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  • linq with Include and criteria

    - by JMarsch
    How would I translate this into LINQ? Say I have A parent table (Say, customers), and child (addresses). I want to return all of the Parents who have addresses in California, and just the california address. (but I want to do it in LINQ and get an object graph of Entity objects) Here's the old fashioned way: SELECT c.blah, a.blah FROM Customer c INNER JOIN Address a on c.CustomerId = a.CustomerId where a.State = 'CA' The problem I'm having with LINQ is that i need an object graph of concrete Entity types (and it can't be lazy loaded. Here's what I've tried so far: // this one doesn't filter the addresses -- I get the right customers, but I get all of their addresses, and not just the CA address object. from c in Customer.Include(c = c.Addresses) where c.Addresses.Any(a = a.State == "CA") select c // this one seems to work, but the Addresses collection on Customers is always null from c in Customer.Include(c = c.Addresses) from a in c.Addresses where a.State == "CA" select c; Any ideas?

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  • Caching strategies for entities and collections

    - by Rob West
    We currently have an application framework in which we automatically cache both entities and collections of entities at the business layer (using .NET cache). So the method GetWidget(int id) checks the cache using a key GetWidget_Id_{0} before hitting the database, and the method GetWidgetsByStatusId(int statusId) checks the cache using GetWidgets_Collections_ByStatusId_{0}. If the objects are not in the cache they are retrieved from the database and added to the cache. This approach is obviously quick for read scenarios, and as a blanket approach is quick for us to implement, but requires large numbers of cache keys to be purged when CRUD operations are carried out on entities. Obviously as additional methods are added this impacts performance and the benefits of caching diminish. I'm interested in alternative approaches to handling caching of collections. I know that NHibernate caches a list of the identifiers in the collection rather than the actual entities. Is this an approach other people have tried - what are the pros and cons? In particular I am looking for options that optimise performance and can be implemented automatically through boilerplate generated code (we have our own code generation tool). I know some people will say that caching needs to be done by hand each time to meet the needs of the specific situation but I am looking for something that will get us most of the way automatically.

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  • State changes in entities or components

    - by GriffinHeart
    I'm having some trouble figuring how to deal with state management in my entities. I don't have trouble with Game state management, like pause and menus, since these are not handled as an entity component system; just with state in entities/components. Drawing from Orcs Must Die as an example, I have my MainCharacter and Trap entities which only have their components like PositionComponent, RenderComponent, PhysicsComponent. On each update the Entity will call update on its components. I also have a generic EventManager with listeners for different event types. Now I need to be able to place the traps: first select the trap and trap position then place the trap. When placing a trap it should appear in front of the MainCharacter, rendered in a different way and following it around. When placed it should just respond to collisions and be rendered in the normal way. How is this usually handled in component based systems? (This example is specific but can help figure out the general way to deal with entities states.)

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  • Do entity collections and object sets implement IQueryable<T>?

    - by Chevex
    I am using Entity Framework for the first time and noticed that the entities object returns entity collections. DBEntities db = new DBEntities(); db.Users; //Users is an ObjectSet<User> User user = db.Users.Where(x => x.Username == "test").First(); //Is this getting executed in the SQL or in memory? user.Posts; //Posts is an EntityCollection<Post> Post post = user.Posts.Where(x => x.PostID == "123").First(); //Is this getting executed in the SQL or in memory? Do both ObjectSet and EntityCollection implement IQueryable? I am hoping they do so that I know the queries are getting executed at the data source and not in memory. EDIT: So apparently EntityCollection does not while ObjectSet does. Does that mean I would be better off using this code? DBEntities db = new DBEntities(); User user = db.Users.Where(x => x.Username == "test").First(); //Is this getting executed in the SQL or in memory? Post post = db.Posts.Where(x => (x.PostID == "123")&&(x.Username == user.Username)).First(); // Querying the object set instead of the entity collection. Also, what is the difference between ObjectSet and EntityCollection? Shouldn't they be the same? Thanks in advance!

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  • what possible workarounds are there for "only parameterless constructors are support in Linq to Enti

    - by Ralph Shillington
    In my query I need to return instances of a class that doesn't have a default constructor (specifically this is in a custom Membership provider, and MembershipUser is the culprit) var users = from l in context.Logins select new MembershipUser( Name, l.Username, // username l.Id, // provider key l.MailTo, l.PasswordQuestion, l.Notes.FirstOrDefault().NoteText, l.IsApproved, l.IsLockedOut, l.CreatedOn, l.LastLoginOn.HasValue ? l.LastLoginOn.Value : DateTime.MinValue, l.LastActivityOn.HasValue ? l.LastActivityOn.Value : DateTime.MinValue, DateTime.MinValue, l.LastLockedOutOn.HasValue ? l.LastLockedOutOn.Value : DateTime.MinValue ); is syntacitally correct, but results in a runtime error as Only parameterless constructors and initializers are supported in LINQ to Entities.

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  • Group by/count in LINQ against SQL Compact 3.5 SP2

    - by bash74
    Hello, I am using LINQ-To-Entities in C# and run queries against a SQL Compact Server 3.5 SP2. What I try to achieve is a simple group by with an additional where clause which includes a Count(). var baseIdent="expression"; var found=from o in ObservedElements where o.ObservedRoots.BaseIdent==baseIdent group o by o.ID into grouped where grouped.Count()==1 select new {key=grouped.Key, val=grouped}; foreach(var res in found){ //do something here } This query throws the famous exception "A parameter is not allowed in this location. Ensure that the '@' sign and all other parameters are in a valid location in the SQL statement." When I either omit the where clause OR directly enter the expression "expression" in the query (where o.ObservedRoots.BaseIdent=="expression") everything just works fine. Does anybody know how to solve this? Workaround would also be fine? Thanks in advance, Sebastian

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  • for vs. foreach vs. LINQ

    - by beccoblu
    When I write code in Visual Studio, ReSharper (God bless it!) often suggests me to change my old-school for loop in the more compact foreach form. And often, when I accept this change, ReSharper goes a step forward, and suggests me to change it again, in a shiny LINQ form. So, I wonder: are there some real advantages, in these improvements? In pretty simple code execution, I cannot see any speed boost (obviously), but I can see the code becoming less and less readable... So I wonder: is it worth it?

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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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  • 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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  • 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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  • Help regarding database and logic layer for my ASP.NET MVC application

    - by Ismail S
    I'm going to start a new project which is going to be small initially but may grow to big over the years. I'm strongly convinced that I'm going to use ASP.NET MVC with jQuery for UI. I want to go for MySQL as database for some reasons but worried on few things. I've a good years of experience working on SQL Server databases and on one project I've had a bad experience creating and managing stored procedures on MySQL database. I'm totally new to Linq but I see that it is easier to use once you are familiar with it. First thing is that accessing data should be easy. So I thought I should use MySQL to Linq but somewhere I read that it is not directly supported but MySQL .NET connector adds support for EntityFramework. I don't know what are the pros and cons of it. I would love if I can implement repository pattern. Will it be possible if I use Entity Framework? I'm not clear on how I should go about all this or I should just forget every thing and directly use SQL to Linq on SQL Server. I'm also concerned about the performance. Someone told me that if we use Entity framework it fetches lot of data and then filter it. Is that right?

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  • How does an Engine like Source process entities?

    - by Júlio Souza
    [background information] On the Source engine (and it's antecessor, goldsrc, quake's) the game objects are divided on two types, world and entities. The world is the map geometry and the entities are players, particles, sounds, scores, etc (for the Source Engine). Every entity has a think function, which do all the logic for that entity. So, if everything that needs to be processed comes from a base class with the think function, the game engine could store everything on a list and, on every frame, loop through it and call that function. On a first look, this idea is reasonable, but it can take too much resources, if the game has a lot of entities.. [end of background information] So, how does a engine like Source take care (process, update, draw, etc) of the game objects?

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  • Simulating simultaneous entities

    - by Steven Jeuris
    Consider the need to simulate a set of entitities in an accurate way. All entities exist in an artificial timeline. Within 'steps' of this timeline, all entities can do certain operations. It is imperative that timed events, are handled accurately, and not in processing order. So simple threading isn't a proper simulation, nor is procedurally walking across all entities. Processing may be slow, accuracy is key here. I have some ideas how to implement this myself, but most likely something like this has been done before. Are there any frameworks available for these purposes? Is there any particular paradigm more suitable?

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  • Funky Behavior NoTracking Query Entities

    I’ve been using a lot of NoTracking queries to grab lists of data that I don’t need change tracked. It enhances performance and cuts down on resources. There are some nuances about these entities, however. One of the interesting behaviors of EF4’s Lazy Loading is that even if you have entities that you have queried with NoTracking on, they will still lazy load related entities. Unless you’ve read this somewhere (it’s on the ADO.NET team’s blog post which introduces...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Using HTML entities in XML Literals (Avner Aharoni)

    One of the common use-cases of XML literals is creating HTML. However, HTML entities cannot be used in XML literals since LINQ to XML directly supports only the Data type definitions (DTD) defined in the XML 1.0 spec. You can read more about it here. The workaround is to use the Unicode representation of the entity, although its not as readable as the HTML entities, the output is the same. Here are two examples of HTML entities from the XHTML spec :   Entity...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Using HTML entities in XML Literals (Avner Aharoni)

    One of the common use-cases of XML literals is creating HTML. However, HTML entities cannot be used in XML literals since LINQ to XML directly supports only the Data type definitions (DTD) defined in the XML 1.0 spec. You can read more about it here. The workaround is to use the Unicode representation of the entity, although its not as readable as the HTML entities, the output is the same. Here are two examples of HTML entities from the XHTML spec :   Entity...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Azure Table&ndash;Entities having different Schema (Implementation Approach)

    - by kaleidoscope
    Below is the approach that can be implemented whenever there is a requirement of creating an Azure Table having entities with different schema definitions.   We can have a Parent Entity defined which will hold the data common in all the entity types and then rest all entities should inherit from this parent class. There will be only on DataServiceContext class which will accept the object of the Parent class and this can be used for CRUD operations of all the entities. Hope this approach helps! Thanks. Technorati Tags: Azure Table,Geeta

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  • NHibernate Linq Timeout

    - by DarrenMcD
    How do I increase the timeout in NHibernate Linq To Sql? Not the Connection Timeout but the ado command timeout. using (ISession session = NHibernateHelper.OpenSession(NHibernateHelper.Databases.CarrierCDR)) using (session.BeginTransaction(IsolationLevel.ReadUncommitted)) { lCdrs = (from verizon in session.Linq<Domain.Verizon>() where verizon.Research == true && verizon.ReferenceTable == null orderby verizon.CallBillingDate descending select verizon).ToList(); }

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  • LINQ to XML vs. XmlReader

    - by Vadim
    In my Silverlight application I'm using mostly XmlReader but I'm playing with idea to replace XmlReader implementation with LINQ to XML. What are pros and cons between LINQ to XML and XmlReader in Silverlight?

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  • "Push" linq vs reactive framework

    - by Benjol
    (Once again exposing the depths of my ignorance here by combining two concepts which I haven't grokked) I read here about the Reactive framework being a 'Push' model compared to Linq's 'Pull' model. This reminded me of reading an article about 'Push' Linq. Is there really any similarity between these two 'frameworks'? UPDATE Since I asked this question, Jon Skeet has asked it too, here are his first and second impressions.

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  • mysql and linq support

    - by darko petreski
    Hi All, I have read in many forums that there is no good linq for mysql (free) but his forums are 2 years old. In the meantime is there any good free linq for mysql ? Hog good is for professional use? Regards

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  • LINQ and Storedprocedure

    - by Amutha
    The interview i faced was "What is the difference between LINQ and Stored procedure?". I don't know whether it is a vague question or proper one. I answered "In Linq there is a support for Closure so you can refer the value of outer parameter inside the anonymous body,you can't do the same with Stored procedure". Just i am requesting you the proper answer.

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