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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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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 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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• 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 use Linq to select and group complex child object from a parents list.

  - by Daoming Yang

  How to use Linq to select and group complex child object from a parents list. I have an OrderList each of order object has a OrderProductVariantList(OrderLineList), and each of OrderProductVariant object has ProductVariant, and then the ProductVariant object will have a Product object which contains product information. My goal is to select and group the most popular products from the order list. Can anyone help me with this? Many thanks.

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• Linq to Entity Dynamic where clause

  - by GodSmart

  I have Linq to Entity query like you can see below I am using it five times in my code, everything that change is where clause. is it possible to create a method and pass just where values, not to write all code five times. Thank you items = from t1 in _entities.table1 join t2 in _entities.Table2 on t1.column1 equals t2.column1 join t3 in _entities.Table3 on t1.column2 equals t3.column2 join t4 in _entities.Table4 on t1.column3 equals t4.column3 where **t1.column5 == Something** select new { t1.column7, t2.column8, t3.column9, t4.column10 };

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• How to convert this SQL query to Linq to Entity query?

  - by George

  Hi, could you help me please convert this SQL query to Linq to Entity query? Thank you select distinct item, count(item) as count from TableName where ColumnName = @parameter and (ColumnName2 = @parameter2 OR ColumnName3 = @parameter3) group by item order by item asc

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• Converting &amp; to & in Objective-C

  - by nbojja

  Hi All, I have a URL string in the following format. http://myserver.com/_layouts/feed.aspx?xsl=4&amp;web=%2F&amp;page=dda3fd10-c776-4d69-8c55-2f1c74b343e2&amp;wp=476f174a-82df-4611-a3df-e13255d97533 I want to replace &amp; with & in the above URL. My result should be: http://myserver.com/_layouts/feed.aspx?xsl=4&web=%2F&page=dda3fd10-c776-4d69-8c55-2f1c74b343e2&amp;wp=476f174a-82df-4611-a3df-e13255d97533 Can someone post me the code to get this done? Thanks

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• LINQ to Entites: How should I handle System.InvalidOperationException when checking for existance of

  - by chris

  I have a many-to-one relationship that users can edit via checkboxes. PK of Foo is ID, and fid contains the id from the checkbox. I'm checking to see if an element exists with: Foo ent; try { ent = ctx.Foo.First(f => f.ID == fid); } catch (System.InvalidOperationException ioe) { ent = new Foo(); } It seems to me that I should be able to do this without throwing an exception. What would be the best way to do this?

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• How to limit select items with L2E/S?

  - by orlon

  This code is a no-go var errors = (from error in db.ELMAH_Error select new { error.Application, error.Host, error.Type, error.Source, error.Message, error.User, error.StatusCode, error.TimeUtc }).ToList(); return View(errors); as it results in a 'requires a model of type IEnumerable' error. The following code of course works fine, but selects all the columns, some of which I'm simply not interested in: var errors = (from error in db.ELMAH_Error select error).ToList(); return View(errors); I'm brand spanking new to MVC2 + L2E, so maybe I'm just not thinking in the right mindset yet, but this seems counter-intuitive. Is there an easy way to select a limited number of columns, or is this just part of using an ORM?

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• Cannot perform an ORDERBY against my EF4 data

  - by Jaxidian

  I have a query hitting EF4 using STEs and I'm having an issue with user-defined sorting. In debugging this, I have removed the dynamic sorting and am hard-coding it and I still have the issue. If I swap/uncomment the var results = xxx lines in GetMyBusinesses(), my results are not sorted any differently - they are always sorting it ascendingly. FYI, Name is a varchar(200) field in SQL 2008 on my Business table. private IQueryable<Business> GetMyBusinesses(MyDBContext CurrentContext) { var myBusinesses = from a in CurrentContext.A join f in CurrentContext.F on a.FID equals f.id join b in CurrentContext.Businesses on f.BID equals b.id where a.PersonID == 52 select b; var results = from r in myBusinesses orderby "Name" ascending select r; //var results = from r in results // orderby "Name" descending // select r; return results; } private PartialEntitiesList<Business> DoStuff() { var myBusinesses = GetMyBusinesses(); var myBusinessesCount = GetMyBusinesses().Count(); Results = new PartialEntitiesList<Business>(myBusinesses.Skip((PageNumber - 1)*PageSize).Take(PageSize).ToList()) {UnpartialTotalCount = myBusinessesCount}; return Results; } public class PartialEntitiesList<T> : List<T> { public PartialEntitiesList() { } public PartialEntitiesList(int capacity) : base(capacity) { } public PartialEntitiesList(IEnumerable<T> collection) : base(collection) { } public int UnpartialTotalCount { get; set; } }

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• how to execute Sql Raw Query in Microsoft Entity Model Framework.

  - by kamal

  Hi I'm using Microsoft Entity model framework to access my database. I get an issue while i use this execute query command for executing Sql raw query. Let me know how could i resolve it. svdc.CreateQuery("select * from videomastertable WHERE FREETEXT(*, '"+keyword+"')").ToList(); Thanks in Advance, Kanal

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• Manual Linq to SQL entity framework mapping

  - by kprobst

  I've been playing with the O/R designer in VS and I was wondering if someone could shed come light on this. I'm used to OR mappers that are largely manual (homegrown and e.g., NHibernate). I don't mind encoding the entity classes myself, since they don't change all that often to begin with, and I have this irrational fear of designers and auto generated code as it is. I have noticed that the generated entity classes contain a lot of boilerplate extensibility methods, e.g. On[Property]Changed() and so on where [Property] is a mapped member of the class. These are placed in the setters of the property accessors. I assume it's OK if I don't include these when I do my hand coding, correct? They would be nice if I needed some sort of interception pattern but that's certainly not the case. I guess I just need to know if any of those methods are required by the entity framework to keep track of changes to the mapping types in order for things to work when updating the database. Thanks!

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• LINQ TO SQL, Dynamic query with DATE type fields

  - by acanthus

  Hello, I'm building a query with the LINQ dynamic library so I don't know how many potential parameters will I have and I get an error when trying to query DATE type fields: Operator '=' incompatible with operand types 'DateTime' and 'String' When I step through the debugger in the Dynamic.cs it shows that the value is of type string and the field is of type date so the problem is obvious but I have no idea how to approach it. Any ideas? BR

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• How to model localized items

  - by tweir

  I'm currently designing a e-commerce solution. One of the primary requirements is for the store to support localized item details. The same store must be able to support multiple languages via the user's language selection and/or browser preference. I have two tables: Item (id, sku, price, ...) ItemDetails (item_id, language, title, ...) For each Item, there will be multiple rows corresponding to the item, where the (item_id,language) pair will be unique. I would like to model this as: class Item { public string sku; public double price; public ItemDetails Details; } Based on the user's session, I would like the items returned to have the Details object corresponds to the user's selected language (from their session). What are some approaches for representing this?

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