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  • [C#][Design] Appropriate programming design questions.

    - by Edward
    I have a few questions on good programming design. I'm going to first describe the project I'm building so you are better equipped to help me out. I am coding a Remote Assistance Tool similar to TeamViewer, Microsoft Remote Desktop, CrossLoop. It will incorporate concepts like UDP networking (using Lidgren networking library), NAT traversal (since many computers are invisible behind routers nowadays), Mirror Drivers (using DFMirage's Mirror Driver (http://www.demoforge.com/dfmirage.htm) for realtime screen grabbing on the remote computer). That being said, this program has a concept of being a client-server architecture, but I made only one program with both the functionality of client and server. That way, when the user runs my program, they can switch between giving assistance and receiving assistance without having to download a separate client or server module. I have a Windows Form that allows the user to choose between giving assistance and receiving assistance. I have another Windows Form for a file explorer module. I have another Windows Form for a chat module. I have another Windows Form form for a registry editor module. I have another Windows Form for the live control module. So I've got a Form for each module, which raises the first question: 1. Should I process module-specific commands inside the code of the respective Windows Form? Meaning, let's say I get a command with some data that enumerates the remote user's files for a specific directory. Obviously, I would have to update this on the File Explorer Windows Form and add the entries to the ListView. Should I be processing this code inside the Windows Form though? Or should I be handling this in another class (although I have to eventually pass the data to the Form to draw, of course). Or is it like a hybrid in which I process most of the data in another class and pass the final result to the Form to draw? So I've got like 5-6 forms, one for each module. The user starts up my program, enters the remote machine's ID (not IP, ID, because we are registering with an intermediary server to enable NAT traversal), their password, and connects. Now let's suppose the connection is successful. Then the user is presented with a form with all the different modules. So he can open up a File Explorer, or he can mess with the Registry Editor, or he can choose to Chat with his buddy. So now the program is sort of idle, just waiting for the user to do something. If the user opens up Live Control, then the program will be spending most of it's time receiving packets from the remote machine and drawing them to the form to provide a 'live' view. 2. Second design question. A spin off question #1. How would I pass module-specific commands to their respective Windows Forms? What I mean is, I have a class like "NetworkHandler.cs" that checks for messages from the remote machine. NetworkHandler.cs is a static class globally accessible. So let's say I get a command that enumerates the remote user's files for a specific directory. How would I "give" that command to the File Explorer Form. I was thinking of making an OnCommandReceivedEvent inside NetworkHandler, and having each form register to that event. When the NetworkHandler received a command, it would raise the event, all forms would check it to see if it was relevant, and the appropriate form would take action. Is this an appropriate/the best solution available? 3. The networking library I'm using, Lidgren, provides two options for checking networking messages. One can either poll ReadMessage() to return null or a message, or one can use an AutoResetEvent OnMessageReceived (I'm guessing this is like an event). Which one is more appropriate?

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  • iPad Split View Controller - Master View and Detial View contain TableViews

    - by vman9999
    Hi, I've managed to read some values into a table view and display them in the Master View of a SplitViewController. What I would like to do is to tap on a row of the Master View and display the details on the detailViewController but in a TableView. When I tap on the row in the MasterView table, I can't seem to get the detail to populate the detailview TableView. Any suggestions? Thanks in advance.

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  • Convert table base design to table less design in best way

    - by Brij
    What is the best optimized way to convert following in table less design? the layout should be cross browser compatible and SEO Friendly. <table cellpadding="0" cellspacing="0"> <tr> <td>Row 1 Column 1</td> <td>Row 1 Column 2</td> <td>Row 1 Column 3</td> </tr> <tr> <td colspan="3" align="center">Row 2</td> </tr> <tr> <td>Row 3</td> <td align="right" colspan="2"><img src="test.jpg" alt="test" /></td> </tr> </table>

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  • Software Design & Web Service Design

    - by 001
    I'm about to design my Web service API, most of the functions of my API is basically very simular to my web application. Now the question is, should I create 1 single method and reuse them for both the web application and the web service api? (This seems to be the logical solution, however its very complicated; it's much easier to duplicate the method used by the web application, and keep both separate, ie one method for the web application and one method for the web service.) How do you guys do it? 1) REUSE: one main method and reuse them for both web application and web service application (I like this but it's complicated) WebAppMethodX --uses-- COMMONFUNCTIONMETHOD_X APIMethodX ---uses---- COMMONFUNCTIONMETHOD_X ie common function performs functions such as creating/updating/deleting records etc 2) DUPLICATE: two methods, one method for the web application and one method for the web service. WebAppMethodX APIMethodX

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  • Creating a dummy design before the development starts

    - by NLV
    Hello How can i create a dummy design of an application before the actual development starts? How to simulate the UI of the application. After completing the analysis phase do i need to start the design directly using dev tools or can i create some dummies (even images, using Visio or something) with other tools? Thank you

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  • Learn Domain-Driven Design

    - by Ben Griswold
    I just wrote about how I like to present on unfamiliar topics. With this said, Domain-Driven Design (DDD) is no exception. This is yet another area I knew enough about to be dangerous but I certainly was no expert.  As it turns out, researching this topic wasn’t easy. I could be wrong, but it is as if DDD is a secret to which few are privy. If you search the Interwebs, you will likely find little information about DDD until you start rolling over rocks to find that one great write-up, a handful of podcasts and videos and the Readers’ Digest version of the Blue Book which apparently you must read if you really want to get the complete, unabridged skinny on DDD.  Even Wikipedia’s write-up is skimpy which I didn’t know was possible…   Here’s a list of valuable resources.  If you, too, are interested in DDD, this is a good starting place.  Domain-Driven Design: Tackling Complexity in the Heart of Software by Eric Evans Domain-Driven Design Quickly, by Abel Avram & Floyd Marinescu An Introduction to Domain-Driven Design by David Laribee Talking Domain-Driven Design with David Laribee Part 1, Deep Fried Bytes Talking Domain-Driven Design with David Laribee Part 2, Deep Fried Bytes Eric Evans on Domain Driven Design, .NET Rocks Domain-Driven Design Community Eric Evans on Domain Driven Design Jimmy Nilsson on Domain Driven Design Domain-Driven Design Wikipedia What I’ve Learned About DDD Since the Book, Eric Evans Domain Driven Design, Alt.Net Podcast Applying Domain-Driven Design and Patterns: With Examples in C# and .NET, Jimmy Nilsson Domain-Driven Design Discussion Group DDD: Putting the Model to Work by Eric Evans The Official DDD Site

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  • Smart View és az Office verziók

    - by Fekete Zoltán
    A Smart View többek között az Oracle Essbase (Hyperion) lekérdezo-elemzo-kontrolling-adatbeviteli stb felülete is. A Smart View egy MS Excel add-in-ként áll rendelkezésre. Teljes mértékben támogatja a tervezési, költségvetéskészítési, kontrolling és elemzési munkát. Az Essbase a kontrollerek szívéhez és kezéhez közelálló OLAP szerver, ami a Hyperion Planningnek is az alapja. Milyen MS Office verziókat támogat a Smart View? MS Office 2000 (XP), 2003, 2007 verziókat. Ezt az információt az Oracle Enterprise Performance Management Products - Supported Platforms Matrices helyen felsorolt dokumentumok írják le. Az Oracle Enterprise Performance Management aktuális verziójának 11.1.1.3 teljes dokumentácója megtalálható itt.

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  • Tips for adapting Date table to Power View forecasting #powerview #powerbi

    - by Marco Russo (SQLBI)
    During the keynote of the PASS Business Analytics Conference, Amir Netz presented the new forecasting capabilities in Power View for Office 365. I immediately tried the new feature (which was immediately available, a welcome surprise in a Microsoft announcement for a new release) and I had several issues trying to use existing data models. The forecasting has a few requirements that are not compatible with the “best practices” commonly used for a calendar table until this announcement. For example, if you have a Year-Month-Day hierarchy and you want to display a line chart aggregating data at the month level, you use a column containing month and year as a string (e.g. May 2014) sorted by a numeric column (such as 201405). Such a column cannot be used in the x-axis of a line chart for forecasting, because you need a date or numeric column. There are also other requirements and I wrote the article Prepare Data for Power View Forecasting in Power BI on SQLBI, describing how to create columns that can be used with the new forecasting capabilities in Power View for Office 365.

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  • Massive Google Street View Update: 250,000 Miles of Roadways, New Special Collections, and More

    - by Jason Fitzpatrick
    If you like tooling around in Google Street View to check out attractions near and far, you just got a whole lot more to look at. Street View’s new update adds in 250,000 miles of roads, increased coverage in over a dozen countries, and a whole pile of new special collections. From Russia to Taiwan to Canada, there’s thousands of new places and tens of thousands of new roads to explore. Hit up the link below to read the full announcement at the Google Maps blog. Making Google Maps More Comprehensive with Ciggest Street View Update Ever [Google Maps] HTG Explains: What is the Windows Page File and Should You Disable It? How To Get a Better Wireless Signal and Reduce Wireless Network Interference How To Troubleshoot Internet Connection Problems

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  • Tips for adapting Date table to Power View forecasting #powerview #powerbi

    - by Marco Russo (SQLBI)
    During the keynote of the PASS Business Analytics Conference, Amir Netz presented the new forecasting capabilities in Power View for Office 365. I immediately tried the new feature (which was immediately available, a welcome surprise in a Microsoft announcement for a new release) and I had several issues trying to use existing data models. The forecasting has a few requirements that are not compatible with the “best practices” commonly used for a calendar table until this announcement. For example, if you have a Year-Month-Day hierarchy and you want to display a line chart aggregating data at the month level, you use a column containing month and year as a string (e.g. May 2014) sorted by a numeric column (such as 201405). Such a column cannot be used in the x-axis of a line chart for forecasting, because you need a date or numeric column. There are also other requirements and I wrote the article Prepare Data for Power View Forecasting in Power BI on SQLBI, describing how to create columns that can be used with the new forecasting capabilities in Power View for Office 365.

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  • Can't select View Content dropdown when adding view in MVC using Interfaces

    - by fearofawhackplanet
    I have my Model defined externally in two projects - a Core project and an Interface project. I am opening the Add View dialogue from my controller, and selecting Create a strongly typed view. In the drop down list, I can select the concrete types like MyProject.Model.Core.OrderDetails, but the interface types like MyProject.Model.Interface.IOrderDetails aren't there. I can type the interface class in manually and everything works, but then the View content menu that lets you select the Create, Delete, List, etc scaffolding is disabled. Is there some problem with using interfaces in MVC? Or is it something else I'm missing?

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  • OO Design - polymorphism - how to design for handing streams of different file types

    - by Kache4
    I've little experience with advanced OO practices, and I want to design this properly as an exercise. I'm thinking of implementing the following, and I'm asking if I'm going about this the right way. I have a class PImage that holds the raw data and some information I need for an image file. Its header is currently something like this: #include <boost/filesytem.hpp> #include <vector> namespace fs = boost::filesystem; class PImage { public: PImage(const fs::path& path, const unsigned char* buffer, int bufferLen); const vector<char> data() const { return data_; } const char* rawData() const { return &data_[0]; } /*** other assorted accessors ***/ private: fs::path path_; int width_; int height_; int filesize_; vector<char> data_; } I want to fill the width_ and height_ by looking through the file's header. The trivial/inelegant solution would be to have a lot of messy control flow that identifies the type of image file (.gif, .jpg, .png, etc) and then parse the header accordingly. Instead of using vector<char> data_, I was thinking of having PImage use a class, RawImageStream data_ that inherits from vector<char>. Each type of file I plan to support would then inherit from RawImageStream, e.g. RawGifStream, RawPngStream. Each RawXYZStream would encapsulate the respective header-parsing functions, and PImage would only have to do something like height_ = data_.getHeight();. Am I thinking this through correctly? How would I create the proper RawImageStream subclass for data_ to be in the PImage ctor? Is this where I could use an object factory? Anything I'm forgetting?

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  • Which design is better (OO Design)?

    - by Tattat
    I have an "Enemy" object, that have many "gun" . Each "gun" can fire "bullet". Storing "gun" is using an array. when the "gun" is fired, the "bullet" will be created. And the enemy object will have an array to store the "bullet". So, I am thinking about the fire method. I am think making a firebulletFromGun in the "enemy". It need have a parameter: "gun". while this method is called. The "enemy" 's bullet will be added in the Array. Another design is writing the fire method in the "gun". The "enemy" use the "gun"'s fire method. And the "gun" will return a "bullet" object, and it will be added in the Array of "enemy". Both method can work, but which way is better? or they are similar the same? plx drop ur ideas/suggestions. thz.

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  • Object Design catalog and resources

    - by Tauren
    I'm looking for web sites, books, or other resources that provide a catalog of object designs used in common scenarios. I'm not looking for generic design patterns, but for samples of actual object designs that were used to solve real problems. For instance, I'm about to build an internal messaging system for a web application, similar to Facebook's messaging system. This system will allow administrators to send messages to all members, to selected groups of members, or to individuals. Members can send messages to other members or groups of members. Fairly common stuff and a feature that I'm sure thousands of web applications require. I know each situation is different and there are a million ways to design this solution. Although this scenario isn't really all that complex, I'm sure the basic design of the necessary objects and relationships for a system like this has already been done many times. It would be nice to review other similar designs before building my own. Is there a place where people can share their designs and others can browse/search through the catalog to review and provide feedback on them? StackOverflow could be used to a degree for this, but doesn't really provide a catalog of designs. Any other resources that would relate?

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  • Olympics data available for all on Windows Azure SQL Database and Power View

    - by jamiet
    Are you looking around for some decent test data for your BI demos? Well, if so, Microsoft have provided some data about all medals won at the Olympics Games (1900 to 2008) at OlympicsData workbook - Excel, SSIS, Azure sample; it provides analysis over athletes, countries, medal type, sport, discipline and various other dimensions. The data has been provided in an Excel workbook along with instructions on how to load the data into a Windows Azure SQL Database using SQL Server Integration Services (SSIS). Frankly though, the rigmarole of standing up your own Windows Azure SQL Database ok, SQL Azure database, is both costly (SQL Azure isn’t free) and time consuming (the provided instructions aren’t exactly an idiot’s guide and getting SSIS to work properly with Excel isn’t a barrel of laughs either). To ease the pain for all you BI folks out there that simply want to party on the data I have loaded it all into the SQL Azure database that I use for hosting AdventureWorks on Azure. You can read more about AdventureWorks on Azure below however I’ll summarise here by saying it is a SQL Azure database provided for the use of the SQL Server community and which is supported by voluntary donations. To view the data the credentials you need are: Server mhknbn2kdz.database.windows.net  Database AdventureWorks2012 User sqlfamily Password sqlf@m1ly Type those into SSMS and away you go, the data is provided in four tables [olympics].[Sport], [olympics].[Discipline], [olympics].[Event] & [olympics].[Medalist]: I figured this would be a good candidate for a Power View report so I fired up Excel 2013 and built such a report to slice’n’dice through the data – here are some screenshots that should give you a flavour of what is available: A view of all the available data Where do all the gymastics medals go? Which countries do top ten all-time medal winners come from? You get the idea. There is masses of information here and if you have Excel 2013 handy Power View provides a quick and easy way of surfing through it. To save you the bother of setting up the Power View report yourself you can have the one that I took these screenshots from, it is available on my SkyDrive at OlympicsAnalysis.xlsx so just hit the link and download to play to your heart’s content. Party on, people! As I said above the data is hosted on a SQL Azure database that I use for hosting “AdventureWorks on Azure” which I first announced in March 2013 at AdventureWorks2012 now available for all on SQL Azure. I’ll repeat the pertinent parts of that blog post here: I am pleased to announce that as of today … [AdventureWorks2012] now resides on SQL Azure and is available for anyone, absolutely anyone, to connect to and use for their own means. This database is free for you to use but SQL Azure is of course not free so before I give you the credentials please lend me your ears eyes for a short while longer. AdventureWorks on Azure is being provided for the SQL Server community to use and so I am hoping that that same community will rally around to support this effort by making a voluntary donation to support the upkeep which, going on current pricing, is going to be $119.88 per year. If you would like to contribute to keep AdventureWorks on Azure up and running for that full year please donate via PayPal to [email protected] Any amount, no matter how small, will help. If those 50+ people that retweeted me beforehand all contributed $2 then that would just about be enough to keep this up for a year. If the community contributes more than we need then there are a number of additional things that could be done: Host additional databases (Northwind anyone??) Host in more datacentres (this first one is in Western Europe) Make a charitable donation That last one, a charitable donation, is something I would really like to do. The SQL Community have proved before that they can make a significant contribution to charitable orgnisations through purchasing the SQL Server MVP Deep Dives book and I harbour hopes that AdventureWorks on Azure can continue in that vein. So please, if you think AdventureWorks on Azure is something that is worth supporting please make a contribution. I’d like to emphasize that last point. If my hosting this Olympics data is useful to you please support this initiative by donating. Thanks in advance. @Jamiet

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  • who are software design engineers?

    - by Sepala
    My question is, who are software design engineers? And, what is the meaning of the following statement (from a software design engineer job ad)? "Application domain knowledge is essential and....." What is application domain? SDLC? My hope is to become a software engineer one day (OK, to be honest, more than that. I need to be a legend), that who do programming (They say this job has no programming). I am following final year of my Bsc(Hons) in computing and I have completed a foreign diploma, majoring software engineering - Java technologies. Will this job experience help me out to get a job in my desired position, which is mentioned above, after the degree? Wikipedia and google never gave a clear straight forward answer!! Please help!

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  • Code Structure / Level Design: Plants vs Zombies game level dissection

    - by lalan
    Hi Friends, I am interested in learning the class structure of Plants vs Zombies, particularly level design; for those who haven't played it - this video contains nice play-through: http://www.youtube.com/watch?v=89DfdOIJ4xw. How would I go ahead and design the code, mostly structure & classes, which allows for maximum flexibility & clean development? I am familiar with data driven design concepts, and would use events to handle most of dynamic behavior. Dissection at macro level: (Once every Level) Load tilemap, props, etc -- basically build the map (Once every Level) Camera Movement - might consider it as short cut-scene (Once every Level) Show Enemies you'll face during present level (Once every Level) Unit Selection Window/Panel - selection of defensive plants (Once every Level) Camera Movement - might consider it as short cut-scene (Once every Level) HUD Creation - based on unit selection (Level Loop) Enemy creation - based on types of zombies allowed (Level Loop) Sun/Resource generation (Level Loop) Show messages like 'huge wave of zombies coming', 'final wave' (Level Loop) Other unique events - Spawn gifts, money, tombstones, etc (Once every Level) Unlock new plant Potential game scripts: a) Level definitions: Level_1_1.xml, Level_1_2.xml, etc. Level_1_1.xml :: Sample script <map> <tilemap>tilemapFrontLawn</tilemap> <SpawnPoints> tiles where particular type of zombies (land vs water) may spawn</spawnPoints> <props> position, entity array -- lawnmower, </props> </map> <zombies> <... list of zombies who gonna attack by ids...> </zombies> <plants> <... list by plants which are available for defense by ids...> </plants> <progression> <ZombieWave name='first wave' spawnScript='zombieLightWave.lua' unlock='null'> <startMessages time=1.5>Ready</startMessages> <endMessages time=1.5>Huge wave of zombies incoming</endMessages> </ZombieWave> </progression> b) Entities definitions: .xmls containing zombies, plants, sun, lawnmower, coins, etc description. Potential classes: //LevelManager - Based on the level under play, it will load level script. Few of the // functions it may have: class LevelManager { public: bool load(string levelFileName); bool enter(); bool update(float deltatime); bool exit(); private: LevelData* mLevelData; } // LevelData - Contains the details of level loaded by LevelManager. class LevelData { private: string file; // array of camera,dialog,attackwaves, etc in active level LevelCutSceneCamera** mArrayCutSceneCamera; LevelCutSceneDialog** mArrayCutSceneDialog; LevelAttackWave** mArrayAttackWave; .... // which camera,dialog,attackwave is active in level uint mCursorCutSceneCamera; uint mCursorCutSceneDialog; uint mCursorAttackWave; public: // based on cursor, get the next camera,dialog,attackwave,etc in active level // return false/true based on failure/success bool nextCutSceneCamera(LevelCutSceneCamera**); bool nextCutSceneDialog(LevelCutSceneDialog**); } // LevelUnderPlay- LevelManager class LevelUnderPlay { private: LevelCutSceneCamera* mCutSceneCamera; LevelCutSceneDialog* mCutSceneDialog; LevelAttackWave* mAttackWave; Entities** mSelectedPlants; Entities** mAllowedZombies; bool isCutSceneCameraActive; public: bool enter(); bool update(float deltatime); bool exit(); } I am totally confused.. :( Does it make sense of using class composition (have flat class hierarchy) for managing levels. Is it a good idea to just add/remove/update sprites (or any drawable stuff) to current scene from LevelManager or LevelUnderPlay? If I want to make non-linear level design, how should I go ahead? Perhaps I would need a LevelProgression class, which would decide what to do based on decision tree. Any suggestions would be appreciated very much. Thank for your time, lalan

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  • Relationship between TDD and Software Architecture/Design

    - by Christopher Francisco
    I'm new to TDD and have been reading the theory since applying it is more complicated than it sounds when you're learning by yourself. As far as I know, the objective is to write test cases for each requirement and run the test so it fails (to prevent a false positive). Afterward, you should write the minimum amount of code that can pass the test and move to the next one. That being said, is it true that you get a fast development, but what about the code itself? this theory makes me think you are not considering things like abstraction, delegation of responsibilities, design patterns, architecture and others since you're just writing "the minimum amount of code that can pass the test". I know I'm probably wrong because if this were true, we'd have a lot of crappy developers with poor software architecture and documentation so I'm asking for a guide here, what's the relationship between TDD and Software Architecture/Design?

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  • Design patterns frequently seen in embedded systems programming

    - by softwarelover
    I don't have any question related to coding. My concerns are about embedded systems programming independent of any particular programming language. Because I am new in the realm of embedded programming, I would quite appreciate responses from those who consider themselves experienced embedded systems programmers. I basically have 2 questions. Of the design patterns listed below are there any seen frequently in embedded systems programming? Abstraction-Occurrence pattern General Hierarchy pattern Player-Role pattern Singleton pattern Observer pattern Delegation pattern Adapter pattern Facade pattern Immutable pattern Read-Only Interface pattern Proxy pattern As an experienced embedded developer, what design patterns have you, as an individual, come across? There is no need to describe the details. Only the pattern names would suffice. Please share your own experience. I believe the answers to the above questions would work as a good starting point for any novice programmers in the embedded world.

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  • Modified Strategy Design Pattern

    - by Samuel Walker
    I've started looking into Design Patterns recently, and one thing I'm coding would suit the Strategy pattern perfectly, except for one small difference. Essentially, some (but not all) of my algorithms, need an extra parameter or two passed to them. So I'll either need to pass them an extra parameter when I invoke their calculate method or store them as variables inside the ConcreteAlgorithm class, and be able to update them before I call the algorithm. Is there a design pattern for this need / How could I implement this while sticking to the Strategy Pattern? I've considered passing the client object to all the algorithms, and storing the variables in there, then using that only when the particular algorithm needs it. However, I think this is both unwieldy, and defeats the point of the strategy pattern. Just to be clear I'm implementing in Java, and so don't have the luxury of optional parameters (which would solve this nicely).

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  • Adventures in Windows 8: Understanding and debugging design time data in Expression Blend

    - by Laurent Bugnion
    One of my favorite features in Expression Blend is the ability to attach a Visual Studio debugger to Blend. First let’s start by answering the question: why exactly do you want to do that? Note: If you are familiar with the creation and usage of design time data, feel free to scroll down to the paragraph titled “When design time data fails”. Creating design time data for your app When a designer works on an app, he needs to see something to design. For “static” UI such as buttons, backgrounds, etc, the user interface elements are going to show up in Blend just fine. If however the data is fetched dynamically from a service (web, database, etc) or created dynamically, most probably Blend is going to show just an empty element. The classical way to design at that stage is to run the application, navigate to the screen that is under construction (which can involve delays, need to log in, etc…), to measure what is on the screen (colors, margins, width and height, etc) using various tools, going back to Blend, editing the properties of the elements, running again, etc. Obviously this is not ideal. The solution is to create design time data. For more information about the creation of design time data by mocking services, you can refer to two talks of mine “Deep dive MVVM” and “MVVM Applied From Silverlight to Windows Phone to Windows 8”. The source code for these talks is here and here. Design time data in MVVM Light One of the main reasons why I developed MVVM Light is to facilitate the creation of design time data. To illustrate this, let’s create a new MVVM Light application in Visual Studio. Install MVVM Light from here: http://mvvmlight.codeplex.com (use the MSI in the Download section). After installing, make sure to read the Readme that opens up in your favorite browser, you will need one more step to install the Project Templates. Start Visual Studio 2012. Create a new MvvmLight (Win8) app. Run the application. You will see a string showing “Welcome to MVVM Light”. In the Solution explorer, right click on MainPage.xaml and select Open in Blend. Now you should see “Welcome to MVVM Light [Design]” What happens here is that Expression Blend runs different code at design time than the application runs at runtime. To do this, we use design-time detection (as explained in a previous article) and use that information to initialize a different data service at design time. To understand this better, open the ViewModelLocator.cs file in the ViewModel folder and see how the DesignDataService is used at design time, while the DataService is used at runtime. In a real-life applicationm, DataService would be used to connect to a web service, for instance. When design time data fails Sometimes however, the creation of design time data fails. It can be very difficult to understand exactly what is happening. Expression Blend is not giving a lot of information about what happened. Thankfully, we can use a trick: Attaching a debugger to Expression Blend and debug the design time code. In WPF and Silverlight (including Windows Phone 7), you could simply attach the debugger to Blend.exe (using the “Managed (v4.5, v4.0) code” option even for Silverlight!!) In Windows 8 however, things are just a bit different. This is because the designer that renders the actual representation of the Windows 8 app runs in its own process. Let’s illustrate that: Open the file DesignDataService in the Design folder. Modify the GetData method to look like this: public void GetData(Action<DataItem, Exception> callback) { throw new Exception(); // Use this to create design time data var item = new DataItem("Welcome to MVVM Light [design]"); callback(item, null); } Go to Blend and build the application. The build succeeds, but now the page is empty. The creation of the design time data failed, but we don’t get a warning message. We need to investigate what’s wrong. Close MainPage.xaml Go to Visual Studio and select the menu Debug, Attach to Process. Update: Make sure that you select “Managed (v4.5, v4.0) code” in the “Attach to” field. Find the process named XDesProc.exe. You should have at least two, one for the Visual Studio 2012 designer surface, and one for Expression Blend. Unfortunately in this screen it is not obvious which is which. Let’s find out in the Task Manager. Press Ctrl-Alt-Del and select Task Manager Go to the Details tab and sort the processes by name. Find the one that says “Blend for Microsoft Visual Studio 2012 XAML UI Designer” and write down the process ID. Go back to the Attach to Process dialog in Visual Studio. sort the processes by ID and attach the debugger to the correct instance of XDesProc.exe. Open the MainViewModel (in the ViewModel folder) Place a breakpoint on the first line of the MainViewModel constructor. Go to Blend and open the MainPage.xaml again. At this point, the debugger breaks in Visual Studio and you can execute your code step by step. Simply step inside the dataservice call, and find the exception that you had placed there. Visual Studio gives you additional information which helps you to solve the issue. More info and Conclusion I want to thank the amazing people on the Expression Blend team for being very fast in guiding me in that matter and encouraging me to blog about it. More information about the XDesProc.exe process can be found here. I had to work on a Windows 8 app for a few days without design time data because of an Exception thrown somewhere in the code, and it was really painful. With the debugger, finding the issue was a simple matter of stepping into the code until it threw the exception.   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • Design review for application facing memory issues

    - by Mr Moose
    I apologise in advance for the length of this post, but I want to paint an accurate picture of the problems my app is facing and then pose some questions below; I am trying to address some self inflicted design pain that is now leading to my application crashing due to out of memory errors. An abridged description of the problem domain is as follows; The application takes in a “dataset” that consists of numerous text files containing related data An individual text file within the dataset usually contains approx 20 “headers” that contain metadata about the data it contains. It also contains a large tab delimited section containing data that is related to data in one of the other text files contained within the dataset. The number of columns per file is very variable from 2 to 256+ columns. The original application was written to allow users to load a dataset, map certain columns of each of the files which basically indicating key information on the files to show how they are related as well as identify a few expected column names. Once this is done, a validation process takes place to enforce various rules and ensure that all the relationships between the files are valid. Once that is done, the data is imported into a SQL Server database. The database design is an EAV (Entity-Attribute-Value) model used to cater for the variable columns per file. I know EAV has its detractors, but in this case, I feel it was a reasonable choice given the disparate data and variable number of columns submitted in each dataset. The memory problem Given the fact the combined size of all text files was at most about 5 megs, and in an effort to reduce the database transaction time, it was decided to read ALL the data from files into memory and then perform the following; perform all the validation whilst the data was in memory relate it using an object model Start DB transaction and write the key columns row by row, noting the Id of the written row (all tables in the database utilise identity columns), then the Id of the newly written row is applied to all related data Once all related data had been updated with the key information to which it relates, these records are written using SqlBulkCopy. Due to our EAV model, we essentially have; x columns by y rows to write, where x can by 256+ and rows are often into the tens of thousands. Once all the data is written without error (can take several minutes for large datasets), Commit the transaction. The problem now comes from the fact we are now receiving individual files containing over 30 megs of data. In a dataset, we can receive any number of files. We’ve started seen datasets of around 100 megs coming in and I expect it is only going to get bigger from here on in. With files of this size, data can’t even be read into memory without the app falling over, let alone be validated and imported. I anticipate having to modify large chunks of the code to allow validation to occur by parsing files line by line and am not exactly decided on how to handle the import and transactions. Potential improvements I’ve wondered about using GUIDs to relate the data rather than relying on identity fields. This would allow data to be related prior to writing to the database. This would certainly increase the storage required though. Especially in an EAV design. Would you think this is a reasonable thing to try, or do I simply persist with identity fields (natural keys can’t be trusted to be unique across all submitters). Use of staging tables to get data into the database and only performing the transaction to copy data from staging area to actual destination tables. Questions For systems like this that import large quantities of data, how to you go about keeping transactions small. I’ve kept them as small as possible in the current design, but they are still active for several minutes and write hundreds of thousands of records in one transaction. Is there a better solution? The tab delimited data section is read into a DataTable to be viewed in a grid. I don’t need the full functionality of a DataTable, so I suspect it is overkill. Is there anyway to turn off various features of DataTables to make them more lightweight? Are there any other obvious things you would do in this situation to minimise the memory footprint of the application described above? Thanks for your kind attention.

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  • C++ Library API Design

    - by johannes
    I'm looking for a good resource for learning about good API design for C++ libraries, looking at shared objects/dlls etc. There are many resources on writing nice APIs, nice classes, templates and so on at source level, but barely anything about putting things together in shared libs and executables. Books like Large-Scale C++ Software Design by John Lakos are interesting but massively outdated. What I'm looking for is advice i.e. on handling templates. With templates in my API I often end up with library code in my executable (or other library) so if I fix a bug in there I can't simply roll out the new library but have to recompile and redistribute all clients of that code. (and yes, I know some solutions like trying to instantiate at least the most common versions inside the library etc.) I'm also looking for other caveats and things to mind for keeping binary compatibility while working on C++ libraries. Is there a good website or book on such things?

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