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• What 'best practices' exist for handing enum heirarchies?

  - by FerretallicA

  I'm curious as to any solutions out there for addressing enum heirarchies. I'm working through some docs on Entity Framework 4 and trying to apply it to a simple inventory tracking program. The possible types for inventory to fall into are as follows: INVENTORY ITEM TYPES: Hardware PC Desktop Server Laptop Accessory Input (keyboards, scanners etc) Output (monitors, printers etc) Storage (USB sticks, tape drives etc) Communication (network cards, routers etc) Software What recommendations are there for handling enums in a situation like this? Are enums even the solution? I don't really want to have a ridiculously normalised database for such a relatively simple experiment (eg tables for InventoryType, InventorySubtype, InventoryTypeToSubtype etc). I don't really want to over-complicate my data model with each subtype being inherited even though no additional properties or methods are included (except PC types which would ideally have associated accessories and software but that's probably out of scope here). It feels like there should be a really simple, elegant solution to this but I can't put my finger on it. Any assistance or input appreciated!

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• Cocoa Core Data - Efficient Related Entities Counts

  - by Gary

  I am working on my first iPhone application and I've hit a wall. I'm trying to develop a 'statistics' page for a three entity relationship. My entities are the following: Department - Name, Address, Building, etc. People - Name, Gender (BOOL), Phone, etc If I have fetched a specific department how do I filter those results and only return people that are Male (Gender == 0)? If I do NSLog(@"%d", [department.people count]); I get the correct number of people in that department so I know I'm in the neighborhood. I know I could re-fetch and modify the predicate each time but with 20+ stats in my app that seems inefficient. Thanks for any advice!

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• Closing an EDM ObjectContext?

  - by David Veeneman

  I am getting started with the ADO.NET Entity Framework 4.0. I have created an EDM and data store for the app, and it successfully retrieves entities. The application holds the EDM's ObjectContext as a member-level variable, which it uses to call ObjectContext.SaveChanges(). So far, so good. I am going to refactor to repositories later. Right now, my question is a bit more basic: When I am finished with the EDM, what do I need to do to release it? Is it as simple as calling Dispose() on the ObjectContext? Thanks for your help.

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• C# LINQ Where Predicate Type Arguments

  - by blu

  I have an XElement with values for mock data. I have an expression to query the xml: Expression<Func<XElement, bool>> simpleXmlFunction = b => int.Parse(b.Element("FooId").Value) == 12; used in: var simpleXml = xml.Elements("Foo").Where(simpleXmlFunction).First(); The design time error is: The type arguments for method 'System.Linq.Enumerable.Where(System.Collections.Generic.IEnumerable, System.Func)' cannot be inferred from the usage. Try specifying the type arguments explicitly' The delegate supplied to Where should take in an XElement and return a bool, marking if the item matches the query, I am not sure how to add anything more to the delegate or the where clause to mark the type. Also, the parallel method for the real function against the Entity Framework does not have this issue. What is not correct with the LINQ-to-XML version?

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• Sorting the data returned by a database

  - by Rishabh Ohri

  hi all, In our project we have a requirement that when a set of records are returned by the database the records should be sorted with respect to the TITLE field in the record. The records will have to be sorted alphabetically but if the title of a record has a number in it then it should come after the records whose title only consists of alphabets. Details: we are using SQL Server , and c#. The data from the database comes to an Entity class whic forwards the data to other layers. So, What will be the possible and effective solution for this requirement.

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• Core Data Relationships in pre-populated SQLite database

  - by Cardinal

  Hi All, I'm new to Core Data. Currently I have following tables on hand: tbl_teahcer tbl_student tbl_course tbl_student_course_map ----------- ----------- ---------- ---------------------- teacher_id student_id course_id student_id name name name course_id teahcer_id And I'm going to make the xcdatamodel as below: Course Teacher ------ ------- name name teacher <<----------> courses students <<---| | Student | ------- | name |----->> courses My questions are as follows: As I'd like to create TableView for Cource Entity, is it a must to create the Inverse Relationship from Teacher to Course, and Student to Course? What is the beneit for having the Inverse Relationship? I got some pre-defined data on hand, and I'd like to create a SQLite storage for pre-populated source. How can I set up the relationships (both directions) in SQLite? Thank you for your help! Regards, Cardinal

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• Deleting objects through foreign key relationship with T-SQL query

  - by LaserBeak

  Looking for a way to write the following LinQ to entities query as a T-SQL statement. repository.ProductShells.Where(x => x.ShellMembers.Any(sm => sm.ProductID == pid)).ToList().ForEach(x => repository.ProductShells.Remove(x)); The below is obviously not correct but I need it to delete respective ProductShell object where any ShellMember contains a ProductID equal to the passed in variable pid. I would presume this would involve a join statement to get the relevant ShellMembers. repository.Database.ExecuteSqlCommand("FROM Shellmembers WHERE ProductID={0} DELETE FK_ProductShell", pid); I have cascade delete enabled for the FK_ShellMembers_ProductShells foreign key, so when I delete the ProductShell it will delete all the ShellMembers that are associated with it. I am going to pass this statement to System.Data.Entity Database.ExecuteSqlCommand method.

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• Entities Framework 4 doing a bulk delete

  - by Adan

  I wish to know if there is a good way to do a bulk delete or delete multiple rows using the Entities Framework 4. I can't seam to find a DeleteAll command. The only one that is available is DeleteObject() which only takes one entity, I would like to perform a delete on a list of entities.Is there a better way than to loop trough the list? I did see an article that used ExecuteStoreQuery and created some sql that would perform the delete. Is there a better way than to perform any of these two options Please advice what is the best way to perform this action.

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• How to serve a View as CSV in ASP.NET Web Forms

  - by ChessWhiz

  Hi, I have a MS SQL view that I want to make available as a CSV download in my ASPNET Web Forms app. I am using Entity Framework for other views and tables in the project. What's the best way to enable this download? I could add a HyperLink whose click handler iterates over the view, writes its CSV form to the disk, and then serves that file. However, I'd prefer not to write to the disk if it can be avoided, and that involves iteration code that may be avoided with some other solution. Any ideas?

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• dynamically create sitemap xml using php

  - by rekhasathvika

  Hi, I have created sitemap for my site using some reference code in the below link http://stackoverflow.com/questions/2747801/creating-an-xml-sitemap-with-php But I am getting error as XML Parsing Error: undefined entity Location: as my content is as follows << alt attribute and it says something like < loc http://www.example.com/700- & laquo;alt & raquo;-attributes-in-images.php< /loc Can anyone tell me how to get rid of this error.

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• EF4 - What's all the hype over objectsets?

  - by Kohan

  I am an intermediate user of EF in .net 3.5 and have recently moved to working with .net 4. One think i keep coming across when reading various tutorials is the use of ObjectSets instead of ObjectQuerys and that they are a great new feature. What is so great about them? Reading this MSDN article titled "Working with ObjectSet (Entity Framework)" It shows two examples for on how to add a Product.. one for 3.5 and another for 4.0. http://msdn.microsoft.com/en-us/library/ee473442.aspx Though my lack of knowledge I am possibly bringing up a seperate point here, but i never added a Product like this: //In .NET Framework 3.5 SP1, use the following code: using (AdventureWorksEntities context = new AdventureWorksEntities()) { // Add the new object to the context. context.AddObject("Products", newProduct); } I would have just used context.AddToProducts(newProduct); Please enlighten me. Kind regards, Kohan

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• Differences between query using LINQ and IQueryable interface directly?

  - by JohnMetta

  Using Entity Framework 4, and given: ObjectSet<Thing> AllThings = Context.CreateObjectSet<Thing>; public IQueryable<Thing> ByNameA(String name) { IQueryable<Thing> query = from o in AllThings where o.Name == name select o; return query; } public IQueryable<Thing> ByNameB(String name) { return AllThings.Where((o) => o.Name == name); } Both return IQueryable< instances, and thus the query doesn't hit the server until something like ToList() is called, right? Is it purely readability that is the difference, or are the using fundamentally different technologies on the back-end?

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• Microsoft SQL Server 2008 - 99% fragmentation on non-clustered, non-unique index

  - by user550441

  I have a table with several indexes (defined below). One of the indexes (IX_external_guid_3) has 99% fragmentation regardless of rebuilding/reorganizing the index. Anyone have any idea as to what might cause this, or the best way to fix it? We are using Entity Framework 4.0 to query this, the EF queries on the other indexed fields about 10x faster on average then the external_guid_3 field, however an ADO.Net query is roughly the same speed on both (though 2x slower than the EF Query to indexed fields). Table id(PK, int, not null) guid(uniqueidentifier, null, rowguid) external_guid_1(uniqueidentifier, not null) external_guid_2(uniqueidentifier, null) state(varchar(32), null) value(varchar(max), null) infoset(XML(.), null) -- usually 2-4K created_time(datetime, null) updated_time(datetime, null) external_guid_3(uniqueidentifier, not null) FK_id(FK, int, null) locking_guid(uniqueidentifer, null) locked_time(datetime, null) external_guid_4(uniqueidentifier, null) corrected_time(datetime, null) is_add(bit, not null) score(int, null) row_version(timestamp, null) Indexes PK_table(Clustered) IX_created_time(Non-Unique, Non-Clustered) IX_external_guid_1(Non-Unique, Non-Clustered) IX_guid(Non-Unique, Non-Clustered) IX_external_guid_3(Non-Unique, Non-Clustered) IX_state(Non-Unique, Non-Clustered)

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• First try StructureMap and MVC3 via NuGet

  - by Angel Escobedo

  Hello Guys, I'm trying to figure how to config StructureMap for ASP.NET MVC3 I've already using NuGet and I notice that it creates App_Start Folder with a cs file named as StructuremapMVC, so I check it and notice that is the same code but simplified that will be written manually on App_Start section placed on Global.asax... My Question is when I inject some IoC on my Controllers as the follow (I use this pattern : Entity Framework 4 CTP 4 / CTP 5 Generic Repository Pattern and Unit Testable) : private readonly IAsambleaRepository _aRep; private readonly IUnitOfWork _uOw; public AsambleaController(IAsambleaRepository aRep, IUnitOfWork uOw) { _aRep = aRep; this._uOw = uOw; } public ActionResult List(string period) { var rs = _aRep.ByPeriodo(period).ToList<Asamblea>(); return View(); } I got an Exception Exception Details: System.MissingMethodException: No parameterless constructor defined for this object.

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• EntityFramework & RowNumber

  - by Dan

  Hello. How can I query RowNumber with Entity Framework? For example: var result = data.Users .OrderByDescending("Birthday") .ThenBy("LastName") .ThenBy("FirstName") .Select(u => { RowNumber = ???, u.FirstName, u.LastName }); I want to implement paging for my grid, but I cannot solve problem with finding page with needed user. I'm using EF4.0. Select method with index(http://msdn.microsoft.com/en-us/vcsharp/aa336758.aspx#SelectIndexed) not works with EF. May be there is another way to implement this?

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• How to implement multi relationship in SQL Server?

  - by Ethan

  I’m trying to design a database to use with ASP.net MVC application. Here is the scenario: There are three entities and users can post their comments for each of these different entities. I just wonder how just put one table for Comments and link all other entities to it. Obviously, Comments table needs 3 references (foreign key) to those tables but as you know these foreign keys can’t be null and just one of them can be filled for each row. Is there any better way than implementing three different tables for each entity’s comments?

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• Architecture Guidance for designing Workflow Foundation with WCF

  - by Matrix

  We are planning to use WF 3.5 with WCF 3.5 and Entity Framework 1.0 for the upcoming major project. I'm looking for guidance on the architecture side. This new application will be based on typical 3-tier architecture as depicted below: Presentation Tier: ASP.NET Web Forms 3.5 Business Tier: WF 3.5 + BLL's that expose the business logic through WCF service interfaces (using EF for Data Access) Data Tier: SQL Server 2000 Here are the questions: Though the Workflow Foundation has Workflow Services, where we can map the WCF service contracts to a workflow, is this the right way to design the applications? Is EF 1.0 business entities can be used in n-tier apps without sacrificing the tracking changes in the entities? Is there a sample reference application available to look? Thanks.

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• Manipulating individual rows of a datagrid

  - by pfranchise

  Hey, recently I started working on a webpage that has a datagrid. I understand how to add datasources and that sort of thing, or at least I am starting to get it. But my question is about manipulating individual rows or cells. Is that only possible during the databind event handler, that is the only place I have been able to do it so far. I am sure there is a more abstract way of doing the things I want to do, but there are times where I just want to say Datagrid.add(row). I mean, if the datagrid is made up of a certain object type, can I make a new object of that type and just chuck it on the end? I am still new to this stuff, so perhaps what I want to do would defeat the purpose of this added abstraction, but figured I would ask around. Thanks for any advice, tips, or tricks people feel like sharing. Edit: for clarification I am using c#, entity framework, asp.net, and an SQL database.

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• Error 3032 during EF 4.0 validation

  - by Mohammadreza

  Hi guys. I have a table that has a column called "rowguid" with default value of newguid(). After I delete the generated property in the Entity Framework 4.0 designer, whenever I try to build or validate the model I receive the following error message. Error 3023: Problem in mapping fragments starting at line 1460:Column People.rowguid in table People must be mapped: It has no default value and is not nullable. It's an obvious error message but the problem is that the column HAS default value. Does anyone knows what the problem is? Thanks.

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• Is EF4 "Code Only" ready for production use?

  - by Tommy Jakobsen

  I've been looking at the new Entity Framework 4 Code Only features, and I really like them. But I'm having a hard time finding good resource on the feature. Everything seems to be spread around blongs here and there, so this make me wonder if it's ready to be used for a serious project? What do you think? Is it ready for production use or should I use the more traditional approach (EDMX designer, POCO objects)? Also, I would like to know if there are any features that Code Only does not support yet, compared to the EDMX designer? What do you think about the Code Only feature? Is it "mature" yet? Thank you.

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• Why do a small amount of add/deletes take several seconds in EF4?

  - by TomWij

  Using the Entity Framework 4. I have created a Code First database in the past and a piece of code needs to delete and add 16 objects, this takes 6 seconds each. That's 300+ ms for each query! The deletes/adds occur in a foreach scope and there is a SaveChanges() outside the foreach. In the above image you see that each takes 6 seconds, which is 34% of the time, for 16 calls. That doesn't sound normal to me... Why is this and how can I improve the performance? If there is no solution: Are there any workarounds I can use? It would be a pain to rewrite my project...

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• iPhone - Create non-persistent entities in core data

  - by ncohen

  Hi everyone, I would like to use entity objects but not store them... I read that I could create them like this: myElement = (Element *)[NSEntityDescription insertNewObjectForEntityForName:@"Element" inManagedObjectContext:managedObjectContext]; And right after that remove them: [managedObjectContext deleteObject:myElement]; then I can use my elements: myElement.property1 = @"Hello"; This works pretty well even though I think this is probably not the most optimal way to do it... Then I try to use it in my UITableView... the problem is that the object get released after the initialization. My table becomes empty when I move it! Thanks edit: I've also tried to copy the element ([myElement copy]) but I get an error...

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• How to properly reserve identity values for usage in a database?

  - by esac

  We have some code in which we need to maintain our own identity (PK) column in SQL. We have a table in which we bulk insert data, but we add data to related tables before the bulk insert is done, thus we can not use an IDENTITY column and find out the value up front. The current code is selecting the MAX value of the field and incrementing it by 1. Although there is a highly unlikely chance that two instances of our application will be running at the same time, it is still not thread-safe (not to mention that it goes to the database everytime). I am using the ADO.net entity model. How would I go about 'reserving' a range of id's to use, and when that range runs out, grab a new block to use, and guarantee that the same range will not be used.

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• Eager loading in EF1.0

  - by Dave Swersky

  I have a many-to-many relationship: Application - Applications_Servers - Server This is set up in my Entity Data Model and all is well. My problem is that I'd like to eager-load the whole graph of Applications so that I have an IEnumerable<Applications>, each Application member populated with the Servers collection associated by the many-to-many relationship. Normally this wouldn't be a problem, but according to my research there must be a navigation property between Application and Server. This is not the case for me because my Applications_Servers join table has more in it than just the two keys. Therefore, there is no navigation property directly between Application and Server, and this doesn't work: var apps = (from a in context.Application.Include("Server") select a).ToList(); I get an error saying there is no navigation property on Application called "Server", and that's correct, there is none. How do I write the query to eager-load my Applications with their Servers in this case?

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• What is the best way to add attributes to auto-generated entities (using VS2010 and EF4)

  - by Dani

  ASP.NET MVC2 has strong support for using attributes on entities (validation, and extending Html helper class and more). If I generated my Model from the Database using VS2010 EF4 Entity Data Model (edmx and it's cs class), And I want to add attributes on some of the entities. what would be the best practice ? how should I cope with updating the model (adding more fields / tables to the database and merging them into the edmx) - will it keep my attributes or generate a new cs file erasing everything ? (Manual changes to this file may cause unexpected behavior in your application.) (Manual changes to this file will be overwritten if the code is regenerated.)

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