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  • Using 'new' in a projection?

    - by davenewza
    I wish to project a collection from one type (Something) to another type (SomethingElse). Yes, this is a very open-eneded question, but which of the two options below do you prefer? Creating a new instance using new: var result = query.Select(something => new SomethingElse(something)); Using a factory: var result = query.Select(something => SomethingElse.FromSomething(something)); When I think of a projection, I generally think of it as a conversion. Using new gives me this idea that I'm creating new objects during a conversion, which doesn't feel right. Semantically, SomethingElse.FromSomething() most definitely fits better. Although, the second option does require addition code to setup a factory, which could become unnecessarily compulsive.

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  • Extension methods on a null object instance – something you did not know

    - by nmarun
    Extension methods gave developers with a lot of bandwidth to do interesting (read ‘cool’) things. But there are a couple of things that we need to be aware of while using these extension methods. I have a StringUtil class that defines two extension methods: 1: public static class StringUtils 2: { 3: public static string Left( this string arg, int leftCharCount) 4: { 5: if (arg == null ) 6: { 7: throw new ArgumentNullException( "arg" ); 8: } 9: return arg.Substring(0, leftCharCount); 10...(read more)

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  • how can I code a recursive query in an Entity Framework model?

    - by Greg
    Hi, I have a model which includes NODES, and RELATIONSHIPS (that tie the nodes together, via a parent_node, child_node arrangement). Q1 - Is there any way in EF / Linq-to-entities to perform a query on nodes (e.g. context.Nodes..) to find say "all parents" or "or children" in the graph? Q2 - If there's not in Linq-to-entities, is there any other way to do this other than writing a method that manually goes through and doing it? Q3 - If manual is the only way to do it, should I be concerned about the number of database hits that will be going out to the database as the method keeps recursing through the data? Or more specifically, is there any EF caching type feature that might assist here in ensuring the method is performance from a "number of database hits" point of view? thanks thanks

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  • EF4, self tracking, repository pattern, SQL Server 2008 AND SQL Server Compact

    - by Darren
    Hi, I am creating a project using Entity Frameworks 4 and self tracking entities. I want to be able to either get the data from a sql server 2008 database or from sql server compact database (with the switch being in the config file). I am using the repository pattern and I will have the self tracking entities sitting in a separate assembly. Do I need two edmx files? If so, how do I generate only one set of STE's in the separate assembly? Also do I need to generate two context classes as well? I am unsure of the plumbing for all this. Can anyone help? Darren I forgot to add that the two databases will be identical and that the compact version is for offline usage.

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  • Dynamic Data with Subsonic 3

    - by Ezequiel Bertti
    i want to make a webproject with Subsonic and Dynamic Data... But when i go register the ContextData a don't have it in subsonic with LINQ... in Global.asax.cs a have to do something like this model.RegisterContext(SubSonicRepo, new ContextConfiguration() { ScaffoldAllTables = true }); how can i make it work? have some way to make it work? using entities or LINQ everything work... but using Subsonic with linq it not work...

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  • Passing integer lists in a sql query, best practices

    - by Artiom Chilaru
    I'm currently looking at ways to pass lists of integers in a SQL query, and try to decide which of them is best in which situation, what are the benefots of each, and what are the pitfalls, what should be avoided :) Right now I know of 3 ways that we currently use in our application. 1) Table valued parameter: Create a new Table Valued Parameter in sql server: CREATE TYPE [dbo].[TVP_INT] AS TABLE( [ID] [int] NOT NULL ) Then run the query against it: using (var conn = new SqlConnection(DataContext.GetDefaultConnectionString)) { var comm = conn.CreateCommand(); comm.CommandType = CommandType.Text; comm.CommandText = @" UPDATE DA SET [tsLastImportAttempt] = CURRENT_TIMESTAMP FROM [Account] DA JOIN @values IDs ON DA.ID = IDs.ID"; comm.Parameters.Add(new SqlParameter("values", downloadResults.Select(d => d.ID).ToDataTable()) { TypeName = "TVP_INT" }); conn.Open(); comm.ExecuteScalar(); } The major disadvantages of this method is the fact that Linq doesn't support table valued params (if you create an SP with a TVP param, linq won't be able to run it) :( 2) Convert the list to Binary and use it in Linq! This is a bit better.. Create an SP, and you can run it within linq :) To do this, the SP will have an IMAGE parameter, and we'll be using a user defined function (udf) to convert this to a table.. We currently have implementations of this function written in C++ and in assembly, both have pretty much the same performance :) Basically, each integer is represented by 4 bytes, and passed to the SP. In .NET we have an extension method that convers an IEnumerable to a byte array The extension method: public static Byte[] ToBinary(this IEnumerable intList) { return ToBinaryEnum(intList).ToArray(); } private static IEnumerable<Byte> ToBinaryEnum(IEnumerable<Int32> intList) { IEnumerator<Int32> marker = intList.GetEnumerator(); while (marker.MoveNext()) { Byte[] result = BitConverter.GetBytes(marker.Current); Array.Reverse(result); foreach (byte b in result) yield return b; } } The SP: CREATE PROCEDURE [Accounts-UpdateImportAttempts] @values IMAGE AS BEGIN UPDATE DA SET [tsLastImportAttempt] = CURRENT_TIMESTAMP FROM [Account] DA JOIN dbo.udfIntegerArray(@values, 4) IDs ON DA.ID = IDs.Value4 END And we can use it by running the SP directly, or in any linq query we need using (var db = new DataContext()) { db.Accounts_UpdateImportAttempts(downloadResults.Select(d => d.ID).ToBinary()); // or var accounts = db.Accounts .Where(a => db.udfIntegerArray(downloadResults.Select(d => d.ID).ToBinary(), 4) .Select(i => i.Value4) .Contains(a.ID)); } This method has the benefit of using compiled queries in linq (which will have the same sql definition, and query plan, so will also be cached), and can be used in SPs as well. Both these methods are theoretically unlimited, so you can pass millions of ints at a time :) 3) The simple linq .Contains() It's a more simple approach, and is perfect in simple scenarios. But is of course limited by this. using (var db = new DataContext()) { var accounts = db.Accounts .Where(a => downloadResults.Select(d => d.ID).Contains(a.ID)); } The biggest drawback of this method is that each integer in the downloadResults variable will be passed as a separate int.. In this case, the query is limited by sql (max allowed parameters in a sql query, which is a couple of thousand, if I remember right). So I'd like to ask.. What do you think is the best of these, and what other methods and approaches have I missed?

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  • Import Namespace System.Query

    - by GateKiller
    I am trying to load Linq on my .Net 3.5 enabled web server by adding the following to my .aspx page: <%@ Import Namespace="System.Query" %> However, this fails and tells me it cannot find the namespace. The type or namespace name 'Query' does not exist in the namespace 'System' I have also tried with no luck: System.Data.Linq System.Linq System.Xml.Linq I believe that .Net 3.5 is working because var hello = "Hello World" seems to work. Can anyone help please? Cheers, Stephen PS: I just want to clarify that I don't use Visual Studio, I simple have a Text Editor and write my code directly into .aspx files.

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  • LinqKit stack overflow exception using predicate builder

    - by MLynn
    I am writing an application in C# using LINQ and LINQKit. I have a very large database table with company registration numbers in it. I want to do a LINQ query which will produce the equivalent SQL: select * from table1 where regno in('123','456') The 'in' clause may have thousands of terms. First I get the company registration numbers from a field such as Country. I then add all the company registration numbers to a predicate: var predicate = PredicateExtensions.False<table2>(); if (RegNos != null) { foreach (int searchTerm in RegNos) { int temp = searchTerm; predicate = predicate.Or(ec => ec.regno.Equals(temp)); } } On Windows Vista Professional a stack overflow exception occured after 4063 terms were added. On Windows Server 2003 a stack overflow exception occured after about 1000 terms were added. I had to solve this problem quickly for a demo. To solve the problem I used this notation: var predicate = PredicateExtensions.False<table2>(); if (RegNosDistinct != null) { predicate = predicate.Or(ec => RegNos.Contains(ec.regno)); } My questions are: Why does a stack overflow occur using the foreach loop? I take it Windows Server 2003 has a much smaller stack per process\thread than NT\2000\XP\Vista\Windows 7 workstation versions of Windows. Which is the fastest and most correct way to achieve this using LINQ and LINQKit? It was suggested I stop using LINQ and go back to dynamic SQL or ADO.NET but I think using LINQ and LINQKit is far better for maintainability.

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  • Converting HTML special characters into their value using Python

    - by tipu
    I have a file that's littered with these: http://www.utexas.edu/learn/html/spchar.html That link just displays all sorts of HTML entities, such as – &ndash; — &mdash; ¡ &iexcl; and so on. Is it possible in Python to natively convert these characters back into their values so any occurrences of &ndash; will appear as – instead? My current approach was just to make a dict of key html entities and their utf-8 values and do search and replace, but I was wondering if there are any libraries that can take care of this for me.

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  • Best practice. Do I save html tags in DB or store the html entity value?

    - by Matt
    Hi Guys, I was wondering about which way i should do the following. I am using the tiny MCE wysiwyg editor which formats the users data with the right html tags. Now, i need to save this data entered into the editor into a database table. Should I encode the html tags to their corresponding entities when inserting into the DB, then when i get the data back from the table, not have the encode it for XSS purposes but I'd still have to use eval for the html tags to format the text. OR Do i save the html tags into the database, then when i get the data back from the database encode the html tags to their entities, but then as the tags will appear to the user, I'd have to use the eval function to actually format the data as it was entered. My thoughts are with the first option, I just wondered on what you guys thought.

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  • PHP: best practice. Do i save html tags in DB or store the html entity value?

    - by Matt
    Hi Guys, I was wondering about which way i should do the following. I am using the tiny MCE wysiwyg editor which formats the users data with the right html tags. Now, i need to save this data entered into the editor into a database table. Should i encode the html tags to their corresponding entities when inserting into the DB, then when i get the data back from the table, not have the encode it for XSS purposes but i'd still have to use eval for the html tags to format the text. OR Do i save the html tags into the database, then when i get the data back from the database encode the html tags to their entities, but then as the tags will appear to the user, i'd have to use the eval function to actually format the data as it was entered. My thoughts are with the first option, i just wondered on what you guys thought. Thanks M

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  • extracting only elements with text (or value)

    - by guy
    hay all. i am trying to transform html to xml meaning extracting all elements with text using this code is not working maybe some one has the answer ? System.Xml.Linq.XElement query1 = new System.Xml.Linq.XElement("RawHTMLData", from q in hDoc.Descendants("TABLE") where q.HasElements select new System.Xml.Linq.XElement("TABLE" + (++i).ToString(), from j in q.Elements("TR") where j.HasElements && j.Descendants("div") != null select new System.Xml.Linq.XElement("Row", from hh in j.Descendants("div") where tt => j.Descendants("div").Contains(hh.Value) select(TT(hh)))));

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  • Leave entity intact in XML + XSLT

    - by Kuroki Kaze
    I transform XML to (sort of) HTML with XSL stylesheets (using Apache Xalan). In XML there can be entities like &mdash;, which must be left as is. In beginning of XML file I have a doctype which references these entities. What should I do for entity to be left unchanged? <!DOCTYPE article [ <!ENTITY mdash "&mdash;"><!-- em dash --> ]> gives me SAXParseException: Recursive entity expansion, 'mdash' when encountering &mdash in XML text.

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  • How to reflect over T to build an expression tree for a query?

    - by Alex
    Hi all, I'm trying to build a generic class to work with entities from EF. This class talks to repositories, but it's this class that creates the expressions sent to the repositories. Anyway, I'm just trying to implement one virtual method that will act as a base for common querying. Specifically, it will accept a an int and it only needs to perform a query over the primary key of the entity in question. I've been screwing around with it and I've built a reflection which may or may not work. I say that because I get a NotSupportedException with a message of LINQ to Entities does not recognize the method 'System.Object GetValue(System.Object, System.Object[])' method, and this method cannot be translated into a store expression. So then I tried another approach and it produced the same exception but with the error of The LINQ expression node type 'ArrayIndex' is not supported in LINQ to Entities. I know it's because EF will not parse the expression the way L2S will. Anyway, I'm hopping someone with a bit more experience can point me into the right direction on this. I'm posting the entire class with both attempts I've made. public class Provider<T> where T : class { protected readonly Repository<T> Repository = null; private readonly string TEntityName = typeof(T).Name; [Inject] public Provider( Repository<T> Repository) { this.Repository = Repository; } public virtual void Add( T TEntity) { this.Repository.Insert(TEntity); } public virtual T Get( int PrimaryKey) { // The LINQ expression node type 'ArrayIndex' is not supported in // LINQ to Entities. return this.Repository.Select( t => (((int)(t as EntityObject).EntityKey.EntityKeyValues[0].Value) == PrimaryKey)).Single(); // LINQ to Entities does not recognize the method // 'System.Object GetValue(System.Object, System.Object[])' method, // and this method cannot be translated into a store expression. return this.Repository.Select( t => (((int)t.GetType().GetProperties().Single( p => (p.Name == (this.TEntityName + "Id"))).GetValue(t, null)) == PrimaryKey)).Single(); } public virtual IList<T> GetAll() { return this.Repository.Select().ToList(); } protected virtual void Save() { this.Repository.Update(); } }

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  • DeleteOnSubmit doesnt exist?

    - by Anders Metnik
    using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Data; Thats my namespaces.. i was looking for System.Data.Linq; but it doesnt seem to be anywhere, and i guess that is what have been moved to System.Linq, since i have access to most other things in Linq. EDIT: found System.Data:Linq, no difference Here is my method: public void deleteStudienummer(int studienummer) { dbcontent = new DBEntities(); var dQry = from members in dbcontent.Medlemmer where members.Studienummer == studienummer select members; foreach (var member in dQry) { dbcontent.*** } dbcontent.AcceptAllChanges(); Console.WriteLine("delete member should have occured"); } The * was supposed to be DeleteOnSubmit, but i only have DeleteDatabase and DeleteObject, i tried with object but it doesnt work.. Have also tried dbcontent.Medlemmer.* but still not present. And AcceptAllChanges() was supposed to be .submitChanges() but that wasnt present either.

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  • DDD: Where to create entity objects?

    - by ciscoheat
    I have three entities that must interact: User, SupportTicketand PhoneConversation. When someone calls in requesting help, the User should have a SupportTicket assigned to him, with a PhoneConversation assigned to the Ticked describing the call. My question is: In what entity should I put the method CreatePhoneSupportTicket() that creates a new SupportTicket and a PhoneConversation, relates them to each other and finally relates the SupportTicket to the User? I'm guessing it can't be on the user because that would violate the SRP (the user does a few more things). But the method itself does more than one thing, it should create both a SupportTicket and a PhoneConversation. Is this a situation when a Service is a better solution then putting methods on entities? Thanks for your help!

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  • LINQ. Grouping by days. How to do this easily?

    - by punkouter
    I can't seem to find any god reference on this. I have alot of data in SQL with dates. So I wanted to make a line chart to show this data over time. If I want to show it over a perioud of days then I need to group by days.. But the LOGDATE is the full date.. not the DAY.. So I have this below.. but LINQ doesnt know what 'DayOfYear' property is.. HELP var q = from x in dc.ApplicationLogs let dt = x.LogDate group x by new { dayofyear = dt.Value.DayOfYear } into g select new { iCount = g.Count(), strDate = g.Key };

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  • ASP.NET MVC 2 - Saving child entities on form submit

    - by Justin
    Hey, I'm using ASP.NET MVC 2 and am struggling with saving child entities. I have an existing Invoice entity (which I create on a separate form) and then I have a LogHours view that I'd like to use to save InvoiceLog's, which are child entities of Invoice. Here's the view: <%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<TothSolutions.Data.Invoice>" %> <asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server"> Log Hours </asp:Content> <asp:Content ID="Content3" ContentPlaceHolderID="HeadContent" runat="server"> <script type="text/javascript"> $(document).ready(function () { $("#InvoiceLogs_0__Description").focus(); }); </script> </asp:Content> <asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server"> <h2>Log Hours</h2> <% using (Html.BeginForm("SaveHours", "Invoices")) {%> <%: Html.ValidationSummary(true) %> <fieldset> <legend>Fields</legend> <table> <tr> <th>Date</th> <th>Description</th> <th>Hours</th> </tr> <% int index = 0; foreach (var log in Model.InvoiceLogs) { %> <tr> <td><%: log.LogDate.ToShortDateString() %></td> <td><%: Html.TextBox("InvoiceLogs[" + index + "].Description")%></td> <td><%: Html.TextBox("InvoiceLogs[" + index + "].Hours")%></td> <td>Hours</td> </tr> <% index++; } %> </table> <p> <%: Html.Hidden("InvoiceID") %> <%: Html.Hidden("CreateDate") %> <input type="submit" value="Save" /> </p> </fieldset> <% } %> <div> <%: Html.ActionLink("Back to List", "Index") %> </div> </asp:Content> And here's the controller code: //GET: /Secure/Invoices/LogHours/ public ActionResult LogHours(int id) { var invoice = DataContext.InvoiceData.Get(id); if (invoice == null) { throw new Exception("Invoice not found with id: " + id); } return View(invoice); } //POST: /Secure/Invoices/SaveHours/ [AcceptVerbs(HttpVerbs.Post)] public ActionResult SaveHours([Bind(Exclude = "InvoiceLogs")]Invoice invoice) { TryUpdateModel(invoice.InvoiceLogs, "InvoiceLogs"); invoice.UpdateDate = DateTime.Now; invoice.DeveloperID = DeveloperID; //attaching existing invoice. DataContext.InvoiceData.Attach(invoice); //save changes. DataContext.SaveChanges(); //redirect to invoice list. return RedirectToAction("Index"); } And the data access code: public static void Attach(Invoice invoice) { var i = new Invoice { InvoiceID = invoice.InvoiceID }; db.Invoices.Attach(i); db.Invoices.ApplyCurrentValues(invoice); } In the SaveHours action, it properly sets the values of the InvoiceLog entities after I call TryUpdateModel but when it does SaveChanges it doesn't update the database with the new values. Also, if you manually update the values of the InvoiceLog entries in the database and then go to this page it doesn't populate the textboxes so it's clearly not binding correctly. Thanks, Justin

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  • nhibernate cascade - problem with detached entities

    - by Chev
    I am going nuts here trying to resolve a cascading update/delete issue :-) I have a Parent Entity with a collection Child Entities. If I modify the list of Child entities in a detached Parent object, adding, deleting etc - I am not seeing the updates cascaded correctly to the Child collection. Mapping Files: <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="Domain" namespace="Domain"> <class name="Parent" table="Parent" > <id name="Id"> <generator class="guid.comb" /> </id> <version name="LastModified" unsaved-value="0" column="LastModified" /> <property name="Name" type="String" length="250" /> <bag name="ParentChildren" lazy="false" table="Parent_Children" cascade="all-delete-orphan" inverse="true"> <key column="ParentId" on-delete="cascade" /> <one-to-many class="ParentChildren" /> </bag> </class> <class name="ParentChildren" table="Parent_Children"> <id name="Id"> <generator class="guid.comb" /> </id> <version name="LastModified" unsaved-value="0" column="LastModified" /> <many-to-one name="Parent" class="Parent" column="ParentId" lazy="false" not-null="true" /> </class> </hibernate-mapping> Test [Test] public void Test() { Guid id; int lastModified; // add a child into 1st session then detach using(ISession session = Store.Local.Get<ISessionFactory>("SessionFactory").OpenSession()) { Console.Out.WriteLine("Selecting..."); Parent parent = (Parent) session.Get(typeof (Parent), new Guid("4bef7acb-bdae-4dd0-ba1e-9c7500f29d47")); id = parent.Id; lastModified = parent.LastModified + 1; // ensure the detached version used later is equal to the persisted version Console.Out.WriteLine("Adding Child..."); Child child = (from c in session.Linq<Child>() select c).First(); parent.AddChild(child, 0m); session.Flush(); session.Dispose(); // not needed i know } // attach a parent, then save with no Children using (ISession session = Store.Local.Get<ISessionFactory>("SessionFactory").OpenSession()) { Parent parent = new Parent("Test"); parent.Id = id; parent.LastModified = lastModified; session.Update(parent); session.Flush(); } } I assume that the fact that the product has been updated to have no children in its collection - the children would be deleted in the Parent_Child table. The problems seems to be something to do with attaching the Product to the new session? As the cascade is set to all-delete-orphan I assume that changes to the collection would be propagated to the relevant entities/tables? In this case deletes? What am I missing here? C

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  • Please clarify how create/update happens against child entities of an aggregate root

    - by christian
    After much reading and thinking as I begin to get my head wrapped around DDD, I am a bit confused about the best practices for dealing with complex hierarchies under an aggregate root. I think this is a FAQ but after reading countless examples and discussions, no one is quite talking about the issue I'm seeing. If I am aligned with the DDD thinking, entities below the aggregate root should be immutable. This is the crux of my trouble, so if that isn't correct, that is why I'm lost. Here is a fabricated example...hope it holds enough water to discuss. Consider an automobile insurance policy (I'm not in insurance, but this matches the language I hear when on the phone w/ my insurance company). Policy is clearly an entity. Within the policy, let's say we have Auto. Auto, for the sake of this example, only exists within a policy (maybe you could transfer an Auto to another policy, so this is potential for an aggregate as well, which changes Policy...but assume it simpler than that for now). Since an Auto cannot exist without a Policy, I think it should be an Entity but not a root. So Policy in this case is an aggregate root. Now, to create a Policy, let's assume it has to have at least one auto. This is where I get frustrated. Assume Auto is fairly complex, including many fields and maybe a child for where it is garaged (a Location). If I understand correctly, a "create Policy" constructor/factory would have to take as input an Auto or be restricted via a builder to not be created without this Auto. And the Auto's creation, since it is an entity, can't be done beforehand (because it is immutable? maybe this is just an incorrect interpretation). So you don't get to say new Auto and then setX, setY, add(Z). If Auto is more than somewhat trivial, you end up having to build a huge hierarchy of builders and such to try to manage creating an Auto within the context of the Policy. One more twist to this is later, after the Policy is created and one wishes to add another Auto...or update an existing Auto. Clearly, the Policy controls this...fine...but Policy.addAuto() won't quite fly because one can't just pass in a new Auto (right!?). Examples say things like Policy.addAuto(VIN, make, model, etc.) but are all so simple that that looks reasonable. But if this factory method approach falls apart with too many parameters (the entire Auto interface, conceivably) I need a solution. From that point in my thinking, I'm realizing that having a transient reference to an entity is OK. So, maybe it is fine to have a entity created outside of its parent within the aggregate in a transient environment, so maybe it is OK to say something like: auto = AutoFactory.createAuto(); auto.setX auto.setY or if sticking to immutability, AutoBuilder.new().setX().setY().build() and then have it get sorted out when you say Policy.addAuto(auto) This insurance example gets more interesting if you add Events, such as an Accident with its PolicyReports or RepairEstimates...some value objects but most entities that are all really meaningless outside the policy...at least for my simple example. The lifecycle of Policy with its growing hierarchy over time seems the fundamental picture I must draw before really starting to dig in...and it is more the factory concept or how the child entities get built/attached to an aggregate root that I haven't seen a solid example of. I think I'm close. Hope this is clear and not just a repeat FAQ that has answers all over the place.

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  • Data Transfer Objects VS Domain/ActiveRecord Entities in the View in RoR

    - by leypascua
    I'm coming from a .NET background, where it is a practice to not bind domain/entity models directly to the view in not-so-basic CRUD-ish applications where the view does not directly project entity fields as-is. I'm wondering what's the practice in RoR, where the default persistence mechanism is ActiveRecord. I would assert that presentation-related info should not be leaked to the entities, not sure though if this is how real RoR heads would do it. If DTOs/model per view is the approach, how will you do it in Rails? Your thoughts? EDIT: Some examples: - A view shows a list of invoices, with the number of unique items in one column. - A list of credit card accounts, where possibly fraudulent transactions were executed. For that, the UI needs to show this row in red. For both scenarios, The lists don't show all of the fields of the entities, just a few to show in the list (like invoice #, transaction date, name of the account, the amount of the transaction) For the invoice example, The invoice entity doesn't have a field "No. of line items" mapped on it. The database has not been denormalized for perf reasons and it will be computed during query time using aggregate functions. For the credit card accounts example, surely the card transaction entity doesn't have a "Show-in-red" or "IsFraudulent" invariant. Yes it may be a business rule, but for this example, that is a presentation concern, so I would like to keep it out of my domain model.

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  • Data sharing amongst JPA Entities

    - by Nick
    Setup: I have a simple web app that has a handfull of forms, each on a separate page. These forms represent patient data. There is a one-to-one relationship between patient and all these forms/entities. Each form maps directly to a db table and a JPA entity, maybe not the best architecture but it works and is simple. Question: If form/entity A and form/entity B share a common chunk of data (one of more fields), what is the best way to handle that in JPA. I.E. - If the data gets inserted via form A, I need it to show up in form B as existing data and vice versa. In other words its logical for both entities to contain that data. I believe I will have to move the common data into its own entity and define the relationships that way, but I have tried many different ways and none gets me all the way, at least with basic JPA. Can this be done through pure JPA relationships or will I have to write a bunch of code to make this happen manually. Not looking for code specifically, just the correct way to model this data. Thanks.

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  • Entity Framework - Insert/Update new entity with child-entities

    - by Christina Mayers
    I have found many questions here on SO and articles all over the internet but none really tackled my problem. My model looks like this (I striped all non essential Properties): Everyday or so "Play" gets updated (via a XML-file containing the information). internal Play ParsePlayInfo(XDocument doc) { Play play = (from p in doc.Descendants("Play") select new Play { Theatre = new Theatre() { //Properties }, //Properties LastUpdate = DateTime.Now }).SingleOrDefault(); var actors = (from a in doc.XPathSelectElement(".//Play//Actors").Nodes() select new Lecturer() { //Properties }); var parts = (from p in doc.XPathSelectElement(".//Play//Parts").Nodes() select new Part() { //Properties }).ToList(); foreach (var item in parts) { play.Parts.Add(item); } var reviews = (from r in doc.XPathSelectElement(".//Play//Reviews").Nodes() select new Review { //Properties }).ToList(); for (int i = 0; i < reviews.Count(); i++) { PlayReviews pR = new PlayReviews() { Review = reviews[i], Play = play, //Properties }; play.PlayReviews.Add(pR); } return play; } If I add this "play" via Add() every Childobject of Play will be inserted - regardless if some exist already. Since I need to update existing entries I have to do something about that. As far as I can tell I have the following options: add/update the child entities in my PlayRepositories Add-Method restructure and rewrite ParsePlayInfo() so that get all the child entities first, add or update them and then create a new Play. The only problem I have here is that I wanted ParsePlayInfo() to be persistence ignorant, I could work around this by creating multiple parse methods (eg ParseActors() ) and assign them to play in my controller (I'm using ASP.net MVC) after everything was parsed and added Currently I am implementing option 1 - but it feels wrong. I'd appreciate it if someone could guide me in the right direction on this one.

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  • Loading child entities with JPA on Google App Engine

    - by Phil H
    I am not able to get child entities to load once they are persisted on Google App Engine. I am certain that they are saving because I can see them in the datastore. For example if I have the following two entities. public class Parent implements Serializable{ @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Extension(vendorName="datanucleus", key="gae.encoded-pk", value="true") private String key; @OneToMany(cascade=CascadeType.ALL) private List<Child> children = new ArrayList<Child>(); //getters and setters } public class Child implements Serializable{ @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Extension(vendorName="datanucleus", key="gae.encoded-pk", value="true") private String key; private String name; @ManyToOne private Parent parent; //getters and setters } I can save the parent and a child just fine using the following: Parent parent = new Parent(); Child child = new Child(); child.setName("Child Object"); parent.getChildren().add(child); em.persist(parent); However when I try to load the parent and then try to access the children (I know GAE lazy loads) I do not get the child records. //parent already successfully loaded parent.getChildren.size(); // this returns 0 I've looked at tutorial after tutorial and nothing has worked so far. I'm using version 1.3.3.1 of the SDK. I've seen the problem mentioned on various blogs and even the App Engine forums but the answer is always JDO related. Am I doing something wrong or has anyone else had this problem and solved it for JPA?

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