_id - field_value so now I can store any custom form into the database and if I want to get the values for an individual form I can simply join it by "form_id" .. the problem: I want to be able to search through all the forms for a specific field value. How can I do that with EAV model? Also, I thought about just storing the custom data as a serialized (JSON) object but then I am not sure how can I query that data. Please note that I am using Codeigniter with MYSQL. So if conversation can use Codeigniter libraries if needed.

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  • Entity Framework 4: Inheritance and Optimistic Concurrency

    - by Mohammadreza
    Hi guys, I'm using AdventureWorks 2008 R2 database and added the BusinessEntity and Person tables to my EDMX. Then I changed the model in which the Person table inherits from the BusinessEntity table. As you may know these two tables have ModifiedDate and rowguid columns so the Person class should not have these properties because it inherits them from the BusinessEntity class. My question is, how can I modify the model to support inheritance and optimistic concurrency on both Person and BusinessEntity classes/tables on ModifiedDate property/column. PS. It also get me an error message that I have asked here. Thanks

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  • entity framework - getting null exception using foreign key

    - by Nick
    Having some trouble with what should be a very simple scenario. For example purposes, I have two tables: -Users -Comments There is a one-to-many relationship set up for this; there is a foreign key from Comments.CommentorID to Users.UserID. When I do the LINQ query and try to bind to a DataList, I get a null exception. Here is the code: FKMModel.FKMEntities ctx = new FKMModel.FKMEntities(); IQueryable<Comment> CommentQuery = from x in ctx.Comment where x.SiteID == 101 select x; List<Comment> Comments = CommentQuery.ToList(); dl_MajorComments.DataSource = Comments; dl_MajorComments.DataBind(); In the ASPX page, I have the following as an ItemTemplate (I simplified it and took out the styling, etc, for purposes of posting here since it's irrelevant): <div> <%# ((FKMModel.Comment)Container.DataItem).FKMUser.Username %> <%# ((FKMModel.Comment)Container.DataItem).CommentDate.Value.ToShortDateString() %> <%# ((FKMModel.Comment)Container.DataItem).CommentTime %> </div> The exception occurs on the first binding (FKMUser.Username). Since the foreign key is set up, I should have no problem accessing any properties from the Users table. Intellisense set up the FKMUser navigation property and it knows the properties of that foreign table. What is going on here??? Thanks, Nick

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  • Entity Framework - refresh objects from database

    - by Nebo
    I'm having trouble with refreshing objects in my database. I have an two PC's and two applications. On the first PC, there's an application which communicates with my database and adds some data to Measurements table. On my other PC, there's an application which retrives the latest Measurement under a timer, so it should retrive measurements added by the application on my first PC too. The problem is it doesn't. On my application start, it caches all the data from database and never get new data added. I use Refresh() method which works well when I change any of the cached data, but it doesn't refresh newly added data. Here is my method which should update the data: public static Entities myEntities = new Entities(); public static Measurement GetLastMeasurement(int conditionId) { myEntities.Refresh(RefreshMode.StoreWins, myEntities.Measurements); return (from measurement in myEntities.Measurements where measurement.ConditionId == conditionId select measurement).OrderByDescending(cd => cd.Timestamp).First(); } P.S. Applications have different connection strings in app.config (different accounts for the same DB).

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  • How to bind gridview using linq/Entity Framework?

    - by Kay
    I need to bind GridView, I am using this code: ProductDBEntities db = new ProductPDBEntities(); var pro = from u in db.Products where u.PID == 1 select u; if (pro != null) { GridView1.DataSource = pro; GridView1.DataBind(); } and getting this error. System.InvalidOperationException: Sequence contains more than one element Can somebody please tell me what am I doin wrong?

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  • How to get IQueryable<> from stored procedure (entity framework)

    - by mmcteam
    I want to get IQueryable<> result when executing stored procedure. Here is peace of code that works fine: IQueryable<SomeEntitiy> someEntities; var globbalyFilteredSomeEntities = from se in m_Entities.SomeEntitiy where se.GlobalFilter == 1234 select se; I can use this to apply global filter, and later use result in such way result = globbalyFilteredSomeEntities .OrderByDescending(se => se.CreationDate) .Skip(500) .Take(10); What I want to do - use some stored procedures in global filter. I tried: Add stored procedure to m_Entities, but it returns IEnumerable<> and executes sp immediately: var globbalyFilteredSomeEntities = from se in m_Entities.SomeEntitiyStoredProcedure(1234); Materialize query using EFExtensions library, but it is IEnumerable<>. If I use AsQueryable() and OrderBy(), Skip(), Take() and after that ToList() to execute that query - I get exception that DataReader is open and I need to close it first(can't paste error - it is in russian). var globbalyFilteredSomeEntities = m_Entities.CreateStoreCommand("exec SomeEntitiyStoredProcedure(1234)") .Materialize<SomeEntitiy>(); //.AsQueryable() //.OrderByDescending(se => se.CreationDate) //.Skip(500) //.Take(10) //.ToList(); Also just skipping .AsQueryable() is not helpful - same exception.

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