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• What is the C++ memory model?

  - by yesraaj

  What is the C++ memory model as defined by current standard? What about upcoming C++0x standard? Will it change the memory model to support concurrency better?

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• Is there an industry standard for systems registered user permissions in terms of database model?

  - by EASI

  I developed many applications with registered user access for my enterprise clients. In many years I have changed my way of doing it, specially because I used many programming languages and database types along time. Some of them not very simple as view, create and/or edit permissions for each module in the application, or light as access or can't access certain module. But now that I am developing a very extensive application with many modules and many kinds of users to access them, I was wondering if there is an standard model for doing it, because I already see that's the simple or the light way won't be enough.

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• Where to place logic in a rich domain model

  - by Fino

  I have a model "news item" which contains text, image etc to display as latest news on several pages in a website. This "news item" can also be posted to Twitter or Facebook. Is it clean to implement a method post inside the news item model and inject the different post implementations as a strategy? Or is it better to have a separate application service for this? Thanks

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• Model won't render in my XNA game

  - by Daniel Lopez

  I am trying to create a simple 3D game but things aren't working out as they should. For instance, the mode will not display. I created a class that does the rendering so I think that is where the problem lies. P.S I am using models from the MSDN website so I know the models are compatible with XNA. Code: class ModelRenderer { private float aspectratio; private Model model; private Vector3 camerapos; private Vector3 modelpos; private Matrix rotationy; float radiansy = 0; public ModelRenderer(Model m, float AspectRatio, Vector3 initial_pos, Vector3 initialcamerapos) { model = m; if (model.Meshes.Count == 0) { throw new Exception("Invalid model because it contains zero meshes!"); } modelpos = initial_pos; camerapos = initialcamerapos; aspectratio = AspectRatio; return; } public Vector3 CameraPosition { set { camerapos = value; } get { return camerapos; } } public Vector3 ModelPosition { set { modelpos = value; } get { return modelpos; } } public void RotateY(float radians) { radiansy += radians; rotationy = Matrix.CreateRotationY(radiansy); } public float AspectRatio { set { aspectratio = value; } get { return aspectratio; } } public void Draw() { Matrix world = Matrix.CreateTranslation(modelpos) * rotationy; Matrix view = Matrix.CreateLookAt(this.CameraPosition, this.ModelPosition, Vector3.Up); Matrix projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.ToRadians(45.0f), this.AspectRatio, 1.0f, 10000f); model.Draw(world, view, projection); } } If you need more code just make a comment.

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• Can I remove the systems from a component entity system?

  - by nathan

  After reading a lot about entity/component based engines. I feel like there is no real definition for this kind of engine. Reading this thread: Implementing features in an Entity System and the linked article made me think a lot. I did not feel that comfortable using System concept so I'll write something else, inspired by this pattern. I'd like to know if you think it's a good way to organize game code and what improvements can be made. Regarding a more strict implementation of entity/component based engine, is my solution viable? Do I risk getting stuck at any point due to the lack of flexibility of this implementation (or anything else)? My engine, as for entity/component patterns has entities and components, no systems since the game logic is handled by components. Also, I think the main difference is the fact that my engine will use inherence and OOP concepts in general, I mean, I don't try to minimize them. Entity: an entity is an abstract class. It holds his position, width and height, scale and a list of linked components. The current implementation can be found here (java). Every frame, the entity will be updated (i.e all the components linked to this entity will be updated), and rendered, if a render component is specified. Component: like for entity, a component is an abstract class that must be extended to create new components. The behavior of an entity is created through his components collection. The component implementation can be found here. Components are updated when the owning entity is updated or for only one specific component (render component), rendered. Here is an example of a logic component (i.e not a renderable component, a component that's updated each frame) in charge of listening for keyboard events and a render component in charge of display a plain sprite (i.e not animated).

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• MVC and individual elements of the model under a common base class

  - by Stewart

  Admittedly my experience of using the MVC pattern is limited. It might be argued that I don't really separate the V from the C, though I keep the M separate from the VC to the extent I can manage. I'm considering the scenario in which the application's model includes a number of elements that have a common base class. For example, enemy characters in a video game, or shape types in a vector graphics app. The view wants to render these elements. Of course, the different subclasses call for different rendering. The problem is that the elements are part of the model. Rendering them is conceptually part of the view. But how they are to be rendered depends on parameters of both: Attributes and state of the element are parameters of the model User settings are parameters of the view - and to support multiple platforms and/or view modes, different views may be used What's your preferred way of dealing with this? Put the rendering code in the model classes, passing in any view parameters? Put the rendering code in the view, using a switch or similar to select the right rendering for the model element type? Have some intermediate classes as a model-view interface, of which the model will create objects on demand and the view will then render them? Something else?

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• relationship between the model and the renderer

  - by acrilige

  I tried to build a simple graphics engine, and faced with this problems: i have a list of models that i need to draw, and object (renderer) that implements IRenderer interface with method DrawObject(Object* obj). Implementation of renderer depends on using graphics library (opengl/directx). 1st question: model should not know nothing about renderer implementation, but in this case where can i hold (cache) information that depends on renderer implementation? For example, if model have this definition: class Model { public: Model(); Vertex* GetVertices() const; private: Vertex* m_vertices; }; what is the best way to cache, for example, vertex buffer of this model for dx11? Hold it in renderer object? 2nd question: what is the best way for model to say renderer HOW it must be rendered (for example with texture, bump mapping, or may be just in one color). I thought it can be done with flags, like this: model-SetRenderOptions(RENDER_TEXTURE | RENDER_BUMPMAPPING | RENDER_LIGHTING); and in Renderer::DrawModel method check for each flag. But looks like it will become uncomfortable with the options count growth...

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• Argument exception after trying to use TryGetObjectByKey

  - by Rickjaah

  Hi, I'm trying to retrieve an object from my database using entity (framework 4) When I use the following code it gives an ArgumentException: An item with the same key has already been added. if (databaseContext.TryGetObjectByKey(entityKey, out result)) { return (result != null && result is TEntityObject) ? result as TEntityObject : null; } else { return null; } When I check the objectContext, I see the entities, but only if I enumerate the specific list of entities manually using VS2010, it works. What am I missing? Do I have to do something else before i can get the item from the database? I have lazy loading set to true. I searched google, but could not find any results, the same for the msdn library

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• Need help understanding Generics, How To Abstract Types Question.

  - by kmacmahon

  I could use some really good links that explain Generics and how to use them. But I also have a very specific question, relater to working on a current project. Given this class constructor: public class SecuredDomainViewModel<TDomainContext, TEntity> : DomainViewModel<TDomainContext, TEntity> where TDomainContext : DomainContext, new() where TEntity : Entity, new() public SecuredDomainViewModel(TDomainContext domainContext, ProtectedItem protectedItem) : base(domainContext) { this.protectedItem = protectedItem; } And its creation this way: DomainViewModel d; d = new SecuredDomainViewModel<MyContext, MyEntityType>(this.context, selectedProtectedItem); Assuming I have 20 different EntityTypes within MyContext, is there any easier way to call the constructor without a large switch statement? Also, since d is DomainViewModel and I later need to access methods from SecuredDomainViewModel, it seems I need to do this: if (((SecuredDomainViewModel<MyContext, MyEntityType>)d).CanEditEntity) But again "MyEntityType" could actually be one of 20 diffent types. Is there anyway to write these types of statements where MyEntityType is returned from some sort of Reflection?

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• Need help understanding Generics, How To Abstract Types Question.

  - by kmacmahon

  I could use some really good links that explain Generics and how to use them. But I also have a very specific question, relater to working on a current project. Given this class constructor: public class SecuredDomainViewModel<TDomainContext, TEntity> : DomainViewModel<TDomainContext, TEntity> where TDomainContext : DomainContext, new() where TEntity : Entity, new() And its creation this way: DomainViewModel d; d = new SecuredDomainViewModel<MyContext, MyEntityType>(this.context, selectedProtectedItem); Assuming I have 20 EntityTypes within MyContext, is there any easier way to call the constructor without a large switch statement? Also, since d is DomainViewModel and I want to access methods for SecuredDomainViewModel, it seems I need to do this: if (((SecuredDomainViewModel<MyContext, MyEntityType>)d).IsBusy) But again "MyEntityType" could actually be one of 20 types. Is there anyway to write these types of statements where MyEntityType is returned from some sort of Reflection?

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• Instantiating a context in LINQ to Entities

  - by Jagd

  I've seen two different manners that programmers approach when creating an entity context in their code. The first is like such, and you can find it all over the MSDN code examples: public void DoSomething() { using TaxableEducationEntities context = new TaxableEducationEntities()) { // business logic and whatever else } } The second is to create the context as a private attribute in some class that encapsulates your business logic. So you would have something like: public class Education_LINQ { private TaxableEducationEntities context = new TaxableEducationEntities(); public void DoSomething() { var result = from a in context.luAction select a; // business logic and whatever else } } Which way is more efficient? Assume that you have two methods, one called DoSomething1() and another called DoSomething2(), and both methods incorporate the using statement to open the context and do whatever with it. Were you to call one method after the other, would there be any superfluous overhead going on, since essentially both methods create the context and then clean it up when they're done? As opposed to having just one private attribute that is created when a class object is instantiated, and then in turn cleaned up when the object goes out of scope?

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• How do I Relate these 4 Tables

  - by Baddie

  Trying to setup a simple Thread/Poll table mapping. Here is what I have: Threads table ThreadID (Primary Key/Identity Column) Polls table PollID (Primary Key, FK for ThreadID for one-to-one relation) Question PollOptions table PollOptionID (Identity/Primary Key) Text PollID PollVotes table PollVoteID (Primary Key/Identity) PollOptionID I'm not sure if this is a proper relationship. It seems wrong but I'm not sure whats wrong with it. A Thread can have 0 or 1 Poll. A Poll can have 2 or more PollOptions. A PollOption can have 0 or many PollVotes. I'm going to be using Entity Framework and before I generate the code for it (VS 2010, .NET 4) I want to make sure I have the proper relationship mapping.

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• A generic Find method to search by Guid type for class implementing IDbSet interface

  - by imak

  I am implementing a FakeDataSet class by implementing IDbSet interface. As part of implementing this interface, I have to implement Find method. All my entity classes has an Guid type Id column. I am trying to implement Find method for this FakeDbSet class but having hard time to write it in a generic way. Below is my attempts for writing this method but since it does not know about Id been Guid type, I am getting compilation error on m.Id call. Any ideas on how this could be accomplished? public class FakeDataSet<T> : IDbSet<T> where T: class, new() { // Other methods for implementing IDbSet interface public T Find(params object[] keyValues) { var keyValue = (Guid)keyValues.FirstOrDefault(); return this.SingleOrDefault(m => m.Id == keyValue); // How can I write this } }

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• Entity Framework 4.3.1 Code based Migrations and Connector/Net 6.6

  - by GABMARTINEZ

   Code-based migrations is a new feature as part of the Connector/Net support for Entity Framework 4.3.1. In this tutorial we'll see how we can use it so we can keep track of the changes done to our database creating a new application using the code first approach. If you don't have a clear idea about how code first works we highly recommend you to check this subject before going further with this tutorial. Creating our Model and Database with Code First  From VS 2010  1. Create a new console application 2.  Add the latest Entity Framework official package using Package Manager Console (Tools Menu, then Library Package Manager -> Package Manager Console). In the Package Manager Console we have to type  Install-Package EntityFramework This will add the latest version of this library.  We will also need to make some changes to your config file. A <configSections> was added which contains the version you have from EntityFramework.  An <entityFramework> section was also added where you can set up some initialization. This section is optional and by default is generated to use SQL Express. Since we don't need it for now (we'll see more about it below) let's leave this section empty as shown below. 3. Create a new Model with a simple entity. 4. Enable Migrations to generate the our Configuration class. In the Package Manager Console we have to type  Enable-Migrations; This will make some changes in our application. It will create a new folder called Migrations where all the migrations representing the changes we do to our model.  It will also create a Configuration class that we'll be using to initialize our SQL Generator and some other values like if we want to enable Automatic Migrations.  You can see that it already has the name of our DbContext. You can also create you Configuration class manually. 5. Specify our Model Provider. We need to specify in our Class Configuration that we'll be using MySQLClient since this is not part of the generated code. Also please make sure you have added the MySql.Data and the MySql.Data.Entity references to your project. using MySql.Data.Entity;   // Add the MySQL.Data.Entity namespace public Configuration() { this.AutomaticMigrationsEnabled = false; SetSqlGenerator("MySql.Data.MySqlClient", new MySql.Data.Entity.MySqlMigrationSqlGenerator());    // This will add our MySQLClient as SQL Generator } 6. Add our Data Provider and set up our connection string <connectionStrings> <add name="PersonalContext" connectionString="server=localhost;User Id=root;database=Personal;" providerName="MySql.Data.MySqlClient" /> </connectionStrings> <system.data> <DbProviderFactories> <remove invariant="MySql.Data.MySqlClient" /> <add name="MySQL Data Provider" invariant="MySql.Data.MySqlClient" description=".Net Framework Data Provider for MySQL" type="MySql.Data.MySqlClient.MySqlClientFactory, MySql.Data, Version=6.6.2.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d" /> </DbProviderFactories> </system.data> * The version recommended to use of Connector/Net is 6.6.2 or earlier. At this point we can create our database and then start working with Migrations. So let's do some data access so our database get's created. You can run your application and you'll get your database Personal as specified in our config file. Add our first migration Migrations are a great resource as we can have a record for all the changes done and will generate the MySQL statements required to apply these changes to the database. Let's add a new property to our Person class public string Email { get; set; } If you try to run your application it will throw an exception saying  The model backing the 'PersonelContext' context has changed since the database was created. Consider using Code First Migrations to update the database (http://go.microsoft.com/fwlink/?LinkId=238269). So as suggested let's add our first migration for this change. In the Package Manager Console let's type Add-Migration AddEmailColumn Now we have the corresponding class which generate the necessary operations to update our database. namespace MigrationsFromScratch.Migrations { using System.Data.Entity.Migrations; public partial class AddEmailColumn : DbMigration { public override void Up(){ AddColumn("People", "Email", c => c.String(unicode: false)); } public override void Down() { DropColumn("People", "Email"); } } } In the Package Manager Console let's type Update-Database Now you can check your database to see all changes were succesfully applied. Now let's add a second change and generate our second migration public class Person   {       [Key]       public int PersonId { get; set;}       public string Name { get; set; }       public string Address {get; set;}       public string Email { get; set; }       public List<Skill> Skills { get; set; }   }   public class Skill   {     [Key]     public int SkillId { get; set; }     public string Description { get; set; }   }   public class PersonelContext : DbContext   {     public DbSet<Person> Persons { get; set; }     public DbSet<Skill> Skills { get; set; }   } If you would like to customize any part of this code you can do that at this step. You can see there is the up method which can update your database and the down that can revert the changes done. If you customize any code you should make sure to customize in both methods. Now let's apply this change. Update-database -verbose I added the verbose flag so you can see all the SQL generated statements to be run. Downgrading changes So far we have always upgraded to the latest migration, but there may be times when you want downgrade to a specific migration. Let's say we want to return to the status we have before our last migration. We can use the -TargetMigration option to specify the migration we'd like to return. Also you can use the -verbose flag. If you like to go  back to the Initial state you can do: Update-Database -TargetMigration:$InitialDatabase  or equivalent: Update-Database -TargetMigration:0  Migrations doesn't allow by default a migration that would ocurr in a data loss. One case when you can got this message is for example in a DropColumn operation. You can override this configuration by setting AutomaticMigrationDataLossAllowed to true in the configuration class. Also you can set your Database Initializer in case you want that these Migrations can be applied automatically and you don't have to go all the way through creating a migration and updating later the changes. Let's see how. Database Initialization by Code We can specify an initialization strategy by using Database.SetInitializer (http://msdn.microsoft.com/en-us/library/gg679461(v=vs.103)). One of the strategies that I found very useful when you are at a development stage (I mean not for production) is the MigrateDatabaseToLatestVersion. This strategy will make all the necessary migrations each time there is a change in our model that needs a database replication, this also implies that we have to enable AutomaticMigrationsEnabled flag in our Configuration class. public Configuration()         {             AutomaticMigrationsEnabled = true;             AutomaticMigrationDataLossAllowed = true;             SetSqlGenerator("MySql.Data.MySqlClient", new MySql.Data.Entity.MySqlMigrationSqlGenerator());    // This will add our MySQLClient as SQL Generator          } In the new EntityFramework section of your Config file we can set this at a context level basis.  The syntax is as follows: <contexts> <context type="Custom DbContext name, Assembly name"> <databaseInitializer type="System.Data.Entity.MigrateDatabaseToLatestVersion`2[[ Custom DbContext name, Assembly name],  [Configuration class name, Assembly name]],  EntityFramework" /> </context> </contexts> In our example this would be: The syntax is kind of odd but very convenient. This way all changes will always be applied when we do any data access in our application. There are a lot of new things to explore in EF 4.3.1 and Migrations so we'll continue writing some more posts about it. Please let us know if you have any questions or comments, also please check our forums here where we keep answering questions in general for the community.  Hope you found this information useful. Happy MySQL/.Net Coding! 

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• Binding a list belonging to another object in a custom model binder in ASP.NET MVC

  - by Dan

  I realize something like this has been asked, but this may be a little different Below is my Event object: Event : IEvent public int Id public string Title public List<EventContact> Contacts And EventContact: EventContact public int Id public string Name So, an Event has a list of EventContact' objects. Now, Event also implements IEvent - hence the custom model binder. I useIEventinstead of Event, so when the default model binder tries to do its thing, it lets me know it can't create anIEvent'. I have my view with populated with the contact info: <input type="text" name="contact[0].Name" value="DB Value"/> <input type="text" name="contact[1].Name" value="DB Value"/> <input type="text" name="contact[2].Name" value="DB Value"/> <!-- Event fields, etc --> So, in my custom model binder I am able to see all the value - sweet! The only thing is, I'm really not sure how to get all the contact fields and create a list of contacts from them, along with binding all the Event fields. Any and all help is appreciated!

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• Rails Tableless Model

  - by mplacona

  I'm creating a tableless Rails model, and am a bit stuck on how I should use it. Basically I'm trying to create a little application using Feedzirra that scans a RSS feed every X seconds, and then sends me an email with only the updates. I'm actually trying to use it as an activerecord model, and although I can get it to work, it doesn't seem to "hold" data as expected. As an example, I have an initializer method that parses the feed for the first time. On the next requests, I would like to simply call the get_updates method, which according to feedzirra, is the existing object (created during the initialize) that gets updated with only the differences. I'm finding it really hard to understand how this all works, as the object created on the initialize method doesn't seem to persist across all the methods on the model. My code looks something like: def initialize feed parse here end def get_updates feedzirra update passing the feed object here end Not sure if this is the right way of doing it, but it all seems a bit confusing and not very clear. I could be over or under-doing here, but I'd like your opinion about this approach. Thanks in advance

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• Rails - Scalable calculation model

  - by H O

  I currently have a calculation structure in my rails app that has models metric, operand and operation_type. Presently, the metric model has many operands, and can perform calculations based on the operation_type (e.g. sum, multiply, etc.), and each operand is defined as being right or left (i.e. so that if the operation is division, the numerator and denominator can be identified). Presently, an operand is always an attribute of some model, e.g. @customer.sales.selling_price.sum. In order to make this scalable, in need to allow an operand to be either an attribute of some kind, or the results of a previous operation, i.e. an operand can be a metric. I have included a diagram of how my models currently look: Can anyone assist me with the most elegant way of allowing an operand to be an actual operand, or another metric? Thanks! EDIT: It seems based on the only answer so far that perhaps polymorphic associations are the way to go on this, but the answer is so brief I have no idea how they could be used in this way - can anyone elaborate? EDIT 2: OK, I think I'm getting somewhere - essentially i presently have a metric, which has_many operands, and an operand has_many metrics. I need a polymorphic self join, where a metric can also have many metrics - do I need to call this something else, perhaps calculated_metrics, so that the metric model can use itself? That would leave me with a situation where a metric has_many operands, and a metric has many calculated_metrics.

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• Where to start when doing a Domain Model?

  - by devoured elysium

  Let's say I've made a list of concepts I'll use to draw my Domain Model. Furthermore, I have a couple of Use Cases from which I did a couple of System Sequence Diagrams. When drawing the Domain Model, I never know where to start from: Designing the model as I believe the system to be. This is, if I am modelling a the human body, I start by adding the class concepts of Heart, Brain, Bowels, Stomach, Eyes, Head, etc. Start by designing what the Use Cases need to get done. This is, if I have a Use Case which is about making the human body swallow something, I'd first draw the class concepts for Mouth, Throat, Stomatch, Bowels, etc. The order in which I do things is irrelevant? I'd say probably it'd be best to try to design from the Use Case concepts, as they are generally what you want to work with, not other kind of concepts that although help describe the whole system well, much of the time might not even be needed for the current project. Is there any other approach that I am not taking in consideration here? How do you usually approach this? Thanks

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• Domain model for an online WYSYWG webpage generator / runtime

  - by CharlieBrown

  Hi all, I'm using C#, MVC, NHibernate and StructureMap as my IoC container, and need some ideas regarding my domain model. The application I'm working has two parts: an Authoring part and a Runtime part. The idea is to allow the user to create a webpage in Authoring (mostly a form actually) by choosing from a set of predefined controls. That webpage will be later used as a form in a call center environment (Runtime part), or may be used in an intranet portal, etc. Basically something similar to what a CMS would do. The difference is, of course, that the webpage/form the author generates will be used and fulfilled in runtime, and that authros should be able to freely create the webpage they want without limitations. I have a draft working model that allows a RunController to iterate over the ScriptPage (my class for the "generated webpage") Controls collection and uses partial views to render each of them. Works kind of fine. Basically I have a common ScriptControl class, and then I can create for example a TextInputControl or a DropDownControl by inheriting from that base class. I can also figure out the Authoring part of the app, although that will surely be fun in itself for sure. :) The biggest problem I have now is persistance. In order to be flexible, I want to be able to add more controls, and template controls (think of an Address composite control) in sepparate DLLs, so I think having a relational model that handles very possible control is not the way to go. My current thinking is using a kind of ObjectStore: binary-serializing the ScriptPage object that contains the List collection and deserializing at Runtime, but I'm not sure how good will it work with NHibernate and how good the performance will be. Serializing a small "page" with 10 controls results in 7964 bytes, for example. Any ideas out there? Thanks in advance, excuse the length. ;)

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• Problem with Entity Framework : "The underlying provider failed on Open"

  - by pokrate

  Hi, When I try to insert a record, I get this error : The underlying provider failed on Open. This error occurs only with IIS and not with VWD 2008's webserver. In the EventViewer I get this Application Error : Failed to generate a user instance of SQL Server due to a failure in starting the process for the user instance. The connection will be closed. [CLIENT: ] <add name="ASPNETDBEntities" connectionString="metadata=res://*/Models.FriendList.csdl|res://*/Models.FriendList.ssdl|res://*/Models.FriendList.msl;provider=System.Data.SqlClient;provider connection string=&quot;Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\ASPNETDB.MDF;Integrated Security=True;Connect Timeout=30;User Instance=True;MultipleActiveResultSets=True&quot;" providerName="System.Data.EntityClient" /> I am using aspnetdb.mdf file, and not any external database. I have searched enough for this, but no use. Everything works fine with VWD webserver

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• SqlBulkCopy and Entity Framework

  - by KP

  My current project consists of 3 standard layers: data, business, and presentation. I would like to use data entities for all my data access needs. Part of the functionality of the app will that it will need to copy all data within a flat file into a database. The file is not so big so I can use SqlBulkCopy. I have found several articles regarding the usage of SqlBulkCopy class in .NET. However, all the articles are using DataTables to move data back and forth. Is there a way to use data entities along with SqlBulkCopy or will I have to use DataTables?

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• IQueryable<> from stored procedure (entity framework)

  - by mmcteam

  I want to get IQueryable<> result when executing stored procedure. Here is peace of code that works fine: IQueryable<SomeEntitiy> someEntities; var globbalyFilteredSomeEntities = from se in m_Entities.SomeEntitiy where se.GlobalFilter == 1234 select se; I can use this to apply global filter, and later use result in such way result = globbalyFilteredSomeEntities .OrderByDescending(se => se.CreationDate) .Skip(500) .Take(10); What I want to do - use some stored procedures in global filter. I tried: Add stored procedure to m_Entities, but it returns IEnumerable<> and executes sp immediately: var globbalyFilteredSomeEntities = from se in m_Entities.SomeEntitiyStoredProcedure(1234); Materialize query using EFExtensions library, but it is IEnumerable<>. If I use AsQueryable() and OrderBy(), Skip(), Take() and after that ToList() to execute that query - I get exception that DataReader is open and I need to close it first(can't paste error - it is in russian). var globbalyFilteredSomeEntities = m_Entities.CreateStoreCommand("exec SomeEntitiyStoredProcedure(1234)") .Materialize<SomeEntitiy>(); //.AsQueryable() //.OrderByDescending(se => se.CreationDate) //.Skip(500) //.Take(10) //.ToList(); Also just skipping .AsQueryable() is not helpful - same exception. When I put ToList() query executes, but it is too expensive to execute query without Skip(), Take().

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• Entity Framework - Condition on one to many join (Lambda)

  - by nirpi

  Hi, I have 2 entities: Customer & Account, where a customer can have multiple accounts. On the account, I have a "PlatformTypeId" field, which I need to condition on (multiple values), among other criterions. I'm using Lambda expressions, to build the query. Here's a snippet: var customerQuery = (from c in context.CustomerSet.Include("Accounts") select c); if (criterions.UserTypes != null && criterions.UserTypes.Count() > 0) { List<short> searchCriterionsUserTypes = criterions.UserTypes.Select(i => (short)i).ToList(); customerQuery = customerQuery.Where(CommonDataObjects.LinqTools.BuildContainsExpression<Customer, short>(c => c.UserTypeId, searchCriterionsUserTypes)); } // Other criterions, including the problematic platforms condition (below) var customers = customerQuery.ToList(); I can't figure out how to build the accounts' platforms condition: if (criterions.Platforms != null && criterions.Platforms.Count() > 0) { List<short> searchCriterionsPlatforms = criterions.Platforms.Select(i => (short)i).ToList(); customerQuery = customerQuery.Where(c => c.Accounts.Where(LinqTools.BuildContainsExpression<Account, short>(a => a.PlatformTypeId, searchCriterionsPlatforms))); } (The BuildContainsExpression is a method we use to build the expression for the multi-select) I'm getting a compilation error: 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. Any idea how to fix this? Thanks, Nir.

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• Entity Framework: Delete Object and its related entities

  - by Waheed

  Hi, Does anyone know how to delete an object and all of it's related entities. For example i have tables, Products, Category, ProductCategory and productDetails, the productCategory is joining table of both Product and Category. I have red from http://msdn.microsoft.com/en-us/library/bb738580.aspx that Deleting the parent object also deletes all the child objects in the constrained relationship. This result is the same as enabling the CascadeDelete property on the association for the relationship. I am using this code Product productObj = this.ObjectContext.Product.Where(p => p.ProductID.Equals(productID)).First(); if (!productObj.ProductCategory.IsLoaded) productObj.ProductCategory.Load(); if (!productObj.ProductDetails.IsLoaded) productObj.ProductDetails.Load(); //my own methods. base.Delete(productObj); base.SaveAllObjectChanges(); But i am getting error on ObjectContext.SaveChanges(); i.e A relationship is being added or deleted from an AssociationSet 'FK_ProductCategory_Product'. With cardinality constraints, a corresponding 'ProductCategory' must also be added or deleted. Thanks in advance....

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• Random sort list with LINQ and Entity Framework in vb.net

  - by Sander Versluys

  I've seen many examples in LINQ but i'm not able to reproduce the same result in vb.net. I have following code: Dim context As New MyModel.Entities() Dim rnd As New System.Random() Dim gardens As List(Of Tuin) = (From t In context.Gardens Where _ t.Approved = True And _ Not t.Famous = True _ Order By rnd.Next() _ Select t).ToList() But i receive an error when binding this list to a control. LINQ to Entities does not recognize the method 'Int32 Next()' method, and this method cannot be translated into a store expression. Any suggestion on how to get this to work?

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