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• ViewModel updates after Model server roundtrip

  - by Pavel Savara

  I have stateless services and anemic domain objects on server side. Model between server and client is POCO DTO. The client should become MVVM. The model could be graph of about 100 instances of 20 different classes. The client editor contains diverse tab-pages all of them live-connected to model/viewmodel. My problem is how to propagate changes after server round-trip nice way. It's quite easy to propagate changes from ViewModel to DTO. For way back it would be possible to throw away old DTO and replace it whole with new one, but it will cause lot of redrawing for lists/DataTemplates. I could gather the server side changes and transmit them to client side. But the names of fields changed would be domain/DTO specific, not ViewModel specific. And the mapping seems nontrivial to me. If I should do it imperative way after round-trip, it would break SOC/modularity of viewModels. I'm thinking about some kind of mapping rule engine, something like automappper or emit mapper. But it solves just very plain use-cases. I don't see how it would map/propagate/convert adding items to list or removal. How to identify instances in collections so it could merge values to existing instances. As well it should propagate validation/error info. Maybe I should implement INotifyPropertyChanged on DTO and try to replay server side events on it ? And then bind ViewModel to it ? Would binding solve the problems with collection merges nice way ? Is EventAgregator from PRISM useful for that ? Is there any event record-replay component ? Is there better client side pattern for architecture with server side logic ?

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• WPF Textbox & Borders - curious resizing behavior

  - by CitizenParker

  The following XAML produces a window with strange behavior around the textbox: <Window x:Class="WpfSandbox.CuriousExample" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="CuriousExample" Height="300" Width="300"> <DockPanel Margin="15"> <TextBox BorderThickness="1" BorderBrush="#FF000000"></TextBox> </DockPanel> </Window> What happens, at least during my limited testing, is that the textbox renders with an inset border pattern (top/left is black, right/bottom is grey). However, when you resize to any position except the original, the entire textbox border goes to black. Whenever you return the window to the exact number of on-screen pixels the form had when it first loaded, it's inset again. I'm guessing it isn't pixel snapping as I can easily correct the problem with this code: <Window x:Class="WpfSandbox.CuriousExample" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="CuriousExample" Height="300" Width="300"> <DockPanel Margin="15"> <Border BorderThickness="1" BorderBrush="#FF000000"> <TextBox BorderThickness="0" ></TextBox> </Border> </DockPanel> </Window> Anyone care to venture an explanation as to what I'm seeing? Or is it all in my head? Like I said, the above workaround can resolve this problem - just trying to understand what is happening here. Thanks, -Scott

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• Naming convention for non-virtual and abstract methods

  - by eagle

  I frequently find myself creating classes which use this form (A): abstract class Animal { public void Walk() { // TODO: do something before walking // custom logic implemented by each subclass WalkInternal(); // TODO: do something after walking } protected abstract void WalkInternal(); } class Dog : Animal { protected override void WalkInternal() { // TODO: walk with 4 legs } } class Bird : Animal { protected override void WalkInternal() { // TODO: walk with 2 legs } } Rather than this form (B): abstract class Animal { public abstract void Walk(); } class Dog : Animal { public override void Walk() { // TODO: do something before walking // custom logic implemented by each subclass // TODO: walk with 4 legs // TODO: do something after walking } } class Bird : Animal { public override void Walk() { // TODO: do something before walking // custom logic implemented by each subclass // TODO: walk with 2 legs // TODO: do something after walking } } As you can see, the nice thing about form A is that every time you implement a subclass, you don't need to remember to include the initialization and finalization logic. This is much less error prone than form B. What's a standard convention for naming these methods? I like naming the public method Walk since then I can call Dog.Walk() which looks better than something like Dog.WalkExternal(). However, I don't like my solution of adding the suffix "Internal" for the protected method. I'm looking for a more standardized name. Btw, is there a name for this design pattern?

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• Strip parity bits in C from 8 bits of data followed by 1 parity bit

  - by dubnde

  I have a buffer of bits with 8 bits of data followed by 1 parity bit. This pattern repeats itself. The buffer is currently stored as an array of octets. Example (p are parity bits): 0001 0001 p000 0100 0p00 0001 00p01 1100 ... should become 0001 0001 0000 1000 0000 0100 0111 00 ... Basically, I need to strip of every ninth bit to just obtain the data bits. How can I achieve this? This is related to another question asked here sometime back. This is on a 32 bit machine so the solution to the related question may not be applicable. The maximum possible number of bits is 45 i.e. 5 data octets This is what I have tried so far. I have created a "boolean" array and added the bits into the array based on the the bitset of the octet. I then look at every ninth index of the array and through it away. Then move the remaining array down one index. Then I've got only the data bits left. I was thinking there may be better ways of doing this.

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• How to not pass around the container when using IoC in Winforms

  - by L2Type

  I'm new to the world of IoC and having a problem with implementing it in a Winforms application. I have an extremely basic application Winform application that uses MVC, it is one controller that does all the work and a working dialog (obviously with a controller). So I load all my classes in to my IoC container in program.cs and create the main form controller using the container. But this is where I am having problems, I only want to create the working dialog controller when it's used and inside a using statement. At first I passed in the container but I've read this is bad practice and more over the container is a static and I want to unit test this class. So how do you create classes in a unit test friendly way without passing in the container, I was considering the abstract factory pattern but that alone would solve my problem without using the IoC. I'm not using any famous framework, I borrowed a basic one from this blog post http://www.kenegozi.com/Blog/2008/01/17/its-my-turn-to-build-an-ioc-container-in-15-minutes-and-33-lines.aspx How do I do this with IoC? Is this the wrong use for IoC?

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• problem generating pgp keys?

  - by pavankumar

  I'm using RSACryptoServiceProvider I've generated public key and private key. The keys generated by it are in the following format: Public key: <RSAKeyValue> <Modulus>m9bAoh2...eGNKYs=</Modulus> <Exponent>AQAB</Exponent> </RSAKeyValue> Private key: <RSAKeyValue> <Modulus>m9bAo...ZAIeGNKYs=</Modulus> <Exponent>AQAB</Exponent> <P>xGj/UcXs...R1lmeVQ==</P> <Q>yx6e18aP...GXzXIXw==</Q> <DP>NyxvnJ...1xAsEyQ==</DP> <DQ>La17Jycd...FhApEqwznQ==</DQ> <InverseQ>JrG7WCT...Hp3OWA==</InverseQ> <D>RdWsOFn....KL699Vh6HK0=</D> </RSAKeyValue> but using PGP Desktop i've generated keys like this - Public key: mQCNBEoOlp8BBACi/3EvBZ83ZduvG6YHu5F0P7Z3xOnpIsaPvTk0q+dnjwDUa5sU lEFbUZgDXSz7ZRhyiNqUOy+IG3ghPxpiKGBtldVpi33qaFCCEBiqsxRRpVCLgTUK HP2kH5ysrlFWkxTo =a4t9 Private key: lQHgBEoOlp8BBACi/3EvBZ83ZduvG6YHu5F0P7Z3xOnpIsaPvTk0q+dnjwDUa5sU lEFbUZgDXSz7ZRhyiNqUOy+IG3ghPxpiKGBtldVpi33qaFCCEBiqsxRRpVCLgTUK waBnEitQti3XgUUEZnz/rnXcQVM0QFBe6H5x8fMDUw== =CVPD So when I'm passing the keys generated by PGP Desktop it is able to do encryption and decryption perfectly but when im passing the keys generated by RSACryptoServiceProvider I'm not able to encrypt and decrypt? Can anyone please tell me how to generate keys in the pattern generated by PGP?

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• How to avoid game rendering component circular references?

  - by CodexArcanum

  I'm working on a simple game design, and I wanted to break up my game objects into more reusable components. But I'm getting stuck on how exactly to implement the design I have in mind. Here's an example: I have a Logger object, whose job is simply to store a list of messages and render them to screen. You know, logging. Originally the Logger just held the list, and the game loop rendered it's contents. Then I moved the rendering logic into the Logger.Draw() method, and now I want to move it further into a LoggerRenderer object. In effect, I want to have the game loop call RenderAll, which will then call Logger.Render, which will in turn call the LoggerRenderer.Render and finally output the text. So the Logger needs to contain a Renderer object, but the Renderer needs access to the Logger's state (the message queue) in order to render. How do I resolve that? Should I be passing in the message queue and other state information explicitly to the Render method? Or should the game loop be calling the Renderer directly and it links back to the logger, but the RenderAll method never actually sees the logger object itself? This feels kind of like Command pattern, but I'm botching it up terribly.

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• Q on Python serialization/deserialization

  - by neil

  What chances do I have to instantiate, keep and serialize/deserialize to/from binary data Python classes reflecting this pattern (adopted from RFC 2246 [TLS]): enum { apple, orange } VariantTag; struct { uint16 number; opaque string<0..10>; /* variable length */ } V1; struct { uint32 number; opaque string[10]; /* fixed length */ } V2; struct { select (VariantTag) { /* value of selector is implicit */ case apple: V1; /* VariantBody, tag = apple */ case orange: V2; /* VariantBody, tag = orange */ } variant_body; /* optional label on variant */ } VariantRecord; Basically I would have to define a (variant) class VariantRecord, which varies depending on the value of VariantTag. That's not that difficult. The challenge is to find a most generic way to build a class, which serializes/deserializes to and from a byte stream... Pickle, Google protocol buffer, marshal is all not an option. I made little success with having an explicit "def serialize" in my class, but I'm not very happy with it, because it's not generic enough. I hope I could express the problem. My current solution in case VariantTag = apple would look like this, but I don't like it too much import binascii import struct class VariantRecord(object): def __init__(self, number, opaque): self.number = number self.opaque = opaque def serialize(self): out = struct.pack('>HB%ds' % len(self.opaque), self.number, len(self.opaque), self.opaque) return out v = VariantRecord(10, 'Hello') print binascii.hexlify(v.serialize()) >> 000a0548656c6c6f Regards

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• NHibernate Session per Call in WCF - How to Rollback

  - by Corey Coogan

  I've implemented some components to use WCF with both an IoC Container (StructureMap) and the Session per Call pattern. The NHibernate stuff is most taken from here: http://realfiction.net/Content/Entry/133. It seems to be OK, but I want to open a transaction with each call and commit at the end, rather than just Flush() which how its being done in the article. Here's where I am running into some problems and could use some advice. I haven't figured out a good way to rollback. I realize I can check the CommunicationState and if there's an exception, rollback, like so: public void Detach(InstanceContext owner) { if (Session != null) { try { if(owner.State == CommunicationState.Faulted) RollbackTransaction(); else CommitTransaction(); } finally { Session.Dispose(); } } } void CommitTransaction() { if(Session.Transaction != null && Session.Transaction.IsActive) Session.Transaction.Commit(); } void RollbackTransaction() { if (Session.Transaction != null && Session.Transaction.IsActive) Session.Transaction.Rollback(); } However, I almost never return a faulted state from a service call. I would typically handle the exception and return an appropriate indicator on my response object and rollback the transaction myself. The only way I can think of handling this would be to inject not only repositories into my WCF services, but also an ISession so I can rollback and handle the way I want. That doesn't sit well with me and seems kind of leaky. Anyone else handling the same problem?

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• Should DAL always return business objects in MVP

  - by Chathuranga

  In Model View Presenter (MVP) pattern, it is said that our DAL always should returns business models. But let's say if I want to get just a number from database like the last ClientID (the latest clients ID) which is a string, should my DAL method returns a ClientInfo object which has about 10 other fields as well like ClientName, Address etc.? If I want to get a list of business objects from my DAL, is it acceptable to do it as follows or better to get a DataTable from DAL and then in the applications BLL, converts it a List? public List<Employee> GetNewEmployees() { string selectStatement = "SELECT Employee.Emp_ID, Employee.Initials + ' ' + Employee.Surname AS Name,..."; using (SqlConnection sqlConnection = new SqlConnection(db.GetConnectionString)) { using (SqlCommand sqlCommand = new SqlCommand(selectStatement, sqlConnection)) { sqlConnection.Open(); using (SqlDataReader dataReader = sqlCommand.ExecuteReader()) { List<Employee> list = new List<Employee>(); while (dataReader.Read()) { list.Add ( new EpfEtfMaster { EmployeeID = (int) dataReader ["emp_id"], EmployeeName = (string) dataReader ["Name"], AppointmentDate = (DateTime) dataReader["appointment_date"], }); } return list; } } } }

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• jQuery Tools alert works once (but only once)

  - by Jim Miller

  I'm trying to build a simple alert mechanism with jQuery Tools -- in response to a bit of Javascript code, pop up an overlay with a message and an OK button that, when clicked, makes the overlay go away. Trivial, or it should be. I've been slavishly following http://flowplayer.org/tools/demos/overlay/trigger.html, and have something that works fine the first time it's invoked, but only that time. If I repeat the JS action that should expose the overlay, it doesn't. My content/DIV: <div class='modal' id='the_alert'> <div id='modal_content' class='modal_content'> <h2>hi there</h2> this is the body <p> <button class='close'>OK</button> </p> </div> <div id='modal_background' class='modal_background'><img src='/images/overlay/f9f9f9-180.png' class='stretch' alt='' /></div> </div> and the Javascript: function showOverlayDialog() { $('#the_alert').overlay({ mask: {color: '#cccccc', loadSpeed: 200, opacity: 0.9}, closeOnClick: false, load: true }); } As I said: When showOverlayDialog() is invoked the first time, the overlay appears just like it should, and goes away when the "OK" button is clicked. But if I cause showOverlayDialog() to run again, without reloading the page, nothing happens. If I reload the page, then the pattern repeats -- the first invocation brings up the overlay, but the second one doesn't. I'm obviously missing something -- any advice out there? Thanks!

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• How to log correct context with Threadpool threads using log4net?

  - by myotherme

  I am trying to find a way to log useful context from a bunch of threads. The problem is that a lot of code is dealt with on Events that are arriving via threadpool threads (as far as I can tell) so their names are not in relation to any context. The problem can be demonstrated with the following code: class Program { private static readonly log4net.ILog log = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType); static void Main(string[] args) { new Thread(TestThis).Start("ThreadA"); new Thread(TestThis).Start("ThreadB"); Console.ReadLine(); } private static void TestThis(object name) { var nameStr = (string)name; Thread.CurrentThread.Name = nameStr; log4net.ThreadContext.Properties["ThreadContext"] = nameStr; log4net.LogicalThreadContext.Properties["LogicalThreadContext"] = nameStr; log.Debug("From Thread itself"); ThreadPool.QueueUserWorkItem(x => log.Debug("From threadpool Thread: " + nameStr)); } } The Conversion pattern is: %date [%thread] %-5level %logger [%property] - %message%newline The output is like so: 2010-05-21 15:08:02,357 [ThreadA] DEBUG LogicalContextTest.Program [{LogicalThreadContext=ThreadA, log4net:HostName=xxx, ThreadContext=ThreadA}] - From Thread itself 2010-05-21 15:08:02,357 [ThreadB] DEBUG LogicalContextTest.Program [{LogicalThreadContext=ThreadB, log4net:HostName=xxx, ThreadContext=ThreadB}] - From Thread itself 2010-05-21 15:08:02,404 [7] DEBUG LogicalContextTest.Program [{log4net:HostName=xxx}] - From threadpool Thread: ThreadA 2010-05-21 15:08:02,420 [16] DEBUG LogicalContextTest.Program [{log4net:HostName=xxx}] - From threadpool Thread: ThreadB As you can see the last two rows have no Names of useful information to distinguish the 2 threads, other than manually adding the name to the message (which I want to avoid). How can I get the Name/Context into the log for the threadpool threads without adding it to the message at every call?

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• Good patterns for loose coupling in Java?

  - by Eye of Hell

  Hello. I'm new to java, and while reading documentation so far i can't find any good ways for programming with loose coupling between objects. For majority of languages i know (C++, C#, python, javascript) i can manage objects as having 'signals' (notification about something happens/something needed) and 'slots' (method that can be connected to signal and process notification/do some work). In all mentioned languages i can write something like this: Object1 = new Object1Class(); Object2 = new Object2Class(); Connect( Object1.ItemAdded, Object2.OnItemAdded ); Now if object1 calls/emits ItemAdded, the OnItemAdded method of Object2 will be called. Such loose coupling technique is often referred as 'delegates', 'signal-slot' or 'inversion of control'. Compared to interface pattern, technique mentioned don't need to group signals into some interfaces. Any object's methods can be connected to any delegate as long as signatures match ( C++Qt even extends this by allowing only partial signature match ). So i don't need to write additional interface code for each methods / groups of methods, provide default implementation for interface methods not used etc. And i can't see anything like this in Java :(. Maybe i'm looking a wrong way?

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• Serializing MDI Winforms for persistency

  - by Serge

  Hello, basically my project is an MDI Winform application where a user can customize the interface by adding various controls and changing the layout. I would like to be able to save the state of the application for each user. I have done quite a bit of searching and found these: http://stackoverflow.com/questions/2076259/how-to-auto-save-and-auto-load-all-properties-in-winforms-c http://stackoverflow.com/questions/1669522/c-save-winform-or-controls-to-file Basically from what I understand, the best approach is to serialize the data to XML, however winform controls are not serializable, so I would have use surrogate classes: http://www.codeproject.com/KB/dotnet/Surrogate_Serialization.aspx Now, do I need to write a surrogate class for each of my controls? I would need to write some sort of a recursive algorithm to save all my controls, what is the best approach to do accomplish that? How would I then restore all the windows, should I use the memento design pattern for that? If I want to implement multiple users later, should I use Nhibernate to store all the object data in a database? I am still trying to wrap my head around the problem and if anyone has any experience or advice I would greatly appreciate it, thanks.

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• javascript regex: replace url text link with image,but not in html tags

  Hi this is my pice of code: <div style="overflow: hidden; width: 445px;">[IMG]http://i29.tinypic.com/mydog.png[/IMG] tak si to http://i29.tinypic.com/mycat.png Lorem ipsum loremai <img width="15" border="0" align="middle" src="images/smejo.gif" valign="middle"/> <img src=http://www.example.com/index.png alt> <img src="http://www.example.com/index.png" alt>     <a href="#reakcia" title="reagovat na temu"><span class="poradna-tl-reaguj"><reaction> </span></a></div> </td> </tr><img src=http://www.example.com/index.png alt><img src="http://www.example.com/index.png" alt> and i need regex pattern to replace ONLY text image links with image without touch of inner url tags. But i can't use "Lookbehind" or possessive quantifiers because JS don't support them=/ So i want to catch only "http://i29.tinypic.com/mydog.png" and "http://i29.tinypic.com/mycat.png". I using array method to replacing (will be greasemonkey script.) Many Thanks

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• filterSecurityInterceptor and metadatasource implementation spring-security

  - by Mike

  Hi! I created a class that implements the FilterInvocationSecurityMetadataSource interface. I implemented it like this: public List<ConfigAttribute> getAttributes(Object object) { FilterInvocation fi = (FilterInvocation) object; Object principal = SecurityContextHolder.getContext().getAuthentication().getPrincipal(); Long companyId = ((ExtenededUser) principal).getCompany().getId(); String url = fi.getRequestUrl(); // String httpMethod = fi.getRequest().getMethod(); List<ConfigAttribute> attributes = new ArrayList<ConfigAttribute>(); FilterSecurityService service = (FilterSecurityService) SpringBeanFinder.findBean("filterSecurityService"); Collection<Role> roles = service.getRoles(companyId); for (Role role : roles) { for (View view : role.getViews()) { if (view.getUrl().equalsIgnoreCase(url)) attributes.add(new SecurityConfig(role.getName() + "_" + role.getCompany().getName())); } } return attributes; } when I debug my application I see it reaches this class, it only reaches getAllConfigAttributes method, that is empty as I said, and return null. after that it prints this warning: Could not validate configuration attributes as the SecurityMetadataSource did not return any attributes from getAllConfigAttributes(). My aplicationContext- security is like this: <beans:bean id="filterChainProxy" class="org.springframework.security.web.FilterChainProxy"> <filter-chain-map path-type="ant"> <filter-chain filters="sif,filterSecurityInterceptor" pattern="/**" /> </filter-chain-map> </beans:bean> <beans:bean id="filterSecurityInterceptor" class="org.springframework.security.web.access.intercept.FilterSecurityInterceptor"> <beans:property name="authenticationManager" ref="authenticationManager" /> <beans:property name="accessDecisionManager" ref="accessDecisionManager" /> <beans:property name="securityMetadataSource" ref="filterSecurityMetadataSource" /> </beans:bean> <beans:bean id="filterSecurityMetadataSource" class="com.mycompany.filter.FilterSecurityMetadataSource"> </beans:bean> what could be the problem?

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• When virtual inheritance IS a good design?

  - by 7vies

  EDIT3: Please be sure to clearly understand what I am asking before answering (there are EDIT2 and lots of comments around). There are (or were) many answers which clearly show misunderstanding of the question (I know that's also my fault, sorry for that) Hi, I've looked over the questions on virtual inheritance (class B: public virtual A {...}) in C++, but did not find an answer to my question. I know that there are some issues with virtual inheritance, but what I'd like to know is in which cases virtual inheritance would be considered a good design. I saw people mentioning interfaces like IUnknown or ISerializable, and also that iostream design is based on virtual inheritance. Would those be good examples of a good use of virtual inheritance, is that just because there is no better alternative, or because virtual inheritance is the proper design in this case? Thanks. EDIT: To clarify, I'm asking about real-life examples, please don't give abstract ones. I know what virtual inheritance is and which inheritance pattern requires it, what I want to know is when it is the good way to do things and not just a consequence of complex inheritance. EDIT2: In other words, I want to know when the diamond hierarchy (which is the reason for virtual inheritance) is a good design

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• Troubleshooting ASP .NET Application on Shared Hosting

  - by James

  Hi, My company has a CRM site hosted externally on a shared server and recently it has been very problematic. Users are being logged out randomly, sometimes only seconds after logging in. We are also getting viewstate validation errors at times. Both problems seem to occur more often when there are two or more people logged in at the same time, but I can't really see any particular pattern. I am using log4net to track the application state and from what I can tell it seems that the application is frequently restarting, causing all sorts of issues. I can see log messages from the Application_Start event handler but there is not always a corresponding message from the Application_End event handler. There is also logging code in the Application_Error event handler but it is not catching anything at the time of the restart. These errors started to occur soon after we moved our site to this shared server, although I don't remember it being this bad at first. Any advice on how to track down these problems would be appreciated. The server is running Windows Server 2003 and IIS 6.0. Sadly I don't have access to the server other than through Parallels Plesk and it doesn't seem to have any useful diagnostic information.

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• DDD: Persisting aggregates

  - by Mosh

  Hello, Let's consider the typical Order and OrderItem example. Assuming that OrderItem is part of the Order Aggregate, it an only be added via Order. So, to add a new OrderItem to an Order, we have to load the entire Aggregate via Repository, add a new item to the Order object and persist the entire Aggregate again. This seems to have a lot of overhead. What if our Order has 10 OrderItems? This way, just to add a new OrderItem, not only do we have to read 10 OrderItems, but we should also re-insert all these 10 OrderItems again. (This is the approach that Jimmy Nillson has taken in his DDD book. Everytime he wants to persists an Aggregate, he clears all the child objects, and then re-inserts them again. This can cause other issues as the ID of the children are changed everytime because of the IDENTITY column in database.) I know some people may suggest to apply Unit of Work pattern at the Aggregate Root so it keeps track of what has been changed and only commit those changes. But this violates Persistence Ignorance (PI) principle because persistence logic is leaking into the Domain Model. Has anyone thought about this before? Mosh

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• Correct way to trigger object clone/memento when property changes

  - by Jay

  Hi, I have a big doubt about the correct way to save an object state (clone object), if necessary to rollback the changes, when a property has changed. I know that the IEditableObject interface exists for those cases but during some tests the BeginEdit would just fire like crazy (I have a DataGrid whose values can be edited but I won't need to keep the state of the object in these cases). I'm following the MVP design pattern in my project and the view's DataContext is a wrapper of my presenter.Let's say I have a CheckBox/TextBox in my UI and when that textbox's value changes, the property bound in the wrapper gets set.Currently, before setting the new value i'm raising an event to the presenter (something like PropertyChanging) that clones my wrapper. I'm doing this because I don't think that job should be done by the wrapper itself but by the presenter.Is this a correct approach? Raising the event is an acceptable solution? I thought of other possible ideas: Interface between presenter and wrapper; Use explicit binding and trigger the binding after saving object's state; What is your opinion about the best way to do this? Should I just keep IEditableObject, is this the best way? Best Regards

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• Data Access Layer, Best Practices

  - by labratmatt

  I'm looking for input on the best way to refactor the data access layer (DAL) in my PHP based web app. I follow an MVC pattern: PHP/HTML/CSS/etc. views on the front end, PHP controllers/services in the middle, and a PHP DAL sitting on top of a relational database in the model. Pretty standard stuff. Things are working fine, but my DAL is getting large (codesmell?) and becoming a bit unwieldy. My DAL contains almost all of the logic to interface with my database and is full of functions that look like this: function getUser($user_id) { $statement = "select id, name from users where user_id=:user_id"; PDO builds statement and fetchs results as an array return $array_of_results_generated_by_PDO_fetch_method; } Notes: The logic in my controller only interacts with the model using functions like the above in the DAL I am not using a framework (I'm of the opinion that PHP is a templating language and there's no need to inject complexity via a framework) I generally use PHP as a procedural language and tend to shy away from its OOP approach (I enjoy OOP development but prefer to keep that complexity out of PHP) What approaches have you taken when your DAL has reached this point? Do I have a fundamental design problem? Do I simply need to chop my DAL into a number of smaller files (logically divide it)? Thanks.

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• Resolving Circular References for Objects Implementing ISerializable

  - by Chris

  I'm writing my own IFormatter implementation and I cannot think of a way to resolve circular references between two types that both implement ISerializable. Here's the usual pattern: [Serializable] class Foo : ISerializable { private Bar m_bar; public Foo(Bar bar) { m_bar = bar; m_bar.Foo = this; } public Bar Bar { get { return m_bar; } } protected Foo(SerializationInfo info, StreamingContext context) { m_bar = (Bar)info.GetValue("1", typeof(Bar)); } public void GetObjectData(SerializationInfo info, StreamingContext context) { info.AddValue("1", m_bar); } } [Serializable] class Bar : ISerializable { private Foo m_foo; public Foo Foo { get { return m_foo; } set { m_foo = value; } } public Bar() { } protected Bar(SerializationInfo info, StreamingContext context) { m_foo = (Foo)info.GetValue("1", typeof(Foo)); } public void GetObjectData(SerializationInfo info, StreamingContext context) { info.AddValue("1", m_foo); } } I then do this: Bar b = new Bar(); Foo f = new Foo(b); bool equal = ReferenceEquals(b, b.Foo.Bar); // true // Serialise and deserialise b equal = ReferenceEquals(b, b.Foo.Bar); If I use an out-of-the-box BinaryFormatter to serialise and deserialise b, the above test for reference-equality returns true as one would expect. But I cannot conceive of a way to achieve this in my custom IFormatter. In a non-ISerializable situation I can simply revisit "pending" object fields using reflection once the target references have been resolved. But for objects implementing ISerializable it is not possible to inject new data using SerializationInfo. Can anyone point me in the right direction?

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• model view controller question

  - by songBong

  Hi, I've been working on my iphone game recently and came across a forked road when deciding the design of my various classes. So far I've adhered to the MVC pattern but the following situation had me confused: I have 4 buttons displayed visually. Each button though consists of a container UIView (which I've subclassed) and 2 UIButtons (also subclassed) as subviews. When you press a button, it does the flip effect plus other stuff. The user input is using target-action from my container UIView to my controller. This part is ok, the following part is the debatable part: So I've subclassed the container view as well as the UIButtons and I need to add more data/methods (somewhere) to do more things. Putting data that needs to be serialized and non-rendering related code in the view classes seems to break the MVC design but at the moment, it makes the most sense to me to put it there. It's almost like my subclassed views are their own little MVC's and it seems neat. Separating out the data/methods from the view to my main controller in this case seems unnecessary and a more work. How should I be doing it? Thanks heaps.

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• Is it valid to use unsafe struct * as an opaque type instead of IntPtr in .NET Platform Invoke?

  - by David Jeske

  .NET Platform Invoke advocates declaring pointer types as IntPtr. For example, the following [DllImport("user32.dll")] static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, Int32 wParam, Int32 lParam); However, I find when interfacing with interesting native interfaces, that have many pointer types, flattening everything into IntPtr makes the code very hard to read and removes the typical typechecking that a compiler can do. I've been using a pattern where I declare an unsafe struct to be an opaque pointer type. I can store this pointer type in a managed object, and the compiler can typecheck it form me. For example: class Foo { unsafe struct FOO {}; // opaque type unsafe FOO *my_foo; class if { [DllImport("mydll")] extern static unsafe FOO* get_foo(); [DllImport("mydll")] extern static unsafe void do_something_foo(FOO *foo); } public unsafe Foo() { this.my_foo = if.get_foo(); } public unsafe do_something_foo() { if.do_something_foo(this.my_foo); } While this example may not seem different than using IntPtr, when there are several pointer types moving between managed and native code, using these opaque pointer types for typechecking is a godsend. I have not run into any trouble using this technique in practice. However, I also have not seen an examples of anyone using this technique, and I wonder why. Is there any reason that the above code is invalid in the eyes of the .NET runtime? My main question is about how the .NET GC system treats "unsafe FOO *my_foo". Is this pointer something the GC system is going to try to trace, or is it simply going to ignore it? My hope is that because the underlying type is a struct, and it's declared unsafe, that the GC would ignore it. However, I don't know for sure. Thoughts?

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• Linq to SQL generates StackOverflowException in tight Insert loop

  - by ChrisW

  I'm parsing an XML file and inserting the rows into a table (and related tables) using LinqToSQL. I parse the XML file using LinqToXml into IEnumerable. Then, I create a foreach loop, where I build my LinqToSQL objects and call InsertOnSubmit and SubmitChanges at the end of each loop. Nothing special here. Usually, I make it through around 4,100 records before receiving a StackOverflowException from LinqToSql, right as I call SubmitChanges. It's not always on 4,100... sometimes it's 4102, sometimes, less, etc. I've tried inserting the records that generate the failure individually, but putting them in their own Xml file, but that inserts fine... so it's not the data. I'm running the whole process from an MVC2 app that is uploading the Xml file to the server. I've adjusted my WebRequest timeouts to appropriate values, and again, I'm not getting timeout errors, just StackOverflowExceptions. So is there some pattern that I should follow for times when I have to do many insertions into the database? I never encounter this exception on smaller Xml files, just larger ones.

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