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  • ASP.NET MVC CRUD Validation

    - by Ricardo Peres
    One thing I didn’t refer on my previous post on ASP.NET MVC CRUD with AJAX was how to retrieve model validation information into the client. We want to send any model validation errors to the client in the JSON object that contains the ProductId, RowVersion and Success properties, specifically, if there are any errors, we will add an extra Errors collection property. Here’s how: 1: [HttpPost] 2: [AjaxOnly] 3: [Authorize] 4: public JsonResult Edit(Product product) 5: { 6: if (this.ModelState.IsValid == true) 7: { 8: using (ProductContext ctx = new ProductContext()) 9: { 10: Boolean success = false; 11:  12: ctx.Entry(product).State = (product.ProductId == 0) ? EntityState.Added : EntityState.Modified; 13:  14: try 15: { 16: success = (ctx.SaveChanges() == 1); 17: } 18: catch (DbUpdateConcurrencyException) 19: { 20: ctx.Entry(product).Reload(); 21: } 22:  23: return (this.Json(new { Success = success, ProductId = product.ProductId, RowVersion = Convert.ToBase64String(product.RowVersion) })); 24: } 25: } 26: else 27: { 28: Dictionary<String, String> errors = new Dictionary<String, String>(); 29:  30: foreach (KeyValuePair<String, ModelState> keyValue in this.ModelState) 31: { 32: String key = keyValue.Key; 33: ModelState modelState = keyValue.Value; 34:  35: foreach (ModelError error in modelState.Errors) 36: { 37: errors[key] = error.ErrorMessage; 38: } 39: } 40:  41: return (this.Json(new { Success = false, ProductId = 0, RowVersion = String.Empty, Errors = errors })); 42: } 43: } As for the view, we need to change slightly the onSuccess JavaScript handler on the Single view: 1: function onSuccess(ctx) 2: { 3: if (typeof (ctx.Success) != 'undefined') 4: { 5: $('input#ProductId').val(ctx.ProductId); 6: $('input#RowVersion').val(ctx.RowVersion); 7:  8: if (ctx.Success == false) 9: { 10: var errors = ''; 11:  12: if (typeof (ctx.Errors) != 'undefined') 13: { 14: for (var key in ctx.Errors) 15: { 16: errors += key + ': ' + ctx.Errors[key] + '\n'; 17: } 18:  19: window.alert('An error occurred while updating the entity: the model contained the following errors.\n\n' + errors); 20: } 21: else 22: { 23: window.alert('An error occurred while updating the entity: it may have been modified by third parties. Please try again.'); 24: } 25: } 26: else 27: { 28: window.alert('Saved successfully'); 29: } 30: } 31: else 32: { 33: if (window.confirm('Not logged in. Login now?') == true) 34: { 35: document.location.href = '<% 1: : FormsAuthentication.LoginUrl %>?ReturnURL=' + document.location.pathname; 36: } 37: } 38: } The logic is as this: If the Edit action method is called for a new entity (the ProductId is 0) and it is valid, the entity is saved, and the JSON results contains a Success flag set to true, a ProductId property with the database-generated primary key and a RowVersion with the server-generated ROWVERSION; If the model is not valid, the JSON result will contain the Success flag set to false and the Errors collection populated with all the model validation errors; If the entity already exists in the database (ProductId not 0) and the model is valid, but the stored ROWVERSION is different that the one on the view, the result will set the Success property to false and will return the current (as loaded from the database) value of the ROWVERSION on the RowVersion property. On a future post I will talk about the possibilities that exist for performing model validation, stay tuned!

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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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  • 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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  • 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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  • 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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  • Deleting entity with child relationships using .Net Entity Framework problem

    - by Am
    My God, EF is so frustrating. I can't seem to be able to get my head around what I need to do so I can delete an object. I seem to be able to remove the object but not the related child objects. Can anyone tell me what is the rule of thumb when you want to delete all related child objects of a given object? I've tried loading all related objects like this: if (!object.childobjects.IsLoaded) object.childobjects.Load(); but once I do the following I get errors related to the relationships: modelcontext.DeleteObject(object); modelcontext.SaveChanges(); Why can't I just load the object using modelcontext.GetObjectByKey and remove it along with its child objects? My other question is can I delete an object using Entity command like so? DELETE e from objectset as e where e.id = 12 I've tried few variations and all of them throw exceptions.

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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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  • Entity Framework 4.1 auto generate with DbContext when creating ADO.NET Entity Data Model

    - by smudgedlens
    I would like to work with DbContext instead of ObjectContext. I updated EF so now I have the DbContext, but I want to generate my strongly-typed context based on the DbContext and not the ObjectContext. When I add new ADO.NET Entity Data Model, it is still based on the ObjectContext. Is it not possible to have it base off of DbContext in Visual Studio 2010 with EF 4.1? UPDATE: Okay, I followed the directions in this link and was able to generate the DbContext template objects. However, now it is saying there is ambiguity between the template entities and the entities in my .edmx file. How do I resovle this? Do I blow away the ones in the .edmx file?

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  • Role of an entity state in a component based system?

    - by Paul
    Component-based entity systems are all the rage these days; everyone seems to agree they are the way to go, but no one really has a definitive implementation of such a system. I was wondering, what role do entity states (walking-left, standing, jumping, etc) have in a CBS? Do they act like controllers (i.e. they handle events and change the entity's attributes based on those events)? What about cases where a state would, for example, require that the entity enters no-clip mode? Should, that state, when it enters, maybe set the CollisionComponent of the entity to a null pointer or something? (Then, on exit, the state should restore the entity's CollisionComponent to its previous state.) Also, I guess it's the current state's job to change the entity's state to something else, right?

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  • Entity Framework - Foreign key constraints not added for inherited entity

    - by Tri Q
    Hello, It appears to me that a strange phenomenon is occurring with inherited entities (TPT) in EF4. I have three entities. 1. Asset 2. Property 3. Activity Property is a derived-type of Asset. Property has many activities (many-to-many) When modeling this in my EDMX, everything seems fine until I try to insert a new Property into the database. If the property does not contain any Activity, it works, but all hell breaks loose when I add some new activities to the new Property. As it turns out after 2 days of crawling the web and fiddling around, I noticed that in the EF store (SSDL) some of the constraints between entities were not picked up during the update process. Property_Activity table which links properties and activities show only one constraint FK_Property_Activity_Activity but FK_Property_Activity_Property was missing. I knew this is an Entity Framework anomoly because when I switched the relationship in the database to: Asset <-- Asset_Activity <-- Activity After an update, all foreign key constraints are picked up and the save is successful, with or without activities in the new property. Is this intended or a bug in EF? How do I get around this problem? Should I abandon inheritance altogether?

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  • Entity Framework and differences between Contains between SQL and objects using ToLower

    - by John Ptacek
    I have run into an "issue" I am not quite sure I understand with Entity Framework. I am using Entity Framework 4 and have tried to utilize a TDD approach. As a result, I recently implemented a search feature using a Repository pattern. For my test project, I am implementing my repository interface and have a set of "fake" object data I am using for test purposes. I ran into an issue trying to get the Contains clause to work for case invariant search. My code snippet for both my test and the repository class used against the database is as follows: if (!string.IsNullOrEmpty(Description)) { items = items.Where(r => r.Description.ToLower().Contains(Description.ToLower())); } However, when I ran my test cases the results where not populated if my case did not match the underlying data. I tried looking into what I thought was an issue for a while. To clear my mind, I went for a run and wondered if the same code with EF would work against a SQL back end database, since SQL will explicitly support the like command and it executed as I expected, using the same logic. I understand why EF against the database back end supports the Contains clause. However, I was surprised that my unit tests did not. Any ideas why other than the SQL server support of the like clause when I use objects I populate in a collection instead of against the database server? Thanks! John

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  • Seeding many to many tables with Entity Framework

    - by Doozer1979
    I have a meeting entity and a users entity which have a many to many relationship. I'm using Autopoco to create seed data for the Users and meetings How do i seed the UserMeetings linking table that is created by EntityFramework with seed data? The linking table has two fields in it; User_Id, and Meeting_ID. I'm looping through the list of users that autopoco creates and attaching a random number of meetings Here's what i've got so far. foreach (var user in userList) { var rand = new Random(); var amountOfMeetingsToAdd = rand.Next(1, 300); for (var i = 0; i <= amountOfMeetingsToAdd; i++) { var randomMeeting = rand.Next(1, MeetingRecords); //Error occurs on This line user.Meetings.Add(_meetings[randomMeeting]); } } I got an 'Object reference not set to an instance of an object.' even though the meeting record that i'm trying to attach does exist. For info all this is happening prior to me saving the context to the DB.

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  • Entity Framework one-to-one relationship mapping flattened in code

    - by Josh Close
    I have a table structure like so. Address: AddressId int not null primary key identity ...more columns AddressContinental: AddressId int not null primary key identity foreign key to pk of Address County State AddressInternational: AddressId int not null primary key identity foreign key to pk of Address ProvinceRegion I don't have control over schema, this is just the way it is. Now, what I want to do is have a single Address object. public class Address { public int AddressId { get; set; } public County County { get; set; } public State State { get; set } public ProvinceRegion { get; set; } } I want to have EF pull it out of the database as a single entity. When saving, I want to save the single entity and have EF know to split it into the three tables. How would I map this in EF 4.1 Code First? I've been searching around and haven't found anything that meets my case yet. UPDATE An address record will have a record in Address and one in either AddressContinental or AddressInternational, but not both.

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  • Entity Framework naming conventions for many-to-many link tables

    - by TimothyP
    Hi, We are designing a SQL Server database with link tables for many-to-many relations. The question is are there any best practices for naming these kinds of tables for use with the entity framework? Let's say there's a table Customer and Address Then there is a link table between them, what do we call it? CustomerAddress ? Or something else? Thnx

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  • SQL Server backward compatibility in Entity Framework?

    - by shake
    Is there any backward compatibility in the entity framework between SQL Server 2008 and 2005? It seems the framework forces you to use the same provider for all the .edmx files in a solution. If you use the 2008 provider, data types like DateTime2 and functions like SysDateTime that are emitted by the framework to the underlying SQL query make it useless to use them against a SQL 2005 Server. Any way around this?

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  • How to create entities in one Entity group ?

    - by Gopi
    I am building an app based on google app engine (Java) using JDO for persistence. Can someone give me an example or a point me to some code which shows persisting of multiple entities (of same type) using javax.jdo.PersistenceManager.makePersistentAll() within a transaction. Basically I need to understand how to put multiple entites in one Entity Group so that they can be saved using makePersistentAll() inside transaction.

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  • Entity Framework Code-First to Provide Replacement for ASP.NET Profile Provider

    - by Ken Cox [MVP]
    A while back, I coordinated a project to add support for the SQL Table Profile Provider in ASP.NET 4 Web Applications.  We urged Microsoft to improve ASP.NET’s built-in Profile support so our workaround wouldn’t be necessary. Instead, Microsoft plans to provide a replacement for ASP.NET Profile in a forthcoming release. In response to my feature suggestion on Connect, Microsoft says we should look for something even better using Entity Framework: “When code-first is officially released the final piece of a full replacement of the ASP.NET Profile will have arrived. Once code-first for EF4 is released, developers will have a really easy and very approachable way to create any arbitrary class, and automatically have the .NET Framework create a table to provide storage for that class. Furthermore developer will also have full LINQ-query capabilities against code-first classes. “ The downside is that there won’t be a way to retrofit this Profile replacement to pre- ASP.NET 4 Web applications. At least there’ll still be the MVP workaround code. It looks like it’s time for me to dig into a CTP of EF Code-First to see what’s available.   Scott Guthrie has been blogging about Code-First Development with Entity Framework 4. It’s not clear when the EF Code-First is coming, but my guess is that it’ll be part of the VS 2010/.NET 4 service pack.

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  • Entity Association Mapping with Code First Part 1 : Mapping Complex Types

    - by mortezam
    Last week the CTP5 build of the new Entity Framework Code First has been released by data team at Microsoft. Entity Framework Code-First provides a pretty powerful code-centric way to work with the databases. When it comes to associations, it brings ultimate flexibility. I’m a big fan of the EF Code First approach and am planning to explain association mapping with code first in a series of blog posts and this one is dedicated to Complex Types. If you are new to Code First approach, you can find a great walkthrough here. In order to build a solid foundation for our discussion, we will start by learning about some of the core concepts around the relationship mapping.   What is Mapping?Mapping is the act of determining how objects and their relationships are persisted in permanent data storage, in our case, relational databases. What is Relationship mapping?A mapping that describes how to persist a relationship (association, aggregation, or composition) between two or more objects. Types of RelationshipsThere are two categories of object relationships that we need to be concerned with when mapping associations. The first category is based on multiplicity and it includes three types: One-to-one relationships: This is a relationship where the maximums of each of its multiplicities is one. One-to-many relationships: Also known as a many-to-one relationship, this occurs when the maximum of one multiplicity is one and the other is greater than one. Many-to-many relationships: This is a relationship where the maximum of both multiplicities is greater than one. The second category is based on directionality and it contains two types: Uni-directional relationships: when an object knows about the object(s) it is related to but the other object(s) do not know of the original object. To put this in EF terminology, when a navigation property exists only on one of the association ends and not on the both. Bi-directional relationships: When the objects on both end of the relationship know of each other (i.e. a navigation property defined on both ends). How Object Relationships Are Implemented in POCO domain models?When the multiplicity is one (e.g. 0..1 or 1) the relationship is implemented by defining a navigation property that reference the other object (e.g. an Address property on User class). When the multiplicity is many (e.g. 0..*, 1..*) the relationship is implemented via an ICollection of the type of other object. How Relational Database Relationships Are Implemented? Relationships in relational databases are maintained through the use of Foreign Keys. A foreign key is a data attribute(s) that appears in one table and must be the primary key or other candidate key in another table. With a one-to-one relationship the foreign key needs to be implemented by one of the tables. To implement a one-to-many relationship we implement a foreign key from the “one table” to the “many table”. We could also choose to implement a one-to-many relationship via an associative table (aka Join table), effectively making it a many-to-many relationship. Introducing the ModelNow, let's review the model that we are going to use in order to implement Complex Type with Code First. It's a simple object model which consist of two classes: User and Address. Each user could have one billing address. The Address information of a User is modeled as a separate class as you can see in the UML model below: In object-modeling terms, this association is a kind of aggregation—a part-of relationship. Aggregation is a strong form of association; it has some additional semantics with regard to the lifecycle of objects. In this case, we have an even stronger form, composition, where the lifecycle of the part is fully dependent upon the lifecycle of the whole. Fine-grained domain models The motivation behind this design was to achieve Fine-grained domain models. In crude terms, fine-grained means “more classes than tables”. For example, a user may have both a billing address and a home address. In the database, you may have a single User table with the columns BillingStreet, BillingCity, and BillingPostalCode along with HomeStreet, HomeCity, and HomePostalCode. There are good reasons to use this somewhat denormalized relational model (performance, for one). In our object model, we can use the same approach, representing the two addresses as six string-valued properties of the User class. But it’s much better to model this using an Address class, where User has the BillingAddress and HomeAddress properties. This object model achieves improved cohesion and greater code reuse and is more understandable. Complex Types: Splitting a Table Across Multiple Types Back to our model, there is no difference between this composition and other weaker styles of association when it comes to the actual C# implementation. But in the context of ORM, there is a big difference: A composed class is often a candidate Complex Type. But C# has no concept of composition—a class or property can’t be marked as a composition. The only difference is the object identifier: a complex type has no individual identity (i.e. no AddressId defined on Address class) which make sense because when it comes to the database everything is going to be saved into one single table. How to implement a Complex Types with Code First Code First has a concept of Complex Type Discovery that works based on a set of Conventions. The convention is that if Code First discovers a class where a primary key cannot be inferred, and no primary key is registered through Data Annotations or the fluent API, then the type will be automatically registered as a complex type. Complex type detection also requires that the type does not have properties that reference entity types (i.e. all the properties must be scalar types) and is not referenced from a collection property on another type. Here is the implementation: public class User{    public int UserId { get; set; }    public string FirstName { get; set; }    public string LastName { get; set; }    public string Username { get; set; }    public Address Address { get; set; }} public class Address {     public string Street { get; set; }     public string City { get; set; }            public string PostalCode { get; set; }        }public class EntityMappingContext : DbContext {     public DbSet<User> Users { get; set; }        } With code first, this is all of the code we need to write to create a complex type, we do not need to configure any additional database schema mapping information through Data Annotations or the fluent API. Database SchemaThe mapping result for this object model is as follows: Limitations of this mappingThere are two important limitations to classes mapped as Complex Types: Shared references is not possible: The Address Complex Type doesn’t have its own database identity (primary key) and so can’t be referred to by any object other than the containing instance of User (e.g. a Shipping class that also needs to reference the same User Address). No elegant way to represent a null reference There is no elegant way to represent a null reference to an Address. When reading from database, EF Code First always initialize Address object even if values in all mapped columns of the complex type are null. This means that if you store a complex type object with all null property values, EF Code First returns a initialized complex type when the owning entity object is retrieved from the database. SummaryIn this post we learned about fine-grained domain models which complex type is just one example of it. Fine-grained is fully supported by EF Code First and is known as the most important requirement for a rich domain model. Complex type is usually the simplest way to represent one-to-one relationships and because the lifecycle is almost always dependent in such a case, it’s either an aggregation or a composition in UML. In the next posts we will revisit the same domain model and will learn about other ways to map a one-to-one association that does not have the limitations of the complex types. References ADO.NET team blog Mapping Objects to Relational Databases Java Persistence with Hibernate

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  • Texture switching with a entity system

    - by GameDev-er
    I'm using thinking of using an entity system in my game. So far I've been using Artemis with success. However, I have a question about texture switching. I read that switching textures too often is bad. So I load all the textures when the game loads like so: import org.newdawn.slick.opengl.TextureLoader; ... public HashMap<String, Texture> Textures; ... Then for each texture I do this: Texture tex = TextureLoader.getTexture("PNG", this.getClass().getResourceAsStream(texturePath)); Textures.put(textureName, tex); Then when drawing entities I do this: drawEntity() { glBindTexture(GL_TEXTURE_2D, Textures.get(entityTexture).getTextureID()); ... } Say I have 50 entities, using 10 different 3D models, each with their own texture. When the drawEntity system runs, it doesn't group by which entities use which texture. So I could be switching textures before drawing each entity! Is there a more efficient way to switch textures between entities? Or is glBindTexture() a good option?

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