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  • Entity framework architecture

    - by user1741807
    I want to make a entity framework application in Winforms C#. I'm new to entity framework, and don't know how to make the architecture. I want to have the model in a class library, and a GUI layer, and maybe a controller layer. I'm used to that architecture, but don't know have to handle the objects in other layers than the model. Have do I manage objects in the gui layer, when I can't have a reference to the model? I'm used to have some kind of dto, but what's the best way?

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  • One Model to Rule Them All - VS2010 UML, ADO.NET Entity Data Model, and T4

    - by Eric J.
    I worked on a fairly large project a while back where we modeled the classes in Enterprise Architect and generated the (partial) POCO classes (complete with model-driven business rule validations), persistence (NHibernate mapping file) and DDL. Based on certain model attributes we could flag alternate generation strategies or indicate that a particular portion would be entirely hand-coded. There was a good deal of initial investment, but it paid large dividends over the lifetime of a 15 developer, 3 year project. I'm investigating doing something similar with the current Microsoft technology stack. The place I'm stuck is that class modeling is done with the VS 2010 UML tools, but logical data modeling is done with Entity Data Modeler. Is it a reasonable path to use VS 2010 UML as the "single source of truth" and code generate the edmx files based on the class model? That's the inverse of the common path to create the entity model and use a POCO generator to generate classes. However, a good class model can be used to generate much more than just the properties so I tend to view it as a better choice than the entity model.

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  • Self join in Entity Framework

    - by Waheed
    Hi, I want to have following type of query in entity frame work SELECT c2.* FROM Category c1 INNER JOIN Category c2 ON c1.CategoryID = c2.ParentCategoryID WHERE c1.ParentCategoryID is NULL How to do the above work in Entity framework...

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  • Data Access example using Entity Framework

    - by Dan
    Does anyone know of or having any good examples of how to use Entity Framework version 2 in the Data Access layer and put an interface on it so the business layer uses the interface rather than knowing about EF? I have found some examples but they are all from 2009 and I'm not sure how they relate to Entity Framework version 2.

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  • RIA Services - Two entity models share an entity name

    - by Alex
    I have two entity models hooked up to two different databases. However, the two databases both have a table named 'brand', for example. As such, there is a naming conflict in my models. Now, I've been able to add a namespace to each model, via Custom Tool Namespace in the model's properties, but the generated code in my Silverlight project will try to use both namespaces, and come up with this, Imports MyProject.ModelA Imports MyProject.ModelB Public ReadOnly Property brands() As EntitySet(Of brand) Get Return MyBase.EntityContainer.GetEntitySet(Of brand) End Get End Property giving me this exception: 'Error 1 'brand' is ambiguous, imported from the namespaces or types 'MyProject.ModelA,MyProject.ModelB'. Has anyone had experience with naming conflicts like this using RIA services? How did you solve it?

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  • Model binding & derived model classes

    - by Richard Ev
    Does ASP.NET MVC offer any simple way to get model binding to work when you have model classes that inherit from others? In my scenario I have a View that is strongly typed to List<Person>. I have a couple of classes that inherit from Person, namely PersonTypeOne and PersonTypeTwo. I have three strongly typed partial views with names that match these class names (and render form elements for the properties of their respective models). This means that in my main View I can have the following code: <% for(int i = 0; i < Model.Count; i++) { Html.RenderPartial(Model[i].GetType().Name, Model[i]); } %> This works well, apart from when the user submits the form the relevant controller action method just gets a List<Person>, rather than a list of Person, PersonTypeOne and PersonTypeTwo. This is pretty much as expected as the form submission doesn't contain enough information to tell the default model binder to create any instances of PersonTypeOne and PersonTypeTwo classes. So, is there any way to get such functionality from the default model binder?

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  • The Interaction between Three-Tier Client/Server Model and Three-Tier Application Architecture Model

    The three-tier client/server model is a network architectural approach currently used in modern networking. This approach divides a network in to three distinct components. Three-Tier Client/Server Model Components Client Component Server Component Database Component The Client Component of the network typically represents any device on the network. A basic example of this would be computer or another network/web enabled devices that are connected to a network. Network clients request resources on the network, and are usually equipped with a user interface for the presentation of the data returned from the Server Component. This process is done through the use of various software clients, and example of this can be seen through the use of a web browser client. The web browser request information from the Server Component located on the network and then renders the results for the user to process. The Server Components of the network return data based on specific client request back to the requesting client.  Server Components also inherit the attributes of a Client Component in that they are a device on the network and that they can also request information from other Server Components. However what differentiates a Client Component from a Server Component is that a Server Component response to requests from devices on the network. An example of a Server Component can be seen in a web server. A web server listens for new requests and then interprets the request, processes the web pages, and then returns the processed data back to the web browser client so that it may render the data for the user to interpret. The Database Component of the network returns unprocessed data from databases or other resources. This component also inherits attributes from the Server Component in that it is a device on a network, it can request information from other server components and database components, and it also listens for new requests so that it can return data when needed. The three-tier client/server model is very similar to the three-tier application architecture model, and in fact the layers can be mapped to one another. Three-Tier Application Architecture Model Presentation Layer/Logic Business Layer/Logic Data Layer/Logic The Presentation Layer including its underlying logic is very similar to the Client Component of the three-tiered model. The Presentation Layer focuses on interpreting the data returned by the Business Layer as well as presents the data back to the user.  Both the Presentation Layer and the Client Component focus primarily on the user and their experience. This allows for segments of the Business Layer to be distributable and interchangeable because the Presentation Layer is not directly integrated in with Business Layer. The Presentation Layer does not care where the data comes from as long as it is in the proper format. This allows for the Presentation Layer and Business Layer to be stored on one or more different servers so that it can provide a higher availability to clients requesting data. A good example of this is a web site that uses load balancing. When a web site decides to take on the task of load balancing they must obtain a network device that sits in front of a one or machines in order to distribute the request across multiple servers. When a user comes in through the load balanced device they are redirected to a specific server based on a few factors. Common Load Balancing Factors Current Server Availability Current Server Response Time Current Server Priority The Business Layer and corresponding logic are business rules applied to data prior to it being sent to the Presentation Layer. These rules are used to manipulate the data coming from the Data Access Layer, in addition to validating any data prior to being stored in the Data Access Layer. A good example of this would be when a user is trying to create multiple accounts under one email address. The Business Layer logic can prevent duplicate accounts by enforcing a unique email for every new account before the data is even stored in the Data Access Layer. The Server Component can be directly tied to this layer in that the server typically stores and process the Business Layer before it is returned to the end-user via the Presentation Layer. In addition the Server Component can also run automated process through the Business Layer on the data in the Data Access Layer so that additional business analysis can be derived from the data that has been already collected. The Data Layer and its logic are responsible for storing information so that it can be easily retrieved. Typical in most modern applications data is stored in a database management system however data can also be in the form of files stored on a file server. In addition a database can take on one of several forms. Common Database Formats XML File Pipe Delimited File Tab Delimited File Comma Delimited File (CSV) Plain Text File Microsoft Access Microsoft SQL Server MySql Oracle Sybase The Database component of the Networking model can be directly tied to the Data Layer because this is where the Data Layer obtains the data to return back the Business Layer. The Database Component basically allows for a place on the network to store data for future use. This enables applications to save data when they can and then quickly recall the saved data as needed so that the application does not have to worry about storing the data in memory. This prevents overhead that could be created when an application must retain all data in memory. As you can see the Three-Tier Client/Server Networking Model and the Three-Tiered Application Architecture Model rely very heavily on one another to function especially if different aspects of an application are distributed across an entire network. The use of various servers and database servers are wonderful when an application has a need to distribute work across the network. Network Components and Application Layers Interaction Database components will store all data needed for the Data Access Layer to manipulate and return to the Business Layer Server Component executes the Business Layer that manipulates data so that it can be returned to the Presentation Layer Client Component hosts the Presentation Layer that  interprets the data and present it to the user

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  • Custom ASP.Net MVC 2 ModelMetadataProvider for using custom view model attributes

    - by SeanMcAlinden
    There are a number of ways of implementing a pattern for using custom view model attributes, the following is similar to something I’m using at work which works pretty well. The classes I’m going to create are really simple: 1. Abstract base attribute 2. Custom ModelMetadata provider which will derive from the DataAnnotationsModelMetadataProvider   Base Attribute MetadataAttribute using System; using System.Web.Mvc; namespace Mvc2Templates.Attributes {     /// <summary>     /// Base class for custom MetadataAttributes.     /// </summary>     public abstract class MetadataAttribute : Attribute     {         /// <summary>         /// Method for processing custom attribute data.         /// </summary>         /// <param name="modelMetaData">A ModelMetaData instance.</param>         public abstract void Process(ModelMetadata modelMetaData);     } } As you can see, the class simple has one method – Process. Process accepts the ModelMetaData which will allow any derived custom attributes to set properties on the model meta data and add items to its AdditionalValues collection.   Custom Model Metadata Provider For a quick explanation of the Model Metadata and how it fits in to the MVC 2 framework, it is basically a set of properties that are usually set via attributes placed above properties on a view model, for example the ReadOnly and HiddenInput attributes. When EditorForModel, DisplayForModel or any of the other EditorFor/DisplayFor methods are called, the ModelMetadata information is used to determine how to display the properties. All of the information available within the model metadata is also available through ViewData.ModelMetadata. The following class derives from the DataAnnotationsModelMetadataProvider built into the mvc 2 framework. I’ve overridden the CreateMetadata method in order to process any custom attributes that may have been placed above a property in a view model.   CustomModelMetadataProvider using System; using System.Collections.Generic; using System.Linq; using System.Web.Mvc; using Mvc2Templates.Attributes; namespace Mvc2Templates.Providers {     public class CustomModelMetadataProvider : DataAnnotationsModelMetadataProvider     {         protected override ModelMetadata CreateMetadata(             IEnumerable<Attribute> attributes,             Type containerType,             Func<object> modelAccessor,             Type modelType,             string propertyName)         {             var modelMetadata = base.CreateMetadata(attributes, containerType, modelAccessor, modelType, propertyName);               attributes.OfType<MetadataAttribute>().ToList().ForEach(x => x.Process(modelMetadata));               return modelMetadata;         }     } } As you can see, once the model metadata is created through the base method, a check for any attributes deriving from our new abstract base attribute MetadataAttribute is made, the Process method is then called on any existing custom attributes with the model meta data for the property passed in.   Hooking it up The last thing you need to do to hook it up is set the new CustomModelMetadataProvider as the current ModelMetadataProvider, this is done within the Global.asax Application_Start method. Global.asax protected void Application_Start()         {             AreaRegistration.RegisterAllAreas();               RegisterRoutes(RouteTable.Routes);               ModelMetadataProviders.Current = new CustomModelMetadataProvider();         }   In my next post, I’m going to demonstrate a cool custom attribute that turns a textbox into an ajax driven AutoComplete text box. Hope this is useful. Kind Regards, Sean McAlinden.

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  • Entity Component System for HUD and GUI

    - by Jason L.
    This is a very rough sketch of how I currently have things designed. It should, at least, give an idea of how my ECS is currently designed. If you notice in that diagram, I have basically split the HUD out of the ECS. They have their own set of things (HudLayer, HudComponent, etc) and are handled differently. This is where I'm struggling, though. There are many different instances in which the HUD will need to know about entities. Not just data changing (I have an event dispatcher for that), but the actual entity and all it encompasses. There are also situations where entities will need to be able to query the HUD for data. Let's take a couple examples: First, my equipment screen. On here I can change the equipment on a character (Entity). In order for this to happen, I need to know about the entity. At least I think I do? How can I handle this? The second scenario involves my Systems needing to query a HudComponent for data. A specific example would be my battle system. Each "team" is given a 3x3 grid they can move around in. See here: Skills target these cells, and not the player, so I would need a way for my systems to determine which cells are occupied and which are not. Basically I need a way for two way communication between Systems and my HUD. I know it's recommended (by some people, anyways) to take your HUD out of the ECS. Is that appropriate in my case?

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  • JPA - Entity design problem

    - by Yatendra Goel
    I am developing a Java Desktop Application and using JPA for persistence. I have a problem mentioned below: I have two entities: Country City Country has the following attribute: CountryName (PK) City has the following attribute: CityName Now as there can be two cities with same name in two different countries, the primaryKey for City table in the datbase is a composite primary key composed of CityName and CountryName. Now my question is How to implement the primary key of the City as an Entity in Java @Entity public class Country implements Serializable { private String countryName; @Id public String getCountryName() { return this.countryName; } } @Entity public class City implements Serializable { private CityPK cityPK; private Country country; @EmbeddedId public CityPK getCityPK() { return this.cityPK; } } @Embeddable public class CityPK implements Serializable { public String cityName; public String countryName; } Now as we know that the relationship from Country to City is OneToMany and to show this relationship in the above code, I have added a country variable in City class. But then we have duplicate data(countryName) stored in two places in the City class: one in the country object and other in the cityPK object. But on the other hand, both are necessary: countryName in cityPK object is necessary because we implement composite primary keys in this way. countryName in country object is necessary because it is the standard way of showing relashionship between objects. How to get around this problem?

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  • Entity Framework and WCf

    - by Nihilist
    Hi I am little confused on designing WCf services with EF. When using WCf and EF, where do we draw this line on what properties to return and what not to with the entity. Here is my scenario I have User. Here are the relations. User [1 to many] Address, User [ 1 to many] Email, User [ 1 to many] Phone So now on the webform, on page1 I can edit user information. say I can edit few properties on the user entity and can also edit address, phone, email entities[ like add / delete and update any] On page2, i can only update user properties and nothing related to navigation properties [ address, email, phone]. So when I return the User Entity [ OR DTO] should i be returning the navigation properties too? Or should the client make multiple calls to get navigation properites. Also, how does it go with Save? Like should the client make multiple calls to save user and related entites or just one call to save the graph? Lets say, if I just have a Save(User user) [ where user has all the related entities too] both page1 and page2 will call save and pass me the user. but one page1 i will need a lot more information. but on page2 i just need the user primitive properties. So my question is, where do we draw this line, how do we design theses services ? Is the WCF operation designed on the page and the fields it has ? I am hoping i explained my problem well enough.

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  • Backbone.js (model instanceof Model) via Chrome Extension

    - by Leoncelot
    Hey guys, This is my first time ever posting on this site and the problem I'm about to pose is difficult to articulate due to the set of variables required to arrive at it. Let me just quickly explain the framework I'm working with. I'm building a Chrome Extension using jQuery, jQuery-ui, and Backbone The entire JS suite for the extension is written in CoffeeScript and I'm utilizing Rails and the asset pipeline to manage it all. This means that when I want to deploy my extension code I run rake assets:precompile and copy the resulting compressed JS to my extensions Directory. The nice thing about this approach is that I can actually run the extension js from inside my Rails app by including the library. This is basically the same as my extensions background.js file which injects the js as a content script. Anyway, the problem I've recently encountered was when I tried testing my extension on my buddy's site, whiskeynotes.com. What I was noticing is that my backbone models were being mangled upon adding them to their respective collections. So something like this.collection.add(new SomeModel) created some nonsense version of my model. This code eventually runs into Backbone's prepareModel code _prepareModel: function(model, options) { options || (options = {}); if (!(model instanceof Model)) { var attrs = model; options.collection = this; model = new this.model(attrs, options); if (!model._validate(model.attributes, options)) model = false; } else if (!model.collection) { model.collection = this; } return model; }, Now, in most of the sites on which I've tested the extension, the result is normal, however on my buddy's site the !(model instance Model) evaluates to true even though it is actually an instance of the correct class. The consequence is a super messed up version of the model where the model's attributes is a reference to the models collection (strange right?). Needless to say, all kinds of crazy things were happening afterward. Why this is occurring is beyond me. However changing this line (!(model instanceof Model)) to (!(model instanceof Backbone.Model)) seems to fix the problem. I thought maybe it had something to do with the Flot library (jQuery graph library) creating their own version of 'Model' but looking through the source yielded no instances of it. I'm just curious as to why this would happen. And does it make sense to add this little change to the Backbone source? Update: I just realized that the "fix" doesn't actually work. I can also add that my backbone Models are namespaced in a wrapping object so that declaration looks something like class SomeNamespace.SomeModel extends Backbone.Model

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  • ForEach with EditorFor

    - by hermiod
    I have got an Entity model which contains a collection of Message objects which are of the type Message which has several properties, including content, MessageID, from, and to. I have created an EditorTemplate for type Message, however, I cannot get it to display the contents of the Messages collection. There are no errors, but nothing is output. Please note that the view code is from an EditorTemplate for the parent Talkback class. Can you have an EditorTemplate calling another EditorTemplate for a child collection? Both the Talkback and Message class are generated by Entity framework from an existing database. View code: <% foreach (TalkbackEntityTest.Message msg in Model.Messages) { Html.EditorFor(x=> msg, "Message"); } %> This is my template code. It is the standard auto-generated view code with some minor changes. <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<TalkbackEntityTest.Message>" %> <%: Html.ValidationSummary(true) %> <fieldset> <legend>Fields</legend> <div class="editor-label"> <%: Html.LabelFor(model => model.MessageID) %> </div> <div class="editor-field"> <%: Html.TextBoxFor(model => model.MessageID) %> <%: Html.ValidationMessageFor(model => model.MessageID) %> </div> <div class="editor-label"> <%: Html.LabelFor(model => model.acad_period) %> </div> <div class="editor-field"> <%: Html.TextBoxFor(model => model.acad_period) %> <%: Html.ValidationMessageFor(model => model.acad_period) %> </div> <div class="editor-label"> <%: Html.LabelFor(model => model.talkback_id) %> </div> <div class="editor-field"> <%: Html.TextBoxFor(model => model.talkback_id) %> <%: Html.ValidationMessageFor(model => model.talkback_id) %> </div> <div class="editor-label"> <%: Html.LabelFor(model => model.From) %> </div> <div class="editor-field"> <%: Html.TextBoxFor(model => model.From) %> <%: Html.ValidationMessageFor(model => model.From) %> </div> <div class="editor-label"> <%: Html.LabelFor(model => model.To) %> </div> <div class="editor-field"> <%: Html.TextBoxFor(model => model.To) %> <%: Html.ValidationMessageFor(model => model.To) %> </div> <div class="editor-label"> <%: Html.LabelFor(model => model.SentDatetime) %> </div> <div class="editor-field"> <%: Html.TextBoxFor(model => model.SentDatetime, String.Format("{0:g}", Model.SentDatetime)) %> <%: Html.ValidationMessageFor(model => model.SentDatetime) %> </div> <div class="editor-label"> <%: Html.LabelFor(model => model.content) %> </div> <div class="editor-field"> <%: Html.TextBoxFor(model => model.content) %> <%: Html.ValidationMessageFor(model => model.content) %> </div> <div class="editor-label"> <%: Html.LabelFor(model => model.MessageTypeID) %> </div> <div class="editor-field"> <%: Html.TextBoxFor(model => model.MessageTypeID) %> <%: Html.ValidationMessageFor(model => model.MessageTypeID) %> </div> <p> <input type="submit" value="Save" /> </p> </fieldset> There is definitely content in the Message collection as, if I remove EditorFor and put in response.write on the content property of the Message class, I get the content field for 3 Message objects on the page, which is exactly as expected.

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  • Using MVC2 to update an Entity Framework v4 object with foreign keys fails

    - by jbjon
    With the following simple relational database structure: An Order has one or more OrderItems, and each OrderItem has one OrderItemStatus. Entity Framework v4 is used to communicate with the database and entities have been generated from this schema. The Entities connection happens to be called EnumTestEntities in the example. The trimmed down version of the Order Repository class looks like this: public class OrderRepository { private EnumTestEntities entities = new EnumTestEntities(); // Query Methods public Order Get(int id) { return entities.Orders.SingleOrDefault(d => d.OrderID == id); } // Persistence public void Save() { entities.SaveChanges(); } } An MVC2 app uses Entity Framework models to drive the views. I'm using the EditorFor feature of MVC2 to drive the Edit view. When it comes to POSTing back any changes to the model, the following code is called: [HttpPost] public ActionResult Edit(int id, FormCollection formValues) { // Get the current Order out of the database by ID Order order = orderRepository.Get(id); var orderItems = order.OrderItems; try { // Update the Order from the values posted from the View UpdateModel(order, ""); // Without the ValueProvider suffix it does not attempt to update the order items UpdateModel(order.OrderItems, "OrderItems.OrderItems"); // All the Save() does is call SaveChanges() on the database context orderRepository.Save(); return RedirectToAction("Details", new { id = order.OrderID }); } catch (Exception e) { return View(order); // Inserted while debugging } } The second call to UpdateModel has a ValueProvider suffix which matches the auto-generated HTML input name prefixes that MVC2 has generated for the foreign key collection of OrderItems within the View. The call to SaveChanges() on the database context after updating the OrderItems collection of an Order using UpdateModel generates the following exception: "The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. When a change is made to a relationship, the related foreign-key property is set to a null value. If the foreign-key does not support null values, a new relationship must be defined, the foreign-key property must be assigned another non-null value, or the unrelated object must be deleted." When debugging through this code, I can still see that the EntityKeys are not null and seem to be the same value as they should be. This still happens when you are not changing any of the extracted Order details from the database. Also the entity connection to the database doesn't change between the act of Getting and the SaveChanges so it doesn't appear to be a Context issue either. Any ideas what might be causing this problem? I know EF4 has done work on foreign key properties but can anyone shed any light on how to use EF4 and MVC2 to make things easy to update; rather than having to populate each property manually. I had hoped the simplicity of EditorFor and DisplayFor would also extend to Controllers updating data. Thanks

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  • Upgrading Entity Framework 1.0 to 4.0 to include foreign keys

    - by duthiega
    Currently I've been working with Entity Framework 1.0 which is located under a service façade. Below is one of the save methods I've created to either update or insert the device in question. This currently works but, I can't help feel that its a bit of a hack having to set the referenced properties to null then re-attach them just to get an insert to work. The changedDevice already holds these values, so why do I need to assign them again. So, I thought I'll update the model to EF4. That way I can just directly access the foreign keys. However, on doing this I've found that there doesn't seem to be an easy way to add the foreign keys except by removing the entity from the diagram and re-adding it. I don't want to do this as I've already been through all the entity properties renaming them from the DB column names. Can anyone help? /// <summary> /// Saves the non network device. /// </summary> /// <param name="nonNetworkDeviceDto">The non network device dto.</param> public void SaveNonNetworkDevice(NonNetworkDeviceDto nonNetworkDeviceDto) { using (var context = new AssetNetworkEntities2()) { var changedDevice = TransformationHelper.ConvertNonNetworkDeviceDtoToEntity(nonNetworkDeviceDto); if (!nonNetworkDeviceDto.DeviceId.Equals(-1)) { var originalDevice = context.NonNetworkDevices.Include("Status").Include("NonNetworkType").FirstOrDefault( d => d.DeviceId.Equals(nonNetworkDeviceDto.DeviceId)); context.ApplyAllReferencedPropertyChanges(originalDevice, changedDevice); context.ApplyCurrentValues(originalDevice.EntityKey.EntitySetName, changedDevice); } else { var maxNetworkDevice = context.NonNetworkDevices.OrderBy("it.DeviceId DESC").First(); changedDevice.DeviceId = maxNetworkDevice.DeviceId + 1; var status = changedDevice.Status; var nonNetworkType = changedDevice.NonNetworkType; changedDevice.Status = null; changedDevice.NonNetworkType = null; context.AttachTo("DeviceStatuses", status); if (nonNetworkType != null) { context.AttachTo("NonNetworkTypes", nonNetworkType); } changedDevice.Status = status; changedDevice.NonNetworkType = nonNetworkType; context.AddToNonNetworkDevices(changedDevice); } context.SaveChanges(); } }

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  • entity framework and dirty reads

    - by bryanjonker
    I have Entity Framework (.NET 4.0) going against SQL Server 2008. The database is (theoretically) getting updated during business hours -- delete, then insert, all through a transaction. Practically, it's not going to happen that often. But, I need to make sure I can always read data in the database. The application I'm writing will never do any types of writes to the data -- read-only. If I do a dirty read, I can always access the data; the worst that happens is I get old data (which is acceptable). However, can I tell Entity Framework to always use dirty reads? Are there performance or data integrity issues I need to worry about if I set up EF this way? Or should I take a step back and see about rewriting the process that's doing the delete/insert process?

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  • Web application / Domain model integration using JSON capable DTOs [on hold]

    - by g-makulik
    I'm a bit confused about architectural choices for the web-applications/java/python world. For c/c++ world the available (open source) choices to implement web applications is pretty limited to zero, involving java or python the choices explode to a,- hard to sort out -, mess of available 'frameworks' and application approaches. I want to sort out a clean MVC model, where the M stands for a fully blown (POCO, POJO driven) domain model (according M.Fowler's EAA pattern) using a mature OO language (Java,C++) for implementation. The background is: I have a system with certain hardware components (that introduce system immanent active behavior) and a configuration database for system meta and HW-components configuration data (these are even usually self contained, since the HW-components are capable to persist their configuration data anyway). For realization of the configuration/status data exchange protocol with the HW-components we have chosen the Google Protobuf format, which works well for the directly wired communication with these components. This protocol is already used successfully with a Java based GUI application via TCP/IP connection to the main system controlling HW-component. This application has some drawbacks and design flaws for historical reasons. Now we want to develop an abstract model (domain model) for configuration and monitoring those HW-components, that represents a more use case oriented view to the overall system behavior. I have the feeling that a plain Java class model would fit best for this (c++ implementation seems to have too much implementation/integration overhead with viable language-bridge interfaces). Google Protobuf message definitions could still serve well to describe DTO objects used to interact with a domain model API. But integrating Google Protobuf messages client side for e.g. data binding in the current view doesn't seem to be a good choice. I'm thinking about some extra serialization features, e.g. for JSON based data exchange with the views/controllers. Most lightweight solutions seem to involve a python based presentation layer using JSON based data transfer (I'm at least not sure to be fully informed about this). Is there some lightweight (applicable for a limited ARM Linux platform) framework available, supporting such architecture to realize a web-application? UPDATE: According to my recent research and comments of colleagues I've noticed that using Java (and some JVM) might not be the preferable choice for integration with python on a limited linux system as we have (running on ARM9 with hard to discuss memory and MCU costs), but C/C++ modules would do well for this (since this forms the native interface to python extensions, doesn't it?). I can imagine to provide a domain model from an appropriate C/C++ API (though I still think it's more efforts and higher skill requirements for the involved developers to do with these languages). Still I'm searching for a good approach that supports such architecture. I'll appreciate any pointers!

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  • Entity Component System, weapon

    - by Heorhiy
    I'm new to game programming and currently trying to understand Entity Component System design by implementing simple 2d game. By ECS I mean design, described here for example In my game I have different kind of weapons: automatic, gun, grenade, etc... Each type of weapon has it's own affect area (gun shots along the straight line and grenade explodes and covers some spherical area) , damage impact, visual effect and bullet amount, delay between shots. So I don't completely understand how to implement weapons. Should weapon be an Entity or it should be a component? And how the player should pick up a weapon, switch between different types of weapons and etc.

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  • Camera not staying behind model while moving in circle

    - by ChocoMan
    I have a camera behind a model (3rd Person) and I'm having problems KEEPING it behind the model. When I first start my game, you see the back of the model. If the model moves forward, backward or strafe left or right, the camera moves along accordingly. When the model rotates (stationary), the camera rotates accordingly with the model still pointing at the model's back. So far, so good. The problem comes when the player is BOTH moving and rotating at the same time. Take for example a model moving in a circular pattern like running around a track. As the model moves in this motion, the model rotates slightly more with each complete rotation. Eventually, instead of looking at the model's back, eventually you will see the model in a profile view and before you know it, the model's front is facing the camera. And when you stop moving the model, the model stays in that position. So, as long as my model is stationary and rotating in one place, the camera rotates correctly. But as soon as there is any sort movement while rotating, the model is offset by a mysterious increasing amount. How can I keep the camera maintaining the same view no matter how I move AND rotate at the same time? // Rotates model and pitches camera on its own axis public void modelRotMovement(GamePadState pController) { /* For rotating the model left or right. * Camera maintains distance from model * throughout rotation and if model moves * to a new position. */ Yaw = pController.ThumbSticks.Right.X * MathHelper.ToRadians(speedAngleMAX); AddRotation = Quaternion.CreateFromAxisAngle(Vector3.Up, yaw); //AddRotation = Quaternion.CreateFromYawPitchRoll(Yaw, 0, 0); ModelLoad.MRotation *= AddRotation; MOrientation = Matrix.CreateFromQuaternion(ModelLoad.MRotation); Pitch = pController.ThumbSticks.Right.Y * MathHelper.ToRadians(speedAngleMAX); AddPitch = Quaternion.CreateFromAxisAngle(Vector3.Up, pitch); ModelLoad.CRotation *= AddPitch; COrientation = Matrix.CreateFromQuaternion(ModelLoad.CRotation); } // Orbit (yaw) Camera around model public void cameraYaw(float yaw) { Vector3 yawAngle = ModelLoad.CameraPos - ModelLoad.camTarget; Vector3 axisYaw = Vector3.Up; ModelLoad.CameraPos = Vector3.Transform(yawAngle, Matrix.CreateFromAxisAngle(axisYaw, yaw)) + ModelLoad.camTarget; }

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  • Move model forward base on model orientation

    - by ChocoMan
    My model rotates on it's own Y-axis regardless of where it is in the world. Here are the controls for the left ThumbStick: UP (move model forward on Z-Axis) DOWN (move model backward on Z-Axis) LEFT & RIGHT (strafe to either side) The problem is adjusting the direction the model's orientation UP and DOWN if the player should also rotate the player while moving forward or backwards. An example what Im trying to achieve would be a car doing donuts. The car is always facing the current direction that it interprets as forward (or rear as backwards) in relation to it's local rotation. Here is how Im calling the movement: // Rotate model with Right Thumbstick along X-Axis modelRotation -= pController.ThumbSticks.Right.X * mRotSpeed; // Move Forward if (pController.IsButtonDown(Buttons.LeftThumbstickUp)) { modelPosition.Z -= -pController.ThumbSticks.Left.Y * speed; } // Move Backward if (pController.IsButtonDown(Buttons.LeftThumbstickDown)) { modelPosition.Z += pController.ThumbSticks.Left.Y * speed; } // Strafe Left if (pController.IsButtonDown(Buttons.LeftThumbstickLeft)) { modelPosition.X += -pController.ThumbSticks.Left.X * speed; } // Strafe Right if (pController.IsButtonDown(Buttons.LeftThumbstickRight)) { modelPosition.X -= pController.ThumbSticks.Left.X * speed; } // DeadZone if (!pController.IsButtonDown(Buttons.LeftThumbstickUp) && !pController.IsButtonDown(Buttons.LeftThumbstickDown) && !pController.IsButtonDown(Buttons.LeftThumbstickLeft) && !pController.IsButtonDown(Buttons.LeftThumbstickRight)) { }

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  • Making more complicated systems(entity-component-system model question)

    - by winch
    I'm using a model where entities are collections of components and components are just data. All the logic goes into systems which operate on components. Making basic systems(for Rendering and handling collision) was easy. But how do I do more compilcated systems? For example, in a CollisionSystem I can check if entity A collides with entity B. I have this code in CollisionSystem for checking if B damages A: if(collides(a, b)) { HealthComponent* hc = a->get<HealthComponent(); hc.reduceHealth(b->get<DamageComponent>()->getDamage()); But I feel that this code shouldn't belong to Collision system. Where should code like this be and which additional systems should I create to make this code generic?

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  • Rendering order in an Entity System

    - by Daedalus
    Say I use a basic ES approach, and also inside Systems I hold lists of all entities that Systems are required to process. How do I maintain this list of entities in desired rendering order, i.e. for a dumb 2D RenderingSystem? I saw this discussion, and what they suggest is to do something like Z ordering - what I would probably do is just to store a "layer" int in DrawableComponent and then, inside RenderingSystem, just sort entities by mentioned "layer" whenever the entity list for RenderingSystem changes. They also say we could just delete and recreate the entity whenever we want it on the top, but it seems too inflexible to me. How is this problem usually solved?

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  • Sample domain model for online store

    - by Carel
    We are a group of 4 software development students currently studying at the Cape Peninsula University of Technology. Currently, we are tasked with developing a web application that functions as a online store. We decided to do the back-end in Java while making use of Google Guice for persistence(which is mostly irrelevant for my question). The general idea so far to use PHP to create the website. We decided that we would like to try, after handing in the project, and register a business to actually implement the website. The problem we have been experiencing is with the domain model. These are mostly small issues, however they are starting to impact the schedule of our project. Since we are all young IT students, we have virtually no experience in the business world. As such, we spend quite a significant amount of time planning the domain model in the first place. Now, some of the issues we're picking up is say the reference between the Customer entity and the order entity. Currently, we don't have the customer id in the order entity and we have a list of order entities in the customer entity. Lately, I have wondered if the persistence mechanism will put the client id physically in the order table, even if it's not in the entity? So, I started wondering, if you load a customer object, it will search the entire order table for orders with the customer's id. Now, say you have 10 000 customers and 500 000 orders, won't this take an extremely long time? There are also some business processes that I'm not completely clear on. Finally, my question is: does anyone know of a sample domain model out there that is similar to what we're trying to achieve that will be safe to look at as a reference? I don't want to be accused of stealing anybody's intellectual property, especially since we might implement this as a business.

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  • Adding existing entity to navigation property of a different entity

    - by Shay Friedman
    I'm using EF4 and I'm running into a problem when I try to do something that looks quite trivial to me. I have two entities, let's call them A and B. These entities have a many-to-many association between them with a navigation property on A that contains a list of related B entities. What I want to do is to add existing B entities to a new A entity. When I try to do that, I get an exception: AcceptChanges cannot continue because the object's key values conflict with another object in the ObjectStateManager. Make sure that the key values are unique before calling AcceptChanges. Has anyone run into such a problem?

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