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  • How to detect if a LINQ enumeration is materialized?

    - by Peter Lillevold
    Is there some way of detecting whether an enumerable built using LINQ (to Objects in this case) have been materialized or not? Other than trying to inspect the type of the underlying collection? Specifically, since enumerable.ToArray() will build a new array even if the underlying collection already is an array I'm looking for a way of avoiding ToArray() being called twice on the same collection.

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

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

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  • How to map LINQ EntitySet to List property in property setter?

    - by jlp
    In my model I have these entities: public interface IOrder { string Name {get;set;} List<IProduct> OrderedProducts {get;set;} } public interface IProduct {} In partial class generated by linq-to-sql I map these properties on my entity properties: public partial class Order : IOrder { List<IProduct> OrderedProducts { get { return this.L2SQLProducts.Cast<IProduct>.ToList(); } set { this.L2SQLProducts = ??? } } } How should setter look like?

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  • How can I do a multi level parent-child sort using Linq?

    - by Tenacious T
    How can I do a multi-level parent-child sort using Linq if I have a table structure like the one below: [Table: Sections] Id Seq Name ParentSectionId 1 1 TOP NULL 2 1 AAAA 1 3 2 SSSS 1 4 3 DDDD 1 5 1 SectionA1 2 6 2 SectionA2 2 7 1 SectionS1 3 8 3 ASummary 2 Expected sort result: TOP AAAA SectionA1 SectionA2 ASummary SSSS SectionS1 DDDD

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  • Entity Relationship Diagram - Relationship Strength?

    - by 01010011
    Hi, I am trying to figure out under what circumstances I should use weak (non-identifying) relationships (where the primary key of the related entity does not contain a primary key component of the parent entity), verses when I should use strong (identifying) relationships (primary key of the related entity contains a primary key component of the parent entity). For example, when designing an Entity Relationship Diagram , if I have two entities, (e.g. book and purchaser), how do I know when to choose the solid Crows Foot or the dashed Crows Foot to connect the two entities? Any assistance will be appreciated. Thanks in advance.

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  • Entity Framework, full-text search and temporary tables

    - by markus
    I have a LINQ-2-Entity query builder, nesting different kinds of Where clauses depending on a fairly complex search form. Works great so far. Now I need to use a SQL Server fulltext search index in some of my queries. Is there any chance to add the search term directly to the LINQ query, and have the score available as a selectable property? If not, I could write a stored procedure to load a list of all row IDs matching the full-text search criteria, and then use a LINQ-2-Entity query to load the detail data and evaluate other optional filter criteria in a loop per row. That would be of course a very bad idea performance-wise. Another option would be to use a stored procedure to insert all row IDs matching the full-text search into a temporary table, and then let the LINQ query join the temporary table. Question is: how to join a temporary table in a LINQ query, as it cannot be part of the entity model?

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  • Entity Framework mant to many insert

    - by Jacob
    I've been playing around with Entity Framework v2 and added some code to insert new entity with many to many relationship , lets say this entity is called meeting. I add hours to meeting : meeting.Hours.Add(hour); and I get different errors on different occasions On Update : Cannot insert the value NULL into column 'Meetings_Id', table 'Plan.dbo.MeetingHour'; column does not allow nulls. INSERT fails. The statement has been terminated. On Inset : An item with the same key has already been added. But the tricky party is that if I add this manually trough SQL Server Management Studio , I can update the entity with the same value , clearing it first (meeting.Hour.Clear()) Can't see what could be the problem , maybe entity model isn't mapped correctly ?

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  • flex/actionscript client entity state refresh on JPA update using Pimento EntityManager

    - by Chris
    My Flex application uses a client-side pimento EntityManager which fetches quite a few objects and associations. It does this by forcing eager fetching of particular association ends in the form of fetch plans. I would like to update the client whenever a change has been made to an entity existing in the EntityManager's cache. Is it possible to update the state of the changed entity ONLY, including updating which entities are associated, without resetting the state of these associated entities? I have setup an EntityListener with a JPA post-update method that notifies clients when a persisted entity has been updated. I want this to trigger a refresh for the modified client-side entity, but calling EntityManager.refresh(entity) resets all lazy associations to proxies. Initializing these proxies resets the associated entities, even if they were loaded previously. I'm looking for an efficient way to keep the client's state in synch with the server's state, at least with respect to the entities that have already been retrieved by the initial load.

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  • EF 4.1 Code First Detaching Entity

    - by Nazaf
    I am trying to add an entity to the DB. Once I have added it, I want to detach it, so I can manipulate the object safely without making any changes to the DB. After calling context.SaveChanges() I do the following to detach the entity: // save context.Stories.Add(story); // attach tags. They already exists in the database foreach(var tag in story.Tags) context.Entry(tag).State = System.Data.EntityState.Unchanged; context.SaveChanges(); context.Entry(story).State = System.Data.EntityState.Detached; However, changing the entity state to DETACHED will remove all related entities associated with the my entity. Is there a way to stop this ? If I don't detach the entity, all my changes are sent to the DB next time I call context.SaveChanges() Thanks!!

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  • Slides and links for Entity Framework 4 and Azure from Devweek 2010

    - by Eric Nelson
    Last week (March 2010) I presented on Entity Framework 4 and the Windows Azure Platform at www.devweek.com. As usual, it was a great conference and I caught up with lots of old friends and made some new ones along the way. Entity Framework 4 Entity Framework 4 In Microsoft Visual Studio 2010 View more presentations from Eric Nelson. Windows Azure and SQL Azure Building An Application For Windows Azure And Sql Azure View more presentations from Eric Nelson. Entity Framework 4 Related Links Poll on Entity Framework 4 – one year on 101 EF4 Resources Recent resources on Entity Framework 4 Installing all the bits to demo Entity Framework 4 on the Visual Studio 2010 Release Candidate Azure Related Links UK Azure Online Community – join today. UK Windows Azure Site Start working with Windows Azure TCO and ROI calculator for Windows Azure

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  • Cannot install .NET Framework 4.0 on Windows XP SP3

    - by Bob
    I'm using Windows XP SP3 logged in as the administrator. I had RAID Mirroring running. The motherboard broke earlier in the year. When I got a new battery I did not resync. I just use the disks as two separate disks. I searched Google for the errors but I didn't find anything detailed enough. The following Microsoft components are in Add/Remove programs: .NET Framework 1.1 .NET Framework 2.0 Service Pack 2 .NET Framework 3.0 Service Pack 2 .NET Framework 3.5 SP1 Microsoft Compression Client Pack 1.0 for Windows XP Microsoft Office Enterprise 2007 Microsoft Silverlight Microsoft USB Flash Driver Manager Micrsoft User-mode Driver Framework Feature Pack 1.0 Microsoft Visual C++ 2005 ATL Update KB 973923 x86 8.050727.4053 Microsoft Visual C++ 2005 Redistributable This is the installation log: Exists: evaluating... [10/21/2011, 22:17:14]MsiGetProductInfo with product code {3C3901C5-3455-3E0A-A214-0B093A5070A6} found no matches [10/21/2011, 22:17:14] Exists evaluated to false [10/21/2011, 22:15:50]calling PerformAction on an installing performer [10/21/2011, 22:15:50] Action: Performing actions on all Items... [10/21/2011, 22:15:50]Wait for Item (clr_optimization_v2.0.50727_32) to be available [10/21/2011, 22:15:50]clr_optimization_v2.0.50727_32 is now available to install [10/21/2011, 22:15:50]Creating new Performer for ServiceControl item [10/21/2011, 22:15:50] Action: ServiceControl - Stop clr_optimization_v2.0.50727_32... [10/21/2011, 22:15:50]ServiceControl operation succeeded! [10/21/2011, 22:15:50] Action complete [10/21/2011, 22:15:50]Error 0 is mapped to Custom Error: [10/21/2011, 22:15:50]Wait for Item (Windows6.0-KB956250-v6001-x86.msu) to be available [10/21/2011, 22:15:51]Windows6.0-KB956250-v6001-x86.msu is now available to install [10/21/2011, 22:15:51]Created new DoNothingPerformer for File item [10/21/2011, 22:15:51]No CustomError defined for this item. [10/21/2011, 22:15:51]Wait for Item (Windows6.1-KB958488-v6001-x86.msu) to be available [10/21/2011, 22:15:51]Windows6.1-KB958488-v6001-x86.msu is now available to install [10/21/2011, 22:15:51]Created new DoNothingPerformer for File item [10/21/2011, 22:15:51]No CustomError defined for this item. [10/21/2011, 22:15:51]Wait for Item (netfx_Core.mzz) to be available [10/21/2011, 22:15:52]netfx_Core.mzz is now available to install [10/21/2011, 22:15:52]Created new DoNothingPerformer for File item [10/21/2011, 22:15:52]No CustomError defined for this item. [10/21/2011, 22:15:52]Wait for Item (netfx_Core_x86.msi) to be available [10/21/2011, 22:15:52]netfx_Core_x86.msi is now available to install [10/21/2011, 22:15:52]Creating new Performer for MSI item [10/21/2011, 22:15:52] Action: Performing Action on MSI at F:\DOCUME~1\Owner\LOCALS~1\Temp\Microsoft .NET Framework 4 Client Profile Setup_4.0.30319\netfx_Core_x86.msi... [10/21/2011, 22:15:52]Log File F:\DOCUME~1\Owner\LOCALS~1\Temp\Microsoft .NET Framework 4 Client Profile Setup_20111021_221545515-MSI_netfx_Core_x86.msi.txt does not yet exist but may do at Watson upload time [10/21/2011, 22:15:52]Calling MsiInstallProduct(F:\DOCUME~1\Owner\LOCALS~1\Temp\Microsoft .NET Framework 4 Client Profile Setup_4.0.30319\netfx_Core_x86.msi, EXTUI=1 [10/21/2011, 22:17:14]MSI (F:\DOCUME~1\Owner\LOCALS~1\Temp\Microsoft .NET Framework 4 Client Profile Setup_4.0.30319\netfx_Core_x86.msi) Installation failed. Msi Log: Microsoft .NET Framework 4 Client Profile Setup_20111021_221545515-MSI_netfx_Core_x86.msi.txt [10/21/2011, 22:17:14]PerformOperation returned 1603 (translates to HRESULT = 0x80070643) [10/21/2011, 22:17:14] Action complete [10/21/2011, 22:17:14]OnFailureBehavior for this item is to Rollback. [10/21/2011, 22:17:14] Action: Performing actions on all Items... [10/21/2011, 22:17:14] Action complete [10/21/2011, 22:17:14] Action complete [10/21/2011, 22:17:14]Final Result: Installation failed with error code: (0x80070643), "Fatal error during installation. " (Elapsed time: 0 00:01:29). [10/21/2011, 22:17:41]WM_ACTIVATEAPP: Focus stealer's windows WAS visible, NOT taking back focus SECOND LOG REQUESTED BELOW: MSI (s) (6C:EC) [22:17:13:828]: Invoking remote custom action. DLL: F:\WINDOWS\Installer\MSIBB4.tmp, Entrypoint: NgenUpdateHighestVersionRollback MSI (s) (6C:64) [22:17:13:984]: Executing op: ActionStart(Name=CA_NgenRemoveNicPFROs_I_DEF_x86.3643236F_FC70_11D3_A536_0090278A1BB8,,) MSI (s) (6C:64) [22:17:13:984]: Executing op: ActionStart(Name=CA_NgenRemoveNicPFROs_I_RB_x86.3643236F_FC70_11D3_A536_0090278A1BB8,,) MSI (s) (6C:64) [22:17:13:984]: Executing op: CustomActionRollback(Action=CA_NgenRemoveNicPFROs_I_RB_x86.3643236F_FC70_11D3_A536_0090278A1BB8,ActionType=17729,Source=BinaryData,Target=NgenRemoveNicPFROs,) MSI (s) (6C:AC) [22:17:13:984]: Invoking remote custom action. DLL: F:\WINDOWS\Installer\MSIBB5.tmp, Entrypoint: NgenRemoveNicPFROs MSI (s) (6C:64) [22:17:14:000]: Executing op: End(Checksum=0,ProgressTotalHDWord=0,ProgressTotalLDWord=0) MSI (s) (6C:64) [22:17:14:000]: Error in rollback skipped. Return: 5 MSI (s) (6C:64) [22:17:14:015]: No System Restore sequence number for this installation. MSI (s) (6C:64) [22:17:14:015]: Unlocking Server MSI (s) (6C:64) [22:17:14:015]: PROPERTY CHANGE: Deleting UpdateStarted property. Its current value is '1'. MSI (s) (6C:64) [22:17:14:031]: Note: 1: 1708 MSI (s) (6C:64) [22:17:14:031]: Product: Microsoft .NET Framework 4 Client Profile -- Installation failed. MSI (s) (6C:64) [22:17:14:078]: Cleaning up uninstalled install packages, if any exist MSI (s) (6C:64) [22:17:14:078]: MainEngineThread is returning 1603 MSI (s) (6C:EC) [22:17:14:171]: Destroying RemoteAPI object. MSI (s) (6C:9C) [22:17:14:171]: Custom Action Manager thread ending. MSI (c) (F4:C4) [22:17:14:203]: Decrementing counter to disable shutdown. If counter >= 0, shutdown will be denied. Counter after decrement: -1 MSI (c) (F4:C4) [22:17:14:203]: MainEngineThread is returning 1603 === Verbose logging stopped: 10/21/2011 22:17:14 ===

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  • Complex Entity Framework linked-graphs issue: how to limit change set / break the graph?

    - by Hightechrider
    I have an EDMX containing Sentences, and Words, say and a Sentence contains three Words, say. Appropriate FK relationships exist between the tables. I create some words: Word word1 = new Word(); Word word2 = ... I build a Sentence: Sentence x = new Sentence (word1, word2, word3); I build another Sentence: Sentence y = new Sentence (word1, word4, word5); I try to save x to the database, but EF builds a change set that includes everything, including y, word4 and word5 that aren't ready to save to the database. When SaveChanges() happens it throws an exception: Unable to determine the principal end of the ... relationship. Multiple added entities may have the same primary key. I think it does this because Word has an EntityCollection<Sentence> on it from the FK relationship between the two tables, and thus Sentence y is inextricably linked to Sentence x through word1. So I remove the Navigation Property Sentences from Word and try again. It still tries to put the entire graph into the change set. What suggestions do the Entity Framework experts have for ways to break this connection. Essentially what I want is a one-way mapping from Sentence to Word; I don't want an EntityCollection<Sentence> on Word and I don't want the object graph to get intertwined like this. Code sample: This puts two sentences into the database because Verb1 links them and EF explores the entire graph of existing objects and added objects when you do Add/SaveChanges. Word subject1 = new Word(){ Text = "Subject1"}; Word subject2 = new Word(){ Text = "Subject2"}; Word verb1 = new Word(){ Text = "Verb11"}; Word object1 = new Word(){ Text = "Object1"}; Word object2 = new Word(){ Text = "Object2"}; Sentence s1 = new Sentence(){Subject = subject1, Verb=verb1, Object=object1}; Sentence s2 = new Sentence(){Subject=subject2, Verb=verb1, Object=object2}; context.AddToSentences(s1); context.SaveChanges(); foreach (var s in context.Sentences) { Console.WriteLine(s.Subject + " " + s.Verb + " " + s.Object); }

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  • How far should an entity take care of its properties values by itself?

    - by Kharlos Dominguez
    Let's consider the following example of a class, which is an entity that I'm using through Entity Framework. - InvoiceHeader - BilledAmount (property, decimal) - PaidAmount (property, decimal) - Balance (property, decimal) I'm trying to find the best approach to keep Balance updated, based on the values of the two other properties (BilledAmount and PaidAmount). I'm torn between two practices here: Updating the balance amount every time BilledAmount and PaidAmount are updated (through their setters) Having a UpdateBalance() method that the callers would run on the object when appropriate. I am aware that I can just calculate the Balance in its getter. However, it isn't really possible because this is an entity field that needs to be saved back to the database, where it has an actual column, and where the calculated amount should be persisted to. My other worry about the automatically updating approach is that the calculated values might be a little bit different from what was originally saved to the database, due to rounding values (an older version of the software, was using floats, but now decimals). So, loading, let's say 2000 entities from the database could change their status and make the ORM believe that they have changed and be persisted back to the database the next time the SaveChanges() method is called on the context. It would trigger a mass of updates that I am not really interested in, or could cause problems, if the calculation methods changed (the entities fetched would lose their old values to be replaced by freshly recalculated ones, simply by being loaded). Then, let's take the example even further. Each invoice has some related invoice details, which also have BilledAmount, PaidAmount and Balance (I'm simplifying my actual business case for the sake of the example, so let's assume the customer can pay each item of the invoice separately rather than as a whole). If we consider the entity should take care of itself, any change of the child details should cause the Invoice totals to change as well. In a fully automated approach, a simple implementation would be looping through each detail of the invoice to recalculate the header totals, every time one the property changes. It probably would be fine for just a record, but if a lot of entities were fetched at once, it could create a significant overhead, as it would perform this process every time a new invoice detail record is fetched. Possibly worse, if the details are not already loaded, it could cause the ORM to lazy-load them, just to recalculate the balances. So far, I went with the Update() method-way, mainly for the reasons I explained above, but I wonder if it was right. I'm noticing I have to keep calling these methods quite often and at different places in my code and it is potential source of bugs. It also has a detrimental effect on data-binding because when the properties of the detail or header changes, the other properties are left out of date and the method has no way to be called. What is the recommended approach in this case?

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  • nhibernate activerecord linq Contains problem

    - by Robert Ivanc
    Hi, I am having problems with the following query in Castle ActiveRecord 2.12: var q = from o in SodisceFMClientVAR.Queryable where taxnos2.Contains(o.TaxFileNo) select o; taxNos2 is an array of strings. When run I get an exception: + InnerException {"Index was out of range. Must be non-negative and less than the size of the collection.\r\nParameter name: index"} System.Exception {System.ArgumentOutOfRangeException} StackTrace " at Castle.ActiveRecord.ActiveRecordBase.ExecuteQuery(IActiveRecordQuery query)\r\n at Castle.ActiveRecord.Linq.LinqResultWrapper`1.Populate()\r\n at Castle.ActiveRecord.Linq.LinqResultWrapper`1.GetEnumerator()\r\n at NHibernate.Linq.Query`1.GetEnumerator()\r\n at System.Linq.Buffer`1..ctor(IEnumerable`1 source)\r\n at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)\r\n at prosoft.skb.insolventnostDataAccess.InsolventnostDataAccAR.GetOurUsersListLS(ICollection`1 taxNos) in C:\\svn\\skb\\insolventnostWithAR\\prosoft.skb.insolventnostDataAccess\\InsolventnostDataAR.cs:line 214\r\n at prosoft.skb.insolventnostDataFromWS.InsolventnostFromWS.filterByOurUsers(IEnumerable`1 odprtiPostopki) in C:\\svn\\skb\\insolventnostWithAR\\prosoft.skb.insolventnostDataFromWS\\InsolventnostFromWS.cs:line 237\r\n at prosoft.skb.insolventnostDataFromWS.InsolventnostFromWS.SyncData() in C:\\svn\\skb\\insolventnostWithAR\\prosoft.skb.insolventnostDataFromWS\\InsolventnostFromWS.cs:line 53" string Does Contains even work in linq for nhibernate? I couldn't find anything via google... Is there a workaround? Thanks!

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  • Converting F# Quotations into LINQ Expressions

    - by forki23
    Hi, I can convert a quotation of type Expr<'a -> 'b> to a Linq expression via the following snippet: /// Converts a F# Expression to a LINQ Lambda let toLambda (exp:Expr) = let linq = exp.ToLinqExpression() :?> MethodCallExpression linq.Arguments.[0] :?> LambdaExpression /// Converts a Lambda quotation into a Linq Lamba Expression with 1 parameter let ToLinq (exp : Expr<'a -> 'b>) = let lambda = toLambda exp Expression.Lambda<Func<'a, 'b>>(lambda.Body, lambda.Parameters) Now I want to convert a quotation of type Expr<'a * 'b -> 'c> or maybe even Expr<'a -> 'b -> 'c> to a Linq Lambda Expression of type Expression<Func<'a,'b'c>>. How can I do this? Regards, forki

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  • "Attach or Add an entity that is not new...loaded from another DataContext. This is not supported."

    - by sah302
    Similar error as other questions, but not quite the same, I am not trying to attach anything. What I am trying to do is insert a new row into a linking table, specifically UserAccomplishment. Relations are set in LINQ to User and Accomplishment Tables. I have a generic insert function: Public Function insertRow(ByVal entity As ImplementationType) As Boolean If entity IsNot Nothing Then Dim lcfdatacontext As New LCFDataContext() Try lcfdatacontext.GetTable(Of ImplementationType)().InsertOnSubmit(entity) lcfdatacontext.SubmitChanges() lcfdatacontext.Dispose() Return True Catch ex As Exception Return False End Try Else Return False End If End Function If you try and give UserAccomplishment the two appropriate objects this will naturally crap out if either the User or Accomplishment already exist. It only works when both user and accomplishment don't exist. I expected this behavior. What does work is simply giving the userAccomplishment object a user.id and accomplishment.id and populating the rest of the fields. This works but is kind of awkward to use in my app, it would be much easier to simply pass in both objects and have it work out what already exists and what doesn't. Okay so I made the following (please ignore the fact that this is horribly inefficient because I know it is): Public Class UserAccomplishmentDao Inherits EntityDao(Of UserAccomplishment) Public Function insertLinkerObjectRow(ByVal userAccomplishment As UserAccomplishment) Dim insertSuccess As Boolean = False If Not userAccomplishment Is Nothing Then Dim userDao As New UserDao() Dim accomplishmentDao As New AccomplishmentDao() Dim user As New User() Dim accomplishment As New Accomplishment() 'see if either object already exists in db' user = userDao.getOneByValueOfProperty("Id", userAccomplishment.User.Id) accomplishment = accomplishmentDao.getOneByValueOfProperty("Id", userAccomplishment.Accomplishment.Id) If user Is Nothing And accomplishment Is Nothing Then 'neither the user or the accomplishment exist, both are new so insert them both, typical insert' insertSuccess = Me.insertRow(userAccomplishment) ElseIf user Is Nothing And Not accomplishment Is Nothing Then 'user is new, accomplishment is not new, so just insert the user, and the relation in userAccomplishment' Dim userWithExistingAccomplishment As New UserAccomplishment(userAccomplishment.User, userAccomplishment.Accomplishment.Id, userAccomplishment.LastUpdatedBy) insertSuccess = Me.insertRow(userWithExistingAccomplishment) ElseIf Not user Is Nothing And accomplishment Is Nothing Then 'user is not new, accomplishment is new, so just insert the accomplishment, and the relation in userAccomplishment' Dim existingUserWithAccomplishment As New UserAccomplishment(userAccomplishment.UserId, userAccomplishment.Accomplishment, userAccomplishment.LastUpdatedBy) insertSuccess = Me.insertRow(existingUserWithAccomplishment) Else 'both are not new, just add the relation' Dim userAccomplishmentBothExist As New UserAccomplishment(userAccomplishment.User.Id, userAccomplishment.Accomplishment.Id, userAccomplishment.LastUpdatedBy) insertSuccess = Me.insertRow(userAccomplishmentBothExist) End If End If Return insertSuccess End Function End Class Alright, here I basically check if the supplied user and accomplishment already exists in the db, and if so call an appropriate constructor that will leave whatever already exists empty, but supply the rest of the information so the insert can succeed. However, upon trying an insert: Dim result As Boolean = Me.userAccomplishmentDao.insertLinkerObjectRow(userAccomplishment) In which the user already exists, but the accomplishment does not (the 99% typical scenario) I get the error: "An attempt has been made to Attach or Add an entity that is not new, perhaps having been loaded from another DataContext. This is not supported." I have debugged this multiple times now and am not sure why this is occuring, if either User or Accomplishment exist, I am not including it in the final object to try to insert. So nothing appears to be attempted to be added. Even in debug, upon insert, the object was set to empty. So the accomplishment is new and the user is empty. 1) Why is it still saying that and how can I fix it ..using my current structure 2) Pre-emptive 'use repository pattern answers' - I know this way kind of sucks in general and I should be using the repository pattern. However, I can't use that in the current project because I don't have time to refactor that due to my non existence knowledge of it and time constraints. The usage of the app is going to so small that the inefficient use of datacontext's and what have you won't matter so much. I can refactor it once it's up and running, but for now I just need to 'push through' with my current structure. Edit: I also just tested this when having both already exists, and only insert each object's IDs into the table, that works. So I guess I could manually insert whichever object doesn't exist as a single insert, then put the ids only into the linking table, but I still don't know why when one object exists, and I make it empty, it doens't work.

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  • Zend Framework: Controller Plugins vs Action Helpers

    - by Laimoncijus
    Could someone give few tips and/or examples how Controller Plugins and Action Helpers are different? Are there situations where particular task could be accomplished with one but not another? For me they both look more or less the same and I'm often having trouble having to decide when to use what... Are there any big differences?

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  • LINQ Queries And Context

    - by Soo
    Hello SO, I have a slight issue with some code I'm writing if(parameter == 1) { var linq = from a in db.table select a; } else { var linq = from a in db.table where a.id = 1 select a; } foreach(var b in linq) { ... } So basically what's going on is that the variable "linq" is different depending on the value of "parameter". When I try to loop through "linq" with my foreach loop, I get an error about how linq doesn't exist in the current context. What is the best way to work around this type of issue?

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  • Does LINQ require significantly more processing cycles and memory than lower-level data iteration techniques?

    - by Matthew Patrick Cashatt
    Background I am recently in the process of enduring grueling tech interviews for positions that use the .NET stack, some of which include silly questions like this one, and some questions that are more valid. I recently came across an issue that may be valid but I want to check with the community here to be sure. When asked by an interviewer how I would count the frequency of words in a text document and rank the results, I answered that I would Use a stream object put the text file in memory as a string. Split the string into an array on spaces while ignoring punctuation. Use LINQ against the array to .GroupBy() and .Count(), then OrderBy() said count. I got this answer wrong for two reasons: Streaming an entire text file into memory could be disasterous. What if it was an entire encyclopedia? Instead I should stream one block at a time and begin building a hash table. LINQ is too expensive and requires too many processing cycles. I should have built a hash table instead and, for each iteration, only added a word to the hash table if it didn't otherwise exist and then increment it's count. The first reason seems, well, reasonable. But the second gives me more pause. I thought that one of the selling points of LINQ is that it simply abstracts away lower-level operations like hash tables but that, under the veil, it is still the same implementation. Question Aside from a few additional processing cycles to call any abstracted methods, does LINQ require significantly more processing cycles to accomplish a given data iteration task than a lower-level task (such as building a hash table) would?

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  • Extend base type and automatically update audit information on Entity

    - by Nix
    I have an entity model that has audit information on every table (50+ tables) CreateDate CreateUser UpdateDate UpdateUser Currently we are programatically updating audit information. Ex: if(changed){ entity.UpdatedOn = DateTime.Now; entity.UpdatedBy = Environment.UserName; context.SaveChanges(); } But I am looking for a more automated solution. During save changes, if an entity is created/updated I would like to automatically update these fields before sending them to the database for storage. Any suggestion on how i could do this? I would prefer to not do any reflection, so using a text template is not out of the question. A solution has been proposed to override SaveChanges and do it there, but in order to achieve this i would either have to use reflection (in which I don't want to do ) or derive a base class. Assuming i go down this route how would I achieve this? For example EXAMPLE_DB_TABLE CODE NAME --Audit Tables CREATE_DATE CREATE_USER UPDATE_DATE UPDATE_USER And if i create a base class public abstract class IUpdatable{ public virtual DateTime CreateDate {set;} public virtual string CreateUser { set;} public virtual DateTime UpdateDate { set;} public virtual string UpdateUser { set;} } The end goal is to be able to do something like... public overrride void SaveChanges(){ //Go through state manager and update audit infromation //FOREACH changed entity in state manager if(entity is IUpdatable){ //If state is created... update create audit. //if state is updated... update update audit } } But I am not sure how I go about generating the code that would extend the interface.

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  • Inner join and outer join options in Entity Framework 4.0

    - by bigb
    I am using EF 4.0 and I need to implement query with one inner join and with N outer joins I started to implement this using different approaches but get into trouble at some point. Here is two examples how I started of doing this using ObjectQuery<'T' and Linq to Entity 1)Using ObjectQuery<'T' I implement flexible outer join but I don't know how to perform inner join with entity Rules in that case (by default Include("Rules") doing outer join, but i need to inner join by Id). public static IEnumerable<Race> GetRace(List<string> includes, DateTime date) { IRepository repository = new Repository(new BEntities()); ObjectQuery<Race> result = (ObjectQuery<Race>)repository.AsQueryable<Race>(); //perform outer joins with related entities if (includes != null) foreach (string include in includes) result = result.Include(include); //here i need inner join insteard of default outer join result = result.Include("Rules"); return result.ToList(); } 2)Using Linq To Entity I need to have kind of outer join(somethin like in GetRace()) where i may pass a List with entities to include) and also i need to perform correct inner join with entity Rules public static IEnumerable<Race> GetRace2(List<string> includes, DateTime date) { IRepository repository = new Repository(new BEntities()); IEnumerable<Race> result = from o in repository.AsQueryable<Race>() from b in o.RaceBetRules select new { o }); //I need here: // 1. to perform the same way inner joins with related entities like with ObjectQuery above //here i getting List<AnonymousType> which i cant cast to //IEnumerable<Race> when i did try to cast like //(IEnumerable<Race>)result.ToList(); i did get error: //Unable to cast object of type //'System.Collections.Generic.List`1[<>f__AnonymousType0`1[BetsTipster.Entity.Tip.Types.Race]]' //to type //'System.Collections.Generic.IEnumerable`1[BetsTipster.Entity.Tip.Types.Race]'. return result.ToList(); } May be someone have some ideas about that.

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  • Inheritance Mapping Strategies with Entity Framework Code First CTP5: Part 3 – Table per Concrete Type (TPC) and Choosing Strategy Guidelines

    - by mortezam
    This is the third (and last) post in a series that explains different approaches to map an inheritance hierarchy with EF Code First. I've described these strategies in previous posts: Part 1 – Table per Hierarchy (TPH) Part 2 – Table per Type (TPT)In today’s blog post I am going to discuss Table per Concrete Type (TPC) which completes the inheritance mapping strategies supported by EF Code First. At the end of this post I will provide some guidelines to choose an inheritance strategy mainly based on what we've learned in this series. TPC and Entity Framework in the Past Table per Concrete type is somehow the simplest approach suggested, yet using TPC with EF is one of those concepts that has not been covered very well so far and I've seen in some resources that it was even discouraged. The reason for that is just because Entity Data Model Designer in VS2010 doesn't support TPC (even though the EF runtime does). That basically means if you are following EF's Database-First or Model-First approaches then configuring TPC requires manually writing XML in the EDMX file which is not considered to be a fun practice. Well, no more. You'll see that with Code First, creating TPC is perfectly possible with fluent API just like other strategies and you don't need to avoid TPC due to the lack of designer support as you would probably do in other EF approaches. Table per Concrete Type (TPC)In Table per Concrete type (aka Table per Concrete class) we use exactly one table for each (nonabstract) class. All properties of a class, including inherited properties, can be mapped to columns of this table, as shown in the following figure: As you can see, the SQL schema is not aware of the inheritance; effectively, we’ve mapped two unrelated tables to a more expressive class structure. If the base class was concrete, then an additional table would be needed to hold instances of that class. I have to emphasize that there is no relationship between the database tables, except for the fact that they share some similar columns. TPC Implementation in Code First Just like the TPT implementation, we need to specify a separate table for each of the subclasses. We also need to tell Code First that we want all of the inherited properties to be mapped as part of this table. In CTP5, there is a new helper method on EntityMappingConfiguration class called MapInheritedProperties that exactly does this for us. Here is the complete object model as well as the fluent API to create a TPC mapping: public abstract class BillingDetail {     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } }          public class BankAccount : BillingDetail {     public string BankName { get; set; }     public string Swift { get; set; } }          public class CreditCard : BillingDetail {     public int CardType { get; set; }     public string ExpiryMonth { get; set; }     public string ExpiryYear { get; set; } }      public class InheritanceMappingContext : DbContext {     public DbSet<BillingDetail> BillingDetails { get; set; }              protected override void OnModelCreating(ModelBuilder modelBuilder)     {         modelBuilder.Entity<BankAccount>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("BankAccounts");         });         modelBuilder.Entity<CreditCard>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("CreditCards");         });                 } } The Importance of EntityMappingConfiguration ClassAs a side note, it worth mentioning that EntityMappingConfiguration class turns out to be a key type for inheritance mapping in Code First. Here is an snapshot of this class: namespace System.Data.Entity.ModelConfiguration.Configuration.Mapping {     public class EntityMappingConfiguration<TEntityType> where TEntityType : class     {         public ValueConditionConfiguration Requires(string discriminator);         public void ToTable(string tableName);         public void MapInheritedProperties();     } } As you have seen so far, we used its Requires method to customize TPH. We also used its ToTable method to create a TPT and now we are using its MapInheritedProperties along with ToTable method to create our TPC mapping. TPC Configuration is Not Done Yet!We are not quite done with our TPC configuration and there is more into this story even though the fluent API we saw perfectly created a TPC mapping for us in the database. To see why, let's start working with our object model. For example, the following code creates two new objects of BankAccount and CreditCard types and tries to add them to the database: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount();     CreditCard creditCard = new CreditCard() { CardType = 1 };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Running this code throws an InvalidOperationException with this message: The changes to the database were committed successfully, but an error occurred while updating the object context. The ObjectContext might be in an inconsistent state. Inner exception message: AcceptChanges cannot continue because the object's key values conflict with another object in the ObjectStateManager. Make sure that the key values are unique before calling AcceptChanges. The reason we got this exception is because DbContext.SaveChanges() internally invokes SaveChanges method of its internal ObjectContext. ObjectContext's SaveChanges method on its turn by default calls AcceptAllChanges after it has performed the database modifications. AcceptAllChanges method merely iterates over all entries in ObjectStateManager and invokes AcceptChanges on each of them. Since the entities are in Added state, AcceptChanges method replaces their temporary EntityKey with a regular EntityKey based on the primary key values (i.e. BillingDetailId) that come back from the database and that's where the problem occurs since both the entities have been assigned the same value for their primary key by the database (i.e. on both BillingDetailId = 1) and the problem is that ObjectStateManager cannot track objects of the same type (i.e. BillingDetail) with the same EntityKey value hence it throws. If you take a closer look at the TPC's SQL schema above, you'll see why the database generated the same values for the primary keys: the BillingDetailId column in both BankAccounts and CreditCards table has been marked as identity. How to Solve The Identity Problem in TPC As you saw, using SQL Server’s int identity columns doesn't work very well together with TPC since there will be duplicate entity keys when inserting in subclasses tables with all having the same identity seed. Therefore, to solve this, either a spread seed (where each table has its own initial seed value) will be needed, or a mechanism other than SQL Server’s int identity should be used. Some other RDBMSes have other mechanisms allowing a sequence (identity) to be shared by multiple tables, and something similar can be achieved with GUID keys in SQL Server. While using GUID keys, or int identity keys with different starting seeds will solve the problem but yet another solution would be to completely switch off identity on the primary key property. As a result, we need to take the responsibility of providing unique keys when inserting records to the database. We will go with this solution since it works regardless of which database engine is used. Switching Off Identity in Code First We can switch off identity simply by placing DatabaseGenerated attribute on the primary key property and pass DatabaseGenerationOption.None to its constructor. DatabaseGenerated attribute is a new data annotation which has been added to System.ComponentModel.DataAnnotations namespace in CTP5: public abstract class BillingDetail {     [DatabaseGenerated(DatabaseGenerationOption.None)]     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } } As always, we can achieve the same result by using fluent API, if you prefer that: modelBuilder.Entity<BillingDetail>()             .Property(p => p.BillingDetailId)             .HasDatabaseGenerationOption(DatabaseGenerationOption.None); Working With The Object Model Our TPC mapping is ready and we can try adding new records to the database. But, like I said, now we need to take care of providing unique keys when creating new objects: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount()      {          BillingDetailId = 1                          };     CreditCard creditCard = new CreditCard()      {          BillingDetailId = 2,         CardType = 1     };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Polymorphic Associations with TPC is Problematic The main problem with this approach is that it doesn’t support Polymorphic Associations very well. After all, in the database, associations are represented as foreign key relationships and in TPC, the subclasses are all mapped to different tables so a polymorphic association to their base class (abstract BillingDetail in our example) cannot be represented as a simple foreign key relationship. For example, consider the the domain model we introduced here where User has a polymorphic association with BillingDetail. This would be problematic in our TPC Schema, because if User has a many-to-one relationship with BillingDetail, the Users table would need a single foreign key column, which would have to refer both concrete subclass tables. This isn’t possible with regular foreign key constraints. Schema Evolution with TPC is Complex A further conceptual problem with this mapping strategy is that several different columns, of different tables, share exactly the same semantics. This makes schema evolution more complex. For example, a change to a base class property results in changes to multiple columns. It also makes it much more difficult to implement database integrity constraints that apply to all subclasses. Generated SQLLet's examine SQL output for polymorphic queries in TPC mapping. For example, consider this polymorphic query for all BillingDetails and the resulting SQL statements that being executed in the database: var query = from b in context.BillingDetails select b; Just like the SQL query generated by TPT mapping, the CASE statements that you see in the beginning of the query is merely to ensure columns that are irrelevant for a particular row have NULL values in the returning flattened table. (e.g. BankName for a row that represents a CreditCard type). TPC's SQL Queries are Union Based As you can see in the above screenshot, the first SELECT uses a FROM-clause subquery (which is selected with a red rectangle) to retrieve all instances of BillingDetails from all concrete class tables. The tables are combined with a UNION operator, and a literal (in this case, 0 and 1) is inserted into the intermediate result; (look at the lines highlighted in yellow.) EF reads this to instantiate the correct class given the data from a particular row. A union requires that the queries that are combined, project over the same columns; hence, EF has to pad and fill up nonexistent columns with NULL. This query will really perform well since here we can let the database optimizer find the best execution plan to combine rows from several tables. There is also no Joins involved so it has a better performance than the SQL queries generated by TPT where a Join is required between the base and subclasses tables. Choosing Strategy GuidelinesBefore we get into this discussion, I want to emphasize that there is no one single "best strategy fits all scenarios" exists. As you saw, each of the approaches have their own advantages and drawbacks. Here are some rules of thumb to identify the best strategy in a particular scenario: If you don’t require polymorphic associations or queries, lean toward TPC—in other words, if you never or rarely query for BillingDetails and you have no class that has an association to BillingDetail base class. I recommend TPC (only) for the top level of your class hierarchy, where polymorphism isn’t usually required, and when modification of the base class in the future is unlikely. If you do require polymorphic associations or queries, and subclasses declare relatively few properties (particularly if the main difference between subclasses is in their behavior), lean toward TPH. Your goal is to minimize the number of nullable columns and to convince yourself (and your DBA) that a denormalized schema won’t create problems in the long run. If you do require polymorphic associations or queries, and subclasses declare many properties (subclasses differ mainly by the data they hold), lean toward TPT. Or, depending on the width and depth of your inheritance hierarchy and the possible cost of joins versus unions, use TPC. By default, choose TPH only for simple problems. For more complex cases (or when you’re overruled by a data modeler insisting on the importance of nullability constraints and normalization), you should consider the TPT strategy. But at that point, ask yourself whether it may not be better to remodel inheritance as delegation in the object model (delegation is a way of making composition as powerful for reuse as inheritance). Complex inheritance is often best avoided for all sorts of reasons unrelated to persistence or ORM. EF acts as a buffer between the domain and relational models, but that doesn’t mean you can ignore persistence concerns when designing your classes. SummaryIn this series, we focused on one of the main structural aspect of the object/relational paradigm mismatch which is inheritance and discussed how EF solve this problem as an ORM solution. We learned about the three well-known inheritance mapping strategies and their implementations in EF Code First. Hopefully it gives you a better insight about the mapping of inheritance hierarchies as well as choosing the best strategy for your particular scenario. Happy New Year and Happy Code-Firsting! References ADO.NET team blog Java Persistence with Hibernate book a { color: #5A99FF; } a:visited { color: #5A99FF; } .title { padding-bottom: 5px; font-family: Segoe UI; font-size: 11pt; font-weight: bold; padding-top: 15px; } .code, .typeName { font-family: consolas; } .typeName { color: #2b91af; } .padTop5 { padding-top: 5px; } .padTop10 { padding-top: 10px; } .exception { background-color: #f0f0f0; font-style: italic; padding-bottom: 5px; padding-left: 5px; padding-top: 5px; padding-right: 5px; }

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