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• Understanding many to many relationships and Entity Framework

  - by Anders Svensson

  I'm trying to understand the Entity Framework, and I have a table "Users" and a table "Pages". These are related in a many-to-many relationship with a junction table "UserPages". First of all I'd like to know if I'm designing this relationship correctly using many-to-many: One user can visit multiple pages, and each page can be visited by multiple users..., so am I right in using many2many? Secondly, and more importantly, as I have understood m2m relationships, the User and Page tables should not repeat information. I.e. there should be only one record for each user and each page. But then in the entity framework, how am I able to add new visits to the same page for the same user? That is, I was thinking I could simply use the Count() method on the IEnumerable returned by a LINQ query to get the number of times a user has visited a certain page. But I see no way of doing that. In Linq to Sql I could access the junction table and add records there to reflect added visits to a certain page by a certain user, as many times as necessary. But in the EF I can't access the junction table. I can only go from User to a Pages collection and vice versa. I'm sure I'm misunderstanding relationships or something, but I just can't figure out how to model this. I could always have a Count column in the Page table, but as far as I have understood you're not supposed to design database tables like that, those values should be collected by queries... Please help me understand what I'm doing wrong...

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• Left/Right/Inner joins using C# and LINQ

  - by Keith Barrows

  I am trying to figure out how to do a series of queries to get the updates, deletes and inserts segregated into their own calls. I have 2 tables, one in each of 2 databases. One is a Read Only feeds database and the other is the T-SQL R/W Production source. There are a few key columns in common between the two. What I am doing to setup is this: List<model.AutoWithImage> feedProductList = _dbFeed.AutoWithImage.Where(a => a.ClientID == ClientID).ToList(); List<model.vwCompanyDetails> companyDetailList = _dbRiv.vwCompanyDetails.Where(a => a.ClientID == ClientID).ToList(); foreach (model.vwCompanyDetails companyDetail in companyDetailList) { List<model.Product> productList = _dbRiv.Product.Include("Company").Where(a => a.Company.CompanyId == companyDetail.CompanyId).ToList(); } Now that I have a (source) list of products from the feed, and an existing (target) list of products from my prod DB I'd like to do 3 things: Find all SKUs in the feed that are not in the target Find all SKUs that are in both, that are active feed products and update the target Find all SKUs that are in both, that are inactive and soft delete from the target What are the best practices for doing this without running a double loop? Would prefer a LINQ 4 Objects solution as I already have my objects. EDIT: BTW, I will need to transfer info from feed rows to target rows in the first 2 instances, just set a flag in the last instance. TIA

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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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• Why does this code generate a NotSupportedException?

  - by edg

  This is fine string foo(string f) { return f; } string bar = foo(""); var item = (from f in myEntities.Beer where f.BeerName == bar select f).FirstOrDefault(); and this is fine string foo(string f) { return f; } string bar = ""; var items = from f in myEntities.Beer where f.BeerName == foo(bar) select f; So why does this throw System.NotSupportedException? string foo(string f) { return f; } string bar = ""; var item = (from f in myEntities.Beer where f.BeerName == foo(bar) select f).FirstOrDefault();

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• subqueries linq

  - by user297378

  Hey all I am trying to do a subquery in linq but the subquery is a value and it seems to not be working, can anyone help out? I am using the entit frame work I keep getting and int to string error not sure why. from lrp in remit.log_record_product join lr in remit.log_record on lrp.log_record_id equals lr.log_record_id where (lrp.que_submit_date >= RadDatePickerStartDate.SelectedDate) && (lrp.que_submit_date <= RadDatePickerEndDate.SelectedDate) select new { lrp.que_submit_date, lr.officer_name, lr.c_fname, lr.c_lname, lrp.price_sold, lrp.product_cost, gap_account_number = (from gap in remit.gap_contracts where gap.log_record_product_id == lrp.log_record_product_id select gap.account_number), iui_account_number = (from iui in remit.iui_contracts where iui.log_record_product_id == lrp.log_record_product_id select iui.account_number), dp_account_number = (from dp in remit.dp_contracts where dp.log_record_product_id == lrp.log_record_product_id select dp.account_number), mpd_account_number = (from mpd in remit.mbp_contracts where mpd.log_record_product_id == lrp.log_record_product_id select mpd.product_account_number) }

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• How to join results from two different sets in LINQ?

  - by Inez

  Hi, I get some data about customers in my database with this method: public List<KlientViewModel> GetListOfKlientViewModel() { List<KlientViewModel> list = _klientRepository.List().Select(k => new KlientViewModel { Id = k.Id, Imie = k.Imie, Nazwisko = k.Nazwisko, Nazwa = k.Nazwa, SposobPlatnosci = k.SposobPlatnosci, }).ToList(); return list; } but also I have another method which counts value for extra field in KlientViewModel - field called 'Naleznosci'. I have another method which counts value for this field based on customers ids, it looks like this: public Dictionary<int, decimal> GetNaleznosc(List<int> klientIds) { return klientIds.ToDictionary(klientId => klientId, klientId => (from z in _zdarzenieRepository.List() from c in z.Klient.Cennik where z.TypZdarzenia == (int) TypyZdarzen.Sprzedaz && z.IdTowar == c.IdTowar && z.Sprzedaz.Data >= c.Od && (z.Sprzedaz.Data < c.Do || c.Do == null) && z.Klient.Id == klientId select z.Ilosc*(z.Kwota > 0 ? z.Kwota : c.Cena)).Sum() ?? 0); } So what I want to do is to join data from method GetNaleznosc with data generated in method GetListOfKlientViewModel. I call GetNaleznosc like this: GetNaleznosc(list.Select(k => k.Id).ToList()) but don't know what to do next.

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• How to return all records and whether a related record exists?

  - by David Glenn

  Using Entity Framework 4 CTP5 I have a basic model and a basic DbContext that works public class Customer { public int CustomerId { get; set; } public int Name { get; set; } //... public ICollection<Address> Addresses { get; set; } public bool HasAddress { get { return Addresses.Count > 0; } } } public class Address { public int AddressId { get; set; } public string StreetLine1 { get; set; } //.... public Customer Customer { get; set; } } How can I query my DbContext to return all customers and whether they have an address? A customer can have multiple addresses and I don't want to return all the addresses for each customer when I am only interested in whether they have an address or not. I use context.Customers.Include(c => c.Addresses) but that returns all addresses for each customer

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• Programmatically loading Entity classes with JPA 2.0?

  - by Dennetik

  With Hibernate you can load your Entity classes as: sessionFactory = new AnnotationConfiguration() .addPackage("test.animals") .addAnnotatedClass(Flight.class) .addAnnotatedClass(Sky.class) .addAnnotatedClass(Person.class) .addAnnotatedClass(Dog.class); Is there a way to do the same thing - programmatically loading your Entity classes - in a JPA 2.0 compliant way?

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• .Net Entity Framework & POCO ... querying full table problem

  - by Chris Klepeis

  I'm attempting to implement a repository pattern with my poco objects auto generated from my edmx. In my repository class, I have: IObjectSet<E> _objectSet; private IObjectSet<E> objectSet { get { if (_objectSet == null) { _objectSet = this._context.CreateObjectSet<E>(); } return _objectSet; } } public IQueryable<E> GetQuery(Func<E, bool> where) { return objectSet.Where(where).AsQueryable<E>(); } public IList<E> SelectAll(Func<E, bool> where) { return GetQuery(where).ToList(); } Where E is the one of my POCO classes. When I trace the database and run this: IList<Contact> c = contactRepository.SelectAll(r => r.emailAddress == "[email protected]"); It shows up in the sql trace as a select for everything in my Contact table. Where am I going wrong here? Is there a better way to do this? Does an objectset not lazy load... so it omitted the where clause? This is the article I read which said to use objectSet's... since with POCO, I do not have EntityObject's to pass into "E" http://devtalk.dk/CommentView,guid,b5d9cad2-e155-423b-b66f-7ec287c5cb06.aspx

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• How to efficiently handle Where and OrderBy clauses

  - by Goran

  My business layer passes all the required information to UI layer. From what I have read, in general, best practice is to send fetched data to UI layer, and to avoid passing queries like ObjectQuery. My problem with this approach is next: If I am to make a flexible business layer, then I should allow UI to sort the data anyway it requires. Fetching sorted data from database, and then resorting them in UI is kind of bad practice for me, so the only way is to somehow So what are my options? Is there a way to make it like this: public void OrderByMethod(params ...) { .... } so I can call it like this: OrderByMethod(MyEntity.Property1, MyEntity.Property2 descending....); Thanks, Goran

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• how to call include

  - by user276640

  i have 3 tables with such relationship table1-table2-table3 in code i call include("table2"). but how can i call include table3 so i can access to properties of objects table3? if i call include("table3") it show error A specified Include path is not valid

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• How to turn this linq query to lazy loading

  - by Luke101

  I would like to make a certain select item to lazy load latter in my linq query. Here is my query var posts = from p in context.post where p.post_isdeleted == false && p.post_parentid == null select new { p.post_date, p.post_id, p.post_titleslug, p.post_votecount, FavoriteCount = context.PostVotes.Where(x => x.PostVote_postid == p.post_id).Count() //this should load latter }; I have deleted the FavoriteCount item in the select query and would like it to ba added later based on certain conditions. Here is the way I have it lazy loaded if (GetFavoriteInfo) { posts = posts.Select(x => new { FavoriteCount = context.PostVotes.Where(y => y.PostVote_postid == x.post_id).Count() }); } I am getting a syntax error with this the above query. How do I fix this

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• Walking a hierarchy table with Linq

  - by Retrocoder

  I have a table with two columns, GroupId and ParentId (both are GUIDS). The table forms a hierarchy so I can look for a value in the “GroupId” filed, when I have found it I can look at its ParentId. This ParentId will also appear in the GroupId of a different record. I can use this to walk up the hierarchy tree from any point to the root (root is an empty GUID). What I’d like to do is get a list of records when I know a GroupId. This would be the record with the GroupId and all the parents back to the root record. Is this possible with Linq and if so, can anyone provide a code snippet?

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• Total of float column in linq query

  - by Krummelz

  I have a linq query, that gets data from a table in a DataContext object. One of the columns in this table has a Datatype of float. I would like to get the total of that specific column. How could I go about doing this?

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• How to optimize this Linq query

  - by Luke101

  I am trying to optimize this query. It is not slow for now but I am expecting a spike to hit this query in the near future. Is there anything else i can do to make this query faster? var posts = from p in context.post where p.post_isdeleted == false && p.post_parentid == null select new { p.post_date, p.post_id, p.post_titleslug, p.post_title, p.post_descriptionrender, p.userinfo.user_username, p.userinfo.user_userid, p.userinfo.user_GravatarHash, p.userinfo.user_points, p.category.catid, p.category.name, p.post_answercount, p.post_hasbestanswer, p.post_hits, p.post_isanonymous, p.post_votecount, FavoriteCount = context.favorites.Where(x => x.post.post_id == p.post_id).Count(), tags = from tg in context.posttag where tg.posttag_postid == p.post_id select new { tg.tag.tag_id, tg.tag.tag_title } };

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• what is a performance way to 'tree-walking' through my Entity Framework data

  - by Greg

  Hi, I have a Entity Framework design with a few tables that define a "graph". So there can be a large chain of relationships between objects in the few tables via concept of parent/child relationships. What is a performance way to 'tree-walking' through my Entity Framework data? That is I assume I wouldn't want to load the full set of all NODES and RELATIONSHIPS from the database for the purpose of walking the tree, where the end result may only be identifying leaf nodes? Or would this be OK with the way lazy loading may work at the column/parameter level? Else how could I load just the skeleton of the objects and then when needing to refer to any attributes have them lazy load then?

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• How to convert UTF-8 and Unicode to normal text ?

  - by Mehdi Amrollahi

  I have a downloader program that download pages from internet . the encoding of each page is different , some are in UTF-8 and some are Unicode. For example : &#97; that shows 'a' character ; pages full of this characters .We should convert this encodings to normal text . I used the UnicodeEncoding class in c# , but they do not help me . How can i decode this encodings to real characters? Is there a class or method that converting this ? Thanks .

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• Linq to Sql: Update Entity throug a new Object

  - by Dänu

  Hey Guys I'd like to update an entity via linq, but since I edit the entity in a view after serializing it, I don't have direct access to the entity inside the data context. I could do it like this: entity.property1 = obj.property1; entity.property2 = obj.property2; ... thats not cool... not cool at all. Next thing I tried is to do it via .attach() like so: context.Table.attach(entity, obj); doesn't work either. So is there another option short of reflection?

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• Why can't I insert record with foreign key in a single server request?

  - by Eran Betzalel

  I'm tryring to do a simple insert with foreign key, but it seems that I need to use db.SaveChanges() for every record insert. How can I manage to use only one db.SaveChanges() at the end of this program? var files = new List<File> { new File { Name = "Test1" }, new File { Name = "Test2" }, new File { Name = "Test3" } }; foreach (var file in files) { db.AddToFileSet(file); db.SaveChanges(); db.AddToDirectorySet( new Directory { DirectoryName = file.Name + "Dir", CreationDate = DateTime.UtcNow, file_relation = file }); db.SaveChanges(); }

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• What's the HTML character entity for the # sign?

  - by chimerical

  What's the HTML character entity for the # sign? I've looked around for "pound" (keeps returning the currency), and "hash" and "number", but what I try doesn't seem to turn into the right character.

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• I want to get 2 values returned by my query. How to do, using linq-to-entity

  - by Shantanu Gupta

  var dept_list = (from map in DtMapGuestDepartment.AsEnumerable() where map.Field<Nullable<long>>("GUEST_ID") == DRowGuestPI.Field<Nullable<long>>("PK_GUEST_ID") join dept in DtDepartment.AsEnumerable() on map.Field<Nullable<long>>("DEPARTMENT_ID") equals dept.Field<Nullable<long>>("DEPARTMENT_ID") select new { dept_id=dept.Field<long>("DEPARTMENT_ID") ,dept_name=dept.Field<long>("DEPARTMENT_NAME") }).Distinct(); DataTable dt = new DataTable(); dt.Columns.Add("DEPARTMENT_ID"); dt.Columns.Add("DEPARTMENT_NAME"); foreach (long? dept_ in dept_list) { dt.Rows.Add(dept_[0], dept_[1]); } EDIT In the previous question asked by me. I got an answer like this for single value. What is the difference between the two ? foreach (long? dept in dept_list) { dt.Rows.Add(dept); }

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• LINQ to Entity, joining on NOT IN tables

  - by SlackerCoder

  My brain seems to be mush right now! I am using LINQ to Entity, and I need to get some data from one table that does NOT exist in another table. For example: I need the groupID, groupname and groupnumber from TABLE A where they do not exist in TABLE B. The groupID will exist in TABLE B, along with other relevant information. The tables do not have any relationship. In SQL it would be quite simply (there is a more elegant and efficient solution, but I want to paint a picture of what I need) SELECT GroupID, GroupName, GroupNumber, FROM TableA WHERE GroupID NOT IN (SELECT GroupID FROM TableB) Is there an easy/elegant way to do this? Right now I have a bunch of queries hitting the db, then comparing, etc. It's pretty messy. Thanks.

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• odd nullreference error at foreach when rendering view

  - by giddy

  This error is so weird I Just can't really figure out what is really wrong! In UserController I have public virtual ActionResult Index() { var usersmdl = from u in RepositoryFactory.GetUserRepo().GetAll() select new UserViewModel { ID = u.ID, UserName = u.Username, UserGroupName = u.UserGroupMain.GroupName, BranchName = u.Branch.BranchName, Password = u.Password, Ace = u.ACE, CIF = u.CIF, PF = u.PF }; if (usersmdl != null) { return View(usersmdl.AsEnumerable()); } return View(); } My view is of type @model IEnumerable<UserViewModel> on the top. This is what happens: Where and what exactly IS null!? I create the users from a fake repository with moq. I also wrote unit tests, which pass, to ensure the right amount of mocked users are returned. Maybe someone can point me in the right direction here? Top of the stack trace is : at lambda_method(Closure , User ) at System.Linq.Enumerable.WhereSelectArrayIterator`2.MoveNext() at ASP.Index_cshtml.Execute() Is it something to do with linq here? Tell me If I should include the full stack trace.

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• How to start with entity framework and service oriented architecture?

  - by citronas

  At work I need to create a new web application, that will connection to an MySql Database. (So far I only have expercience with Linq-To-Sql classes and MSSQL Servers.) My superior tells me to use the entity framework (he probably refers to Linq-To-Entity) and provide everything as a service based architecture. Unfortunatly nobody at work has experience with that framework and with a real nice server oriented architecture. (till now no customer wanted to pay for architecture that he can't see. This speficic project I'm leading will be long-term, meaning multiple years, so it would be best to design it the way, that multiple targetting plattforms like asp.net, c# wpf, ... could use it) For now, the main target plattform is ASP.net So I do have the following questions: 1) Where can I read best what's really behind service oriented architecture (but for now beginner tutorials work fine as well) and how to do it in best practise? 2) So far I can't seem a real difference between Linq-To-Sql classes and the information I've google so far on the 'entity framework'. So, whats the difference? Where do I find nice tutorials for it. 3) Is there any difference in the entity framework regarding the database server (MSSQL or MySQL). If not, does that mean that code snipperts I will stumble across will word database independent? 4) I do you Visual Studio 2010. Do I have to regard something specific?

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• How to create view model without sorting collections in memory.

  - by Chevex

  I have a view model (below). public class TopicsViewModel { public Topic Topic { get; set; } public Reply LastReply { get; set; } } I want to populate an IQueryable<TopicsViewModel> with values from my IQueryable<Topic> collection and IQueryable<Reply> collection. I do not want to use the attached entity collection (i.e. Topic.Replies) because I only want the last reply for that topic and doing Topic.Replies.Last() loads the entire entity collection in memory and then grabs the last one in the list. I am trying to stay in IQueryable so that the query is executed in the database. I also don't want to foreach through topics and query replyRepository.Replies because looping through IQueryable<Topic> will start the lazy loading. I'd prefer to build one expression and have all the leg work done in the lower layers. I have the following: IQueryable<TopicsViewModel> topicsViewModel = from x in topicRepository.Topics from y in replyRepository.Replies where y.TopicID == x.TopicID orderby y.PostedDate ascending select new TopicsViewModel { Topic = x, LastReply = y }; But this isn't working. Any ideas how I can populate an IQueryable or IEnumerable of TopicsViewModel so that it queries the database and grabs topics and that topic's last reply? I am trying really hard to avoid grabbing all replies related to that topic. I only want to grab the last reply. Thank you for any insight you have to offer.

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