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• CQRS - Should a Command try to create a "complex" master-detail entity?

  - by Simon Crabtree

  I've been reading Greg Young and Udi Dahan's thoughts on Command Query Responsibilty Separation and a lot of what I read strikes a chord with me. My domain (we track vehicles which are doing deliveries) has the concept of a Route which contains one or more Stops. I need my customers to be able to set these up in our system by calling a webservice, and then be able to retrieve information about a Route and how the vehicle is progressing. In the past I would have "cut-down" DTO classes which closely resemble my domain classes, and the customer would create a RouteDto with an array of StopDto(s), and call our CreateRoute webmethod, passing in the RouteDto. When they query our system by calling the GetRouteDetails method, I would return exactly the same objects to them. One of the appealing aspects of CQRS is that the RouteDto might have all manner of properties that the customer wants to query, but have no business setting when they create a Route. So I create a separate CreateRouteRequest class which is passed in when calling the CreateRoute "command", and a Route DTO class which gets returned as a query result. class Route{ string Reference; List<Stop> Stops; } But I need my customer to provide me with Route AND Stop details when they create a route. As I see it I could either... Give my CreateRouteRequest class a Stops(s) property which is an array of "something" representing the data they need to provide about each stop - but what do I call this class? It's not a Stop as that's what I'm calling the list of DTO inside my Route DTO, but I don't like "CreateStopRequest". I also wonder if I'm stuck in a CRUD mindset here thinking in terms of master-detail information and asking the customer to think like that too. class CreateRouteRequest{ string Reference; ... List<CreateStopRequest> Stops; } or They call CreateRoute, and then make a number of calls to an AddStopToRoute method. This feels a bit more "behavioural" but I'm going to lose the ability to treat creating a route including its stops as a single atomic command. If they create a Route and then try to add a Stop which fails due to some validation problem they're going to have a partially correct Route. The fact that I can't come up with a good name for the list of "StopCreationData" objects I'd be working with in option 1, makes me wonder if there's something I'm missing.

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• Updating query results

  - by Francisco Garcia

  Within a DDD and CQRS context, a query result is displayed as table rows. Whenever new rows are inserted or deleted, their positions must be calculated by comparing the previous query result with the most recent one. This is needed to visualize with an animation new or deleted rows. The model of my view contains an array of the displayed query results. But I need a place to compare its contents against the latest query. Right now I consider my model view part of my application layer, but the comparison of two query result sets seems something that must be done within the domain layer. Which component should cache a query result and which one compare them? Are view models (and their cached contents) supposed to be in the application layer?

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• Designing a hierarchical structure with lots of reads and writes?

  - by JD01

  I am in the process of working on a video on demand system part of it involves the management of a hierarchical tree structure (think windows explorer) which allows users to upload videos, move folders around, create new folders etc. User action will be allowed depending on which permissions they have. In addition to managing the structure (creating folders and uploading videos), subscribers will be viewing content (read access). The number of reads will be significantly more than the writes. My question (and it is big one) is should I store the data in a database (for the writes) and also have some sort of cache which will be used for the reads? or do I use two databases? or is there a better solution? Also I will have to resolve concurrency issues which I think optimistic locking on the database will resolve. I have a fair bit about CQRS over the last few months but not sure if this is the way to go. Any ideas?

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• Is it bad practice for services to share a database in SOA?

  - by Paul T Davies

  I have recently been reading Hohpe and Woolf's Enterprise Integration Patterns, some of Thomas Erl's books on SOA and watching various videos and podcasts by Udi Dahan et al. on CQRS and Event Driven systems. Systems in my place of work suffer from high coupling. Although each system theoretically has its own database, there is a lot of joining between them. In practice this means there is one huge database that all systems use. For example, there is one table of customer data. Much of what I've read seems to suggest denormalising data so that each system uses only its database, and any updates to one system are propagated to all the others using messaging. I thought this was one of the ways of enforcing the boundaries in SOA - each service should have its own database, but then I read this: http://stackoverflow.com/questions/4019902/soa-joining-data-across-multiple-services and it suggests this is the wrong thing to do. Segregating the databases does seem like a good way of decoupling systems, but now I'm a bit confused. Is this a good route to take? Is it ever recommended that you should segregate a database on, say an SOA service, an DDD Bounded context, an application, etc?

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• Pushing complete notifications to client

  - by ton.yeung

  So with cqrs, we accept that consistency is eventual. However, that doesn't mean that the user has to continually poll, or that eventual means an update has to take more then 500ms to sync. For the sake of UX, we want to at least give the illusion of consistency, or if not possible, be as transparent as possible. With that in mind, I have this setup: angularjs web client, consumes webapi restful services, sends commands to nservicebus command handlers, saves to neventstore, dispatches events to nservicebus event handlers, sends message to signalr hub, sends notifications to angularjs web client so with that setup, theoretically some initiates a request the server validates the request sends out the necessary commands In the mean time the client gets a 200 response updates the view: working on it gets message sometime later: done, here's the updated data Here's where things get interesting, each command could spawn multiple events. Not sure if this is a serious no, no, or not, but that's how it is currently. For example, a new customer spawns CustomerIDCreated, CustomerNameUpdated, CustomerAddressUpdated, etc... Which event handler needs to notify the client? Should all of them in a progress bar style update?

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• Does command/query separation apply to a method that creates an object and returns its ID?

  - by Gilles

  Let's pretend we have a service that calls a business process. This process will call on the data layer to create an object of type A in the database. Afterwards we need to call again on another class of the data layer to create an instance of type B in the database. We need to pass some information about A for a foreign key. In the first method we create an object (modify state) and return it's ID (query) in a single method. In the second method we have two methods, one (createA) for the save and the other (getId) for the query. public void FirstMethod(Info info) { var id = firstRepository.createA(info); secondRepository.createB(id); } public void SecondMethod(Info info) { firstRepository.createA(info); var key = firstRepository.getID(info); secondRepository.createB(key); } From my understanding the second method follows command query separation more fully. But I find it wasteful and counter-intuitive to query the database to get the object we have just created. How do you reconcile CQS with such a scenario? Does only the second method follow CQS and if so is it preferable to use it in this case?

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• Inheritance, commands and event sourcing

  - by Arthis

  In order not to redo things several times I wanted to factorize common stuff. For Instance, let's say we have a cow and a horse. The cow produces milk, the horse runs fast, but both eat grass. public class Herbivorous { public void EatGrass(int quantity) { var evt= Build.GrassEaten .WithQuantity(quantity); RaiseEvent(evt); } } public class Horse : Herbivorous { public void RunFast() { var evt= Build.FastRun; RaiseEvent(evt); } } public class Cow: Herbivorous { public void ProduceMilk() { var evt= Build.MilkProduced; RaiseEvent(evt); } } To eat Grass, the command handler should be : public class EatGrassHandler : CommandHandler<EatGrass> { public override CommandValidation Execute(EatGrass cmd) { Contract.Requires<ArgumentNullException>(cmd != null); var herbivorous= EventRepository.GetById<Herbivorous>(cmd.Id); if (herbivorous.IsNull()) throw new AggregateRootInstanceNotFoundException(); herbivorous.EatGrass(cmd.Quantity); EventRepository.Save(herbivorous, cmd.CommitId); } } so far so good. I get a Herbivorous object , I have access to its EatGrass function, whether it is a horse or a cow doesn't matter really. The only problem is here : EventRepository.GetById<Herbivorous>(cmd.Id) Indeed, let's imagine we have a cow that has produced milk during the morning and now wants to eat grass. The EventRepository contains an event MilkProduced, and then come the command EatGrass. With the CommandHandler, we are no longer in the presence of a cow and the herbivorious doesn't know anything about producing milk . what should it do? Ignore the event and continue , thus allowing the inheritance and "general" commands? or throw an exception to forbid execution, it would mean only CowEatGrass, and HorseEatGrass might exists as commands ? Thanks for your help, I am just beginning with these kinds of problem, and I would be glad to have some news from someone more experienced.

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• Version hash to solve Event Sourcing problems

  - by SystematicFrank

  The basic examples I have seen about Event Sourcing do not deal with out of order events, clock offsets in different systems and late events from system partitions. I am wondering if more polished Event Sourcing implementations rely on a version stamp of modified objects? For example, assuming that the system is rendering the entity Client with version id ABCD1234. If the user modifies the entity, the system will create an event with the modified fields AND the version id reference to which version it applies. Later the event responder would detect out of order events and merge them.

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• Should an event-sourced aggregate root have query access to the event sourcing repository?

  - by JD Courtoy

  I'm working on an event-sourced CQRS implementation, using DDD in the application / domain layer. I have an object model that looks like this: public class Person : AggregateRootBase { private Guid? _bookingId; public Person(Identification identification) { Apply(new PersonCreatedEvent(identification)); } public Booking CreateBooking() { // Enforce Person invariants var booking = new Booking(); Apply(new PersonBookedEvent(booking.Id)); return booking; } public void Release() { // Enforce Person invariants // Should we load the booking here from the aggregate repository? // We need to ensure that booking is released as well. var booking = BookingRepository.Load(_bookingId); booking.Release(); Apply(new PersonReleasedEvent(_bookingId)); } [EventHandler] public void Handle(PersonBookedEvent @event) { _bookingId = @event.BookingId; } [EventHandler] public void Handle(PersonReleasedEvent @event) { _bookingId = null; } } public class Booking : AggregateRootBase { private DateTime _bookingDate; private DateTime? _releaseDate; public Booking() { //Enforce invariants Apply(new BookingCreatedEvent()); } public void Release() { //Enforce invariants Apply(new BookingReleasedEvent()); } [EventHandler] public void Handle(BookingCreatedEvent @event) { _bookingDate = SystemTime.Now(); } [EventHandler] public void Handle(BookingReleasedEvent @event) { _releaseDate = SystemTime.Now(); } // Some other business activities unrelated to a person } With my understanding of DDD so far, both Person and Booking are seperate aggregate roots for two reasons: There are times when business components will pull Booking objects separately from the database. (ie, a person that has been released has a previous booking modified due to incorrect information). There should not be locking contention between Person and Booking whenever a Booking needs to be updated. One other business requirement is that a Booking can never occur for a Person more than once at a time. Due to this, I'm concerned about querying the query database on the read side as there could potentially be some inconsistency there (due to using CQRS and having an eventually consistent read database). Should the aggregate roots be allowed to query the event-sourced backing store for objects (lazy-loading them as needed)? Are there any other avenues of implementation that would make more sense?

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• Should an event-sourced aggregate root have access to the event sourcing repository?

  - by JD Courtoy

  I'm working on an event-sourced CQRS implementation, using DDD in the application / domain layer. I have an object model that looks like this: public class Person : AggregateRootBase { private Guid? _bookingId; public Person(Identification identification) { Apply(new PersonCreatedEvent(identification)); } public Booking CreateBooking() { // Enforce Person invariants var booking = new Booking(); Apply(new PersonBookedEvent(booking.Id)); return booking; } public void Release() { // Enforce Person invariants // Should we load the booking here from the aggregate repository? // We need to ensure that booking is released as well. var booking = BookingRepository.Load(_bookingId); booking.Release(); Apply(new PersonReleasedEvent(_bookingId)); } [EventHandler] public void Handle(PersonBookedEvent @event) { _bookingId = @event.BookingId; } [EventHandler] public void Handle(PersonReleasedEvent @event) { _bookingId = null; } } public class Booking : AggregateRootBase { private DateTime _bookingDate; private DateTime? _releaseDate; public Booking() { //Enforce invariants Apply(new BookingCreatedEvent()); } public void Release() { //Enforce invariants Apply(new BookingReleasedEvent()); } [EventHandler] public void Handle(BookingCreatedEvent @event) { _bookingDate = SystemTime.Now(); } [EventHandler] public void Handle(BookingReleasedEvent @event) { _releaseDate = SystemTime.Now(); } // Some other business activities unrelated to a person } With my understanding of DDD so far, both Person and Booking are seperate aggregate roots for two reasons: There are times when business components will pull Booking objects separately from the database. (ie, a person that has been released has a previous booking modified due to incorrect information). There should not be locking contention between Person and Booking whenever a Booking needs to be updated. One other business requirement is that a Booking can never occur for a Person more than once at a time. Due to this, I'm concerned about querying the query database on the read side as there could potentially be some inconsistency there (due to using CQRS and having an eventually consistent read database). Should the aggregate roots be allowed to query the event-sourced backing store by id for objects (lazy-loading them as needed)? Are there any other avenues of implementation that would make more sense?

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• How to implement message queuing and handling in AWS with NServiceBus

  - by Pete Lunenfeld

  I am creating a new ASP MVC order application in the Amazon (AWS) cloud with the persistence layer at my local datacenter. I will be using the CQRS pattern. The goal of the project is high availability using Queue(s) to store and forward writes (commands/events) that can be picked up and handled asynchronously at my local datacenter. Then, ff the WAN or my local datacenter fails, my cloud MVC app can still take orders and just queue them up until processing can resume. My first thought was to use AWS SQS for the queuing and create my own queue consumer/dispatcher/handler in my own c# application to process the incoming messages/events. MVC (@ Amazon) -- Event/POCO -- SQS -- QueueReader (@ my datacenter) -- DB Then I found NServiceBus. NSB seems to handle lots of details very nicely: message handling, retries, error handling, etc. I hate to reinvent the wheel, and NServiceBus seems like a full featured and mature product that would be perfect for me. But on further research, it does NOT look like NServiceBus is really meant to be used over the WAN in physically separated environments (Cloud to my Datacenter). Google and SO don't really paint a good picture of using NServiceBus across the WAN like I need. How can I use NServiceBus across the WAN? Or is there a better solution to handle queuing and message handling between Amazon an my local datacenter?

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• How To Implement The Query Side Of CQS in DDD?

  - by Laz

  I have implemented the command side of DDD using the domain model and repositories, but how do I implement the query side? Do I create an entirely new domain model for the UI, and where is this kept in the project structure...in the domain layer, the UI layer, etc? Also, what do I use as my querying mechanism, do I create new repositories specifically for the UI domain objects, something other than repositories, or something else?

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• How do I call exec in psake to an executable with a variable path?

  - by Josh Kodroff

  I can't seem to call this executable correctly in my psake deploy script. If I do this: exec { "$ArchiverOutputDir\NServiceBus.Host.exe /install" } It simply outputs this (and is clearly not calling the executable - just outputting the value of that expression): c:\ReloDotNet2_ServiceEndpoints\Archiver\NServiceBus.Host.exe /install But if I do this: exec { c:\ReloDotNet2_ServiceEndpoints\Archiver\NServiceBus.Host.exe /install } I get the expected output from the executable. How do I correctly call an executable with a variable in the path to the executable in psake? If this is actually a PowerShell issue, please feel free to correct the question to reflect that insight. I

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• Event sourcing: Write event before or after updating the model

  - by Magnus

  I'm reasoning about event sourcing and often I arrive at a chicken and egg problem. Would be grateful for some hints on how to reason around this. If I execute all I/O-bound processing async (ie writing to the event log) then how do I handle, or sometimes even detect, failures? I'm using Akka Actors so processing is sequential for each event/message. I do not have any database at this time, instead I would persist all the events in an event log and then keep an aggregated state of all the events in a model stored in memory. Queries are all against this model, you can consider it to be a cache. Example Creating a new user: Validate that the user does not exist in model Persist event to journal Update model (in memory) If step 3 breaks I still have persisted my event so I can replay it at a later date. If step 2 breaks I can handle that as well gracefully. This is fine, but since step 2 is I/O-bound I figured that I should do I/O in a separate actor to free up the first actor for queries: Updating a user while allowing queries (A0 = Front end/GUI actor, A1 = Processor Actor, A2 = IO-actor, E = event bus). (A0-E-A1) Event is published to update user 'U1'. Validate that the user 'U1' exists in model (A1-A2) Persist event to journal (separate actor) (A0-E-A1-A0) Query for user 'U1' profile (A2-A1) Event is now persisted continue to update model (A0-E-A1-A0) Query for user 'U1' profile (now returns fresh data) This is appealing since queries can be processed while I/O-is churning along at it's own pace. But now I can cause myself all kinds of problems where I could have two incompatible commands (delete and then update) be persisted to the event log and crash on me when replayed up at a later date, since I do the validation before persisting the event and then update the model. My aim is to have a simple reasoning around my model (since Actor processes messages sequentially single threaded) but not be waiting for I/O-bound updates when Querying. I get the feeling I'm modeling a database which in itself is might be a problem. If things are unclear please write a comment.

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• Can I architect a web app so it can be deployed to either the cloud or a dedicated server / VPS ? Ho

  - by CAD bloke

  Is there are an architecture versatile enough that it may be deployed to either a cloud server or to a dedicated (or VPS) server with minimal change? Obviously there would be config changes but I'd rather leave the rest of the app consistent, keeping one maintainable codebase. The app would be ASP.NET &/or ASP.MVC. My dev environment is VS 2010. The cloud may, or may not be, Azure. Dedicated or VPS would be Win Server 2008. Probably. It is not a public-facing web site. The web app I have in mind would be a separate deployment for each client. Some clients would be small-scale, some will prefer the app to run on a local intranet rather than on the web. Other clients may prefer the cloud approach for a black-box solution. The app may run for a few hours or it may run indefinitely, it depends on the client and the project. Other than deployment scenarios the apps would be more or less identical. As you may see from the tags, I'm assuming a message-based architecture is probably the most versatile but I'm also used to being wrong about this stuff. All suggestions and pointers welcome regarding general architectures and also specific solutions.

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• Command Query Separation validating for retries

  - by Neil Barnwell

  So I'm comfortable with the basic concept of CQS, where you might have a command that writes to one database, and that updates the query database that you read from. However, consider the scenario where you are entering data, and want to prevent duplicates. Using new employee data entry an employee register as an example, working through a pile of application forms to key in the new employees' details: Take top sheet. Key in employee name and unique payroll number to UI. Submit. Put paper in "completed pile". Repeat. How would you now prevent the user from keying in the same payroll number again, say for instance if they get distracted and can't remember whether they've keyed one in already and the "message" hasn't got all the way back to the query db for the user to search?

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• CodePlex Daily Summary for Saturday, March 06, 2010

  CodePlex Daily Summary for Saturday, March 06, 2010New ProjectsAgr.CQRS: Agr.CQRS is a C# framework for DDD applications that use the Command Query Responsibility Segregation pattern (CQRS) and Event Sourcing. BigDays 2010: Big>Days 2010BizTalk - Controlled Admin: Hi .NET folks, I am planning to start project on a Controlled BizTalk Admin tool. This tool will be useful for the organizations which have "Sh...Blacklist of Providers: Blacklist of Providers - the application for department of warehouse logistics (warehouse) at firms.Career Vector: A job board software.Chargify Demo: This is a sample website for ChargifyConceptual: Concept description and animationEric Hexter: My publicly available source code and examplesFluentNHibernate.Search: A Fluent NHibernate.Search mapping interface for NHibernate provider implementation of Lucene.NET.FreelancePlanner: FreelancePlanner is a project tracking tool for freelance translators.HTMLx - JavaScript on the Server for .NET: HTMLx is a set of libraries based on ASP.NET engine to provide JavaScript programmability on the server side. It allows Web developers to use JavaS...IronMSBuild: IronMSBuild is a custom MSBuild Task, which allows you to execute IronRuby scripts. // have to provide some examples LINQ To Blippr: LINQ to Blippr is an open source LINQ Provider for the micro-reviewing service Blippr. LINQ to Blippr makes it easier and more efficent for develo...Luk@sh's HTML Parser: library that simplifies parsing of the HTML documents, for .NETMeta Choons: Unsure as yet but will be a kind of discogs type site but different..NetWork2: NetWork2Regular Expression Chooser: Simple gui for choosing the regular expressions that have become more than simple.See.Sharper: Hopefully useful C# extensions.SharePoint 2010 Toggle User Interface: Toggle the SharePoint 2010 user interface between the new SharePoint 2010 user interface and SharePoint 2007 user interface.Silverlight DiscussionBoard for SharePoint: This is a sharepoint 3.0 webpart that uses a silverlight treeview to display metadata about sharepoint discussions anduses the html bridge to show...Simple Sales Tracking CRM API Wrapper: The Simple Sales Tracking API Wrapper, enables easy extention development and integration with the hosted service at http://www.simplesalestracking...Syntax4Word: A syntax addin for word 2007.TortoiseHg installer builder: TortoiseHg and Mercurial installer builder for Windowsunbinder: Model un binding for route value dictionariesWindows Workflow Foundation on Codeplex: This site has previews of Workflow features which are released out of band for the purposes of adoption and feedback.XNA RSM Render State Manager: Render state management idea for XNA games. Enables isolation between draw calls whilst reducing DX9 SetRenderState calls to the minimum.New ReleasesAgr.CQRS: Sourcecode package: Agr.CQRS is a C# framework for DDD applications that use the Command Query Responsibility Segregation pattern (CQRS) and Event Sourcing. This dow...Book Cataloger: Preview 0.1.6a: New Features: Export to Word 2007 Bibliography format Dictionary list editors for Binding, Condition Improvements: Stability improved Content ...Braintree Client Library: Braintree-1.1.2: Includes minor enhancements to CreditCard and ValidationErrors to support upcoming example application.CassiniDev - Cassini 3.5 Developers Edition: CassiniDev v3.5.0.5: For usage see Readme.htm in download. New in CassiniDev v3.5.0.5 Reintroduced the Lib project and signed all Implemented the CassiniSqlFixture -...Composure: Calcium-64420-VS2010rc1.NET4.SL3: This is a simple conversion of Calcium (rev 64420) built in VS2010 RC1 against .NET4 and Silverlight 3. No source files were changed and ALL test...Composure: MS AJAX Library (46266) for VS2010 RC1 .NET4: This is a quick port of Microsoft's AJAX Library (rev 46266) for Visual Studio 2010 RC1 built against .NET 4.0. Since this conversion was thrown t...Composure: MS Web Test Lightweight for VS2010 RC1 .NET4: A simple conversion of Microsoft's Web Test Lightweight for Visual Studio 2010 RC1 .NET 4.0. This is part of a larger "special request" conversion...CoNatural Components: CoNatural Components 1.5: Supporting new data types: Added support for binary data types -> binary, varbinary, etc maps to byte[] Now supporting SQL Server 2008 new types ...Extensia: Extensia 2010-03-05: Extensia is a very large list of extension methods and a few helper types. Some extension methods are not practical (e.g. slow) whilst others are....Fluent Assertions: Fluent Assertions release 1.1: In this release, we've worked hard to add some important missing features that we really needed, and also improve resiliance against illegal argume...Fluent Ribbon Control Suite: Fluent Ribbon Control Suite 1.0 RC: Fluent Ribbon Control Suite 1.0 (Release Candidate)Includes: Fluent.dll (with .pdb and .xml, debug and release version) Showcase Application Sa...FluentNHibernate.Search: 0.1 Beta: First beta versionFolderSize: FolderSize.Win32.1.0.7.0: FolderSize.Win32.1.0.6.0 A simple utility intended to be used to scan harddrives for the folders that take most place and display this to the user...Free Silverlight & WPF Chart Control - Visifire: Silverlight and WPF Step Line Chart: Hi, With this release Visifire introduces Step Line Chart. This release also contains fix for the following issues: * In WPF, if AnimatedUpd...Html to OpenXml: HtmlToOpenXml 1.0: The dll library to include in your project. The dll is signed for GAC support. Compiled with .Net 3.5, Dependencies on System.Drawing.dll and Docu...Line Counter: 1.5.1: The Line Counter is a tool to calculate lines of your code files. The tool was written in .NET 2.0. Line Counter 1.5.1 Added outline icons and lin...Lokad Cloud - .NET O/C mapper (object to cloud) for Windows Azure: Lokad.Cloud v1.0.662.1: You can get the most recent release directly from the build server at http://build.lokad.com/distrib/Lokad.Cloud/Lost in Translation: LostInTranslation v0.2: Alpha release: function complete but not UX complete.MDownloader: MDownloader-0.15.7.56349: Supported large file resumption. Fixed minor bugs.Mini C# Lab: Mini CSharp Lab Ver 1.4: The primary new feature of Ver 1.4 is batch mode! Now you can run Mini C# Lab program as a scheduled task, no UI interactivity is needed. Here ar...Mobile Store: First drop: First droppatterns & practices SharePoint Guidance: SPG2010 Drop6: SharePoint Guidance Drop Notes Microsoft patterns and practices ****************************************** ***************************************...Picasa Downloader: PicasaDownloader (41446): Changelog: Replaced some exception messages by a Summary dialog shown after downloading if there have been problems. Corrected the Portable vers...Pod Thrower: Version 1: This is the first release, I'm sure there are bugs, the tool is fully functional and I'm using it currently.PowerShell Provider BizTalk: BizTalkFactory PowerShell Provider - 1.1-snapshot: This release constitutes the latest development snapshot for the Provider. Please, leave feedback and use the Issue Tracker to help improve this pr...Resharper Settings Manager: RSM 1.2.1: This is a bug fix release. Changes Fixed plug-in crash when shared settings file was modified externally.Reusable Library Demo: Reusable Library Demo v1.0.2: A demonstration of reusable abstractions for enterprise application developerSharePoint 2010 Toggle User Interface: SharePoint Toggle User Interface: Release 1.0.0.0Starter Kit Mytrip.Mvc.Entity: Mytrip.Mvc.Entity(net3.5 MySQL) 1.0 Beta: MySQL VS 2008 EF Membership UserManager FileManager Localization Captcha ClientValidation Theme CrossBrowserTortoiseHg: TortoiseHg 1.0: http://bitbucket.org/tortoisehg/stable/wiki/ReleaseNotes Please backup your user Mercurial.ini file and then uninstall any 0.9.X release before in...Visual Studio 2010 and Team Foundation Server 2010 VM Factory: Rangers Virtualization Guidance: Rangers Virtualization Guidance Focused guidance on creating a Rangers base image manually and introduction of PowerShell scripts to automate many ...Visual Studio DSite: Advanced Email Program (Visual Basic 2008): This email program can send email to any one using your email username and email credentials. The email program can also attatch attactments to you...WPF ShaderEffect Generator: WPF ShaderEffect Generator 1.6: Several improvements and bug fixes have gone into the comment parsing code for the registers. The plug-in should now correctly pay attention to th...WSDLGenerator: WSDLGenerator 0.0.0.3: - Fixed SharePoint generated *.wsdl.aspx file - Added commandline option -wsdl which does only generate the wsdl file.Most Popular ProjectsMetaSharpRawrWBFS ManagerAJAX Control ToolkitMicrosoft SQL Server Product Samples: DatabaseSilverlight ToolkitWindows Presentation Foundation (WPF)ASP.NETLiveUpload to FacebookMicrosoft SQL Server Community & SamplesMost Active ProjectsUmbraco CMSRawrSDS: Scientific DataSet library and toolsBlogEngine.NETjQuery Library for SharePoint Web Servicespatterns & practices – Enterprise LibraryIonics Isapi Rewrite FilterFluent AssertionsComposureDiffPlex - a .NET Diff Generator

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• Command Query Separation

  - by Liam McLennan

  Command query separation is a strategy, proposed by Bertrand Meyer, that each of an object’s methods should be either a command or a query. A command is an operation that changes the state of a system, and a query is an operation that returns a value. This is not the same thing as CQRS, hence why I think that CQRS is poorly named. An Example of Command Query Separation Consider a system that models books and shelves. There is a rule that a shelf may not be removed if it holds any books. One way to implement the removal is to write a method Shelf.Remove() that internally checks to make sure that the shelf is empty before removing it. If the shelf is not empty then it is not removed and an error is returned. To implement this feature following the principle of command query separation would require two methods, one to query the shelf and determine if it is empty and a second method to remove the shelf. Separating the query from the command makes the shelf class simpler to use because the state change is clear and explicit.

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• DDD9 - voting now open for the UK's premier community event

  - by Liam Westley

  If you are interested in software development including a heap of great open source frameworks, then get over to the DDD9 web site and vote for some sessions for the next DDD conference.  It will take place at Microsoft's UK headquarters in Reading on 29th January 2011.     http://developerdeveloperdeveloper.com/ddd9/ProposedSessions.aspx I've proposed a session on the new Async CTP announced at PDC, but there's loads more interesting stuff such as Ruby, CQRS and jQuery Mobile, so get your votes in now so it's the content you want to see.

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• How granular should a command be in a CQ[R]S model?

  - by Aaronaught

  I'm considering a project to migrate part of our WCF-based SOA over to a service bus model (probably nServiceBus) and using some basic pub-sub to achieve Command-Query Separation. I'm not new to SOA, or even to service bus models, but I confess that until recently my concept of "separation" was limited to run-of-the-mill database mirroring and replication. Still, I'm attracted to the idea because it seems to provide all the benefits of an eventually-consistent system while sidestepping many of the obvious drawbacks (most notably the lack of proper transactional support). I've read a lot on the subject from Udi Dahan who is basically the guru on ESB architectures (at least in the Microsoft world), but one thing he says really puzzles me: As we get larger entities with more fields on them, we also get more actors working with those same entities, and the higher the likelihood that something will touch some attribute of them at any given time, increasing the number of concurrency conflicts. [...] A core element of CQRS is rethinking the design of the user interface to enable us to capture our users’ intent such that making a customer preferred is a different unit of work for the user than indicating that the customer has moved or that they’ve gotten married. Using an Excel-like UI for data changes doesn’t capture intent, as we saw above. -- Udi Dahan, Clarified CQRS From the perspective described in the quotation, it's hard to argue with that logic. But it seems to go against the grain with respect to SOAs. An SOA (and really services in general) are supposed to deal with coarse-grained messages so as to minimize network chatter - among many other benefits. I realize that network chatter is less of an issue when you've got highly-distributed systems with good message queuing and none of the baggage of RPC, but it doesn't seem wise to dismiss the issue entirely. Udi almost seems to be saying that every attribute change (i.e. field update) ought to be its own command, which is hard to imagine in the context of one user potentially updating hundreds or thousands of combined entities and attributes as it often is with a traditional web service. One batch update in SQL Server may take a fraction of a second given a good highly-parameterized query, table-valued parameter or bulk insert to a staging table; processing all of these updates one at a time is slow, slow, slow, and OLTP database hardware is the most expensive of all to scale up/out. Is there some way to reconcile these competing concerns? Am I thinking about it the wrong way? Does this problem have a well-known solution in the CQS/ESB world? If not, then how does one decide what the "right level" of granularity in a Command should be? Is there some "standard" one can use as a starting point - sort of like 3NF in databases - and only deviate when careful profiling suggests a potentially significant performance benefit? Or is this possibly one of those things that, despite several strong opinions being expressed by various experts, is really just a matter of opinion?

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• CodePlex Daily Summary for Wednesday, May 12, 2010

  CodePlex Daily Summary for Wednesday, May 12, 2010New ProjectsAMP (Adamo Media Player): AMP is a custom media player that specializes in large media collections! Change the way you manage your media!BoogiePartners: BoogiePartners provides a loose collection of utilities or extensions for Boogie and SpecSharp developers.C# Developer Utility Library: Collection of helpful code functions including zero-config rolling file logging, parameter validation, reflection & object construction, I18N count...Commerce Server 2009 Orders using Pipelines in a Console Application: Using Commerce Server 2009 outside of a Web Application this project show how to create dummy Orders using Pipelines in a NON WEB CONTEXT, an examp...CRM Queue Manager C#: CRM 4 Queue Manager written in C#. Based on the original VB.Net CRM Queue Manager with some changes, additions and feature changes. Converts emai...DbBuilder: This is a tool indended for creation of MS SQL database from scratch, incremental updates, management of redeployable objects, etc. using scripted ...DbNetData: A collection of cross vendor database interface classes for .NET written in C# providing a consistent and simplified way of accessing SQL Server,Or...Deploy Workflow Manager: Kick off a workflow associated with a SharePoint List on all list items at once. SharePoint Designer Workflows will also be included. This projec...DigiLini - digital on screen ruler: Handy desktop tool for everyone who does ever do something graphical on his computer. There is an sizable horizontal and vertial ruler. You can pos...Dynamic Grid Data Type for Umbraco: The Dynamic Grid Data Type for Umbraco is a custom ASCX/C# control that was created to store tabular data as an Umbraco "Data Type". There's an abi...FlashPlus: An extension for Google Chrome and a bookmarklet for Internet Explorer and Firefox, this project makes media content on browsers more usable. This...Flat Database: Simple project making it really quick and easy, to implement a simple flat-file database for an application.Flood Watch Spam Control: Flood watch is a C# based application meant to help prevent site black listings. This application monitors outbound smtp streams, if a stream excee...Gamebox: gameboxKill Bill: Kill Bill covers the areas of customers, suppliers, products, sales and administration divided into modules which together form the system for the ...KND Decoder: Der KND Decoder konvertiert die lästigen Zahlenwerte, in den Java Dateien vom Knuddels Applet, zu lesbaren Strings. Die neue dekodier Methode wurde...Moonbeam: D3D11 FrameworkSite Defender: Add-on for blogs or anywhere else there could be people spamming your website.sMODfix: -Stringzilla: A string formatting classes designed for .NET 4 to enable named string formatting and conditional string formatting options based upon bound data c...The CQRS Kitchen: The CQRS Kitchen is an example application build with Silverlight 4 that demonstrates how to implement a CQRS / Event Sourcing application with the...XELF Framework for XNA / .NET: XELF Framework for XNA / .NET 　XNA Game Studioおよび.NET Framework用のライブラリ・フレームワークとしてXELFが開発したC#ソースコードを含むプロジェクトです。 　現在は、「XELF.Framework」のWindows用XNA G...xxxxxxxxx: xxxxxxxNew ReleasesASP.NET MVC 2 - CommonLibrary.CMS: CommonLibrary CMS - Alpha: CommonLibrary CMSA simple yet powerful CMS system in ASP.NET MVC 2 using C# 3.5. ActiveRecord based support for Blogs, Widgets, Pages, Parts, Ev...ASP.NET MVC Extensions: v1.0 RTM: v1.0 RTMAWS SimpleDB Browser: Release 2: Miscellaneous fixes from the Alpha release. Built to work with the released version of the .Net Framework 4.0.BIDS Helper: 1.4.3.0: This release addresses the following issues: For some people the BIDS Helper extensions to the Project Properties page for the SSIS Deploy plugin w...Bojinx: Bojinx Core V4.5.13: Fixes / Enhancements: Sequencer now accepts Commands directly without using events. Command queue now accepts both events and commands EventBu...CF-Soft: TestCases_DROP1: TestCases_DROP1CodePlex Runtime Intelligence Integration: PreEmptive.Attributes distributable: Contains a signed redistributable version of the PreEmptive.Attributes.dll library that non .NET 4 applications can use support in-code instrumenta...Convection Game Engine (Basic Edition): Convection Basic (44772): Compiled version of Convection Basic change set 44772.CRM Queue Manager C#: Initial release: Initial release of the CRM Queue Manager in C#. Release includes both the installer as well as the latest source code in zippped format. Running...DbNetData: DbNetData.1.0: Initial releaseDigiLini - digital on screen ruler: DigiLini 1.0: First stable version.Facturator - Create invoices easy and fast: Facturator.zip: current stable versionFlat Database: Initial Release: This is the working initial release of FlatDBKharaPOS: MSDN Magazine Sample: This is the release that supports the MSDN magazine article "Enterprise Patterns with WCF RIA Services. Some of the project was affected by the upg...Let's Up: 1.1 (Build 100511): - Add short and long break feature.Mesopotamia Experiment: Mesopotamia 1.2.88: Primarly bug fixes... Bug Fixes - fixed bug in synapse mutating whereby new ones were of one side only eg, source or target - fixed bug in screen ...NodeXL: Network Overview, Discovery and Exploration for Excel: NodeXL Class Libraries, version 1.0.1.123: The NodeXL class libraries can be used to display network graphs in .NET applications. To include a NodeXL network graph in a WPF desktop or Windo...NodeXL: Network Overview, Discovery and Exploration for Excel: NodeXL Excel 2007 Template, version 1.0.1.123: The NodeXL Excel 2007 template displays a network graph using edge and vertex lists stored in an Excel 2007 workbook. What's NewThis version makes...Over Store: OverStore 1.18.0.0: Version number is increased. New callback events added: Persisting and Persisted, which are raised on actually writing object data into the stora...Reusable Library: V1.0.7: A collection of reusable abstractions for enterprise application developerReusable Library Demo: V1.0.5: A demonstration of reusable abstractions for enterprise application developerRuntime Intelligence Endpoint Starter Kit: Runtime Intelligence Endpoint Starter Kit 20100511: Added crossdomain policy files so Silverlight applications can send usage data from anywhere.Scorm2CC: SCORM2CC Release 0.12.0.58711 net-2.0 Alpha: SCORM2CC Release 0.12.0.58711 net-2.0 AlphaShake - C# Make: Shake v0.1.14: Updated API to match with the current documentation.SharePoint LogViewer: SharePoint Log Viewer 2.6: This is a maintenance release. It has bug several fixes.Site Directory for SharePoint 2010 (from Microsoft Consulting Services, UK): v1.4: As 1.3 with the following changes Addition of a 'Site Data' webpart Site Directory can now be a site collection root or sub-site Scan job now ...sMODfix: sMODfix v1.0: Basic Versionsmtp4dev: smtp4dev 2.0: Smtp4dev 2.0 is powered by a completely re-written server component and now offers SSL/TLS and AUTH support.SocialScapes: SocialScapes Sidebar 1.0: The SocialScapes Sidebar is the first release of the new SocialScapes suite. There will be more modules to come along with a complete data aggrega...SSIS Multiple Hash: Multiple Hash V1.2: This is version 1.2 of the Multiple Hash SSIS Component. It supports SQL 2005 and SQL 2008, although you have to download the correct install pack...Surfium: Beta build: Somehow testedTerminals: Terminals 1.9a - RDP6 Support: The major change in this release is that Terminals has been upgraded to require RDP Client 6 to be installed for creating RDP connections. Backward...TFS Compare: Release 3.0: This release provides a new feature - the ability to navigate back and forth between document differences. Also, this release provides support for...VCC: Latest build, v2.1.30511.0: Automatic drop of latest buildyoutubeFisher: youtubeFisher v2.0: What's new new method of youtube parameters capturing HD 720p video support full-HD 1080p video support add Cancel option to stop file downl...Most Popular ProjectsWBFS ManagerRawrAJAX Control ToolkitMicrosoft SQL Server Product Samples: DatabaseSilverlight ToolkitWindows Presentation Foundation (WPF)patterns & practices – Enterprise LibraryMicrosoft SQL Server Community & SamplesPHPExcelASP.NETMost Active Projectspatterns & practices – Enterprise LibraryMirror Testing SystemRawrThe Information Literacy Education Learning Environment (ILE)Caliburn: An Application Framework for WPF and SilverlightwhiteBlogEngine.NETPHPExceljQuery Library for SharePoint Web ServicesTweetSharp

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• CodePlex Daily Summary for Tuesday, December 14, 2010

  CodePlex Daily Summary for Tuesday, December 14, 2010Popular ReleasesFlickrNet API Library: 3.1.4000: Newest release. Now contains dedicated Windows Phone 7 DLL as well as all previous DLLs. Also contains Windows Help file documentation now as standard.mojoPortal: 2.3.5.8: see release notes on mojoportal.com http://www.mojoportal.com/mojoportal-2358-released.aspx Note that we have separate deployment packages for .NET 3.5 and .NET 4.0 The deployment package downloads on this page are pre-compiled and ready for production deployment, they contain no C# source code. To download the source code see the Source Code Tab I recommend getting the latest source code using TortoiseHG, you can get the source code corresponding to this release here.Microsoft All-In-One Code Framework: Visual Studio 2010 Code Samples 2010-12-13: Code samples for Visual Studio 2010SuperWebSocket: SuperWebSocket Drop 2: Changes: based on SuperSocket 1.3 supported sub protocol supported SSL/TLS encryption (wss) in Sync socket mode fixed some data communication bugsSSH.NET Library: 2010.12.13: Fixes SFTP issue when you try to uploaded or download multiple files simultaneously. Usage example can be found hereRequest Tracker Data Access: 1.0.0.0: First releaseSQL Monitor: SQL Monitor 2.4: 1. auto adjust datagrids in query 2. disable activities related commands until activities tab is active.SuperSocket, an extensible socket application framework: SuperSocket 1.3 beta 1: SuperSocket 1.3 is built on .NET 4.0 framework. Bug fixes: fixed a potential bug that the running state hadn't been updated after socket server stopped fixed a synchronization issue when clearing timeout session fixed a bug in ArraySegmentList fixed a bug on getting configuration value Third-part library upgrades: upgraded SuperSocket to .NET 4.0 upgraded EntLib 4.1 to 5.0 New features: supported UDP socket support custom protocol (can support binary protocol and other complecate...Wii Backup Fusion: Wii Backup Fusion 0.9 Beta: - Aqua or brushed metal style for Mac OS X - Shows selection count beside ID - Game list selection mode via settings - Compare Files <-> WBFS game lists - Verify game images/DVD/WBFS - WIT command line for log (via settings) - Cancel possibility for loading games process - Progress infos while loading games - Localization for dates - UTF-8 support - Shortcuts added - View game infos in browser - Transfer infos for log - All transfer routines rewritten - Extract image from image/WBFS - Support....NETTER Code Starter Pack: v1.0.beta: '.NETTER Code Starter Pack ' contains a gallery of Visual Studio 2010 solutions leveraging latest and new technologies and frameworks based on Microsoft .NET Framework. Each Visual Studio solution included here is focused to provide a very simple starting point for cutting edge development technologies and framework, using well known Northwind database (for database driven scenarios). The current release of this project includes starter samples for the following technologies: ASP.NET Dynamic...NuGet (formerly NuPack): NuGet 1.0 Release Candidate: NuGet is a free, open source developer focused package management system for the .NET platform intent on simplifying the process of incorporating third party libraries into a .NET application during development. This release is a Visual Studio 2010 extension and contains the the Package Manager Console and the Add Package Dialog. This new build targets the newer feed (http://go.microsoft.com/fwlink/?LinkID=206669) and package format. See http://nupack.codeplex.com/documentation?title=Nuspe...Free Silverlight & WPF Chart Control - Visifire: Visifire Silverlight, WPF Charts v3.6.5 Released: Hi, Today we are releasing final version of Visifire, v3.6.5 with the following new feature: * New property AutoFitToPlotArea has been introduced in DataSeries. AutoFitToPlotArea will bring bubbles inside the PlotArea in order to avoid clipping of bubbles in bubble chart. You can visit Visifire documentation to know more. http://www.visifire.com/visifirechartsdocumentation.php Also this release includes few bug fixes: * Chart threw exception while adding new Axis in Chart using Vi...PHPExcel: PHPExcel 1.7.5 Production: DonationsDonate via PayPal via PayPal. If you want to, we can also add your name / company on our Donation Acknowledgements page. PEAR channelWe now also have a full PEAR channel! Here's how to use it: New installation: pear channel-discover pear.pearplex.net pear install pearplex/PHPExcel Or if you've already installed PHPExcel before: pear upgrade pearplex/PHPExcel The official page can be found at http://pearplex.net. Want to contribute?Please refer the Contribute page.SwapWin: SwapWin 0.2: Updates: Bring all windows that are swapped to foreground. Make the window sent to primary screen active.??????????: All-In-One Code Framework ??? 2010-12-10: ?????All-In-One Code Framework（??） 2010?12??????！！http://i3.codeplex.com/Project/Download/FileDownload.aspx?ProjectName=1code&DownloadId=128165 ?????release?，???????ASP.NET, WinForm, Silverlight????12?Sample Code。???，??????????sample code。 ?????：http://blog.csdn.net/sjb5201/archive/2010/12/13/6072675.aspx ??，??????MSDN????????????。 http://social.msdn.microsoft.com/Forums/zh-CN/codezhchs/threads ?????????????????，??Email ????UOB & ME: UOB_ME 2.5: latest versionAutoLoL: AutoLoL v1.4.3: AutoLoL now supports importing the build pages from Mobafire.com as well! Just insert the url to the build and voila. (For example: http://www.mobafire.com/league-of-legends/build/unforgivens-guide-how-to-build-a-successful-mordekaiser-24061) Stable release of AutoChat (It is still recommended to use with caution and to read the documentation) It is now possible to associate *.lolm files with AutoLoL to quickly open them The selected spells are now displayed in the masteries tab for qu...SubtitleTools: SubtitleTools 1.2: - Added auto insertion of RLE (RIGHT-TO-LEFT EMBEDDING) Unicode character for the RTL languages. - Fixed delete rows issue.PHP Manager for IIS: PHP Manager 1.1 for IIS 7: This is a final stable release of PHP Manager 1.1 for IIS 7. This is a minor incremental release that contains all the functionality available in 53121 plus additional features listed below: Improved detection logic for existing PHP installations. Now PHP Manager detects the location to php.ini file in accordance to the PHP specifications Configuring date.timezone. PHP Manager can automatically set the date.timezone directive which is required to be set starting from PHP 5.3 Ability to ...Algorithmia: Algorithmia 1.1: Algorithmia v1.1, released on December 8th, 2010.New ProjectsAugmented Reality system in Soccer video: Augmented reality system and camera calibration system in soccer videos based on homography and vanishing points. Code generated with Visual C++ (best compiler is .net)Database Schema Provider: Database Schema Provider gets a database schema in unified format independent on the type of database. It uses ADO.NET data provider for Entity Framework. Dicke Bertha: Many many cool features... DNN Bookmark: DNN Bookmarks is a DNN module that aggregates the most popular social bookmarking tools and also allows you to bookmark your DNN web siteDough: Dough is a UI starter kit built using ASP.Net MVC and ExtJS. It's name comes from the concept of Amish friendship bread, a type of bread or cake made from a sourdough starter that is often shared in a manner similar to a chain letter.Garra - Gerenciador Financeiro: Garra é um sistema completo de controle financeiro: contas a pagar, contas a receber, investimentos, etc...ghcwp7: ghcwp7Hackathon - DotNetNuke Razor User Locator: The DotNetNuke Razor User Locator module demonstrates how Razor can be used to author DNN modules. This module shows where recent users to a web site came from based on their IP address. Hackathon. DotNetNuke Razor. Flickr Badge: Flickr badge desktop module allows you to display image thumbnails from Flickr and preview them inside DotNetNuke or on Flickr (controlled by module settings). Image thumbnails can be loaded by tag, user id, user group id, user set id and more.Hackathon: Razor Youtube Gallery: This is a DotNetNuke module which allows a website admin to add several relevant Youtube videos to a pane. The end user watches the selected Youtube video play, while scrolling through thumbnails of other videos to play those without refreshing the page. jQuery UI MVC3 Demo: Demo and possibly a skeleton for using jQuery UI in MVC3 (currently RC2).Microsoft Office Communicator History manager: Needs to save conversation history just on the local workstation (folder) then application could redstore it and show in simple window (mode) or user could open folder and lock on it manuallyMSTest Extensions - Msbuild: This project contains various msbuild tasks that extend helps with test execution using Mcrosoft testing frameworkRayCharlesTracer: this is a scholar project for a raytracer.Refunctor: F# interactive inside Reflector.Request Tracker Data Access: Best Practical RT (Request Tracker) data access .NET library for REST interface.SurfzApp: An application that does data mining on web resources of interest for Swedish windsurfers...Tesseract Solutions Corp. Data Access Base: Tesseract Data Access speeds up data access in .Net projects. Developed in C# .Net 4. It is a C#, class based ORM.TimBazinga EVoting: Undergrad project - designing an e-voting software system.Tiny Library CQRS: Tiny Library CQRS is a small demonstration project which demonstrates the concept of Domain Driven Design and the CQRS architecture pattern. This project relies on the Apworks DDD framework.Toptoys: toptoysWebGroup: WebGroup makes it easier for your website members to comunicate online. It work like Web IM + Forum + Twitter. It can be easily used in your current project. Developed in C#.WpfCustomChromeLibrary: WpfCustomChromeLibrary makes it easier to create WPF applications with custom chrome and caption buttons (min/max/close). You'll no longer have to do all the dirty work yourself in each application where you want a custom chrome. It's developed in XAML and C#.

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• My architecture has a problem with views that required information from different objects. How can I solve this?

  - by Oscar

  I am building an architecture like this: These are my SW layers ______________ | | | Views | |______________| ______________ | | |Business Logic| |______________| ______________ | | | Repository | |______________| My views are going to generate my HTML to be sent to the user Business logic is where all the business logics are Repository is a layer to access the DB My idea is that the repository uses entities (that are basically the representation of the tables, in order to perform DB queries. The layers communicate between themselves using Business Objects, that are objects that represent the real-world-object itself. They can contain business rules and methods. The views build/use DTOs, they are basically objects that have the information required to be shown on the screen. They expect also this kind of object on actions and, before calling the business logic, they create BO. First question: what is your overall feeling about this architecture? I've used similar architecture for some projects and I always got this problem: If my view has this list to show : Student1, age, course, Date Enrolled, Already paid? It has information from different BO. How do you think one should build the structure? These were the alternatives I could think of: The view layer could call the methods to get the student, then the course it studies, then the payment information. This would cause a lot of DB accesses and my view would have the knowledge about how to act to generate this information. This just seems wrong for me. I could have an "adapter object", that has the required information (a class that would have a properties Student, Course and Payment). But I would required one adapter object for each similar case, this may get very bad for big projects. I still don't like them. Would you have ideas? How would you change the architecture to avoid this kind of problems? @Rory: I read the CQRS and I don't think this suits my needs. As taken from a link references in your link Before describing the details of CQRS we need to understand the two main driving forces behind it: collaboration and staleness That means: many different actors using the same object (collaboration) and once data has been shown to a user, that same data may have been changed by another actor – it is stale (staleness). My problem is that I want to show to the user information from different BO, so I would need to receive them from the service layer. How can my service layer assemble and deliver this information? Edit to @AndrewM: Yes, you understood it correctly, the original idea was to have the view layer to build the BOs, but you have a very nice point about the creation of the BO inside the business layers. Assuming I follow your advice and move the creation logic inside the business layer, my business layer interface would contain the DTOs, for instance public void foo(MyDTO object) But as far as I understand, the DTO is tightly coupled to each view, so it would not be reusable by a second view. In order to use it, the second view would need to build a specific DTO from a specific view or I would have to duplicate the code in the business layer. Is this correct or am I missing something?

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• Visual Studio Talk Show #118 is now online - Command-Query Responsibility Separation (French)

  http://www.visualstudiotalkshow.com Erik Renaud: La sparation des responsabilits entre les commandes et les requtes Nous discutons avec Erik Renaud de la sparation des responsabilits entre les commandes et les requtes (Command-Query Responsibility Separation - CQRS). La plupart des applications lisent les donnes beaucoup plus frquemment qu'ils font des critures. Sur la base de cette dclaration, une bonne ide consiste sparer le code qui est responsable de lcriture des donnes du code qui est...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• ASP.NET mvcConf Videos Available

  - by ScottGu

  Earlier this month the ASP.NET MVC developer community held the 2nd annual mvcConf event.  This was a free, online conference focused on ASP.NET MVC – with more than 27 talks that covered a wide variety of ASP.NET MVC topics.  Almost all of the talks were presented by developers within the community, and the quality and topic diversity of the talks was fantastic. Below are links to free recordings of the talks that you can watch (and optionally download): Scott Guthrie Keynote The NuGet-y Goodness of Delivering Packages (Phil Haack) Industrial Strenght NuGet (Andy Wahrenberger) Intro to MVC 3 (John Petersen) Advanced MVC 3 (Brad Wilson) Evolving Practices in Using jQuery and Ajax in ASP.NET MVC Applications (Eric Sowell) Web Matrix (Rob Conery) Improving ASP.NET MVC Application Performance (Steven Smith) Intro to Building Twilio Apps with ASP.NET MVC (John Sheehan) The Big Comparison of ASP.NET MVC View Engines (Shay Friedman) Writing BDD-style Tests for ASP.NET MVC using MSTestContrib (Mitch Denny) BDD in ASP.NET MVC using SpecFlow, WatiN and WatiN Test Helpers (Brandon Satrom) Going Postal - Generating email with View Engines (Andrew Davey) Take some REST with WCF (Glenn Block) MVC Q&A (Jeffrey Palermo) Deploy ASP.NET MVC with No Effort (Troels Thomsen) IIS Express (Vaidy Gopalakrishnan) Putting the V in MVC (Chris Bannon) CQRS and Event Sourcing with MVC 3 (Ashic Mahtab) MVC 3 Extensibility (Roberto Hernandez) MvcScaffolding (Steve Sanderson) Real World Application Development with Mvc3 NHibernate, FluentNHibernate and Castle Windsor (Chris Canal) Building composite web applications with Open frameworks (Sebastien Lambla) Quality Driven Web Acceptance Testing (Amir Barylko) ModelBinding derived types using the DerivedTypeModelBinder in MvcContrib (Steve Hebert) Entity Framework "Code First": Domain Driven CRUD (Chris Zavaleta) Wrap Up with Jon Galloway & Javier Lozano I’d like to say a huge thank you to all of the speakers who presented, and to Javier Lozano, Eric Hexter and Jon Galloway for all their hard work in organizing the event and making it happen. Hope this helps, Scott P.S. I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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