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  • EF 6 Code First Many to many With Payload and self referencing many to many

    - by lesley86
    I Have the problem where i have a many to many relationship and on one of the tables there will be a self referencing many to many. So basically a school have zero or many groups and many groups can have 0 or many schools. The groups table will contain a parent child many to many with itself because a group can be a child of another group or it can have no children and that child can have a child, one child can also have many parents or a entity can have no parents. I created a mapping table with Payload to solvethe first many to many problem. code snippet public class School { public virtual ICollection<SchoolGroupMap> SchoolGroupMaps } public class SchoolGroup { public virtual ICollection<SchoolGroupMap> SchoolGroupMaps } public class SchoolGroupMap { public virtual School School public virtual SchoolGroup SchoolGroup } i Then tried modifying the code the following way for the the self referencing many to many public class SchoolGroup { public virtual ICollection<SchoolGroupMap> SchoolGroupMaps public virtual ICollection<SchoolGroup> Parents public virtual ICollection<SchoolGroup> Children } I changed the context with has many and an auto mapping table (forgive me i have been trying so many things today i do not have the exact code). I received an error the properties on the classes must match. Can anyone help please. I want to do create navigation properties on the self referencing many to many. Also a seed example would be appreciated regards

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  • How to scrape a _private_ google group?

    - by John
    Hi there, I'd like to scrape the discussion list of a private google group. It's a multi-page list and I might have to this later again so scripting sounds like the way to go. Since this is a private group, I need to login in my google account first. Unfortunately I can't manage to login using wget or ruby Net::HTTP. Surprisingly google groups is not accessible with the Client Login interface, so all the code samples are useless. My ruby script is embedded at the end of the post. The response to the authentication query is a 200-OK but no cookies in the response headers and the body contains the message "Your browser's cookie functionality is turned off. Please turn it on." I got the same output with wget. See the bash script at the end of this message. I don't know how to workaround this. am I missing something? Any idea? Thanks in advance. John Here is the ruby script: # a ruby script require 'net/https' http = Net::HTTP.new('www.google.com', 443) http.use_ssl = true path = '/accounts/ServiceLoginAuth' email='[email protected]' password='topsecret' # form inputs from the login page data = "Email=#{email}&Passwd=#{password}&dsh=7379491738180116079&GALX=irvvmW0Z-zI" headers = { 'Content-Type' => 'application/x-www-form-urlencoded', 'user-agent' => "Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/533.2 (KHTML, like Gecko) Chrome/6.0"} # Post the request and print out the response to retrieve our authentication token resp, data = http.post(path, data, headers) puts resp resp.each {|h, v| puts h+'='+v} #warning: peer certificate won't be verified in this SSL session Here is the bash script: # A bash script for wget CMD="" CMD="$CMD --keep-session-cookies --save-cookies cookies.tmp" CMD="$CMD --no-check-certificate" CMD="$CMD --post-data='[email protected]&Passwd=topsecret&dsh=-8408553335275857936&GALX=irvvmW0Z-zI'" CMD="$CMD --user-agent='Mozilla'" CMD="$CMD https://www.google.com/accounts/ServiceLoginAuth" echo $CMD wget $CMD wget --load-cookies="cookies.tmp" http://groups.google.com/group/mygroup/topics?tsc=2

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  • Entityframework 4.0 .CreateQuery<T> and OrderBy exception

    - by Sammy
    Hi Guys, I thought this was fixed in 4.0 I have this method public IQueryable<T> All(Expression<Func<T,object>> sort) { return EntityContext.CreateQuery<T>(EntityName).AsQueryable<T>().OrderBy(sort); } this throws the following exception Unable to cast the type 'System.Int32' to type 'System.Object'. LINQ to Entities only supports casting Entity Data Model primitive types. Source is System.Data.Entity any idea how to fix this or if theres any workaround

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  • Custom validator not invoked when using Validation Application Block through configuration

    - by Chris
    I have set up a ruleset in my configuration file which has two validators, one of which is a built-in NotNullValidator, the other of which is a custom validator. The problem is that I see the NotNullValidator hit, but not my custom validator. The custom validator is being used to validate an Entity Framework entity object. I have used the debugger to confirm the NotNull is hit (I forced a failure condition so I saw it set an invalid result), but it never steps into the custom one. I am using MVC as the web app, so I defined the ruleset in a config file at that layer, but my custom validator is defined in another project. However, I wouldn't have thought that to be a problem because when I use the Enterprise Library Configuration tool inside Visual Studio 2008 it is able to set the type properly for the custom validator. As well, I believe the custom validator is fine as it builds ok, and the config tool can reference it properly. Does anybody have any ideas what the problem could be, or even what to do/try to debug further? Here is a stripped down version of my custom validator: [ConfigurationElementType(typeof(CustomValidatorData))] public sealed class UserAccountValidator : Validator { public UserAccountValidator(NameValueCollection attributes) : base(string.Empty, "User Account") { } protected override string DefaultMessageTemplate { get { throw new NotImplementedException(); } } protected override void DoValidate(object objectToValidate, object currentTarget, string key, ValidationResults results) { if (!currentTarget.GetType().Equals(typeof(UserAccount))) { throw new Exception(); } UserAccount userAccountToValidate = (UserAccount)currentTarget; // snipped code ... this.LogValidationResult(results, "The User Account is invalid", currentTarget, key); } } Here is the XML of my ruleset in Validation.config (the NotNull rule is only there to force a failure so I could see it getting hit, and it does): <validation> <type defaultRuleset="default" assemblyName="MyProj.Entities, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" name="MyProj.Entities.UserAccount"> <ruleset name="default"> <properties> <property name="HashedPassword"> <validator negated="true" messageTemplate="" messageTemplateResourceName="" messageTemplateResourceType="" tag="" type="Microsoft.Practices.EnterpriseLibrary.Validation.Validators.NotNullValidator, Microsoft.Practices.EnterpriseLibrary.Validation, Version=4.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" name="Not Null Validator" /> </property> <property name="Property"> <validator messageTemplate="" messageTemplateResourceName="" messageTemplateResourceType="" tag="" type="MyProj.Entities.UserAccountValidator, MyProj.Entities, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" name="Custom Validator" /> </property> </properties> </ruleset> </type> </validation> And here is the stripped down version of the way I invoke the validation: var type = entity.GetType() var validator = ValidationFactory.CreateValidator(type, "default", new FileConfigurationSource("Validation.config")) var results = validator.Validate(entity) Any advice would be much appreciated! Thanks, Chris

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  • How do you handle EF Data Contexts combined with asp.net custom membership/role providers

    - by KallDrexx
    I can't seem to get my head around how to implement a custom membership provider with Entity Framework data contexts into my asp.net MVC application. I understand how to create a custom membership/role provider by itself (using this as a reference). Here's my current setup: As of now I have a repository factory interface that allows different repository factories to be created (right now I only have a factory for EF repositories and and in memory repositories). The repository factory looks like this: public class EFRepositoryFactory : IRepositoryFactory { private EntitiesContainer _entitiesContext; /// <summary> /// Constructor that generates the necessary object contexts /// </summary> public EFRepositoryFactory() { _entitiesContext = new EntitiesContainer(); } /// <summary> /// Generates a new entity framework repository for the specified entity type /// </summary> /// <typeparam name="T">Type of entity to generate a repository for </typeparam> /// <returns>Returns an EFRepository</returns> public IRepository<T> GenerateRepository<T>() where T : class { return new EFRepository<T>(_entitiesContext); } } Controllers are passed an EF repository factory via castle Windsor. The controller then creates all the service/business layer objects it requires and passes in the repository factory into it. This means that all service objects are using the same EF data contexts and I do not have to worry about objects being used in more than one data context (which of course is not allowed and causes an exception). As of right now I am trying to decide how to generate my user and authorization service layers, and have run against a design roadblock. The User/Authization service will be a central class that handles the logic for logging in, changing user details, managing roles and determining what users have access to what. The problem is, using the current methodology the asp.net mvc controllers will initialize it's own EF repository factory via Windsor and the asp.net membership/role provider will have to initialize it's own EF repository factory. This means that each part of the site will then have it's own data context. This seems to mean that if asp.net authenticates a user, that user's object will be in the membership provider's data context and thus if I try to retrieve that user object in the service layer (say to change the user's name) I will get a duplication exception. I thought of making the repository factory class a singleton, but I don't see a way for that to work with castle Windsor. How do other people handle asp.net custom providers in a MVC (or any n-tier) architecture without having object duplication issues?

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  • JPA - Removing entities

    - by James P.
    I have a Story entity with the following associations: Story <1-* Chapter Story <1-* Comment Story <*-1 User What is the correct way of removing this entity and handling the all the entities that is referring to? Is there some shorthand way of specifying that associated entities must be handled automatically or is the @PreRemove annoation mentionned in the article below a valid of achieving this? http://blog.xebia.com/2009/04/09/jpa-implementation-patterns-removing-entities/

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  • Core Data - Breaking A Relationship

    - by Garry
    Hi, I have a Patient entity and a List entity. A Patient can belong to several different lists and a list can have several different patients. Say I have a patient who belongs to 3 lists (A, B, C). I want to remove the patient from lists A & B. I do not want to delete lists A & B themselves though obviously. How do I go about doing this?

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  • MVC2 - Dynamic Field Layout

    - by Rob
    I'm new to MVC and ADO.net Entity Framework. Instead of having to create an edit/display for each entity, I'd like to have the controller base class generate the view and validation code based off metadata stored in a table - something along those lines. I would imagine something like this has already been done, or there are good reasons for not doing it. Any insight or suggestions are appreciated.

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  • Entities equals(), hashCode() and toString(). How to correctly implement them?

    - by spike07
    I'm implementing equals(), hashCode() and toString() of my entities using all the available fields in the bean. I'm getting some Lazy init Exception on the frontend when I try to compare the equality or when I print the obj state. That's because some list in the entity can be lazy initialized. I'm wondering what's the correct way to for implementing equals() and toString() on an entity object.

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  • Are there any modeling tools that can visually generate jpa or sql queries?

    - by Shervin
    Does anyone know of a tool like PowerArchitect or SquirrelSQL or maybe eclipse plugin that lets you also generate jpa/sql queries? Imagine you choosing your database, or your entity beans, and the modeling would reverse engineer your database/entity model, so that you could visually just choose the columns you wanted to select, and it would generate jpa or sql queries for you. For instance choosing A.b and X.y would generate something like this: select a.b, x.y from A a, X x join ......

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  • one to many jpa relationship

    - by user309944
    Hai I have created two table first table as student package com.crimson.rship; import javax.persistence.Basic; import javax.persistence.Entity; import javax.persistence.FetchType; import javax.persistence.Id; import javax.persistence.OneToMany; @Entity(name="student") public class student { @Id private String stumailid; @Basic private String fathername; @Basic private String mothername; @Basic private String doa; @Basic private String dob; public student(String stumailid,String fathername,String mothername,String doa,String dob) { // TODO Auto-generated constructor stub this.stumailid=stumailid; this.fathername=fathername; this.mothername=mothername; this.doa=doa; this.dob=dob; } public void setStumailid(String stumailid) { this.stumailid = stumailid; } public String getStumailid() { return stumailid; } public void setFathername(String fathername) { this.fathername = fathername; } public String getFathername() { return fathername; } public void setMothername(String mothername) { this.mothername = mothername; } public String getMothername() { return mothername; } public void setDoa(String doa) { this.doa = doa; } public String getDoa() { return doa; } public void setDob(String dob) { this.dob = dob; } public String getDob() { return dob; } } Second table as mark package com.crimson.rship; import java.util.Collection; import javax.persistence.Basic; import javax.persistence.Entity; import javax.persistence.FetchType; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.JoinTable; import javax.persistence.OneToMany; @Entity(name="mark") public class mark { @Id private String stumailid; @Basic private String fathername; @Basic private String mothername; @OneToMany(mappedBy="mark",targetEntity=student.class,fetch=FetchType.EAGER) private Collection orders; public mark(String stumailid,String fathername,String mothername) { // TODO Auto-generated constructor stub this.stumailid=stumailid; this.fathername=fathername; this.mothername=mothername; } public void setStumailid(String stumailid) { this.stumailid = stumailid; } public String getStumailid() { return stumailid; } public void setFathername(String fathername) { this.fathername = fathername; } public String getFathername() { return fathername; } public void setMothername(String mothername) { this.mothername = mothername; } public String getMothername() { return mothername; } public void setOrders(Collection orders) { this.orders = orders; } public Collection getOrders() { return orders; } } But this above coding working is not working correctly.can any one help me Thanks in advance

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  • ASP MVC2 - Dynamic Field Layout

    - by Rob
    I'm new to MVC and ADO.net Entity Framework. Instead of having to create an edit/display for each entity, I'd like to have the controller base class generate the view and validation code based off metadata stored in a table - something along those lines. I would imagine something like this has already been done, or there are good reasons for not doing it. Any insight or suggestions are appreciated.

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  • Cast IEnumerable<Inherited> To IEnumerable<Base>

    - by david2342
    I'm trying to cast an IEnumerable of an inherited type to IEnumerable of base class. Have tried following: var test = resultFromDb.Cast<BookedResource>(); return test.ToList(); But getting error: You cannot convert these types. Linq to Entities only supports conversion primitive EDM-types. The classes involved look like this: public partial class HistoryBookedResource : BookedResource { } public partial class HistoryBookedResource { public int ResourceId { get; set; } public string DateFrom { get; set; } public string TimeFrom { get; set; } public string TimeTo { get; set; } } public partial class BookedResource { public int ResourceId { get; set; } public string DateFrom { get; set; } public string TimeFrom { get; set; } public string TimeTo { get; set; } } [MetadataType(typeof(BookedResourceMetaData))] public partial class BookedResource { } public class BookedResourceMetaData { [Required(ErrorMessage = "Resource id is Required")] [Range(0, int.MaxValue, ErrorMessage = "Resource id is must be an number")] public object ResourceId { get; set; } [Required(ErrorMessage = "Date is Required")] public object DateFrom { get; set; } [Required(ErrorMessage = "Time From is Required")] public object TimeFrom { get; set; } [Required(ErrorMessage = "Time to is Required")] public object TimeTo { get; set; } } The problem I'm trying to solve is to get records from table HistoryBookedResource and have the result in an IEnumerable<BookedResource> using Entity Framework and LINQ. UPDATE: When using the following the cast seams to work but when trying to loop with a foreach the data is lost. resultFromDb.ToList() as IEnumerable<BookedResource>; UPDATE 2: Im using entity frameworks generated model, model (edmx) is created from database, edmx include classes that reprecent the database tables. In database i have a history table for old BookedResource and it can happen that the user want to look at these and to get the old data from the database entity framework uses classes with the same name as the tables to receive data from db. So i receive the data from table HistoryBookedResource in HistoryBookedResource class. Because entity framework generate the partial classes with the properties i dont know if i can make them virtual and override. Any suggestions will be greatly appreciated.

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  • Entities equals() - hashcode() - toString(). How to correctly implement them?

    - by spike07
    I'm implementing equals() - hashcode() - toString() of my Entities using all the available fields in the bean. I'm getting some Lazy init Exception on the frontend when I try to compare the equality or when I print the obj state. That's because some list in the entity can be lazy initialized. I'm wondering what's the correct way to for implementing equals() and toString() on an Entity Obj

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  • OrderBy on children in a LINQ Query

    - by eka808
    Hello everybody I have a user entity who contains a one to many relationship with a role entity So with this linq expression : from user in USER_TABLE.Include("USERROLE_TABLE") order by user.Name select user I can get users with related roles as a child. My problem is that i want to get roles of each user ordered alphabetically. How can i do that ? I googled a lot and don't find anything Thank's by advance !

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  • Capture Stored Procedure print output in .NET (Different model!)

    - by Workshop Alex
    Basically, this question with a difference... Is it possible to capture print output from a TSQL stored procedure in .NET, using the Entity Framework? The solution in the other question doesn't work for me. It works with the connection type from System.Data.SqlClient but I'm using the one from System.Data.EntityClient which does not have an InfoMessage event. (Of course, I could just create an SQL connection based on the Entity connection settings, but prefer to do it directly.)

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  • how to store xml structure in a persistence layer?

    - by fayer
    i wonder how i could store a xml structure in a persistence layer. cause the relational data looks like: <entity id="1000070"> <name>apple</name> <entities> <entity id="7002870"> <name>mac</name> <entities> <entity id="7002907"> <name>leopard</name> <entities> <entity id="7024080"> <name>safari</name> </entity> <entity id="7024701"> <name>finder</name> </entity> </entities> </entity> </entities> </entity> <entity id="7024080"> <name>iphone</name> <entities> <entity id="7024080"> <name>3g</name> </entity> <entity id="7024701"> <name>3gs</name> </entity> </entities> </entity> <entity id="7024080"> <name>ipad</name> </entity> </entities> </entity> as you can see, it has no static structure but a dynamical one. mac got 2 descendant levels while iphone got 1 and ipad got 0. i wonder how i could store this data the best way? what are my options. cause it seems impossible to store it in a mysql database due to this dynamical structure. is the only way to store it as a xml file then? is the speed of getting information (xpath/xquery/simplexml) from a xml file worse or greater than from mysql? what are the pros and cons? do i have other options? is storing information in xml files, suited for a lot of users accessing it at the same time? would be great with feedbacks!! thanks!

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  • Java OO design confusion: how to handle actions modified by states modified by actions...

    - by Arvanem
    Hi folks, Given an entity, whose action is potentially modified by states (of the entity and other entities) in turn potentially modified by other actions (of the entity and other entities) , what is the best way to code or design to handle the potential existence of the modifiers? Speaking metaphorically, I am coding a Java application representing a piano. As you know a piano has keys (which, when pressed, emit sound) and pedals (which, when pressed, modify the keys' sounds). My base class structure is as follows: Entity (for keys and pedals) State (this holds each entity's states, e.g. name such as "soft pedal", and boolean "Pressed"), Action (this holds each entity's actions, e.g. play sound when pressed, or modify others sounds). By composition, the Entity class has a copy of each of State and Action inside it. e.g.: public class Entity { State entityState = new State(); Action entityAction = new Action(); Thus I have coded a "C-Sharp" key Entity. When I "press" that entity (set its "Pressed" state to true), its action plays a "C-Sharp" sound and then sets its "Pressed" state to false. At the same time, if the "C-Sharp" key entity is not "tuned", its sound deviates from "C-Sharp". Meanwhile I have coded a "soft pedal" Entity. When that entity is "pressed", no sound plays but its action is to make softer the sound of the "C-Sharp" and other key entities. I have also coded a "sustain pedal" Entity. When that entity is "pressed", no sound plays but its action is to enable reverberation of the sound of the "C-Sharp" and other key entities. Both the "soft" and "sustain pedals" can be pressed at the same time with the result that keys entities become both softened and reverberating. In short, I do not understand how to make this simultaneous series of states and actions modify each other in a sensible OO way. I am wary of coding a massive series of "if" statements or "switches". Thanks in advance for any help or links you can offer.

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  • remove the blank rows after i removed xml elements?

    - by fayer
    i removed some elements from a xml file with simpledom. the code: $this->xmlDocument->removeNodes("//entity[name='mac']"); here is the initial file: <entity id="1000070"> <name>apple</name> <type>category</type> <entities> <entity id="7002870"> <name>mac</name> <type>category</type> </entity> <entity id="7024080"> <name>iphone</name> <type>category</type> </entity> <entity id="7024080"> <name>ipad</name> <type>category</type> </entity> </entities> </entity> the file afterwards: <entity id="1000070"> <name>apple</name> <type>category</type> <entities> <entity id="7024080"> <name>iphone</name> <type>category</type> </entity> <entity id="7024080"> <name>ipad</name> <type>category</type> </entity> </entities> </entity> i wonder how i could also remove the blank lines that are left after i ran the removal code? thanks!

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  • How do I combine similar method calls into a delegate pattern?

    - by Daniel T.
    I have three methods: public void Save<T>(T entity) { using (new Transaction()) { Session.Save(entity); } } public void Create<T>(T entity) { using (new Transaction()) { Session.Create(entity); } } public void Delete<T>(T entity) { using (new Transaction()) { Session.Delete(entity); } } As you can see, the only thing that differs is the method call inside the using block. How can I rewrite this so it's something like this instead: public void Save<T>(T entity) { TransactionWrapper(Session.Save(entity)); } public void Create<T>(T entity) { TransactionWrapper(Session.Create(entity)); } public void Save<T>(T entity) { TransactionWrapper(Session.Save(entity)); } So in other words, I pass a method call as a parameter, and the TransactionWrapper method wraps a transaction around the method call.

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  • Implementing a generic repository for WCF data services

    - by cibrax
    The repository implementation I am going to discuss here is not exactly what someone would call repository in terms of DDD, but it is an abstraction layer that becomes handy at the moment of unit testing the code around this repository. In other words, you can easily create a mock to replace the real repository implementation. The WCF Data Services update for .NET 3.5 introduced a nice feature to support two way data bindings, which is very helpful for developing WPF or Silverlight based application but also for implementing the repository I am going to talk about. As part of this feature, the WCF Data Services Client library introduced a new collection DataServiceCollection<T> that implements INotifyPropertyChanged to notify the data context (DataServiceContext) about any change in the association links. This means that it is not longer necessary to manually set or remove the links in the data context when an item is added or removed from a collection. Before having this new collection, you basically used the following code to add a new item to a collection. Order order = new Order {   Name = "Foo" }; OrderItem item = new OrderItem {   Name = "bar",   UnitPrice = 10,   Qty = 1 }; var context = new OrderContext(); context.AddToOrders(order); context.AddToOrderItems(item); context.SetLink(item, "Order", order); context.SaveChanges(); Now, thanks to this new collection, everything is much simpler and similar to what you have in other ORMs like Entity Framework or L2S. Order order = new Order {   Name = "Foo" }; OrderItem item = new OrderItem {   Name = "bar",   UnitPrice = 10,   Qty = 1 }; order.Items.Add(item); var context = new OrderContext(); context.AddToOrders(order); context.SaveChanges(); In order to use this new feature, you first need to enable V2 in the data service, and then use some specific arguments in the datasvcutil tool (You can find more information about this new feature and how to use it in this post). DataSvcUtil /uri:"http://localhost:3655/MyDataService.svc/" /out:Reference.cs /dataservicecollection /version:2.0 Once you use those two arguments, the generated proxy classes will use DataServiceCollection<T> rather than a simple ObjectCollection<T>, which was the default collection in V1. There are some aspects that you need to know to use this feature correctly. 1. All the entities retrieved directly from the data context with a query track the changes and report those to the data context automatically. 2. A entity created with “new” does not track any change in the properties or associations. In order to enable change tracking in this entity, you need to do the following trick. public Order CreateOrder() {   var collection = new DataServiceCollection<Order>(this.context);   var order = new Order();   collection.Add(order);   return order; } You basically need to create a collection, and add the entity to that collection with the “Add” method to enable change tracking on that entity. 3. If you need to attach an existing entity (For example, if you created the entity with the “new” operator rather than retrieving it from the data context with a query) to a data context for tracking changes, you can use the “Load” method in the DataServiceCollection. var order = new Order {   Id = 1 }; var collection = new DataServiceCollection<Order>(this.context); collection.Load(order); In this case, the order with Id = 1 must exist on the data source exposed by the Data service. Otherwise, you will get an error because the entity did not exist. These cool extensions methods discussed by Stuart Leeks in this post to replace all the magic strings in the “Expand” operation with Expression Trees represent another feature I am going to use to implement this generic repository. Thanks to these extension methods, you could replace the following query with magic strings by a piece of code that only uses expressions. Magic strings, var customers = dataContext.Customers .Expand("Orders")         .Expand("Orders/Items") Expressions, var customers = dataContext.Customers .Expand(c => c.Orders.SubExpand(o => o.Items)) That query basically returns all the customers with their orders and order items. Ok, now that we have the automatic change tracking support and the expression support for explicitly loading entity associations, we are ready to create the repository. The interface for this repository looks like this,public interface IRepository { T Create<T>() where T : new(); void Update<T>(T entity); void Delete<T>(T entity); IQueryable<T> RetrieveAll<T>(params Expression<Func<T, object>>[] eagerProperties); IQueryable<T> Retrieve<T>(Expression<Func<T, bool>> predicate, params Expression<Func<T, object>>[] eagerProperties); void Attach<T>(T entity); void SaveChanges(); } The Retrieve and RetrieveAll methods are used to execute queries against the data service context. While both methods receive an array of expressions to load associations explicitly, only the Retrieve method receives a predicate representing the “where” clause. The following code represents the final implementation of this repository.public class DataServiceRepository: IRepository { ResourceRepositoryContext context; public DataServiceRepository() : this (new DataServiceContext()) { } public DataServiceRepository(DataServiceContext context) { this.context = context; } private static string ResolveEntitySet(Type type) { var entitySetAttribute = (EntitySetAttribute)type.GetCustomAttributes(typeof(EntitySetAttribute), true).FirstOrDefault(); if (entitySetAttribute != null) return entitySetAttribute.EntitySet; return null; } public T Create<T>() where T : new() { var collection = new DataServiceCollection<T>(this.context); var entity = new T(); collection.Add(entity); return entity; } public void Update<T>(T entity) { this.context.UpdateObject(entity); } public void Delete<T>(T entity) { this.context.DeleteObject(entity); } public void Attach<T>(T entity) { var collection = new DataServiceCollection<T>(this.context); collection.Load(entity); } public IQueryable<T> Retrieve<T>(Expression<Func<T, bool>> predicate, params Expression<Func<T, object>>[] eagerProperties) { var entitySet = ResolveEntitySet(typeof(T)); var query = context.CreateQuery<T>(entitySet); foreach (var e in eagerProperties) { query = query.Expand(e); } return query.Where(predicate); } public IQueryable<T> RetrieveAll<T>(params Expression<Func<T, object>>[] eagerProperties) { var entitySet = ResolveEntitySet(typeof(T)); var query = context.CreateQuery<T>(entitySet); foreach (var e in eagerProperties) { query = query.Expand(e); } return query; } public void SaveChanges() { this.context.SaveChanges(SaveChangesOptions.Batch); } } For instance, you can use the following code to retrieve customers with First name equal to “John”, and all their orders in a single call. repository.Retrieve<Customer>(    c => c.FirstName == “John”, //Where    c => c.Orders.SubExpand(o => o.Items)); In case, you want to have some pre-defined queries that you are going to use across several places, you can put them in an specific class. public static class CustomerQueries {   public static Expression<Func<Customer, bool>> LastNameEqualsTo(string lastName)   {     return c => c.LastName == lastName;   } } And then, use it with the repository. repository.Retrieve<Customer>(    CustomerQueries.LastNameEqualsTo("foo"),    c => c.Orders.SubExpand(o => o.Items));

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  • Entity Framework v1 &ndash; tips and Tricks Part 3

    - by Rohit Gupta
    General Tips on Entity Framework v1 & Linq to Entities: ToTraceString() If you need to know the underlying SQL that the EF generates for a Linq To Entities query, then use the ToTraceString() method of the ObjectQuery class. (or use LINQPAD) Note that you need to cast the LINQToEntities query to ObjectQuery before calling TotraceString() as follows: 1: string efSQL = ((ObjectQuery)from c in ctx.Contact 2: where c.Address.Any(a => a.CountryRegion == "US") 3: select c.ContactID).ToTraceString(); ================================================================================ MARS or MultipleActiveResultSet When you create a EDM Model (EDMX file) from the database using Visual Studio, it generates a connection string with the same name as the name of the EntityContainer in CSDL. In the ConnectionString so generated it sets the MultipleActiveResultSet attribute to true by default. So if you are running the following query then it streams multiple readers over the same connection: 1: using (BAEntities context = new BAEntities()) 2: { 3: var cons = 4: from con in context.Contacts 5: where con.FirstName == "Jose" 6: select con; 7: foreach (var c in cons) 8: { 9: if (c.AddDate < new System.DateTime(2007, 1, 1)) 10: { 11: c.Addresses.Load(); 12: } 13: } 14: } ================================================================================= Explicitly opening and closing EntityConnection When you call ToList() or foreach on a LINQToEntities query the EF automatically closes the connection after all the records from the query have been consumed. Thus if you need to run many LINQToEntities queries over the same connection then explicitly open and close the connection as follows: 1: using (BAEntities context = new BAEntities()) 2: { 3: context.Connection.Open(); 4: var cons = from con in context.Contacts where con.FirstName == "Jose" 5: select con; 6: var conList = cons.ToList(); 7: var allCustomers = from con in context.Contacts.OfType<Customer>() 8: select con; 9: var allcustList = allCustomers.ToList(); 10: context.Connection.Close(); 11: } ====================================================================== Dispose ObjectContext only if required After you retrieve entities using the ObjectContext and you are not explicitly disposing the ObjectContext then insure that your code does consume all the records from the LinqToEntities query by calling .ToList() or foreach statement, otherwise the the database connection will remain open and will be closed by the garbage collector when it gets to dispose the ObjectContext. Secondly if you are making updates to the entities retrieved using LinqToEntities then insure that you dont inadverdently dispose of the ObjectContext after the entities are retrieved and before calling .SaveChanges() since you need the SAME ObjectContext to keep track of changes made to the Entities (by using ObjectStateEntry objects). So if you do need to explicitly dispose of the ObjectContext do so only after calling SaveChanges() and only if you dont need to change track the entities retrieved any further. ======================================================================= SQL InjectionAttacks under control with EFv1 LinqToEntities and LinqToSQL queries are parameterized before they are sent to the DB hence they are not vulnerable to SQL Injection attacks. EntitySQL may be slightly vulnerable to attacks since it does not use parameterized queries. However since the EntitySQL demands that the query be valid Entity SQL syntax and valid native SQL syntax at the same time. So the only way one can do a SQLInjection Attack is by knowing the SSDL of the EDM Model and be able to write the correct EntitySQL (note one cannot append regular SQL since then the query wont be a valid EntitySQL syntax) and append it to a parameter. ====================================================================== Improving Performance You can convert the EntitySets and AssociationSets in a EDM Model into precompiled Views using the edmgen utility. for e.g. the Customer Entity can be converted into a precompiled view using edmgen and all LinqToEntities query against the contaxt.Customer EntitySet will use the precompiled View instead of the EntitySet itself (the same being true for relationships (EntityReference & EntityCollections of a Entity)). The advantage being that when using precompiled views the performance will be much better. The syntax for generating precompiled views for a existing EF project is : edmgen /mode:ViewGeneration /inssdl:BAModel.ssdl /incsdl:BAModel.csdl /inmsl:BAModel.msl /p:Chap14.csproj Note that this will only generate precompiled views for EntitySets and Associations and not for existing LinqToEntities queries in the project.(for that use CompiledQuery.Compile<>) Secondly if you have a LinqToEntities query that you need to run multiple times, then one should precompile the query using CompiledQuery.Compile method. The CompiledQuery.Compile<> method accepts a lamda expression as a parameter, which denotes the LinqToEntities query  that you need to precompile. The following is a example of a lamda that we can pass into the CompiledQuery.Compile() method 1: Expression<Func<BAEntities, string, IQueryable<Customer>>> expr = (BAEntities ctx1, string loc) => 2: from c in ctx1.Contacts.OfType<Customer>() 3: where c.Reservations.Any(r => r.Trip.Destination.DestinationName == loc) 4: select c; Then we call the Compile Query as follows: 1: var query = CompiledQuery.Compile<BAEntities, string, IQueryable<Customer>>(expr); 2:  3: using (BAEntities ctx = new BAEntities()) 4: { 5: var loc = "Malta"; 6: IQueryable<Customer> custs = query.Invoke(ctx, loc); 7: var custlist = custs.ToList(); 8: foreach (var item in custlist) 9: { 10: Console.WriteLine(item.FullName); 11: } 12: } Note that if you created a ObjectQuery or a Enitity SQL query instead of the LINQToEntities query, you dont need precompilation for e.g. 1: An Example of EntitySQL query : 2: string esql = "SELECT VALUE c from Contacts AS c where c is of(BAGA.Customer) and c.LastName = 'Gupta'"; 3: ObjectQuery<Customer> custs = CreateQuery<Customer>(esql); 1: An Example of ObjectQuery built using ObjectBuilder methods: 2: from c in Contacts.OfType<Customer>().Where("it.LastName == 'Gupta'") 3: select c This is since the Query plan is cached and thus the performance improves a bit, however since the ObjectQuery or EntitySQL query still needs to materialize the results into Entities hence it will take the same amount of performance hit as with LinqToEntities. However note that not ALL EntitySQL based or QueryBuilder based ObjectQuery plans are cached. So if you are in doubt always create a LinqToEntities compiled query and use that instead ============================================================ GetObjectStateEntry Versus GetObjectByKey We can get to the Entity being referenced by the ObjectStateEntry via its Entity property and there are helper methods in the ObjectStateManager (osm.TryGetObjectStateEntry) to get the ObjectStateEntry for a entity (for which we know the EntityKey). Similarly The ObjectContext has helper methods to get an Entity i.e. TryGetObjectByKey(). TryGetObjectByKey() uses GetObjectStateEntry method under the covers to find the object, however One important difference between these 2 methods is that TryGetObjectByKey queries the database if it is unable to find the object in the context, whereas TryGetObjectStateEntry only looks in the context for existing entries. It will not make a trip to the database ============================================================= POCO objects with EFv1: To create POCO objects that can be used with EFv1. We need to implement 3 key interfaces: IEntityWithKey IEntityWithRelationships IEntityWithChangeTracker Implementing IEntityWithKey is not mandatory, but if you dont then we need to explicitly provide values for the EntityKey for various functions (for e.g. the functions needed to implement IEntityWithChangeTracker and IEntityWithRelationships). Implementation of IEntityWithKey involves exposing a property named EntityKey which returns a EntityKey object. Implementation of IEntityWithChangeTracker involves implementing a method named SetChangeTracker since there can be multiple changetrackers (Object Contexts) existing in memory at the same time. 1: public void SetChangeTracker(IEntityChangeTracker changeTracker) 2: { 3: _changeTracker = changeTracker; 4: } Additionally each property in the POCO object needs to notify the changetracker (objContext) that it is updating itself by calling the EntityMemberChanged and EntityMemberChanging methods on the changeTracker. for e.g.: 1: public EntityKey EntityKey 2: { 3: get { return _entityKey; } 4: set 5: { 6: if (_changeTracker != null) 7: { 8: _changeTracker.EntityMemberChanging("EntityKey"); 9: _entityKey = value; 10: _changeTracker.EntityMemberChanged("EntityKey"); 11: } 12: else 13: _entityKey = value; 14: } 15: } 16: ===================== Custom Property ==================================== 17:  18: [EdmScalarPropertyAttribute(IsNullable = false)] 19: public System.DateTime OrderDate 20: { 21: get { return _orderDate; } 22: set 23: { 24: if (_changeTracker != null) 25: { 26: _changeTracker.EntityMemberChanging("OrderDate"); 27: _orderDate = value; 28: _changeTracker.EntityMemberChanged("OrderDate"); 29: } 30: else 31: _orderDate = value; 32: } 33: } Finally you also need to create the EntityState property as follows: 1: public EntityState EntityState 2: { 3: get { return _changeTracker.EntityState; } 4: } The IEntityWithRelationships involves creating a property that returns RelationshipManager object: 1: public RelationshipManager RelationshipManager 2: { 3: get 4: { 5: if (_relManager == null) 6: _relManager = RelationshipManager.Create(this); 7: return _relManager; 8: } 9: } ============================================================ Tip : ProviderManifestToken – change EDMX File to use SQL 2008 instead of SQL 2005 To use with SQL Server 2008, edit the EDMX file (the raw XML) changing the ProviderManifestToken in the SSDL attributes from "2005" to "2008" ============================================================= With EFv1 we cannot use Structs to replace a anonymous Type while doing projections in a LINQ to Entities query. While the same is supported with LINQToSQL, it is not with LinqToEntities. For e.g. the following is not supported with LinqToEntities since only parameterless constructors and initializers are supported in LINQ to Entities. (the same works with LINQToSQL) 1: public struct CompanyInfo 2: { 3: public int ID { get; set; } 4: public string Name { get; set; } 5: } 6: var companies = (from c in dc.Companies 7: where c.CompanyIcon == null 8: select new CompanyInfo { Name = c.CompanyName, ID = c.CompanyId }).ToList(); ;

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  • Updating entities in response to collisions - should this be in the collision-detection class or in the entity-updater class?

    - by Prog
    In a game I'm working on, there's a class responsible for collision detection. It's method detectCollisions(List<Entity> entities) is called from the main gameloop. The code to update the entities (i.e. where the entities 'act': update their positions, invoke AI, etc) is in a different class, in the method updateEntities(List<Entity> entities). Also called from the gameloop, after the collision detection. When there's a collision between two entities, usually something needs to be done. For example, zero the velocity of both entities in the collision, or kill one of the entities. It would be easy to have this code in the CollisionDetector class. E.g. in psuedocode: for(Entity entityA in entities){ for(Entity entityB in entities){ if(collision(entityA, entityB)){ if(entityA instanceof Robot && entityB instanceof Robot){ entityA.setVelocity(0,0); entityB.setVelocity(0,0); } if(entityA instanceof Missile || entityB instanceof Missile){ entityA.die(); entityB.die(); } } } } However, I'm not sure if updating the state of entities in response to collision should be the job of CollisionDetector. Maybe it should be the job of EntityUpdater, which runs after the collision detection in the gameloop. Is it okay to have the code responding to collisions in the collision detection system? Or should the collision detection class only detect collisions, report them to some other class and have that class affect the state of the entities?

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  • JPA/JDO entity to XML XSD generator.

    - by h2g2java
    I am using JDO or JPA on GAE plugin in Eclipse. I am using smartgwt datasource, accepting an xsd. I would like to be educated how to generate an XSD from my jdo/jpa entity, vice versa. Is there a tool to do it? While datanucleas does all its magic enhancing in the Eclipse background, would I be able to somehow operate in a mode that would generate XSDs for me? Can Hibernate operate in an offline mode, to solely help me generate XSDs which I could use in GWT without deploying hibernate with my web-app? Can Hibernate even be capable of generating XSDs from entities, vice versa? Currently, I am about to write a utility to generate an xsd, given an entity class - but I am hoping I don't have to reinvent the wheel if it already exists. I am hoping people here could educate me on any available tools to ease my XSD generation. But btw, I am very wary of anything that uses Maven, because most people (like Spring) who write the Maven scripts and pom don't have the expertise to write it in a way that would spew out messages and verbosity appropriately to make it easy for me to locate model errors.

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