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  • Linq grouping question

    - by Mike C.
    I have the following objects in a collection: Transaction: Type = "Widget" Date = "3/1/2011" Name = "Foo" Transaction: Type = "Widget" Date = "3/4/2011" Name = "Bar" Transaction: Type = "Gadget" Date = "3/2/2011" Name = "Baz" Transaction: Type = "Gizmo" Date = "3/1/2011" Name = "Who" Transaction: Type = "Gizmo" Date = "3/2/2011" Name = "What" Transaction: Type = "Gizmo" Date = "3/6/2011" Name = "When" I want to end up with the following, grouped by Type. If there are multiple, return only the first one chronologically by date. Transaction: Type = "Widget" Date = "3/1/2011" Name = "Foo" Transaction: Type = "Gadget" Date = "3/2/2011" Name = "Baz" Transaction: Type = "Gizmo" Date = "3/1/2011" Name = "Who"

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  • Naked Objects. Good or Bad

    - by Midhat
    I have recently been exposed to naked objects. It looks like a pretty decent framework. However I do not see it in widespread use like say, Spring. So why is this framework not getting any mainstream application credit. What are its shortcomings as you see?

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  • Retaining objects in game iphone

    - by Brodie4598
    Hello - I am trying to create a game and have run into what is probably a pretty easy problem to solve. As the player goes through the game, many objects (Vehicle) will be added and removed. The Vehicles get added to an array called currentVehiclesMutableArray. My problem is I cant figure out how to retain a Vehicle so that it remains in the array until I am finished with it.

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  • LINQ Query with 3 levels

    - by BahaiResearch.com
    I have a business object structured like this: Country has States, State has Cities So Country[2].States[7].Cities[5].Name would be New York Ok, I need to get a list of all the Country objects which have at least 1 City.IsNice == true How do I get that?

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  • Translating Where() to sql

    - by MBoros
    Hi. I saw DamienG's article (http://damieng.com/blog/2009/06/24/client-side-properties-and-any-remote-linq-provider) in how to map client properties to sql. i ran throgh this article, and i saw great potential in it. Definitely mapping client properties to SQL is an awesome idea. But i wanted to use this for something a bit more complicated then just concatenating strings. Atm we are trying to introduce multilinguality to our Business objects, and i hoped we could leave all the existing linq2sql queries intact, and just change the code of the multilingual properties, so they would actually return the given property in the CurrentUICulture. The first idea was to change these fields to XMLs, and then try the Object.Property.Elements().Where(...), but it got stuck on the Elements(), as it couldnt translate it to sql. I read somewhere that XML fields are actually regarded as strings, and only on the app server they become XElements, so this way the filtering would be on the app server anyways, not the DB. Fair point, it wont work like this. Lets try something else... SO the second idea was to create a PolyGlots table (name taken from http://weblogic.sys-con.com/node/102698?page=0,1), a PolyGlotTranslations table and a Culture table, where the PolyGlots would be referenced from each internationalized property. This way i wanted to say for example: private static readonly CompiledExpression<Announcement, string> nameExpression = DefaultTranslationOf<Announcement> .Property(e => e.Name) .Is(e=> e.NamePolyGlot.PolyGlotTranslations .Where(t=> t.Culture.Code == Thread.CurrentThread.CurrentUICulture.Name) .Single().Value ); now unfortunately here i get an error that the Where() function cannot be translated to sql, what is a bit disappointing, as i was sure it will go through. I guess it is failing, cause the IEntitySet is basically an IEnumerable, not IQueryable, am i right? Is there another way to use the compiledExpressions class to achieve this goal? Any help appreciated.

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  • Grouping a list of of entities which has a sublist in c#

    - by mikei
    I have a set of Entities which basically has this structure. {Stats Name="<Product name> (en)" TotalResources="10" ..} {DayStats Date="2009-12-10" TotalResources="5"} {DayStats Date="2009-12-11" TotalResources="5"} {Stats} {Stats Name="<Product name> (us)" TotalResources="10" ..} {DayStats Date="2009-12-10" TotalResources="5"} {DayStats Date="2009-12-11" TotalResources="5"} {Stats} ... What I wan't to extract from this set is a new set entities (or entity in the example above) where the first level has been grouped by the (ignoring the country label) where all/some of the properties has been summmed together, including the the sublist of {DayStas} on a per day basis. So the result set of the example would look something like this: {Stats Name="<Product name>" TotalResources="20" ..} {DayStats Date="2009-12-10" TotalResources="10"} {DayStats Date="2009-12-11" TotalResources="10"} {Stats} ... So my question is: Is it possible to do this in a more elegant way in LINQ rather than the vanilla "loop-trhough-each-entity-and-compare"-way? And I wan't the set to contain the same type of entities as the original set ({Stats}, {DayStats}), your answer doesn't need to include code for that, I can probably work that out by myself. Just letting you know incase you need to take that into account. (I'm sorry if this question has been discussed before, I tried searching to no avail. I guess my searching skills are fuubar ;)) Merry christmas =)

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  • LinqToSql Select to a class then do more queries

    - by fyjham
    I have a LINQ query running with multiple joins and I want to pass it around as an IQueryable<T> and apply additional filters in other methods. The problem is that I can't work out how to pass around a var data type and keep it strongly typed, and if I try to put it in my own class (EG: .Select((a,b) => new MyClass(a,b))) I get errors when I try to add later Where clauses because my class has no translations into SQL. Is there any way I can do one of the following: Make my class map to SQL? Make the var data-type implement an interface (So I can pass it round as though it's that)? Something I haven't though of that'll solve my issue? Example: public void Main() { using (DBDataContext context = new DBDataContext()) { var result = context.TableAs.Join( context.TableBs, a => a.BID, b => b.ID, (a,b) => new {A = a, B = b} ); result = addNeedValue(result, 4); } } private ???? addNeedValue(???? result, int value) { return result.Where(r => r.A.Value == value); } PS: I know in my example I can flatten out the function easily, but in the real thing it'd be an absolute mess if I tried.

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  • Linq2Sql: query - subquery optimisation

    - by Budda
    I have the following query: IList<InfrStadium> stadiums = (from sector in DbContext.sectors where sector.Type=typeValue select new InfrStadium(sector.TeamId) ).ToList(); and InfrStadium class constructor: private InfrStadium(int teamId) { IList<Sector> teamSectors = (from sector in DbContext.sectors where sector.TeamId==teamId select sector) .ToList<>(); ... work with data } Current implementation perform 1+n queries, where n - number of records fetched the 1st time. I want to optimize that. And another one I would love to do using 'group' operator in way like this: IList<InfrStadium> stadiums = (from sector in DbContext.sectors group sector by sector.TeamId into team_sectors select new InfrStadium(team_sectors.Key, team_sectors) ).ToList(); with appropriate constructor: private InfrStadium(int iTeamId, IEnumerable<InfrStadiumSector> eSectors) { IList<Sector> teamSectors = eSectors.ToList(); ... work with data } But attempt to launch query causes the following error: Expression of type 'System.Int32' cannot be used for constructor parameter of type 'System.Collections.Generic.IEnumerable`1[InfrStadiumSector]' Question 1: Could you please explain, what is wrong here, I don't understand why 'team_sectors' is applied as 'System.Int32'? I've tried to change query a little (replace IEnumerable with IQueryeable): IList<InfrStadium> stadiums = (from sector in DbContext.sectors group sector by sector.TeamId into team_sectors select new InfrStadium(team_sectors.Key, team_sectors.AsQueryable()) ).ToList(); with appropriate constructor: private InfrStadium(int iTeamId, IQueryeable<InfrStadiumSector> eSectors) { IList<Sector> teamSectors = eSectors.ToList(); ... work with data } In this case I've received another but similar error: Expression of type 'System.Int32' cannot be used for parameter of type 'System.Collections.Generic.IEnumerable1[InfrStadiumSector]' of method 'System.Linq.IQueryable1[InfrStadiumSector] AsQueryableInfrStadiumSector' Question 2: Actually, the same question: can't understand at all what is going on here... P.S. I have another to optimize query idea (describe here: Linq2Sql: query optimisation) but I would love to find a solution with 1 request to DB).

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  • C# Passing objects and list of objects by reference

    - by David Liddle
    I have a delegate that modifies an object. I pass an object to the delegate from a calling method, however the calling method does not pickup these changes. The same code works if I pass a List as the object. I thought all objects were passed by reference so any modifications would be reflected in the calling method? I can modify my code to pass a ref object to the delegate but am wondering why this is necessary? public class Binder { protected delegate int MyBinder<T>(object reader, T myObject); public void BindIt<T>(object reader, T myObject) { //m_binders is a hashtable of binder objects MyBinder<T> binder = m_binders["test"] as MyBinder<T>; int i = binder(reader, myObject); } } public class MyObjectBinder { public MyObjectBinder() { m_delegates["test"] = new MyBinder<MyObject>(BindMyObject); } private int BindMyObject(object reader, MyObject obj) { //make changes to obj in here } } ///calling method in some other class public void CallingMethod() { MyObject obj = new MyObject(); MyBinder binder = new MyBinder(); binder.BindIt(myReader, obj); //don't worry about myReader //obj should show reflected changes }

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  • Grouping by property value and writing group members

    - by Will S
    I need to group the following list by the department value but am having trouble with the LINQ syntax. Here's my list of objects: var people = new List<Person> { new Person { name = "John", department = new List<fields> {new fields { name = "department", value = "IT"}}}, new Person { name = "Sally", department = new List<fields> {new fields { name = "department", value = "IT"}}}, new Person { name = "Bob", department = new List<fields> {new fields { name = "department", value = "Finance"}}}, new Person { name = "Wanda", department = new List<fields> {new fields { name = "department", value = "Finance"}}}, }; I've toyed around with grouping. This is as far as I've got: var query = from p in people from field in p.department where field.name == "department" group p by field.value into departments select new { Department = departments.Key, Name = departments }; So can iterate over the groups, but not sure how to list the Person names - foreach (var department in query) { Console.WriteLine("Department: {0}", department.Department); foreach (var foo in department.Department) { // ?? } } Any ideas on what to do better or how to list the names of the relevant departments?

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  • Split List into Sublists with LINQ

    - by Felipe Lima
    Hi all, I believe this is another easy one for you LINQ masters out there. Is there any way I can separe a List into several separate lists of SomeObject, using the item index as the delimiter of each split? Let me exemplify: I have a List<SomeObject> and I need a List<List<SomeObject>> or List<SomeObject>[], so that each of these resulting lists will contain a group of 3 items of the original list (sequentially). eg.: Original List: [a, g, e, w, p, s, q, f, x, y, i, m, c] Resulting lists: [a, g, e], [w, p, s], [q, f, x], [y, i, m], [c] I'd also need the resulting lists size to be a parameter of this function. Is it possible?? Thanks!

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  • Linq to sql Invalid column name

    - by Ivo
    I am using VS 2010 and Linq-to-sql I have deleted a couple of columns from my table, whatever I try I keep getting and "invalide column name" error with the old/deleted column when I try to insert a record. What tried: remove table,save, and drag it back on create new dblm with an other name created new project and create new dbml there Also the name of the deleted column does not exist in the generated code of the dbml anymore, but still I get an exception saying that column does not exists. Anyone got a suggestion how to solve this problem?

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  • Linq: Converting flat structure to hierarchical

    - by Stefan Steinegger
    What is the easiest and somewhat efficient way to convert a flat structure: object[][] rawData = new object[][] { { "A1", "B1", "C1" }, { "A1", "B1", "C2" }, { "A2", "B2", "C3" }, { "A2", "B2", "C4" } // .. more }; into a hierarchical structure: class X { public X () { Cs = new List<string>(); } public string A { get; set; } public string B { get; set; } public List<string> Cs { get; private set; } } the result should look like this // pseudo code which describes structure: result = { new X() { A = "A1", B = "B1", Cs = { "C1", "C2" } }, new X() { A = "A2", B = "B2", Cs = { "C3", "C4" } } } Preferably using Linq extension methods. Target class X could be changed (eg. a public setter for the List), only if not possible / useful as it is now.

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  • Use LINQ to query nested OData collection

    - by Kyle Russell
    I'm playing around with the new Netflix OData feed (http://odata.netflix.com/Catalog/) and having some issues. I'm trying to learn LINQ at the same time but having difficulty doing what I thought was going to be quite simple. I'd like to return a list of Titles that match a given Genre. The Titles object contains a collection of Genres. I'm not sure how to write this query. My attempt below does not appear to work using LINQPad. from t in Titles where t.Genres.Name.Contains("ABC") select t

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  • Request all titles by actor using LINQ to Netflix OData

    - by Mark Heath
    I'm experimenting with LINQPad to use LINQ to query the Netflix OData. I'm trying to search for all films with a particular actor in. For example: from t in Titles from p in t.Cast where p.Name == "Morgan Freeman" select t.Name this results in: NotSupportedException: Can only project the last entity type in the query being translated I also tried: from p in People from t in p.TitlesActedIn where p.Name == "Morgan Freeman" select t.Name which results in the following error: NotSupportedException: The method 'Select' is not supported I've tried a few other approaches, such as using Id's in the where clause, and selecting different things, but have got nowhere.

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  • creating Linq to sqlite dbml from DbLinq source code

    - by Veer
    Hi All, I tried to create linq-to-sqlite dbml using DbLinq but in vain. Each time I get different type of errors. May be I'm somewhere wrong. Can anyone tell me the step by step procedure to create the dbml file from the Dblinq source code. Edit: Steps I Followed: I downloaded the source file from this link. Edited the "run_sqliteMetal.bat" file in \\DbLinq-0.19\src\DbMetal folder as 'DbMetal.exe -database:myDb.db3 -namespace:myNS -code:myCode.cs' -dbml:myDbml.dbml Tried to run the DbMetal project file to produce the executable but there was a runtime error since Options object in Parameters.cs was null. Hence downloaded the readymade exe file from this location Copied it into the \DbLinq-0.19\src\DbMetal folder Executed the "run_sqliteMetal.bat" file I got a blank screen and Windows Error Msg "DbLinq has stopped Working" Any help? Thanks in advance, Veer

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  • How to create an ObservableCollection using LINQ in Silverlight

    - by sonofpirate
    In a non-Silverlight world, it is easy to use LINQ to create an ObservableCollection. This is because the ObservableCollection class has constructors that accept any IEnumerable<T or List<T. However, the Silverlight version does not! This means that code such as: var list = (from item in e.Result select new ViewModel(item)).ToList(); Items = new System.Collections.ObjectModel.ObservableCollection<ViewModel>(list); will not work in Silverlight. Is there another option to make this work besides resorting to a for-each statement?

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  • Linq to Entities : using ToLower() on NText fields

    - by Julien N
    I'm using SQL Server 2005, with a case sensitive database.. In a search function, I need to create a Linq To Entities (L2E) query with a "where" clause that compare several strings with the data in the database with these rules : The comparison is a "Contains" mode, not strict compare : easy as the string's Contains() method is allowed in L2E The comparison must be case insensitive : I use ToLower() on both elements to perform an insensitive comparison. All of this performs really well but I ran into the following Exception : "Argument data type ntext is invalid for argument 1 of lower function" on one of my fields. It seems that the field is a NText field and I can't perform a ToLower() on that. What could I do to be able to perform a case insensitive Contains() on that NText field ?

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  • LiNQ to Entities, Include less

    - by Freddy
    Hi, If you are making a LinQ to entities expression for ClassA where A has a relation to ClassB like this: var temp = from p in myEntities.ClassA.Include("ClassB") where ... select p; You will get a set of ClassA:s with the reference to ClassB loaded. The thing in my case is that I dont really need to load ALL the ClassB-references, just a few of them. But I dont want to loop through the list of ClassA:s and load them individually, i want my database operations to be fewer and bigger instead of reading small chunks here and there. Is it possible to put some kind of restrictions on which references to include or do you have to accept this all or nothing style?

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  • Linq filtering an IQueryable<T> (System.Data.Linq.DataQuery) object by a List<T> (System.Collection.

    - by Klaptrap
    My IQueryable line is: // find all timesheets for this period - from db so System.Data.Linq.DataQuery var timesheets = _timesheetRepository.FindByPeriod(dte1, dte2); My List line is: // get my team from AD - from active directory so System.Collection.Generic.List var adUsers = _adUserRepository.GetMyTeam(User.Identity.Name); I wish to only show timesheets for those users in the timesheet collection that are present in the user collection. If I use a standard c# expression such as: var teamsheets = from t in timesheets join user in adUsers on t.User1.username equals user.fullname select t; I get the error "An IQueryable that returns a self-referencing Constant expression is not supported" Any recommendations?

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  • SQL's Rownumber with Linq-to-entities

    - by mariki
    I am converting my project to use EF and also want to covert stored procedures into Linq-to-entities queries. This my SQL query (simple version) that I have trouble to convert: SELECT CategoryID, Title as CategoryTitle,Description, LastProductTitle,LastProductAddedDate FROM ( SELECT C.CategoryID, C.Title,C.Description, C.Section, P.Title as LastProductTitle, P.AddedDate as LastProductAddedDate, ROW_NUMBER() OVER (PARTITION BY P.CategoryID ORDER BY P.AddedDate DESC) AS Num FROM Categories C LEFT JOIN Products P ON P.CategoryID = C.CategoryID ) OuterSelect WHERE OuterSelect.Num = 1 In words: I want to return all Categories (from Categories table) and title and date of addition of the product (from Products table) that was added last to this category. How can I achieve this using Entity frame work query? In most efficient way.

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  • List<T>.SelectMany(), Linq and lambda help

    - by jim
    Hi there I have a class. public class MedicalRequest { private int id private IList<MedicalDays> Days private string MedicalUser ... } and another public class MedicalDays { private int id; private DateTime? day private MedicalRequest request ... } I'm using nhibernate to return a list of all the MedicalDays within a time span. I'd like to do something like this to the resulting list //nhibernate query IList<MedicalDays> days = daysDao.FindAll(searchCritCollection); //select a list of days from resulting list IEnumerable<MedicalDays> queriedList = days.SelectMany(i => i.MedicalRequest.MedicalUser == employee); Linq tells me that the type cannot be inferred by the usage. I'd like to know what I'm doing wrong, and if there is a preferred way of doing something like this. Thanks for your time.

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  • SQL Server CE, Visual Studio 2008/2010 RC, and Linq-to-Sql

    - by blu
    I added an .sdf to my project, added a table, added a Linq-to-Sql dmbl, and tried to add the table to the dbml. The result was an error: "The selected object(s) are an unsupported data provider" This happens in both VS 2008 Professional SP1 and 2010 RC Ultimate. I found someone talking about using SQL Metal to generate the file, but I didn't enjoy that 2 years ago, and after a little playing around I recall why. Does anyone know if this is going to be supported in the release version? Should I abandon SQL Server CE and just use SQLite (with DbLinq)? Thanks for any insight.

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  • Crystal report using Linq-to-sql

    - by DATT OZA
    Hello, I am bit confusing in generating crystal report from linq-to-sql object in my WpfApplication. crystalreport1 rpt = new crystalreport1(); datacontextclass1 db = new datacontextclass1(); var q = (from records in db.emp select records).toList(); rpt.setDataSource(q); crystalviewer.reportsource(rpt); I have done above steps... but its prompts error NotSupportedException Was Unhandled Dataset not support system.nullable< please help... thanx in advance..

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