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  • How can I use linq to build an object from 1 row of data?

    - by Hcabnettek
    Hi All, I have a quick linq question. I have a stored proc that should return one row of data. I would like to use a lambda to build an object. Here's what I'm currently doing which works, but I know I should be able to use First instead of Select except I can't seem to get the syntax correct. Can anyone straighten me out here? Thanks for any help. var location = new GeoLocationDC(); DataSet ds = db.ExecuteDataSet(dbCommand); if(ds.Tables[0].Rows.Count == 1) { var rows = ds.Tables[0].AsEnumerable(); var x = rows.Select( c => new GeoLocationDC { Latitude = Convert.ToInt32(c.Field<string>("LATITUDE")), Longitude = Convert.ToInt32(c.Field<string>("LONGITUDE")) }).ToList(); if(x.Count > 0 ) { location = x[0]; } Cheers, ~ck }

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  • LINQ to SQL for tables across databases. Or View?

    - by BritishDeveloper
    I have a Message table and a User table. Both are in separate databases. There is a userID in the Message table that is used to join to the User table to find things like userName. How can I create this in LINQ to SQL? I can't seem to do a cross database join. Should I create a View in the database and use that instead? Will that work? What will happen to CRUD against it? E.g. if I delete a message - surely it won't delete the user? I'd imagine it would throw an error. What to do? I can't move the tables into the same database!

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  • Using Linq, how to separate a list in to grouped objects by name?

    - by Dr. Zim
    I have a table where a record looks like this varchar(255) Name varchar(255) Text varchar(255) Value Name is the DDL name, Text is what is displayed, and Value is returned upon selection. There are between one and twenty options for each Name. Without iterating though each option like a cursor, is there any way to pull out a list of objects, one for each unique DDL Name, using Linq and C#? A sample of the data: Beds '4 (10)' 4 Beds '5 (1)' 5 Beds '7 (1)' 7 Baths 'NA (13)' NULL Baths '0 (1)' 0 Baths '1 (13)' 1 I was thinking about doing an outer select to get the unique Names, then an inner select to get the list of options for it, then return the set as a List of a set of Lists.

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  • Getting XML Numbered Entities with PHP 5 DOM

    - by user343607
    Hello guys, I am new here and got a question that is tricking me all day long. I've made a PHP script, that reads a website source code through cURL, then works with DOMDocument class in order to generate a sitemap file. It is working like a charm in almost every aspect. The problem is with special characters. For compatibility reasons, sitemap files needs to have all special chars encoded as numbered entities. And I am not achieving that. For example, one of my entries - automatically read from site URLs, and wrote to sitemap file - is: http://www.somesite.com/serviços/redesign/ On the source code it should looks like: http://www.somesite.com/servi*ç*os/redesign/ Just this. But unfortunately, I am really not figuring it out how to do it. Source code file, server headers, etc... everything is encoded as UTF-8. I'm using DOMDocument and related extensions to build the XML. (Basically, DOMDocument, $obj-createElement, $obj-appendChild). htmlentities gives ç instead of ç str_replace does not work. It makes the character just vanish in the output. I was using $obj-createElement("loc", $url); on my code, and just now I read in PHP manual that I should use $document-createTextNode($page), in order to have entities encoding support. Well, it is not working either. Any idea on how to get unstuck of this? Thanks.

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  • How to get rank from full-text search query with Linq to SQL?

    - by Stephen Jennings
    I am using Linq to SQL to call a stored procedure which runs a full-text search and returns the rank plus a few specific columns from the table Article. The rank column is the rank returned from the SQL function FREETEXTTABLE(). I've added this sproc to the data model designer with return type Article. This is working to get the columns I need; however, it discards the ranking of each search result. I'd like to get this information so I can display it to the user. So far, I've tried creating a new class RankedArticle which inherits from Article and adds the column Rank, then changing the return type of my sproc mapping to RankedArticle. When I try this, an InvalidOperationException gets thrown: Data member 'Int32 ArticleID' of type 'Heap.Models.Article' is not part of the mapping for type 'RankedArticle'. Is the member above the root of an inheritance hierarchy? I can't seem to find any other questions or Google results from people trying to get the rank column, so I'm probably missing something obvious here.

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  • ASP.NET MVC 2: How to write this Linq SQL as a Dynamic Query (using strings)?

    - by Dr. Zim
    Skip to the "specific question" as needed. Some background: The scenario: I have a set of products with a "drill down" filter (Query Object) populated with DDLs. Each progressive DDL selection will further limit the product list as well as what options are left for the DDLs. For example, selecting a hammer out of tools limits the Product Sizes to only show hammer sizes. Current setup: I created a query object, sent it to a repository, and fed each option to a SQL "table valued function" where null values represent "get all products". I consider this a good effort, but far from DDD acceptable. I want to avoid any "programming" in SQL, hopefully doing everything with a repository. Comments on this topic would be appreciated. Specific question: How would I rewrite this query as a Dynamic Query? A link to something like 101 Linq Examples would be fantastic, but with a Dynamic Query scope. I really want to pass to this method the field in quotes "" for which I want a list of options and how many products have that option. (from p in db.Products group p by p.ProductSize into g select new Category { PropertyType = g.Key, Count = g.Count() }).Distinct(); Each DDL option will have "The selection (21)" where the (21) is the quantity of products that have that attribute. Upon selecting an option, all other remaining DDLs will update with the remaining options and counts.

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  • Can I use the auto-generated Linq-to-SQL entity classes in 'disconnected' mode?

    - by Gary McGill
    Suppose I have an automatically-generated Employee class based on the Employees table in my database. Now suppose that I want to pass employee data to a ShowAges method that will print out name & age for a list of employees. I'll retrieve the data for a given set of employees via a linq query, which will return me a set of Employee instances. I can then pass the Employee instances to the ShowAges method, which can access the Name & Age fields to get the data it needs. However, because my Employees table has relationships with various other tables in my database, my Employee class also has a Department field, a Manager field, etc. that provide access to related records in those other tables. If the ShowAges method were to invoke any of those methods, this would cause lots more data to be fetched from the database, on-demand. I want to be sure that the ShowAges method only uses the data I have already fetched for it, but I really don't want to have to go to the trouble of defining a new class which replicates the Employee class but has fewer methods. (In my real-world scenario, the class would have to be considerably more complex than the Employee class described here; it would have several 'joined' classes that do need to be populated, and others that don't). Is there a way to 'switch off' or 'disconnect' the Employees instances so that an attempt to access any property or related object that's not already populated will raise an exception? If not, then I assume that since this must be a common requirement, there might be an already-established pattern for doing this sort of thing?

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  • Can LINQ expression classes implement the observer pattern instead of deferred execution?

    - by Tormod
    Hi. We have issues within an application using a state machine. The application is implemented as a windows service and is iteration based (it "foreaches" itself through everything) and there are myriads of instances being processed by the state machine. As I'm reading the MEAP version of Jon Skeets book "C# in Depth, 2nd ed", I'm wondering if I can change the whole thing to use linq expression instances so that guards and conditions are represented using expression trees. We are building many applications on this state machine engine and would probably greatly benefit from the new Expression tree visualizer in VS 2010 Now, simple example. If I have an expression tree where there is an OR Expression condition with two sub nodes, is there any way that these can implement the observer pattern so that the expression tree becomes event driven? If a condition change, it should notify its parent node (the OR node). Since the OR node then changes from "false" to "true", then it should notify ITS parent and so on. I love the declarative model of expression trees, but the deferred execution model works in opposite direction of the control flow if you want event based "live" conditions. Am I off on a wild goose chase here? Or is there some concept in the BCL that may help me achieve this?

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  • LINQ to SQL - How to efficiently do either an AND or an OR search for multiple criteria

    - by Dan Diplo
    I have an ASP.NET MVC site (which uses Linq To Sql for the ORM) and a situation where a client wants a search facility against a bespoke database whereby they can choose to either do an 'AND' search (all criteria match) or an 'OR' search (any criteria match). The query is quite complex and long and I want to know if there is a simple way I can make it do both without having to have create and maintain two different versions of the query. For instance, the current 'AND' search looks something like this (but this is a much simplified version): private IQueryable<SampleListDto> GetSampleSearchQuery(SamplesCriteria criteria) { var results = from r in Table where (r.Id == criteria.SampleId) && (r.Status.SampleStatusId == criteria.SampleStatusId) && (r.Job.JobNumber.StartsWith(criteria.JobNumber)) && (r.Description.Contains(criteria.Description)) select r; } I could copy this and replace the && with || operators to get the 'OR' version, but feel there must be a better way of achieving this. Does anybody have any suggestions how this can be achieved in an efficient and flexible way that is easy to maintain? Thanks.

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  • [C#]How to introduce retry logic into LINQ to SQL to deal with timeouts?

    - by codemonkie
    I need to find ways to add retry mechanism to my DB calls in case of timeouts, LINQ to SQL is used to call some sprocs in my code... using (MyDataContext dc = new MyDataContext()) { int result = -1; //denote failure int count = 0; while ((result < 0) && (count < MAX_RETRIES)) { result = dc.myStoredProc1(...); count++; } result = -1; count = 0; while ((result < 0) && (count < MAX_RETRIES)) { result = dc.myStoredProc2(...); count++; } ... ... } Not sure if the code above is right or posed any complications. It'll be nice to throw an exception after MAX_RETRIES has reached, but I dunno how and where to throw them appropriately :-) Any helps appreciated.

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  • Important question about linq to SQL performance on high loaded web applications

    - by Alex
    I started working with linq to SQL several weeks ago. I got really tired of working with SQL server directly through the SQL queries (sqldatareader, sqlcommand and all this good stuff).  After hearing about linq to SQL and mvc I quickly moved all my projects to these technologies. I expected linq to SQL work slower but it suprisongly turned out to be pretty fast, primarily because I always forgot to close my connections when using datareaders. Now I don't have to worry about it. But there's one problem that really bothers me. There's one page that's requested thousands of times a day. The system gets data in the beginning, works with it and updates it. Primarily the updates are ++ @ -- (increase and decrease values). I used to do it like this UPDATE table SET value=value+1 WHERE ID=@I'd It worked with no problems obviously. But with linq to SQL the data is taken in the beginning, moved to the class, changed and then saved. Stats.registeredusers++; Db.submitchanges(); Let's say there were 100 000 users. Linq will say "let it be 100 001" instead of "let it be increased by 1". But if there value of users has already been increased (that happens in my site all the time) then linq will be like oops, this value is already 100 001. Whatever I'll throw an exception" You can change this behavior so that it won't throw an exception but it still will not set the value to 100 002. Like I said, it happened with me all the time. The stas value was increased twice a second on average. I simply had to rewrite this chunk of code with classic ado net. So my question is how can you solve the problem with linq

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  • LINQ Query using UDF that receives parameters from the query

    - by Ben Fidge
    I need help using a UDF in a LINQ which calculates a users position from a fixed point. int pointX = 567, int pointY = 534; // random points on a square grid var q = from n in _context.Users join m in _context.GetUserDistance(n.posY, n.posY, pointX, pointY, n.UserId) on n.UserId equals m.UserId select new User() { PosX = n.PosX, PosY = n.PosY, Distance = m.Distance, Name = n.Name, UserId = n.UserId }; The GetUserDistance is just a UDF that returns a single row in a TVP with that users distance from the points deisgnated in pointX and pointY variables, and the designer generates the following for it: [global::System.Data.Linq.Mapping.FunctionAttribute(Name="dbo.GetUserDistance", IsComposable=true)] public IQueryable<GetUserDistanceResult> GetUserDistance([global::System.Data.Linq.Mapping.ParameterAttribute(Name="X1", DbType="Int")] System.Nullable<int> x1, [global::System.Data.Linq.Mapping.ParameterAttribute(Name="X2", DbType="Int")] System.Nullable<int> x2, [global::System.Data.Linq.Mapping.ParameterAttribute(Name="Y1", DbType="Int")] System.Nullable<int> y1, [global::System.Data.Linq.Mapping.ParameterAttribute(Name="Y2", DbType="Int")] System.Nullable<int> y2, [global::System.Data.Linq.Mapping.ParameterAttribute(Name="UserId", DbType="Int")] System.Nullable<int> userId) { return this.CreateMethodCallQuery<GetUserDistanceResult>(this, ((MethodInfo)(MethodInfo.GetCurrentMethod())), x1, x2, y1, y2, userId); } when i try to compile i get The name 'n' does not exist in the current context

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  • linq: SQL performance on high loaded web applications

    - by Alex
    I started working with linq to SQL several weeks ago. I got really tired of working with SQL server directly through the SQL queries (sqldatareader, sqlcommand and all this good stuff).  After hearing about linq to SQL and mvc I quickly moved all my projects to these technologies. I expected linq to SQL work slower but it suprisongly turned out to be pretty fast, primarily because I always forgot to close my connections when using datareaders. Now I don't have to worry about it. But there's one problem that really bothers me. There's one page that's requested thousands of times a day. The system gets data in the beginning, works with it and updates it. Primarily the updates are ++ @ -- (increase and decrease values). I used to do it like this UPDATE table SET value=value+1 WHERE ID=@I'd It worked with no problems obviously. But with linq to SQL the data is taken in the beginning, moved to the class, changed and then saved. Stats.registeredusers++; Db.submitchanges(); Let's say there were 100 000 users. Linq will say "let it be 100 001" instead of "let it be increased by 1". But if there value of users has already been increased (that happens in my site all the time) then linq will be like oops, this value is already 100 001. Whatever I'll throw an exception" You can change this behavior so that it won't throw an exception but it still will not set the value to 100 002. Like I said, it happened with me all the time. The stas value was increased twice a second on average. I simply had to rewrite this chunk of code with classic ado net. So my question is how can you solve the problem with linq

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  • Storing Entity Framework Entities in a Separate Assembly

    - by Anthony Trudeau
    The Entity Framework has been valuable to me since it came out, because it provided a convenient and powerful way to model against my data source in a consistent way.  The first versions had some deficiencies that for me mostly fell in the category of the tight coupling between the model and its resulting object classes (entities). Version 4 of the Entity Framework pretty much solves this with the support of T4 templates that allow you to implement your entities as self-tracking entities, plain old CLR objects (POCO), et al.  Doing this involves either specifying a new code generation template or implementing them yourselves.  Visual Studio 2010 ships with a self-tracking entities template and a POCO template is available from the Extension Manager.  (Extension Manager is very nice but it's very easy to waste a bunch of time exploring add-ins.  You've been warned.) In a current project I wanted to use POCO; however, I didn't want my entities in the same assembly as the context classes.  It would be nice if this was automatic, but since it isn't here are the simple steps to move them.  These steps detail moving the entity classes and not the context.  The context can be moved in the same way, but I don't see a compelling reason to physically separate the context from my model. Turn off code generation for the template.  To do this set the Custom Tool property for the entity template file to an empty string (the entity template file will be named something like MyModel.tt). Expand the tree for the entity template file and delete all of its items.  These are the items that were automatically generated when you added the template. Create a project for your entities (if you haven't already). Add an existing item and browse to your entity template file, but add it as a link (do not add it directly).  Adding it as a link will allow the model and the template to stay in sync, but the code generation will occur in the new assembly.

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  • How to write this Linq SQL as a Dynamic Query (using strings)?

    - by Dr. Zim
    Skip to the "specific question" as needed. Some background: The scenario: I have a set of products with a "drill down" filter (Query Object) populated with DDLs. Each progressive DDL selection will further limit the product list as well as what options are left for the DDLs. For example, selecting a hammer out of tools limits the Product Sizes to only show hammer sizes. Current setup: I created a query object, sent it to a repository, and fed each option to a SQL "table valued function" where null values represent "get all products". I consider this a good effort, but far from DDD acceptable. I want to avoid any "programming" in SQL, hopefully doing everything with a repository. Comments on this topic would be appreciated. Specific question: How would I rewrite this query as a Dynamic Query? A link to something like 101 Linq Examples would be fantastic, but with a Dynamic Query scope. I really want to pass to this method the field in quotes "" for which I want a list of options and how many products have that option. from p in db.Products group p by p.ProductSize into g select new Category { PropertyType = g.Key, Count = g.Count() } Each DDL option will have "The selection (21)" where the (21) is the quantity of products that have that attribute. Upon selecting an option, all other remaining DDLs will update with the remaining options and counts. Edit: Additional notes: .OrderBy("it.City") // "it" refers to the entire record .GroupBy("City", "new(City)") // This produces a unique list of City .Select("it.Count()") //This gives a list of counts... getting closer .Select("key") // Selects a list of unique City .Select("new (key, count() as string)") // +1 to me LOL. key is a row of group .GroupBy("new (City, Manufacturer)", "City") // New = list of fields to group by .GroupBy("City", "new (Manufacturer, Size)") // Second parameter is a projection Product .Where("ProductType == @0", "Maps") .GroupBy("new(City)", "new ( null as string)")// Projection not available later? .Select("new (key.City, it.count() as string)")// GroupBy new makes key an object Product .Where("ProductType == @0", "Maps") .GroupBy("new(City)", "new ( null as string)")// Projection not available later? .Select("new (key.City, it as object)")// the it object is the result of GroupBy var a = Product .Where("ProductType == @0", "Maps") .GroupBy("@0", "it", "City") // This fails to group Product at all .Select("new ( Key, it as Product )"); // "it" is property cast though What I have learned so far is LinqPad is fantastic, but still looking for an answer. Eventually, completely random research like this will prevail I guess. LOL. Edit:

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  • Linq Left Outer Join

    - by Neil
    I am new to LINQ and am trying to convert a SQL query to LINQ: SQL: left outer join PRODUCT_BEST_USE pbu on pbu.PRODUCT_GUID = @uProductId and pbu.BEST_USE_GUID = bu.BEST_USE_GUID LINQ: from PBU in PRODUCT_BEST_USE.Where(PBU=>PBU.PRODUCT_GUID == p.PRODUCT_GUID).DefaultIfEmpty() When I add and PBU.BEST_USE_GUID equals BU.BEST_USE_GUID, I get an error: "A query body must end with a select clause or a group clause" Here is the full Linq query: from p in PRODUCT join BU in BEST_USE on p.CATEGORY_GUID equals BU.CATEGORY_GUID from PBU in PRODUCT_BEST_USE.Where(PBU=>PBU.PRODUCT_GUID == p.PRODUCT_GUID).DefaultIfEmpty() and PBU.BEST_USE_GUID equals BU.BEST_USE_GUID where p.PRODUCT_GUID == new Guid("d317752b-581d-4f43-92fa-4a4af91009f5") select new { BU.NAME, PBU.PRODUCT_BEST_USE_GUID }

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  • Linq To Sql or classic ADO.net?

    - by Spyros
    I am asking my self many times before start writting a new app or data access library , should I use LinqToSql or classic ADO.net , I have used both and the development time I spend on building an app with Linq To sql is like the 1/3 compared to ADO.net. The only think I like using Linq to sql is that I dont have to design the domain objects Linq does that for me and saves me from spend my time on boring things :P But is Linq to sql suitable for large scale projects , is there an overhead that we can avoid when using ADO.net ?

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  • Future of Linq to Sql and Entity Framework

    - by ENES TAYLAN
    I work on a project and want to use an ORM. What should I use: Linq to Sql or Entity Framework? Linq to Sql provides more opportunities, as I see, for example support for enumeration types. However, also it is said that, Linq to Sql was for playing and learning for Linq and future strategy of Microsoft lies on Entity Framework. So which one should I use?

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  • Linq To Text Files

    - by j-t-s
    Hi All I have a Text File (Sorry, I'm not allowed to work on XML files :(), and it includes customer records. Each text file looks like: Account_ID: 98734BLAH9873 User Name: something_85 First Name: ILove Last Name: XML Age: 209 etc... And I need to be able to use LINQ to get the data from these text files and just store them in memory. I have seen many Linq to SQL, Linq to BLAH but nothing for Linq to Text. Can someone please help me out abit? Thank you

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  • How do I generate optimized SQL with my (added) partial methods on LINQ entities

    - by Ra
    Let's say I have a Person table with a FirstName and LastName column. I extended the Person LINQ entity class with a get property "FullName", that concatenates the first and last names. A LINQ query like: from person... select fullName where id = x generates SQL selecting all Patient columns, since FullName is evaluated after firing the query. I would like to limit the select clause to only the 2 columns required. This is a simple example, but the limitation it shows is that I cannot isolate my business/formatting rules but have to embed them in the LINQ query, so they're not reusable (since it is in the select part) or I need select both columns separately, and then concatenate them higher up in the data or business layer with static helper methods. Any ideas for a clean design using the entity partial classes or extensions? Thanks

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  • Are elements returned by Linq-to-Entities query streamed from the DB one at the time or are they retrieved all at once?

    - by carewithl
    Are elements returned by Linq-to-Entities query streamed from the database one at the time ( as they are requested ) or are they retrieved all at once: SampleContext context = new SampleContext(); // SampleContext derives from ObjectContext var search = context.Contacts; foreach (var contact in search) { Console.WriteLine(contact.ContactID); // is each Contact retrieved from the DB // only when foreach requests it? } thank you in advance

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  • Using NHibernate to select entities based on activity of children entities

    - by mannish
    I'm having a case of the Mondays... I need to select blog posts based on recent activity in the post's comments collection (a Post has a List<Comment> property and likewise, a Comment has a Post property, establishing the relationship. I don't want to show the same post twice, and I only need a subset of the entities, not all of the posts. First thought was to grab all posts that have comments, then order those based on the most recent comment. For this to work, I'm pretty sure I'd have to limit the comments for each Post to the first/newest Comment. Last I'd simply take the top 5 (or whatever max results number I want to pass into the method). Second thought would be to grab all of the comments, ordered by CreatedOn, and filter so there's only one Comment per Post. Then return those top (whatever) posts. This seems like the same as the first option, just going through the back door. I've got an ugly, two query option I've got working with some LINQ on the side for filtering, but I know there's a more elegant way to do it in using the NHibernate API. Hoping to see some good ideas here.

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  • What's a good entity hierarchy for a 2D game?

    - by futlib
    I'm in the process of building a new 2D game out of some code I wrote a while ago. The object hierarchy for entities is like this: Scene (e.g. MainMenu): Contains multiple entities and delegates update()/draw() to each Entity: Base class for all things in a scene (e.g. MenuItem or Alien) Sprite: Base class for all entities that just draw a texture, i.e. don't have their own drawing logic Does it make sense to split up entities and sprites up like that? I think in a 2D game, the terms entity and sprite are somewhat synonymous, right? But I do believe that I need some base class for entities that just draw a texture, as opposed to drawing themselves, to avoid duplication. Most entities are like that. One weird case is my Text class: It derives from Sprite, which accepts either the path of an image or an already loaded texture in its constructor. Text loads a texture in its constructor and passes that to Sprite. Can you outline a design that makes more sense? Or point me to a good object-oriented reference code base for a 2D game? I could only find 3D engine code bases of decent code quality, e.g. Doom 3 and HPL1Engine.

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