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• Entity Framework Vote of No Confidence - relevant in .NET 4?

  - by Asaf R

  Hi, I'm deciding on an ORM for a big project and was determined to go for ADO.NET Entity Framework, specifically its new version that ships with .NET 4. During my search for information on EF I stumbled upon ADO .NET Entity Framework Vote of No Confidence which I'm not sure how to take. The Vote of No Confidence was written sometime in 2008 to convince Microsoft to listen to specific criticism for EF v1. It's not clear whether the claims made in the Vote of No Confidence are still valid (in .NET 4) and if they're serious enough to use other solutions. NHibernate is a mature alternative, but I don't know what problems it brings. I'm generally more inclined towards a Ms solution, mainly because I can count on integration with VS and on their developer support. I would appreciate examples of how the problems mentioned in the Vote of No Confidence affect in real world projects. More importantly, are the claims made there still relevant in EF for .NET 4? Thanks, Asaf

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• How to build a setup package for a desktop application using SQL CE 3.5 and Entity Framework?

  - by Emad

  I am having a WPF desktop application that uses SQL CE (compact edition 3.5 ) and using the Entity Framework as a Datalayer. As It turned out in (http://support.microsoft.com/default.aspx?scid=kb;en-us;958478&sd=rss&spid=2855 ) and (http://social.msdn.microsoft.com/Forums/en-US/sqlce/thread/b6bac277-cf66-4c74-a0b3-e48abedbd161/ ) There Is some problem with the Entity Framework and SQL CE and I had to get the hotfix (basically a new build of the SQL CE called 3.5.1) My problem now is how to build a setup package in order to make it work in case some users already had the SQL CE 3.5 installed on their machines? I have included the DLLs directly in the application but when the sql ce is installed, its DLLs are in the GAC and have precedence over the local ones and the application crashes. I need the build a setup that would work "even if" the user already had the old buggy version.

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• Anyone succeeded at injecting Interfaces into Entity Framework 4 Entities, using T4?

  - by Ciel

  Hello: POCO sort of leaves me wanting: (how can I say I use DI/IoC, if the Repository is not the only place that is creating the entities?)...hence my desire to lock it down, get rid of the temptation of newing up POCOs or EntityObjects anywhere in the code, and just allowing entity interfaces above the Repository/Factory layer. For a second there, I nearly thought I had it...was editing EF4's T4 in order to inject in an Interface def. Was going swimmingly, compiled and worked, until I got to the Associations... I wrapped them with a ICollection, and renamed the underlying original collection with a prefix of Wrapped. Unfortunately, when run, throws an error: //The Member 'WrappedSubExamples' in the CLR type 'XAct.App.Data.Model.EF4.Example' is not present in the conceptual model type 'XAct.App.Data.Model.Entity.Example'. var examples = context2.CreateObjectSet(); My T4 segment I used was (this may not work, as it's the longest code snippet I've ever posted here...sorry): #region Generic Property Abstraction <# if (navProperty.ToEndMember.RelationshipMultiplicity == RelationshipMultiplicity.Many) {#> //XAct.App Generic Wrapper: <#=code.SpaceAfter(NewModifier(navProperty))#><#=Accessibility.ForProperty(navProperty)#> ICollection<I<#=MultiSchemaEscape(navProperty.ToEndMember.GetEntityType(), code)#>> <#=code.Escape(navProperty)#> { get { if (_X<#=code.Escape(navProperty)# == null){ _X<#=code.Escape(navProperty)# = new WrappedCollection,<#=MultiSchemaEscape(navProperty.ToEndMember.GetEntityType(), code)#(this.<#=(navProperty.ToEndMember.RelationshipMultiplicity == RelationshipMultiplicity.Many)?"Wrapped":""#<#=code.Escape(navProperty)#); } return _X<#=code.Escape(navProperty)#; } } private ICollection _X<#=code.Escape(navProperty)#; <# } else { # <#=code.SpaceAfter(NewModifier(navProperty))#<#=Accessibility.ForProperty(navProperty)# I<#=MultiSchemaEscape(navProperty.ToEndMember.GetEntityType(), code)# <#=code.Escape(navProperty)# { get { return (I<#=code.Escape(navProperty)#)this.Wrapped<#=code.Escape(navProperty)#; } set { this.Wrapped<#=code.Escape(navProperty)# = value as <#=code.Escape(navProperty)#; } } <# } # #endregion which then wraps the original collection, renamed with the prefix 'Wrapped': /// <summary> /// <#=SummaryComment(navProperty)#> /// </summary><#=LongDescriptionCommentElement(navProperty, region.CurrentIndentLevel) #> [XmlIgnoreAttribute()] [SoapIgnoreAttribute()] [DataMemberAttribute()] [EdmRelationshipNavigationPropertyAttribute("<#=navProperty.RelationshipType.NamespaceName#>", "<#=navProperty.RelationshipType.Name#>", "<#=navProperty.ToEndMember.Name#>")] <# if (navProperty.ToEndMember.RelationshipMultiplicity == RelationshipMultiplicity.Many) { #> <#=code.SpaceAfter(NewModifier(navProperty))#><#=Accessibility.ForProperty(navProperty)#> EntityCollection<<#=MultiSchemaEscape(navProperty.ToEndMember.GetEntityType(), code)#>> Wrapped<#=code.Escape(navProperty)#> { <#=code.SpaceAfter(Accessibility.ForGetter(navProperty))#>get { return ((IEntityWithRelationships)this).RelationshipManager.GetRelatedCollection<<#=MultiSchemaEscape(navProperty.ToEndMember.GetEntityType(), code)#>>("<#=navProperty.RelationshipType.FullName#>", "<#=navProperty.ToEndMember.Name#>"); } <#=code.SpaceAfter(Accessibility.ForSetter(navProperty))#>set { if ((value != null)) { ((IEntityWithRelationships)this).RelationshipManager.InitializeRelatedCollection<<#=MultiSchemaEscape(navProperty.ToEndMember.GetEntityType(), code)#>>("<#=navProperty.RelationshipType.FullName#>", "<#=navProperty.ToEndMember.Name#>", value); } } } <# } else { #> <#=code.SpaceAfter(NewModifier(navProperty))#><#=Accessibility.ForProperty(navProperty)#> <#=MultiSchemaEscape(navProperty.ToEndMember.GetEntityType(), code)#> Wrapped<#=code.Escape(navProperty)#> { <#=code.SpaceAfter(Accessibility.ForGetter(navProperty))#>get { return ((IEntityWithRelationships)this).RelationshipManager.GetRelatedReference<<#=MultiSchemaEscape(navProperty.ToEndMember.GetEntityType(), code)#>>("<#=navProperty.RelationshipType.FullName#>", "<#=navProperty.ToEndMember.Name#>").Value; } <#=code.SpaceAfter(Accessibility.ForSetter(navProperty))#>set { ((IEntityWithRelationships)this).RelationshipManager.GetRelatedReference<<#=MultiSchemaEscape(navProperty.ToEndMember.GetEntityType(), code)#>>("<#=navProperty.RelationshipType.FullName#>", "<#=navProperty.ToEndMember.Name#>").Value = value; } } <# string refPropertyName = navProperty.Name + "Reference"; if (entity.Members.Any(m => m.Name == refPropertyName)) { // 6017 is the same error number that EntityClassGenerator uses. Errors.Add(new System.CodeDom.Compiler.CompilerError(SourceCsdlPath, -1, -1, "6017", String.Format(CultureInfo.CurrentCulture, GetResourceString("Template_ConflictingGeneratedNavPropName"), navProperty.Name, entity.FullName, refPropertyName))); } #> /// <summary> /// <#=SummaryComment(navProperty)#> /// </summary><#=LongDescriptionCommentElement(navProperty, region.CurrentIndentLevel)#> [BrowsableAttribute(false)] [DataMemberAttribute()] <#=Accessibility.ForProperty(navProperty)#> EntityReference<<#=MultiSchemaEscape(navProperty.ToEndMember.GetEntityType(), code)#>> <#=refPropertyName#> { <#=code.SpaceAfter(Accessibility.ForGetter(navProperty))#>get { return ((IEntityWithRelationships)this).RelationshipManager.GetRelatedReference<<#=MultiSchemaEscape(navProperty.ToEndMember.GetEntityType(), code)#>>("<#=navProperty.RelationshipType.FullName#>", "<#=navProperty.ToEndMember.Name#>"); } <#=code.SpaceAfter(Accessibility.ForSetter(navProperty))#>set { if ((value != null)) { ((IEntityWithRelationships)this).RelationshipManager.InitializeRelatedReference<<#=MultiSchemaEscape(navProperty.ToEndMember.GetEntityType(), code)#>>("<#=navProperty.RelationshipType.FullName#>", "<#=navProperty.ToEndMember.Name#>", value); } } } <# } The point is...it bugs out. I've tried various solutions...none worked. Any ideas -- or is this just a wild goose chase, and time to give it up?

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• Under what circumstances would a LINQ-to-SQL Entity "lose" a changed field?

  - by John Rudy

  I'm going nuts over what should be a very simple situation. In an ASP.NET MVC 2 app (not that I think this matters), I have an edit action which takes a very small entity and makes a few changes. The key portion (outside of error handling/security) looks like this: Todo t = Repository.GetTodoByID(todoID); UpdateModel(t); Repository.Save(); Todo is the very simple, small entity with the following fields: ID (primary key), FolderID (foreign key), PercentComplete, TodoText, IsDeleted and SaleEffortID (foreign key). Each of these obviously corresponds to a field in the database. When UpdateModel(t) is called, t does get correctly updated for all fields which have changed. When Repository.Save() is called, by the time the SQL is written out, FolderID reverts back to its original value. The complete code to Repository.Save(): public void Save() { myDataContext.SubmitChanges(); } myDataContext is an instance of the DataContext class created by the LINQ-to-SQL designer. Nothing custom has been done to this aside from adding some common interfaces to some of the entities. I've validated that the FolderID is getting lost before the call to Repository.Save() by logging out the generated SQL: UPDATE [Todo].[TD_TODO] SET [TD_PercentComplete] = @p4, [TD_TodoText] = @p5, [TD_IsDeleted] = @p6 WHERE ([TD_ID] = @p0) AND ([TD_TDF_ID] = @p1) AND /* Folder ID */ ([TD_PercentComplete] = @p2) AND ([TD_TodoText] = @p3) AND (NOT ([TD_IsDeleted] = 1)) AND ([TD_SE_ID] IS NULL) /* SaleEffort ID */ -- @p0: Input BigInt (Size = -1; Prec = 0; Scale = 0) [5] -- @p1: Input BigInt (Size = -1; Prec = 0; Scale = 0) [1] /* this SHOULD be 4 and in the update list */ -- @p2: Input TinyInt (Size = -1; Prec = 0; Scale = 0) [90] -- @p3: Input NVarChar (Size = 4000; Prec = 0; Scale = 0) [changing text] -- @p4: Input TinyInt (Size = -1; Prec = 0; Scale = 0) [0] -- @p5: Input NVarChar (Size = 4000; Prec = 0; Scale = 0) [changing text foo] -- @p6: Input Bit (Size = -1; Prec = 0; Scale = 0) [True] -- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 4.0.30319.1 So somewhere between UpdateModel(t) (where I've validated in the debugger that FolderID updated) and the output of this SQL, the FolderID reverts. The other fields all save. (Well, OK, I haven't validated SaleEffortID yet, because that subsystem isn't really ready yet, but everything else saves.) I've exhausted my own means of research on this: Does anyone know of conditions which would cause a partial entity reset (EG, something to do with long foreign keys?), and/or how to work around this?

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• Is it a good practice to implement aggregate routes in Entity Framework 4?

  - by Kohan

  Having just started working on a new project using Entity Framework 4, I spoke to some of the other team that use NHibernate for advice. They implement aggregate routes on their entities, so instead of adding an order through the orders entity, they would add it through customer.order by having an addOrder method on customer. This is the approach I have taken but I am, alas, running into problems. These are issues that I hope to work out, but it got me thinking ... Is this a good way to work or am I fighting an uphill battle unnecessarily?

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• How can I edit an entity in MVC4 with EF5 which has a unique constraint?

  - by Yoeri

  [HttpPost] public ActionResult Edit(Car car) { if (ModelState.IsValid) { db.Entry(car).State = EntityState.Modified; db.SaveChanges(); return RedirectToAction("Index"); } return View(car); } This is a controller method scaffolded by MCV 4 My "car" entity has a unique field: LicensePlate. I have custom validation on my Entity: Validation: public partial class Car { partial void ValidateObject(ref List<ValidationResult> validationResults) { using (var db = new GarageIncEntities()) { if (db.Cars.Any(c => c.LicensePlate.Equals(this.LicensePlate))) { validationResults.Add( new ValidationResult("This licenseplate already exists.", new string[]{"LicensePlate"})); } } } } should it be usefull, my car entity: public partial class Car:IValidatableObject { public int Id { get; set; } public string Color { get; set; } public int Weight { get; set; } public decimal Price { get; set; } public string LicensePlate { get; set; } public System.DateTime DateOfSale { get; set; } public int Type_Id { get; set; } public int Fuel_Id { get; set; } public virtual CarType Type { get; set; } public virtual Fuel Fuel { get; set; } public IEnumerable<ValidationResult> Validate(ValidationContext validationContext) { var result = new List<ValidationResult>(); ValidateObject(ref result); return result; } partial void ValidateObject(ref List<ValidationResult> validationResults); } QUESTION: Everytime I edit a car, it raises an error: Validation failed for one or more entities. See 'EntityValidationErrors' property for more details. The error is the one raised by my validation, saying it can't edit because there is already a car with that license plate. If anyone could point me in the right direction to fix this, that would be great! I searched but couldn't find anything, so even related posts are welcome!

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• Too Many Left Outer Joins in Entity Framework 4?

  - by Adam

  I have a product entity, which has 0 or 1 "BestSeller" entities. For some reason when I say: db.Products.OrderBy(p = p.BestSeller.rating).ToList(); the SQL I get has an "extra" outer join (below). And if I add on a second 0 or 1 relation ship, and order by both, then I get 4 outer joins. It seems like each such entity is producing 2 outer joins rather than one. LINQ to SQL behaves exactly as you'd expect, with no extra join. Has anyone else experienced this, or know how to fix it? SELECT [Extent1].[id] AS [id], [Extent1].[ProductName] AS [ProductName] FROM [dbo].[Products] AS [Extent1] LEFT OUTER JOIN [dbo].[BestSeller] AS [Extent2] ON [Extent1].[id] = [Extent2].[id] LEFT OUTER JOIN [dbo].[BestSeller] AS [Extent3] ON [Extent2].[id] = [Extent3].[id] ORDER BY [Extent3].[rating] ASC

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• Can I create many tables according to the same entity?

  - by jacob

  What I want to do is that I want to make the many tables dinamically which are the same entity structures. And then I want to refer to the dinamically created tables according to the table name. What I understood from hibernate reference is that I can only create only one table and it should be matched exactly with entity. So I can't find any solution to my problem. If you know any relevent open source related to my problem or any tip or web site, let me know. Thanks allways

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• Can I create a transaction using ADO NET Entity Data Model?

  - by Junior Mayhé

  Hi is it possible on the following try-catch to execute a set of statements as a transaction using ADO NET Entity Data Model? [ValidateInput(false)] [AcceptVerbs(HttpVerbs.Post)] public ActionResult Create(Customer c) { try { c.Created = DateTime.Now; c.Active = true; c.FullName = Request.Form["FirstName"]; db.AddToCustomer(c); db.SaveChanges(); Log log = new Log();//another entity model object log.Created = DateTime.Now; log.Message = string.Format(@"A new customer was created with customerID {0}", c.CustomerID); db.AddToLog(log); db.SaveChanges(); return RedirectToAction("CreateSuccess", "Customer"); } catch { return View(); } } Any thoughts would be very appreciated.

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• Foreign Key vs. Independent Relationships - is there improvement with Entity Framework 5?

  - by zam6ak

  I have read several articles and questions on concept of foreign key vs independent relationship when using Entity Framework. And I am still not 100% sure which way to go.... I would prefer not to "pollute" my domain POCOs by having a property that will be used in FK relationship when I already have a property reference to "has a" object. My questions are (looking at you @EFTeam, @Ladislav Mrnka) are there any improvements on this subject in the upcoming Entity Framework v5? are there more advantages if I use FK instead of independent associations (particularly with code first)?

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• Is it possible to have a dynamic data ASP.net web application using Entity Framework?

  - by Greg

  Is it possible to have a dynamic data ASP.net web application using Entity Framework?

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• Framework 4 Features: Support for Timed Jobs

  - by Anthony Shorten

  One of the new features of the Oracle Utilities Application Framework V4 is the ability for the batch framework to support Timed Batch. Traditionally batch is associated with set processing in the background in a fixed time frame. For example, billing customers. Over the last few versions their has been functionality required by the products required a more monitoring style batch process. The monitor is a batch process that looks for specific business events based upon record status or other pieces of data. For example, the framework contains a fact monitor (F1-FCTRN) that can be configured to look for specific status's or other conditions. The batch process then uses the instructions on the object to determine what to do. To support monitor style processing, you need to run the process regularly a number of times a day (for example, every ten minutes). Traditional batch could support this but it was not as optimal as expected (if you are a site using the old Workflow subsystem, you understand what I mean). The Batch framework was extended to add additional facilities to support times (and continuous batch which is another new feature for another blog entry). The new facilities include: The batch control now defines the job as Timed or Not Timed. Non-Timed batch are traditional batch jobs. The timer interval (the interval between executions) can be specified The timer can be made active or inactive. Only active timers are executed. Setting the Timer Active to inactive will stop the job at the next time interval. Setting the Timer Active to Active will start the execution of the timed job. You can specify the credentials, language to view the messages and an email address to send the a summary of the execution to. The email address is optional and requires an email server to be specified in the relevant feature configuration. You can specify the thread limits and commit intervals to be sued for the multiple executions. Once a timer job is defined it will be executed automatically by the Business Application Server process if the DEFAULT threadpool is active. This threadpool can be started using the online batch daemon (for non-production) or externally using the threadpoolworker utility. At that time any batch process with the Timer Active set to Active and Batch Control Type of Timed will begin executing. As Timed jobs are executed automatically then they do not appear in any external schedule or are managed by an external scheduler (except via the DEFAULT threadpool itself of course). Now, if the job has no work to do as the timer interval is being reached then that instance of the job is stopped and the next instance started at the timer interval. If there is still work to complete when the interval interval is reached, the instance will continue processing till the work is complete, then the instance will be stopped and the next instance scheduled for the next timer interval. One of the key ways of optimizing this processing is to set the timer interval correctly for the expected workload. This is an interesting new feature of the batch framework and we anticipate it will come in handy for specific business situations with the monitor processes.

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• Twitter User/Search Feature Header Support in LINQ to Twitter

  - by Joe Mayo

  LINQ to Twitter’s goal is to support the entire Twitter API. So, if you see a new feature pop-up, it will be in-queue for inclusion. The same holds for the new X-Feature… response headers for User/Search requests.  However, you don’t have to wait for a special property on the TwitterContext to access these headers, you can just use them via the TwitterContext.ResponseHeaders collection. The following code demonstrates how to access the new X-Feature… headers with LINQ to Twitter: var user = (from usr in twitterCtx.User where usr.Type == UserType.Search && usr.Query == "Joe Mayo" select usr) .FirstOrDefault(); Console.WriteLine( "X-FeatureRateLimit-Limit: {0}\n" + "X-FeatureRateLimit-Remaining: {1}\n" + "X-FeatureRateLimit-Reset: {2}\n" + "X-FeatureRateLimit-Class: {3}\n", twitterCtx.ResponseHeaders["X-FeatureRateLimit-Limit"], twitterCtx.ResponseHeaders["X-FeatureRateLimit-Remaining"], twitterCtx.ResponseHeaders["X-FeatureRateLimit-Reset"], twitterCtx.ResponseHeaders["X-FeatureRateLimit-Class"]); The query above is from the User entity, whose type is Search; allowing you to search for the Twitter user whose name is specified by the Query parameter filter. After materializing the query, with FirstOrDefault, twitterCtx will hold all of the headers, including X-Feature… that Twitter returned.  Running the code above will display results similar to the following: X-FeatureRateLimit-Limit: 60 X-FeatureRateLimit-Remaining: 59 X-FeatureRateLimit-Reset: 1271452177 X-FeatureRateLimit-Class: namesearch In addition to getting the X-Feature… headers a capability you might have noticed is that the TwitterContext.ResponseHeaders collection will contain any HTTP that Twitter sends back to a query. Therefore, you’ll be able to access new Twitter headers anytime in the future with LINQ to Twitter. @JoeMayo

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• NHibernate & Cancelling Changes to Entities

  - by user129609

  Hi, This seems like it would be a common issue to be but I don't know the best way to solve it. I want to be able to send an Entity to a view, have changes be made to the entity in the view, but then cancel (remove) those changes if the user cancels out of the view. What is the proper way to do this. Here are two options I have but I think there should be others that are better 1) Take an entity, create a clone, send the clone to the view...if changes are accepted, update the original entity with the clone's values 2) Send the entity to the view, if the user cancels, remove the entity from NHibernate's cache and reload it from the database For (2), the issue for me would be that the old entity could still be referenced throughout my project after it has been removed from the cache.

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• Tuples vs. Anonymous Types vs. Expando object. (in regards to LINQ queries)

  - by punkouter

  I am a beginner who finally started understanding anonymous types. (see old post http://stackoverflow.com/questions/3010147/what-is-the-return-type-for-a-anonymous-linq-query-select-what-is-the-best-way-t) So in LINQ queries you form the type of return value you want within the linq query right? It seems the way to do this is anonymous type right? Can someone explain to me if and when I could use a Tuple/Expando object instead? They all seem very simliar?

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• LINQ to SQL : Too much CPU Usage: What happens when there are multiple users.

  - by soldieraman

  I am using LINQ to SQL and seeing my CPU Usage sky rocketting. See below screenshot. I have three questions What can I do to reduce this CPU Usage. I have done profiling and basically removed everything. Will making every LINQ to SQL statement into a compiled query help? I also find that even with compiled queries simple statements like ByID() can take 3 milliseconds on a server with 3.25GB RAM 3.17GHz - this will just become slower on a less powerful computer. Or will the compiled query get faster the more it is used? The CPU Usage (on the local server goes to 12-15%) for a single user will this multiply with the number of users accessing the server - when the application is put on a live server. i.e. 2 users at a time will mean 15*2 = 30% CPU Usage. If this is the case is my application limited to maximum 4-5 users at a time then. Or doesnt LINQ to SQL .net share some CPU usage.

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• Linq Query Performance , comparing Compiled query vs Non-Compiled.

  - by AG.

  Hello Guys, I was wondering if i extract the common where clause query into a common expression would it make my query much faster, if i have say something like 10 linq queries on a collection with exact same 1st part of the where clause. I have done a small example to explain a bit more . public class Person { public string First { get; set; } public string Last { get; set; } public int Age { get; set; } public String Born { get; set; } public string Living { get; set; } } public sealed class PersonDetails : List<Person> { } PersonDetails d = new PersonDetails(); d.Add(new Person() {Age = 29, Born = "Timbuk Tu", First = "Joe", Last = "Bloggs", Living = "London"}); d.Add(new Person() { Age = 29, Born = "Timbuk Tu", First = "Foo", Last = "Bar", Living = "NewYork" }); Expression<Func<Person, bool>> exp = (a) => a.Age == 29; Func<Person, bool> commonQuery = exp.Compile(); var lx = from y in d where commonQuery.Invoke(y) && y.Living == "London" select y; var bx = from y in d where y.Age == 29 && y.Living == "NewYork" select y; Console.WriteLine("All Details {0}, {1}, {2}, {3}, {4}", lx.Single().Age, lx.Single().First , lx.Single().Last, lx.Single().Living, lx.Single().Born ); Console.WriteLine("All Details {0}, {1}, {2}, {3}, {4}", bx.Single().Age, bx.Single().First, bx.Single().Last, bx.Single().Living, bx.Single().Born); So can some of the guru's here give me some advice if it would be a good practice to write query like var lx = "Linq Expression " or var bx = "Linq Expression" ? Any inputs would be highly appreciated. Thanks, AG

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• How to avoid loading a LINQ to SQL object twice when editting it on a website.

  - by emzero

  Hi guys I know you are all tired of this Linq-to-Sql questions, but I'm barely starting to use it (never used an ORM before) and I've already find some "ugly" things. I'm pretty used to ASP.NET Webforms old school developing, but I want to leave that behind and learn the new stuff (I've just started to read a ASP.NET MVC book and a .NET 3.5/4.0 one). So here's is one thing I didn't like and I couldn't find a good alternative to it. In most examples of editing a LINQ object I've seen the object is loaded (hitting the db) at first to fill the current values on the form page. Then, the user modify some fields and when the "Save" button is clicked, the object is loaded for second time and then updated. Here's a simplified example of ScottGu NerdDinner site. // // GET: /Dinners/Edit/5 [Authorize] public ActionResult Edit(int id) { Dinner dinner = dinnerRepository.GetDinner(id); return View(new DinnerFormViewModel(dinner)); } // // POST: /Dinners/Edit/5 [AcceptVerbs(HttpVerbs.Post), Authorize] public ActionResult Edit(int id, FormCollection collection) { Dinner dinner = dinnerRepository.GetDinner(id); UpdateModel(dinner); dinnerRepository.Save(); return RedirectToAction("Details", new { id=dinner.DinnerID }); } As you can see the dinner object is loaded two times for every modification. Unless I'm missing something about LINQ to SQL caching the last queried objects or something like that I don't like getting it twice when it should be retrieved only one time, modified and then comitted back to the database. So again, am I really missing something? Or is it really hitting the database twice (in the example above it won't harm, but there could be cases that getting an object or set of objects could be heavy stuff). If so, what alternative do you think is the best to avoid double-loading the object? Thank you so much, Greetings!

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• Is it possible to update old database from dbml file ? (C#, .Net 4, Linq, SQL Server)

  - by Emil

  Hi all, I began recently a new job, a very interesting project (C#,.Net 4, Linq, VS 2010 and SQL Server). And immediately I got a very exciting challenge: I must implement either a new tool or integrate the logic when program start, or whatever, but what must happen is the following: the customers have previous application and database (full with their specific data). Now a new version is ready and the customer gets the update. In the mean time we made some modification on DB (new table, columns, maybe an old column deleted, or whatever). I’m pretty new in Linq and also SQL databases and my first solution can be: I check the applications/databases version and implement all the changes step by step comparing all tables, columns, keys, constrains, etc. (all this new information I have in my dbml and the old I asked from the existing DB). And I’ll do this each time the version changed. But somehow I feel, this is NOT a smart solution so I look for a general solution of this problem. Is there a way to update customers DB from the dbml file? To create a new one is not a problem (CreateDatabase with DataContext), is there any update/alter database methods? I guess I’m not the only one who search for such a solution (I found nothing in internet – or I looked for bad keywords). How did you solve this problem? I look also for an external tool, but first for a solution with C#, Linq or something similar. For any idea thank you in advance! Best regards, Emil

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• Using Linq to group a list of objects into a new grouped list of list of objects

  - by Simon G

  Hi, I don't know if this is possible in Linq but here goes... I have an object: public class User { public int UserID { get; set; } public string UserName { get; set; } public int GroupID { get; set; } } I return a list that may look like the following: List<User> userList = new List<User>(); userList.Add( new User { UserID = 1, UserName = "UserOne", GroupID = 1 } ); userList.Add( new User { UserID = 2, UserName = "UserTwo", GroupID = 1 } ); userList.Add( new User { UserID = 3, UserName = "UserThree", GroupID = 2 } ); userList.Add( new User { UserID = 4, UserName = "UserFour", GroupID = 1 } ); userList.Add( new User { UserID = 5, UserName = "UserFive", GroupID = 3 } ); userList.Add( new User { UserID = 6, UserName = "UserSix", GroupID = 3 } ); I want to be able to run a Linq query on the above list that groups all the users by GroupID. So the out pub will be a list of user lists that contains user (if that makes sense?). So the out put would be something like: GroupedUserList UserList UserID = 1, UserName = "UserOne", GroupID = 1 UserID = 2, UserName = "UserTwo", GroupID = 1 UserID = 4, UserName = "UserFour", GroupID = 1 UserList UserID = 3, UserName = "UserThree", GroupID = 2 UserList UserID = 5, UserName = "UserFive", GroupID = 3 UserID = 6, UserName = "UserSix", GroupID = 3 I've tried using the groupby linq clause but this seems to return a list of keys and its not grouped by correctly: var groupedCustomerList = userList.GroupBy( u => u.GroupID ).ToList(); Any help would be much appreciated. Thanks

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• Linq: Why won't Group By work when Querying DataSets?

  - by jrcs3

  While playing with Linq Group By statements using both DataSet and Linq-to-Sql DataContext, I get different results with the following VB.NET 10 code: #If IS_DS = True Then Dim myData = VbDataUtil.getOrdersDS #Else Dim myData = VbDataUtil.GetNwDataContext #End If Dim MyList = From o In myData.Orders Join od In myData.Order_Details On o.OrderID Equals od.OrderID Join e In myData.Employees On o.EmployeeID Equals e.EmployeeID Group By FullOrder = New With { .OrderId = od.OrderID, .EmployeeName = (e.FirstName & " " & e.LastName), .ShipCountry = o.ShipCountry, .OrderDate = o.OrderDate } _ Into Amount = Sum(od.Quantity * od.UnitPrice) Where FullOrder.ShipCountry = "Venezuela" Order By FullOrder.OrderId Select FullOrder.OrderId, FullOrder.OrderDate, FullOrder.EmployeeName, Amount For Each x In MyList Console.WriteLine( String.Format( "{0}; {1:d}; {2}: {3:c}", x.OrderId, x.OrderDate, x.EmployeeName, x.Amount)) Next With Linq2SQL, the grouping works properly, however, the DataSet code doesn't group properly. Here are the functions that I call to create the DataSet and Linq-to-Sql DataContext Public Shared Function getOrdersDS() As NorthwindDS Dim ds As New NorthwindDS Dim ota As New OrdersTableAdapter ota.Fill(ds.Orders) Dim otda As New Order_DetailsTableAdapter otda.Fill(ds.Order_Details) Dim eda As New EmployeesTableAdapter eda.Fill(ds.Employees) Return ds End Function Public Shared Function GetNwDataContext() As NorthwindL2SDataContext Dim s As New My.MySettings Return New NorthwindL2SDataContext(s.NorthwindConnectionString) End Function What am I missing? If it should work, how do I make it work, if it can't work, why not (what interface isn't implemented, etc)?

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• How can one convince a team to use a new technology (LinQ, MVC, etc )?

  - by Atomiton

  Obviously, it's easier to do with some developers, but I'm sure many of us are on teams that prefer the status quo. You know the type. You see some benefit in a piece of new technology and they prefer the tried and true methods. Try, for example, DBA/C# programmer the advantages of using LinQ ( not necessarily LinQ to SQL, just LinQ in general ). For example, When a project requirement is to be cross-platform... instead of thinking about how one can run Windows on a Mac through a VM Machine, introducing the idea of using relatively new Silverlight or creating it in Java ( as an option to look into ). I know most people don't like to be out of their comfort level, so it takes a bit of convincing, and not ALL new technology makes business sense... but how have you convinced your team to look at a new technology? What technologies have you successfully introduced to your workplace? What technologies do you think are hardest to introduce? ( I'm thinking paradigm-shifting ones, like MVC from WebForms... or new languages ) What strategies do you employ to make these new technologies appealing?

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• Why does Ruby have Rails while Python has no central framework?

  - by yar

  This is a(n) historical question, not a comparison-between-languages question: This article from 2005 talks about the lack of a single, central framework for Python. For Ruby, this framework is clearly Rails. Why, historically speaking, did this happen for Ruby but not for Python? (or did it happen, and that framework is Django?) Also, the hypothetical questions: would Python be more popular if it had one, good framework? Would Ruby be less popular if it had no central framework? [Please avoid discussions of whether Ruby or Python is better, which is just too open-ended to answer.] Edit: Though I thought this is obvious, I'm not saying that other frameworks do not exist for Ruby, but rather that the big one in terms of popularity is Rails. Also, I should mention that I'm not saying that frameworks for Python are not as good (or better than) Rails. Every framework has its pros and cons, but Rails seems to, as Ben Blank says in the one of the comments below, have surpassed Ruby in terms of popularity. There are no examples of that on the Python side. WHY? That's the question.

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• Linq. Help me tune this!

  - by dtrick

  I have a linq query that is causing some timeout issues. Basically, I have a query that is returning the top 100 results from a table that has approximately 500,000 records. Here is the query: using (var dc = CreateContext()) { var accounts = string.IsNullOrEmpty(searchText) ? dc.Genealogy_Accounts .Where(a => a.Genealogy_AccountClass.Searchable) .OrderByDescending(a => a.ID) .Take(100) : dc.Genealogy_Accounts .Where(a => (a.Code.StartsWith(searchText) || a.Name.StartsWith(searchText)) && a.Genealogy_AccountClass.Searchable) .OrderBy(a => a.Code) .Take(100); return accounts.Select(a => } } Oddly enough it is the first linq query that is causing the timeout. I thought that by doing a 'Take' we wouldn't need to scan all 500k of records. However, that must be what is happening. I'm guessing that the join to find what is 'searchable' is causing the issue. I'm not able to denormalize the tables... so I'm wondering if there is a way to rewrite the linq query to get it to return quicker... or if I should just write this query as a Stored Procedure (and if so, what might it look like). Thanks.

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• How can I get distinct values using Linq to NHibernate?

  - by Chris

  I've been trying to get distinct values using Linq to NHibernate and I'm failing miserably. I've tried: var query = from requesters in _session.Linq<Requesters>() orderby requesters.Requestor ascending select requesters; return query.Distinct(); As well as var query = from requesters in _session.Linq<Requesters>() orderby requesters.Requestor ascending select requesters; return query.Distinct(new RequestorComparer()); Where RequestorComparer is public class RequestorComparer : IEqualityComparer<Requesters> { #region IEqualityComparer<Requesters> Members bool IEqualityComparer<Requesters>.Equals(Requesters x, Requesters y) { //return x.RequestorId.Value.Equals(y.RequestorId.Value); return ((x.RequestorId == y.RequestorId) && (x.Requestor == y.Requestor)); } int IEqualityComparer<Requesters>.GetHashCode(Requesters obj) { return obj.RequestorId.Value.GetHashCode(); } #endregion } No matter how I structure the syntax, it never seems to hit the .Distinct(). Without .Distinct() there are multiple duplicates by default in the table I'm querying, on order of 195 total records but there should only be 22 distinct values returned. I'm not sure what I'm doing wrong but would greatly appreciate any assistance that can be provided. Thanks

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