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  • Circular Reference exception with JSON Serialisation with MVC3 and EF4 CTP5w

    - by nakchak
    Hi I'm having problems with a circular reference when i try and serialise an object returned via EF4 CTP5. Im using the code first approach and simple poco's for my model. I have added [ScriptIgnore] attributes to any properties that provide a back references to an object and annoyingly every seems to work fine if i manually instantiate the poco's, i.e. they serialise to JSON fine, and the scriptignore attribute is acknowledged. However when i try and serialise an object returned from the DAL i get the circular reference exception "A circular reference was detected while serializing an object of type 'System.Data.Entity.DynamicProxies.xxxx'" I have tried several ways of retreiving the data but they all get stuck with this error: public JsonResult GetTimeSlot(int id) { TimeSlotDao tsDao = new TimeSlotDao(); TimeSlot ts = tsDao.GetById(id); return Json(ts); } The method below works slightly better as rather than the timeslot dynamic proxied object causing the circular refference its the appointment object. public JsonResult GetTimeSlot(int id) { TimeSlotDao tsDao = new TimeSlotDao(); var ts = from t in tsDao.GetQueryable() where t.Id == id select new {t.Id, t.StartTime, t.Available, t.Appointment}; return Json(ts); } Any ideas or solutions to this problem? Update I would prefer to use the out of the box serialiser if possible although Json.Net via nuget is ok as an alternative i would hope its possible to use it as I intended as well...

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  • Detaching all entities of T to get fresh data

    - by Goran
    Lets take an example where there are two type of entites loaded: Product and Category, Product.CategoryId - Category.Id. We have available CRUD operations on products (not Categories). If on another screen Categories are updated (or from another user in the network), we would like to be able to reload the Categories, while preserving the context we currently use, since we could be in the middle of editing data, and we do not want changes to be lost (and we cannot depend on saving, since we have incomplete data). Since there is no easy way to tell EF to get fresh data (added, removed and modified), we thought of twp possible ways: 1) Getting products attached to context, and categories detached from context. This would mean that we loose the ability to access Product.Category.Name, which we do sometimes require, so we would need to manually resolve it (example when printing data). 2) detaching / attaching all Categories from current context. Context.ChangeTracker.Entries().Where(x => x.Entity.GetType() == typeof(T)).ForEach(x => x.State = EntityState.Detached); And then reload the categories, which will get fresh data. Do you find any problem with this second approach? We understand that this will require all constraints to be put on foreign keys, and not navigation properties, since when detaching all Categories, Product.Category navigation properties would be reset to null also. Also, there could be a potential performance problem, which we did not test, since there could be couple of thousand products loaded, and all would need to resolve navigation property when reloading. Which of the two do you prefer, and is there a better way (EF6 + .NET 4.0)?

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  • Effective books for learning the intricacies of business application development?

    - by OffApps Cory
    I am a self taught "developer". I use the term loosely because I only know enough to make myself dangerous. I have no theory background, and I only pick up things to get this little tool to work or make that control do what I want. That said, I am looking for some reading material that explains some of the theory behind application development especially from a business standpoint. Really I need to understand what all of these terms that float around really talk about. Business Logic Layer, UI abstraction level and all that. Anyone got a reading list that they feel helped them understand this stuff? I know how to code stuff up so that it works. It is not pretty mostly because I don't know the elegant way of doing it, and it is not planned out very well (I also don't know how to plan an application). Any help would be appreciated. I have read a number of books on what I thought was the subject, but they all seem to rehash basic coding and what-not. This doesn't have to be specific to VB.NET or WPF (or Entity Framework) but anything with those items would be quite helpful.

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  • Is .NET 4.0 just a show?

    - by Will Marcouiller
    I went to a presentation about the .NET Framework and Visual Studio 2010, last night. The topis were: ASP.NET 4 - Some of the new features of ASP.NET 4 More control over ClientID's in WebForms; Output Caching; ... // Some other stuff I don't really remember being more in framework and WinForms world. Entity Framework 2.0 (.NET 4.0) T4 Templates; Domain driven development; Data driven development; Contexts (edmx files); Some of real-world limitations of EF4 (projects with over 70 to 75 tables); Better POCO support, despite there are still these hidden EntityObject and StructuralObject, but used differently in comparison to EF 1.0 so that it doesn't take off your inheritance; Allows to easily choose how to persist the hierarchy into the underlying database; Code only (start working with EF4 directly from your code!); Design by Contract (DbC). The most interesting feature is, and only, as far as I'm concerned, all related to parallelism made easier. Which really works! No additional assembly references to add. In conclusion, I'm far from impressed about .NET Framework 4.0, apart that it makes some things easier to do. But when you're used to make it a way, it doesn't really change much, in my opinion. Is it me who cannot foresee what .NET 4.0 has to offer? What would you guys base your decision on to migrate to .NET 4.0, in a practical way?

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  • Handling duplicate insertion

    - by Francis
    So I've got this piece of code which, logically should work but Entity Framework is behaving unexpectedly. Here: foreach (SomeClass someobject in allObjects) { Supplier supplier = new Supplier(); supplier.primary_key = someobject.id; supplier.name = someobject.displayname; try { sm.Add(supplier); ro.Created++; } catch (Exception ex) { ro.Error++; } } Here's what I have in sm.Add() public Supplier Add(Supplier supplier) { try { _ctx.AddToSupplier(supplier); _ctx.SaveChanges(); return supplier; } catch (Exception ex) { throw; } } I can have records in allObjects that have the same id. My piece of code needs to support this and just move on to the next and try to insert it, which I think should work. If this happens, an exception is throw, saying that records with dupe PKs cannot be inserted (of course). The exception mentions the value of the PK, for example 1000. All is well, a new supplier is passed to sm.Add() containing a PK that's never been used before. (1001) Weirdly though, when doing SaveChanges(), EF will whine about not being able to insert records with dupe PKs. The exception still mentions 1000 even though supplier contains 10001 in primary_key. I feel this is me not using _ctx properly. Do I need to call something else to sync it ?

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  • Why is my element variable always null in this foreach loop?

    - by ZeroDivide
    Here is the code: public IEnumerable<UserSummary> getUserSummaryList() { var db = new entityContext(); List<UserSummary> model = new List<UserSummary>(); List<aspnet_Users> users = (from user in db.aspnet_Users select user).ToList<aspnet_Users>(); foreach (aspnet_Users u in users) //u is always null while users is a list that contains 4 objects { model.Add(new UserSummary() { UserName = u.UserName, Email = u.aspnet_Membership.Email, Role = Roles.GetRolesForUser(u.UserName).First(), AdCompany = u.AD_COMPANIES.ad_company_name != null ? u.AD_COMPANIES.ad_company_name : "Not an Advertiser", EmployeeName = u.EMPLOYEE.emp_name != null ? u.EMPLOYEE.emp_name : "Not an Employee" }); } return model; } For some reason the u variable in the foreach loop is always null. I've stepped through the code and the users collection is always populated. The table entity for db.aspnet_Users is the users table that comes with asp.net membership services. I've only added a couple associations to it. edit : image of debugger

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  • EFv1 mapping 1 to many Relationship to POCOs

    - by Scott
    I'm trying to work through a problem where I'm mapping EF Entities to POCO which serve as DTO. I have two tables within my database, say Products and Categories. A Product belongs to one category and one category may contain many Products. My EF entities are named efProduct and efCategory. Within each entity there is the proper Navigation Property between efProduct and efCategory. My Poco objects are simple public class Product { public string Name { get; set; } public int ID { get; set; } public double Price { get; set; } public Category ProductType { get; set; } } public class Category { public int ID { get; set; } public string Name { get; set; } public List<Product> products { get; set; } } To get a list of products I am able to do something like public IQueryable<Product> GetProducts() { return from p in ctx.Products select new Product { ID = p.ID, Name = p.Name, Price = p.Price ProductType = p.Category }; } However there is a type mismatch error because p.Category is of type efCategory. How can I resolve this? That is, how can I convert p.Category to type Category? I know in .NET EF has added support for POCO, but I'm forced to use .NET 3.5 SP1.

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  • EF in a UserControl can't see the app.config?

    - by Sven
    I just created a user control. This control also makes use of my static Entity Framework class to load two comboboxes. All is well and runs without a problem. Design and runtime are working. Then when I stop the application all the forms that contain my UserControl don't work any more in design time. I just see two errors: Error1: The specified named connection is either not found in the configuration, not intended to be used with the EntityClient provider, or not valid. Error 2: The variable ccArtikelVelden is either undeclared or was never assigned. (ccArtikelVelde is my UserControl) Runtime everything is still working My static EF Repositoy class: public class BSManagerData { private static BSManagerEntities _entities; public static BSManagerEntities Entities { get { if (_entities == null) _entities = new BSManagerEntities(); return _entities; } set { _entities = value; } } } Some logic happening in my UserControl to load the data in the comboboxes: private void LaadCbx() { cbxCategorie.DataSource = (from c in BSManagerData.Entities.Categories select c).ToList(); cbxCategorie.DisplayMember = "Naam"; cbxCategorie.ValueMember = "Id"; } private void cbxCategorie_SelectedIndexChanged(object sender, EventArgs e) { cbxFabrikant.DataSource = from f in BSManagerData.Entities.Fabrikants where f.Categorie.Id == ((Categorie)cbxCategorie.SelectedItem).Id select f; cbxFabrikant.DisplayMember = "Naam"; cbxFabrikant.ValueMember = "Id"; } The only way to make my forms work again, design time, is to comment out the EF part in the UserControl (see above) and rebuild. It's very strange, everything is in the same assembly, same namespace (for the sake of simplicity). Anyone an idea?

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  • Running an application from an USB device...

    - by Workshop Alex
    I'm working on a proof-of-concept application, containing a WCF service with console host and client, both on a single USB device. On the same device I will also have the client application which will connect to this service. The service uses the entity framework to connect to the database, which in this POC will just return a list of names. If it works, it will be used for a larger project. Creating the client and service was easy and this works well from USB. But getting the service to connect to the database isn't. I've found this site, suggesting that I should modify machine.config but that stops the XCopy deployment. This project cannot change any setting of the PC, so this suggestion is bad. I cannot create a deployment setup either. The whole thing just needs to run from USB disk. So, how do I get it to run? (The service just selects a list of names from the database, which it returns to the client. If this POC works, it will do far more complex things!)

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  • Login fails when recreating database with Code First

    - by Mun
    I'm using ASP.NET Entity Framework's Code First to create my database from the model, and the login seems to fail when the database needs to be recreated after the model changes. In Global.asax, I've got the following: protected void Application_Start() { Database.SetInitializer(new DropCreateDatabaseIfModelChanges<EntriesContext>()); // ... } In my controller, I've got the following: public ActionResult Index() { // This is just to force the database to be created var context = new EntriesContext(); var all = (from e in context.Entries select e).ToList(); } When the database doesn't exist, it is created with no problems. However, when I make a change to the model, rebuild and refresh, I get the following error: Login failed for user 'sa'. My connection string looks like this: <add name="EntriesContext" connectionString="Server=(LOCAL);Database=MyDB;User Id=sa;Password=password" providerName="System.Data.SqlClient" /> The login definitely works as I can connect to the server and the database from Management Studio using these credentials. If I delete the database manually, everything works correctly and the database is recreated as expected with the schema reflecting the changes made to the model. It seems like either the password or access to the database is being lost. Is there something else I need to do to get this working?

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  • Would you allow this type of query?

    - by user564577
    I'm exploring using an ORM tool in our development shop, and in particular Entity Framework 4.0. Since we work with VERY large databases, I'm a bit concerned about the query's it generates. Doing something simple like getting clients with an address in a state looks like below. As a database developer or admin would you allow this? Is it as bad as it looks? Assume every join is on a clustered index. SELECT [Project2].[ClientKey] AS [ClientKey], [Project2].[FirstName] AS [FirstName], [Project2].[LastName] AS [LastName], [Project2].[IsEnabled] AS [IsEnabled], [Project2].[ChangeUser] AS [ChangeUser], [Project2].[ChangeDate] AS [ChangeDate], [Project2].[C1] AS [C1], [Project2].[AddressKey] AS [AddressKey], [Project2].[ClientKey1] AS [ClientKey1], [Project2].[AddressTypeCode] AS [AddressTypeCode], [Project2].[PrimaryAddress] AS [PrimaryAddress], [Project2].[AddressLine1] AS [AddressLine1], [Project2].[AddressLine2] AS [AddressLine2], [Project2].[City] AS [City], [Project2].[State] AS [State], [Project2].[ZIP] AS [ZIP] FROM ( SELECT [Distinct1].[ClientKey] AS [ClientKey], [Distinct1].[FirstName] AS [FirstName], [Distinct1].[LastName] AS [LastName], [Distinct1].[IsEnabled] AS [IsEnabled], [Distinct1].[ChangeUser] AS [ChangeUser], [Distinct1].[ChangeDate] AS [ChangeDate], [Extent3].[AddressKey] AS [AddressKey], [Extent3].[ClientKey] AS [ClientKey1], [Extent3].[AddressTypeCode] AS [AddressTypeCode], [Extent3].[PrimaryAddress] AS [PrimaryAddress], [Extent3].[AddressLine1] AS [AddressLine1], [Extent3].[AddressLine2] AS [AddressLine2], [Extent3].[City] AS [City], [Extent3].[State] AS [State], [Extent3].[ZIP] AS [ZIP], CASE WHEN ([Extent3].[AddressKey] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C1] FROM (SELECT DISTINCT [Extent1].[ClientKey] AS [ClientKey], [Extent1].[FirstName] AS [FirstName], [Extent1].[LastName] AS [LastName], [Extent1].[IsEnabled] AS [IsEnabled], [Extent1].[ChangeUser] AS [ChangeUser], [Extent1].[ChangeDate] AS [ChangeDate] FROM [Common].[Clients] AS [Extent1] INNER JOIN [Common].[ClientAddresses] AS [Extent2] ON [Extent1].[ClientKey] = [Extent2].[ClientKey] WHERE (( CAST(CHARINDEX(UPPER('D'), UPPER([Extent1].[LastName])) AS int)) > 0) AND ([Extent1].[IsEnabled] = 1) AND ([Extent2].[City] IS NOT NULL) AND ((UPPER([Extent2].[City])) = (UPPER('Colorado Springs'))) ) AS [Distinct1] LEFT OUTER JOIN [Common].[ClientAddresses] AS [Extent3] ON [Distinct1].[ClientKey] = [Extent3].[ClientKey] ) AS [Project2] ORDER BY [Project2].[ClientKey] ASC, [Project2].[FirstName] ASC, [Project2].[LastName] ASC, [Project2].[IsEnabled] ASC, [Project2].[ChangeUser] ASC, [Project2].[ChangeDate] ASC, [Project2].[C1] ASC

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  • EF Code First, how can I achieve two foreign keys from one table to other table?

    - by Yoo Matsuo
    I've recently downloaded Entity Framework Code First CTP5, and have a trouble with this scenario. I have two tables as follows: Members table ID Name Comments table ID Comment CommentedMemberID CommentMemberID And, the data should be like the following: Members ID Name 1 Mike 2 John 3 Tom Comments ID Comment CommentedMemberID CommentMemberID 1 Good 1 2 2 Good 1 3 3 Bad 2 1 Then, I coded as shown below: public class Member { public int ID {get; set; } public string Name { get; set;} public virtual ICollection Comments { get; set;} } public class Comment { public int ID { get; set; } public string Comment { get; set; } public int CommentedMemberID { get; set; } public int CommentMemberID{ get; set; } public virtual Member CommentedMember { get; set; } public virtual Member CommentMember { get; set; } } public class TestContext : DbContext { public DbSet Members { get; set; } public DbSet Comments { get; set; } } But when I run these models on my cshtml, it gives me errors saying "Cannot create CommentMember instance" or something like that (Sorry, I already changed my models to proceed the EF Code First evaluation, so can't reproduce the same error). I've also tried to use OnModelCreating on the TestContext, but can't find any good instructions and don't know what to do. I saw a blog post of the EF Code First CTP3, and it seems there was a RelatedTo attribute in that version, but now it has gone. Could anyone know how to get it work properly? Or is this a totally wrong way to go with this scenario? Thanks, Yoo

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  • Hibernate OneToMany and ManyToOne confusion! Null List!

    - by squizz
    I have two tables... For example - Company and Employee (let's keep this real simple) Company( id, name ); Employee( id, company_id ); Employee.company_id is a foreign key. My entity model looks like this... Employee @ManyToOne(cascade = CascadeType.PERSIST) @JoinColumn(name = "company_id") Company company; Company @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER) @JoinColumn(name = "company_id") List<Employee> employeeList = new ArrayList<Employee>(); So, yeah I want a list of employees for a company. When I do the following... Employee e = new Employee(); e.setCompany(c); //c is an Company that is already in the database. DAO.insertEmployee(e); //this works fine! If I then get my Company object it's list is empty! Ive tried endless different ways from the Hibernate documentation! Obviously not tried the correct one yet! I just want the list to be populated for me or find out a sensible alternative. Help would be greatly appreciated, thanks!

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  • EventHandlers saved to databases.

    - by Stacey
    In a database application (using Sql Server right now, in C#, with Entity Framework 4.0) I have a situation where I need to trigger events when some values change. For instance assume a class "Trackable". class Trackable { string Name { get; set; } int Positive { get; set; } int Negative { get; set; } int Total { get; set; } // event OnChanged } Trackable is represented in the database as follows; table Trackables Id | guid name | varchar(32) positive | int negative | int Total is of course, calculated at runtime. When a trackable event changes, I want to inspect its previous value, and then see what it is changing to, and be capable of reacting accordingly. However different trackables need to trigger different events (to avoid a huge, massive cascading switch/if block). If this were just only C# code it would be easy - but they have to be saved to the database. I can't divide up each different trackable into a different table/class, that would be silly - they are all identical, but the event raised is different based on how they are made. So I guess my question is, is there any way to store an event handler in a database such that.. Trackable t1 = new Trackable() { Name = "Trackable1" OnChange += TrackableChangedEventHandler(OnTrackable1Change) } Trackable t2 = new Trackable() { Name = "Trackable2", OnChange += TrackableChangedEventHandler(OnTrackable2Change) }

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  • Bind data of interface properties only

    - by nivpenso
    I am new in all the Entity Framework models and the data bindings. I created an interface and generated a model class from my Candidate table in the db. public interface ICandidate { String ID { get; set; } string Name { get; set; } string Mail { get; set; } } i created a partial class to the generated Candidate model so i will be able to implement the ICandidate interface without changing any generated code. public partial class Candidates : ICandidate { string ICandidate.ID { get { return this.PK; } set { _PK = value; } } string ICandidate.Name { get{ return this._Name; } set { _Name = value; } } string ICandidate.Mail { get { return this._Email; } set { this._Email = value; } } } Of course, the generated class has more properties than the interface has (Like IsDeleted field that is not necessary for the interface). I want to display in a DataGridView all the candidates from the db. But I want that only the interface's properties will be shown as columns in the DataGridView. Is there a way bind only the interface's properties the the DataGridView? In my DB there is a table called Candidate_To_Company with these columns: PK, Candidate_FK, Company_FK, Insertion_Date I would like to bind this table to DataGridView. but instead of displaying Candidate_FK i would like to display the candidate name from ICandidate. Is this possible?

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  • Fix Windows Computer Problems with Microsoft Fix it Center

    - by Matthew Guay
    Fixing computer problems can often be difficult, but Microsoft is aiming to make it as simple as a couple clicks with.  Here’s how you can easily fix computer problems with Microsoft’s new Fix it Center Beta. Last year Microsoft began offering small Fix it scripts that you could download and run to help solve common computer problems automatically.  These were added to some of the most visited Windows help pages, and helped fix problems with things such as printing errors and Aero glass support.  Now, the Fix it scripts have been bundled together with the Fix it Center, making fixing your computer even easier.  This free tool works great on all editions of Windows XP, Vista, and Windows 7. Note: The Fix it Center is currently in beta, so only run if you are comfortable running beta software. Getting Started Download the Fix it Center installer (link below), and install as normal. The installer will download the remaining components, and then finish the installation. In Windows XP, if you have not yet installed .NET 2.0, you may see the following prompt.  Click Yes to go to the download site, and once you’ve installed .NET 2.0, run the Fix it Center setup again. Also, the Fix it Center uses PowerShell to automate its fixes, but if it is not installed yet the installer will automatically download and install it. Find Fixes for Your PC Once Fix it Center is installed, you can personalize it for your computer.  Select Now, and the click Next. It will scan your computer for problems with known solutions, and will offer to go ahead and install these troubleshooters.  If you choose to not install them, you can always download them from within the Fix it Center at a later time. While those troubleshooters are downloading, you can create a Fix it account.  This will give you additional help and support, and let you review Fix it solutions for all your computers from an online dashboard.  You need a Windows Live ID to create an account. Also, choose whether or not to send information to Microsoft about your hardware and software problems. Get Problems Fixed Now that the Fix it Center is installed and has identified issues on your computer, it’s time to get the problems fixed.  Here’s the default front screen in Windows 7, showing all of the available fixes. And here’s the Fix it Center running in Windows XP. Select one of the Troubleshooters to see more information about it, and click Run to start it. You can choose to either detect problems and have them fixed automatically, or you can choose for the Fix it Center to show you the solutions and let you choose whether to apply them or not.  The defaults usually work good, and only take a couple minutes to apply the fixes, but you can select your own fixes if you’d rather be in control. It will scan your computer for known problems in this area, and then will show you the results.  Here, Fix it determined that startup programs may be causing performance issues.  Select Start System Configuration, and uncheck any of the programs you do not usually use. Once you’ve run a troubleshooter, you can see the issues it checked for and any problems it discovered. If you created the online account, you can also choose to view the details online.  This will show all of your computers with Fix it Center and the fixes you’ve run on them.   Conclusion Whether you’re a power user or new to computers, sometimes it’s best to just get your problems fixed and go on with life instead of digging through the registry, forums, and hacking your way to a solution.  Remember the service is still in beta and may not work perfectly or solve your issues every time. But it’s something cool and worth a look. Links Download Microsoft Fix it Center Beta Fix additional problems with Microsoft’s Fix it Center Online Similar Articles Productive Geek Tips Disable Windows Mobility Center in Windows 7 or VistaMake Outlook Faster by Disabling Unnecessary Add-InsUsing Netflix Watchnow in Windows Vista Media Center (Gmedia)Disable Security Center Popup Notifications in Windows VistaHow To Manage Action Center in Windows 7 TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 Icelandic Volcano Webcams Open Multiple Links At One Go NachoFoto Searches Images in Real-time Office 2010 Product Guides Google Maps Place marks – Pizza, Guns or Strip Clubs Monitor Applications With Kiwi

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  • How to decide whether to implement an operation as Entity operation vs Service operation in Domain Driven Design?

    - by Louis Rhys
    I am reading Evans's Domain Driven Design. The book says that there are entity and there are services. If I were to implement an operation, how to decide whether I should add it as a method on an entity or do it in a service class? e.g. myEntity.DoStuff() or myService.DoStuffOn(myEntity)? Does it depend on whether other entities are involved? If it involves other entities, implement as service operation? But entities can have associations and can traverse it from there too right? Does it depend on stateless or not? But service can also access entities' variable, right? Like in do stuff myService.DoStuffOn, it can have code like if(myEntity.IsX) doSomething(); Which means that it will depend on the state? Or does it depend on complexity? How do you define complex operations?

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  • How do I best remove an entity from my game loop when it is dead?

    - by Iain
    Ok so I have a big list of all my entities which I loop through and update. In AS3 I can store this as an Array (dynamic length, untyped), a Vector (typed) or a linked list (not native). At the moment I'm using Array but I plan to change to Vector or linked list if it is faster. Anyway, my question, when an Entity is destroyed, how should I remove it from the list? I could null its position, splice it out or just set a flag on it to say "skip over me, I'm dead." I'm pooling my entities, so an Entity that is dead is quite likely to be alive again at some point. For each type of collection what is my best strategy, and which combination of collection type and removal method will work best?

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  • Why does Linq to Entity Sum return null when the list is empty?

    - by Hannele
    There are quite a few questions on Stack Overflow about the Linq to Entity / Linq to SQL Sum extension method, about how it returns null when the result set is empty: 1, 2, 3, 4, 5, 6, 7, and many more, as well as a blog post discussing the issue here. Now, I could go a flag these as duplicates, but I feel it is still an inconsistency in the Linq implementation. I am assuming at this point that it is not a bug, but is more or less working as designed. I understand that there are workarounds (for example, casting the field to a nullable type, so you can coalesce with ??), and I also understand that for the underlying SQL, a NULL result is expected for an empty list. But because the result of the Sum extension for nullable types is also not nullable, why would the Linq to SQL / Linq to Entity Sum have been designed to behave this way?

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  • Why does Linq to Entity Sum return null when the result set is empty?

    - by Hannele
    There are quite a few questions on Stack Overflow about the Linq to Entity / Linq to SQL Sum extension method, about how it returns null when the result set is empty: 1, 2, 3, 4, 5, 6, 7, and many more, as well as a blog post discussing the issue here. I feel it is an inconsistency in the Linq implementation. I am assuming at this point that it is not a bug, but is more or less working as designed. I understand that there are workarounds (for example, casting the field to a nullable type, so you can coalesce with ??), and I also understand that for the underlying SQL, a NULL result is expected for an empty result set. But because the result of the Sum extension for non-nullable types is also non-nullable, why does the Linq to SQL / Linq to Entity Sum behave this way?

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  • EF4: ObjectContext inconsistent when inserting into a view with triggers

    - by user613567
    I get an Invalid Operation Exception when inserting records in a View that uses “Instead of” triggers in SQL Server with ADO.NET Entity Framework 4. The error message says: {"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: The key-value pairs that define an EntityKey cannot be null or empty. Parameter name: record"} @ at System.Data.Objects.ObjectContext.SaveChanges(SaveOptions options) at System.Data.Objects.ObjectContext.SaveChanges() In this simplified example I created two tables, Contacts and Employers, and one view Contacts_x_Employers which allows me to insert or retrieve rows into/from these two tables at once. The Tables only have a Name and an ID attributes and the view is based on a join of both: CREATE VIEW [dbo].[Contacts_x_Employers] AS SELECT dbo.Contacts.ContactName, dbo.Employers.EmployerName FROM dbo.Contacts INNER JOIN dbo.Employers ON dbo.Contacts.EmployerID = dbo.Employers.EmployerID And has this trigger: Create TRIGGER C_x_E_Inserts ON Contacts_x_Employers INSTEAD of INSERT AS BEGIN SET NOCOUNT ON; insert into Employers (EmployerName) select i.EmployerName from inserted i where not i.EmployerName in (select EmployerName from Employers) insert into Contacts (ContactName, EmployerID) select i.ContactName, e.EmployerID from inserted i inner join employers e on i.EmployerName = e.EmployerName; END GO The .NET Code follows: using (var Context = new TriggersTestEntities()) { Contacts_x_Employers CE1 = new Contacts_x_Employers(); CE1.ContactName = "J"; CE1.EmployerName = "T"; Contacts_x_Employers CE2 = new Contacts_x_Employers(); CE1.ContactName = "W"; CE1.EmployerName = "C"; Context.Contacts_x_Employers.AddObject(CE1); Context.Contacts_x_Employers.AddObject(CE2); Context.SaveChanges(); //? line with error } SSDL and CSDL (the view nodes): <EntityType Name="Contacts_x_Employers"> <Key> <PropertyRef Name="ContactName" /> <PropertyRef Name="EmployerName" /> </Key> <Property Name="ContactName" Type="varchar" Nullable="false" MaxLength="50" /> <Property Name="EmployerName" Type="varchar" Nullable="false" MaxLength="50" /> </EntityType> <EntityType Name="Contacts_x_Employers"> <Key> <PropertyRef Name="ContactName" /> <PropertyRef Name="EmployerName" /> </Key> <Property Name="ContactName" Type="String" Nullable="false" MaxLength="50" Unicode="false" FixedLength="false" /> <Property Name="EmployerName" Type="String" Nullable="false" MaxLength="50" Unicode="false" FixedLength="false" /> </EntityType> The Visual Studio solution and the SQL Scripts to re-create the whole application can be found in the TestViewTrggers.zip at ftp://JulioSantos.com/files/TriggerBug/. I appreciate any assistance that can be provided. I already spent days working on this problem.

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  • Oracle 10g for Windows does not start up on system boot

    - by Mike Dimmick
    We have an Oracle 10g Enterprise Edition installation (10.2.0.1.0) on a Windows Server 2003 virtual machine. It was initially created with Virtual Server 2005 R2 SP1 but has now been migrated to Windows Server 2008 Hyper-V. The services start on system boot, but the instance does not start up. This problem was actually occurring on Virtual Server after a migration from one server to another, but I managed to fix it then with: oradim -edit -sid ORCL -startmode auto However, this now has no effect. oradim.log (in %OracleHome%\database\oradim.log) says: Thu Jun 10 14:14:48 2010 C:\oracle\product\10.2.0\db_3\bin\oradim.exe -startup -sid orcl -usrpwd * -log oradim.log -nocheck 0 Thu Jun 10 14:14:48 2010 ORA-12560: TNS:protocol adapter error sqlnet.log in the same folder has: Fatal NI connect error 12560, connecting to: (DESCRIPTION=(ADDRESS=(PROTOCOL=BEQ)(PROGRAM=oracle)(ARGV0=oracleorcl)(ARGS='(DESCRIPTION=(LOCAL=YES)(ADDRESS=(PROTOCOL=beq)))'))(CONNECT_DATA=(SID=orcl)(CID=(PROGRAM=C:\oracle\product\10.2.0\db_3\bin\oradim.exe)(HOST=ORACLE-VM)(USER=SYSTEM)))) VERSION INFORMATION: TNS for 32-bit Windows: Version 10.2.0.1.0 - Production Oracle Bequeath NT Protocol Adapter for 32-bit Windows: Version 10.2.0.1.0 - Production Time: 10-JUN-2010 14:14:48 Tracing not turned on. Tns error struct: ns main err code: 12560 TNS-12560: TNS:protocol adapter error ns secondary err code: 0 nt main err code: 530 TNS-00530: Protocol adapter error nt secondary err code: 2 nt OS err code: 0 The ORA_ORCL_AUTOSTART registry value is set to TRUE, so it should be auto-starting - and you can see that it's trying to. The problem also occurs when stopping and restarting the OracleServiceORCL service. I've enabled SQL*Net tracing which shows: [10-JUN-2010 15:09:33.919] snlpcss: entry [10-JUN-2010 15:09:34.419] snlpcss: Unable to spawn Oracle oracle (DESCRIPTION=(LOCAL=YES)(ADDRESS=(PROTOCOL=beq))) orcl, error 2. [10-JUN-2010 15:09:34.419] snlpcall: exit On a hunch that error 2 is Windows error 2 (file not found) I tried restarting the service with Process Monitor watching oradim.exe, but this appears to delay things just enough that it always works. Right now I have a horrible hack where I've created a Scheduled Task to run oradim -startup -sid ORCL when the Administrator account logs on, and set the VM to auto-logon. I'd still like to work out why it's not working.

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  • What DBus signal is sent on system suspend?

    - by Paul Robinson
    Hello, I need to detect when a machine is going to sleep in Ubuntu 9.10 and Fedora 13. Both use UPower, so I've been looking on the "org.freedesktop.UPower" DBus bus for such signals. I've been listening for the "sleeping" signal on the UPower bus with the following command: dbus-monitor --system "type='signal',interface='org.freedesktop.UPower',member='Sleeping'" When I sleep the machine (either by closing the lid, selecting "shutdown - suspend" or sending a DBus message) I don't see a "sleeping" event. I notice that the "Sleeping" event is sent when the "org.freedesktop.UPower.AboutToSleep" method is invoked. I can do this manually by calling: dbus-send --print-reply --system --dest=org.freedesktop.UPower /org/freedesktop/UPower org.freedesktop.UPower.AboutToSleep And I notice the "sleeping" signal is fired. My understanding is that anything that sleeps the PC must send the "AboutToSleep" signal before hand. It doesn't seem like this is happening. I've tried these steps on both Fedora 13 and Ubuntu 9.10 and I see the same results. Can anyone explain what's happening or provide me with an alternative DBus signal to listen for? Many thanks, Paul

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  • How to restrict file system when logged into terminal services

    - by pghcpa
    What I need to accomplish: With one login, when user is physically in the building I need them to see everything. When they are using terminal services with same login they should not be able to see the file system on the network. I can lock down the PC running terminal services as that is its only use. Details: Windows/2003 Server with terminal services. One login for a user (e.g., johndoe). When johndoe logs into the network at his desk in the office, he can see the network files according to group policy. When johndoe logs into terminal services from outside the building, we do not want to allow him see the network. Using 2x to do a published app, but that app has a "feature" that allows user to see network. Published application on termina services (only) is a document management system that is tied to windows login, so I can't give them two logins. With one login, when they are in the building I need them to see everything. When they are using terminal services they should not be able to see the network. I can lock down the PC running terminal services as that is its only use.

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  • Put one monitor of a dual monitor windows system into standby

    - by Psycogeek
    Standby not Disabled! When running 2 monitors on windows 7 or Windows XP, I would like to be able to put one of the monitors at a time into standby. The method can be manual. When running 2 monitors , the second monitor is not always needed, shutting off the monitors own power switch will turn off the monitor, that does work Ok. Problems with that are , the delay with the monitor logo at turn on, and the power switch is not very accessable, and the switch might not live forever turning it on and off so many times. Using disable methods like devcon, WIN-P and Display, causes all the windows to properly move to the other monitor. While that is what a person would want to happen so they can get hold of the windows, that is not what I want to happen, and some things on the other monitor have to be re-arranged after a re-enable. By putting it into standby mode, nothing changes other than the monitor going into standby. Disconnecting the DVI cable still can cause the system to (properly) shift all the windows over to the one monitor, just like any of the disable methods do. That makes a mess of the windows, and is so unacceptable, that I would prefer to leave the monitor on, wasting power and the hardware, when it could easily go into standby for some time. For both monitors I am using a "MonitorOff" program that puts both monitors into standby, but I can not find a utility that will put only ONE monitor into standby for the windows system. If someone comes along and suggests "ultramon" you must know for a fact that it will put One of either of the monitors into actual standby. And it does not really suit me to use ultramon, I tested it (it was nice) and I did not feel that it was a program I wanted. The 2 monitors are running off of an ATI 4890 card, they are both hooked up DVI-I, the OS is both Windows 7 (primary) and Windows XP. In addition it would also be interesting to have seperate standby activity timers, and follow mouse kind of standby changes, but any manuel method , shortcut, batch , tray, or gadget kind of operation would be a good start.

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