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  • How can I quantify the amount of technical debt that exists in a project?

    - by Erik Dietrich
    Does anyone know if there is some kind of tool to put a number on technical debt of a code base, as a kind of code metric? If not, is anyone aware of an algorithm or set of heuristics for it? If neither of those things exists so far, I'd be interested in ideas for how to get started with such a thing. That is, how can I quantify the technical debt incurred by a method, a class, a namespace, an assembly, etc. I'm most interested in analyzing and assessing a C# code base, but please feel free to chime in for other languages as well, particularly if the concepts are language transcendent.

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  • Super Joybox 5 HID 0925:8884 not recognized as joystick in Ubuntu 12.04 LTS

    - by Tim Evans
    Problem: When using the "Super JoyBox 5" 4 port playstation 2 to USB adapter, the device is not recognized as a joystick. there is no js0 created, but instead another input eventX and mouseX are created in /dev/input. When using the directional buttons (up down left right) on a Playstation 1 controller attached to the device, the mouse cursor moves to the top, bottom, left, and right edges of the screen respectively. Buttons are unresponsive. The joypads attached to the device cannot be used in any games or other programs. Attempted remedies: Creating a symlink from the eventX to js0 does not solve the problem. Addl Info: joydev is loaded and running peroperly according to LSMOD. evtest can be run on the created eventX (sudo evtest /dev/input/event14 in my case) and the buttons and axes all register inputs. Here is a paste of EVTEST's diagnostic and the first couple button events. [code] sudo evtest /dev/input/event14 Input driver version is 1.0.1 Input device ID: bus 0x3 vendor 0x925 product 0x8884 version 0x100 Input device name: "HID 0925:8884" Supported events: Event type 0 (EV_SYN) Event type 1 (EV_KEY) Event code 288 (BTN_TRIGGER) Event code 289 (BTN_THUMB) Event code 290 (BTN_THUMB2) Event code 291 (BTN_TOP) Event code 292 (BTN_TOP2) Event code 293 (BTN_PINKIE) Event code 294 (BTN_BASE) Event code 295 (BTN_BASE2) Event code 296 (BTN_BASE3) Event code 297 (BTN_BASE4) Event code 298 (BTN_BASE5) Event code 299 (BTN_BASE6) Event code 300 (?) Event code 301 (?) Event code 302 (?) Event code 303 (BTN_DEAD) Event code 304 (BTN_A) Event code 305 (BTN_B) Event code 306 (BTN_C) Event code 307 (BTN_X) Event code 308 (BTN_Y) Event code 309 (BTN_Z) Event code 310 (BTN_TL) Event code 311 (BTN_TR) Event code 312 (BTN_TL2) Event code 313 (BTN_TR2) Event code 314 (BTN_SELECT) Event code 315 (BTN_START) Event code 316 (BTN_MODE) Event code 317 (BTN_THUMBL) Event code 318 (BTN_THUMBR) Event code 319 (?) Event code 320 (BTN_TOOL_PEN) Event code 321 (BTN_TOOL_RUBBER) Event code 322 (BTN_TOOL_BRUSH) Event code 323 (BTN_TOOL_PENCIL) Event code 324 (BTN_TOOL_AIRBRUSH) Event code 325 (BTN_TOOL_FINGER) Event code 326 (BTN_TOOL_MOUSE) Event code 327 (BTN_TOOL_LENS) Event code 328 (?) Event code 329 (?) Event code 330 (BTN_TOUCH) Event code 331 (BTN_STYLUS) Event code 332 (BTN_STYLUS2) Event code 333 (BTN_TOOL_DOUBLETAP) Event code 334 (BTN_TOOL_TRIPLETAP) Event code 335 (BTN_TOOL_QUADTAP) Event type 3 (EV_ABS) Event code 0 (ABS_X) Value 127 Min 0 Max 255 Flat 15 Event code 1 (ABS_Y) Value 127 Min 0 Max 255 Flat 15 Event code 2 (ABS_Z) Value 127 Min 0 Max 255 Flat 15 Event code 3 (ABS_RX) Value 127 Min 0 Max 255 Flat 15 Event code 4 (ABS_RY) Value 127 Min 0 Max 255 Flat 15 Event code 5 (ABS_RZ) Value 127 Min 0 Max 255 Flat 15 Event code 6 (ABS_THROTTLE) Value 127 Min 0 Max 255 Flat 15 Event code 7 (ABS_RUDDER) Value 127 Min 0 Max 255 Flat 15 Event code 8 (ABS_WHEEL) Value 127 Min 0 Max 255 Flat 15 Event code 9 (ABS_GAS) Value 127 Min 0 Max 255 Flat 15 Event code 10 (ABS_BRAKE) Value 127 Min 0 Max 255 Flat 15 Event code 11 (?) Value 127 Min 0 Max 255 Flat 15 Event code 12 (?) Value 127 Min 0 Max 255 Flat 15 Event code 13 (?) Value 127 Min 0 Max 255 Flat 15 Event code 14 (?) Value 127 Min 0 Max 255 Flat 15 Event code 15 (?) Value 127 Min 0 Max 255 Flat 15 Event code 16 (ABS_HAT0X) Value 0 Min -1 Max 1 Event code 17 (ABS_HAT0Y) Value 0 Min -1 Max 1 Event code 18 (ABS_HAT1X) Value 0 Min -1 Max 1 Event code 19 (ABS_HAT1Y) Value 0 Min -1 Max 1 Event code 20 (ABS_HAT2X) Value 0 Min -1 Max 1 Event code 21 (ABS_HAT2Y) Value 0 Min -1 Max 1 Event code 22 (ABS_HAT3X) Value 0 Min -1 Max 1 Event code 23 (ABS_HAT3Y) Value 0 Min -1 Max 1 Event type 4 (EV_MSC) Event code 4 (MSC_SCAN) Testing ... (interrupt to exit) Event: time 1351223176.126127, type 4 (EV_MSC), code 4 (MSC_SCAN), value 90001 Event: time 1351223176.126130, type 1 (EV_KEY), code 288 (BTN_TRIGGER), value 1 Event: time 1351223176.126166, -------------- SYN_REPORT ------------ Event: time 1351223178.238127, type 4 (EV_MSC), code 4 (MSC_SCAN), value 90001 Event: time 1351223178.238130, type 1 (EV_KEY), code 288 (BTN_TRIGGER), value 0 Event: time 1351223178.238167, -------------- SYN_REPORT ------------ Event: time 1351223180.422127, type 4 (EV_MSC), code 4 (MSC_SCAN), value 90002 Event: time 1351223180.422129, type 1 (EV_KEY), code 289 (BTN_THUMB), value 1 Event: time 1351223180.422163, -------------- SYN_REPORT ------------ Event: time 1351223181.558099, type 4 (EV_MSC), code 4 (MSC_SCAN), value 90002 Event: time 1351223181.558102, type 1 (EV_KEY), code 289 (BTN_THUMB), value 0 Event: time 1351223181.558137, -------------- SYN_REPORT ------------ Event: time 1351223182.486137, type 4 (EV_MSC), code 4 (MSC_SCAN), value 90003 Event: time 1351223182.486140, type 1 (EV_KEY), code 290 (BTN_THUMB2), value 1 Event: time 1351223182.486172, -------------- SYN_REPORT ------------ Event: time 1351223183.302130, type 4 (EV_MSC), code 4 (MSC_SCAN), value 90003 Event: time 1351223183.302132, type 1 (EV_KEY), code 290 (BTN_THUMB2), value 0 Event: time 1351223183.302165, -------------- SYN_REPORT ------------ Event: time 1351223184.030133, type 4 (EV_MSC), code 4 (MSC_SCAN), value 90004 Event: time 1351223184.030136, type 1 (EV_KEY), code 291 (BTN_TOP), value 1 Event: time 1351223184.030166, -------------- SYN_REPORT ------------ Event: time 1351223184.558135, type 4 (EV_MSC), code 4 (MSC_SCAN), value 90004 Event: time 1351223184.558138, type 1 (EV_KEY), code 291 (BTN_TOP), value 0 Event: time 1351223184.558168, -------------- SYN_REPORT ------------ [/code] The directional buttons on the pad are being identified as HAT0Y and HAT0X axes, thats zero, not the letter O. Aparently, this device used to work flawlessly on kernel 2.4.x systems, and even as late as ubunto 10.04. Perhaps the Joydev rules for identifying joypads has changed? Currently, this kind of bug is affecting a few different type of controller adapters, but since this is the one that i PERSONALLY have (and has been driving me my own special brand of crazy), its the one im documenting. What i think should be happening instead: The device should be registering js0 through js3, one for each port, or JS0 that will handle all of the connected devices with different numbered axes for each connected joypad. Either way, it should work as a joystick and stop controlling the mouse cursor. Please help!

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  • Should we exclude code for the code coverage analysis?

    - by romaintaz
    I'm working on several applications, mainly legacy ones. Currently, their code coverage is quite low: generally between 10 and 50%. Since several weeks, we have recurrent discussions with the Bangalore teams (main part of the development is made offshore in India) regarding the exclusions of packages or classes for Cobertura (our code coverage tool, even if we are currently migrating to JaCoCo). Their point of view is the following: as they will not write any unit tests on some layers of the application (1), these layers should be simply excluded from the code coverage measure. In others words, they want to limit the code coverage measure to the code that is tested or should be tested. Also, when they work on unit test for a complex class, the benefits - purely in term of code coverage - will be unnoticed due in a large application. Reducing the scope of the code coverage will make this kind of effort more visible... The interest of this approach is that we will have a code coverage measure that indicates the current status of the part of the application we consider as testable. However, my point of view is that we are somehow faking the figures. This solution is an easy way to reach higher level of code coverage without any effort. Another point that bothers me is the following: if we show a coverage increase from one week to another, how can we tell if this good news is due to the good work of the developers, or simply due to new exclusions? In addition, we will not be able to know exactly what is considered in the code coverage measure. For example, if I have a 10,000 lines of code application with 40% of code coverage, I can deduct that 40% of my code base is tested (2). But what happen if we set exclusions? If the code coverage is now 60%, what can I deduct exactly? That 60% of my "important" code base is tested? How can I As far as I am concerned, I prefer to keep the "real" code coverage value, even if we can't be cheerful about it. In addition, thanks to Sonar, we can easily navigate in our code base and know, for any module / package / class, its own code coverage. But of course, the global code coverage will still be low. What is your opinion on that subject? How do you do on your projects? Thanks. (1) These layers are generally related to the UI / Java beans, etc. (2) I know that's not true. In fact, it only means that 40% of my code base

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  • Code Metrics: Number of IL Instructions

    - by DigiMortal
    In my previous posting about code metrics I introduced how to measure LoC (Lines of Code) in .NET applications. Now let’s take a step further and let’s take a look how to measure compiled code. This way we can somehow have a picture about what compiler produces. In this posting I will introduce you code metric called number of IL instructions. NB! Number of IL instructions is not something you can use to measure productivity of your team. If you want to get better idea about the context of this metric and LoC then please read my first posting about LoC. What are IL instructions? When code written in some .NET Framework language is compiled then compiler produces assemblies that contain byte code. These assemblies are executed later by Common Language Runtime (CLR) that is code execution engine of .NET Framework. The byte code is called Intermediate Language (IL) – this is more common language than C# and VB.NET by example. You can use ILDasm tool to convert assemblies to IL assembler so you can read them. As IL instructions are building blocks of all .NET Framework binary code these instructions are smaller and highly general – we don’t want very rich low level language because it executes slower than more general language. For every method or property call in some .NET Framework language corresponds set of IL instructions. There is no 1:1 relationship between line in high level language and line in IL assembler. There are more IL instructions than lines in C# code by example. How much instructions there are? I have no common answer because it really depends on your code. Here you can see some metrics from my current community project that is developed on SharePoint Server 2007. As average I have about 7 IL instructions per line of code. This is not metric you should use, it is just illustrative example so you can see the differences between numbers of lines and IL instructions. Why should I measure the number of IL instructions? Just take a look at chart above. Compiler does something that you cannot see – it compiles your code to IL. This is not intuitive process because you usually cannot say what is exactly the end result. You know it at greater plain but you don’t know it exactly. Therefore we can expect some surprises and that’s why we should measure the number of IL instructions. By example, you may find better solution for some method in your source code. It looks nice, it works nice and everything seems to be okay. But on server under load your fix may be way slower than previous code. Although you minimized the number of lines of code it ended up with increasing the number of IL instructions. How to measure the number of IL instructions? My choice is NDepend because Visual Studio is not able to measure this metric. Steps to make are easy. Open your NDepend project or create new and add all your application assemblies to project (you can also add Visual Studio solution to project). Run project analysis and wait until it is done. You can see over-all stats form global summary window. This is the same window I used to read the LoC and the number of IL instructions metrics for my chart. Meanwhile I made some changes to my code (enabled advanced caching for events and event registrations module) and then I ran code analysis again to get results for this section of this posting. NDepend is also able to tell you exactly what parts of code have problematically much IL instructions. The code quality section of CQL Query Explorer shows you how much problems there are with members in analyzed code. If you click on the line Methods too big (NbILInstructions) you can see all the problematic members of classes in CQL Explorer shown in image on right. In my case if have 10 methods that are too big and two of them have horrible number of IL instructions – just take a look at first two methods in this TOP10. Also note the query box. NDepend has easy and SQL-like query language to query code analysis results. You can modify these queries if you like and also you can define your own ones if default set is not enough for you. What is good result? As you can see from query window then the number of IL instructions per member should have maximally 200 IL instructions. Of course, like always, the less instructions you have, the better performing code you have. I don’t mean here little differences but big ones. By example, take a look at my first method in warnings list. The number of IL instructions it has is huge. And believe me – this method looks awful. Conclusion The number of IL instructions is useful metric when optimizing your code. For analyzing code at general level to find out too long methods you can use the number of LoC metric because it is more intuitive for you and you can therefore handle the situation more easily. Also you can use NDepend as code metrics tool because it has a lot of metrics to offer.

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  • How do you get positive criticism on your code?

    - by burnt1ce
    My team rarely does code review, mainly because we don't have enough time and people lack the energy and will to do so. But I would really like to know what people think about my code when they read it. This way, I have a better understanding how other people think and tailor my code accordingly so it's easier to read. So my question is, how do I get positive criticism on my code? My intent is to understand how people think so I can write more readable code.

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  • How can you get constructive criticism for your code?

    - by burnt1ce
    My team rarely does code review, mainly because we don't have enough time and people lack the energy and will to do so. But I would really like to know what people think about my code when they read it. This way, I have a better understanding how other people think and tailor my code accordingly so it's easier to read. So my question is, how can I get constructive criticism for my code? My intent is to understand how people think so I can write more readable code.

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  • New code base, what experiences/recommendations do you have?

    - by hlovdal
    I will later this year start on a project (embedded hardware, C, small company) where I believe that most (if not all) code will be new. So what experiences do you have to share as advice to starting a new code base? What have you been missing in projects that you have been working on? What has worked really well? What has not worked? Let's limit this question to be about things that relate directly to the code (e.g "banning the use of gets()": in scope, version control: border line, build system: out of scope).

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  • Overwhelmed by complex C#/ASP.NET project in Visual Studio 2008

    - by Darren Cook
    I have been hired as a junior programmer to work on projects that extend existing functionality in a very large, complex solution. The code base consists of C#, ASP.NET, jQuery, javascript, html and xml. I have some knowledge of all these in addition to fair knowledge of object-oriented programming and its fundamental concepts of inheritance, abstraction, polymorphism and encapsulation. I can follow code up through its base classes, interfaces, abstract classes and understand a large part of the code that I read while doing this. However, this solution is so humongous and so many things get tied together whenever I navigate through the code that I feel absolutely overwhelmed. I often find myself unable to fully follow everything that is going on with objects being serialized, large amounts of C# and javascript operating on the same pages and methods being called from template files that consist mainly of markup. I love learning about code, but trying to deal with this really stresses me out. Additionally, I do know that a significant amount of unit testing has been done but I know nothing about unit testing or how to utilize it. Any advice anyone could offer me regarding dealing with a large code base while using Visual Studio 2008 would be greatly appreciated. Are there tools that I can use to help get a handle on what is going on? Perhaps there are things even in Visual Studio that I am not aware of. How can I follow the code to low level functionality in order to get a better grasp of what is going on at a high level?

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  • Beginning with first project on game development [closed]

    - by Tsvetan
    Today is the day I am going to start my first real game project. It will be a Universe simulator. Basically, you can build anything from tiny meteor to quazars and universes. It is going to be my project for an olympiad in IT in my country and I really want to make it perfect(at least a bronze medal). So, I would like to ask some questions about organization and development methodologies. Firstly, my plan is to make a time schedule. In it I would write my plans for the next month or two(because that is the time I have). With this exact plan I hope to make my organisation at its best. Of course, if I am doing sth faster than the schedule I would involve more features for the game and/or continue with the tempo I have. Also, for the organisation I would make a basic pseudocode(maybe) and just rewrite it so it is compilable. Like a basic skeleton of everything. The last is an idea I tought of in the moment, but if it is good I will use it. Secondly, for the development methodologies, obviously, I think of making object-oriented code and make everything perfect(a lot of testing, good code, documentation etc.). Also, I am going to make my own menu system(I read that OpenGL hasn't got very good one). Maybe I would implement it with an xml file, holding the info about position of buttons, text boxes, images and everything. Maybe I would do a specific CSS for it and so on. I think that is very good way of doing the menu system, because it makes the presentation layer separate of the logic. But, if there is a better way, I would do it the better way. For the logic, well, I don't have much to say. OO code, testing, debuging, good and fast algorithms and so on. Also, a good documentation must be written and this is the area I need to make some research in. I think that is for now. I hope I have been enough descriptive. If more questions come on my mind, I will ask them. Edit: I think of blogging every part of the project, or at least writing down everything in a file or something like that. My question is: Is my plan of how to do everything around the project good? And if not, what is necessary to be improved and what other things I can involve for making the project good.

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  • How to motivate as a project leader?

    - by Zenzen
    Ok so some of you might think this is not stackoverflow related, but since I got a similar question during an interview (for a J2EE dev position) I think you guys will help me in the end. The situation is simple: you're working on a project in a small group (4-5 people), you're the project leader and the guy who's the most competent (technology wise) is also slacking the most. What do you do to motivate him? The problem is, I'm having the same issue at the university - this semester we have a lot of projects going on (6 to be exact) so we decided to dived the work so everyone will do 1-2 projects in a technology he knows/wants to learn. It's been working well for the most part, the problem is the person whom we thought would finish his project way before us as he's the most experienced among us. How am I supposed to make him do his share properly? Till now he was just half assing his part by doing the bare minimum, with which the professor wasn't really pleased to say the least... Now it's only a university project, but in the future I might have the same problem in a real job and losing a really smart and experienced worker (as firing him is the only solution I can come up with now) would really be a waste. Aren't there any better ways? p.s. now that I think about it, are there any books that would help me in becoming a better project manager?

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  • Distributed Development Tools -- (Version control and Project Management)

    - by Macy Abbey
    Hello, I've recently become responsible for choosing which source control and project management software to use for a company that employs me. Currently it uses Jira (project management) and Subversion (version control). I know there are many other options out there -- the ones I know about are all in this article http://mashable.com/2010/07/14/distributed-developer-teams/ . I'm leaning towards recommending they just stay with what they have as it seems workable and any change would have to be worth the cost of switching to say github/basecamp or some other solution. Some details on the team: It's a distributed development shop. Meetings of the whole team in one room are rare. It's currently a very small development team (three developers). The project management software is used by developers and a product manager or two. What are you experiences with version control and project management web applications? Are there any you would recommend and you think are worth the switching cost of time to learn new services / implementing the change? Edit: After educating myself further on the options it appears DVCS offer powerful benefits that may be worth investing in now as opposed to later in the company's lifetime when the switching cost is higher: I'm a Subversion geek, why I should consider or not consider Mercurial or Git or any other DVCS?

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  • Are project managers useful in Scrum?

    - by Martin Wickman
    There are three roles defined in Scrum: Team, Product Owner and Scrum Master. There is no project manager, instead the project manager job is spread across the three roles. For instance: The Scrum Master: Responsible for the process. Removes impediments. The Product Owner: Manages and prioritizes the list of work to be done to maximize ROI. Represents all interested parties (customers, stakeholders). The Team: Self manage its work by estimating and distributing it among themselves. Responsible for meeting their own commitments. So in Scrum, there is no longer a single person responsible for project success. There is no command-and-control structure in place. That seems to baffle a lot of people, specifically those not used to agile methods, and of course, PM's. I'm really interested in this and what your experiences are, as I think this is one of the things that can make or break a Scrum implementation. Do you agree with Scrum that a project manager is not needed? Do you think such a role is still required? Why?

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  • Are project managers useful in Scrum?

    - by Martin Wickman
    There are three roles defined in Scrum: Team, Product Owner and Scrum Master. There is no project manager, instead the project manager job is spread across the three roles. For instance: The Scrum Master: Responsible for the process. Removes impediments. The Product Owner: Manages and prioritizes the list of work to be done to maximize ROI. Represents all interested parties (customers, stakeholders). The Team: Self manage its work by estimating and distributing it among themselves. Responsible for meeting their own commitments. So in Scrum, there is no longer a single person responsible for project success. There is no command-and-control structure in place. That seems to baffle a lot of people, specifically those not used to agile methods, and of course, PM's. I'm really interested in this and what your experiences are, as I think this is one of the things that can make or break a Scrum implementation. Do you agree with Scrum that a project manager is not needed? Do you think such a role is still required? Why?

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  • How to properly structure a project in winform?

    - by user850010
    A while ago I started to create a winform application and at that time it was small and I did not give any thought of how to structure the project. Since then I added additional features as I needed and the project folder is getting bigger and bigger and now I think it is time to structure the project in some way, but I am not sure what is the proper way, so I have few questions. How to properly restructure the project folder? At the moment I am thinking of something like this: Create Folder for Forms Create Folder for Utility classes Create Folder for Classes that contain only data What is the naming convention when adding classes? Should I also rename classes so that their functionality can be identified by just looking at their name? For example renaming all forms classes, so that their name ends with Form. Or is this not necessary if special folders for them are created? What to do, so that not all the code for main form ends up in Form1.cs Another problem I encountered is that as the main form is getting more massive with each feature I add, the code file (Form1.cs) is getting really big. I have for example a TabControl and each tab has bunch of controls and all the code ended up in Form1.cs. How to avoid this? Also, Do you know any articles or books that deal with these problems?

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  • Distributed Development Tools -- (Version control and Project Management)

    - by Macy Abbey
    I've recently become responsible for choosing which source control and project management software to use for a company that employs me. Currently it uses Jira (project management) and Subversion (version control). I know there are many other options out there -- the ones I know about are all in this article http://mashable.com/2010/07/14/distributed-developer-teams/ . I'm leaning towards recommending they just stay with what they have as it seems workable and any change would have to be worth the cost of switching to say github/basecamp or some other solution. Some details on the team: It's a distributed development shop. Meetings of the whole team in one room are rare. It's currently a very small development team (three developers). The project management software is used by developers and a product manager or two. What are you experiences with version control and project management web applications? Are there any you would recommend and you think are worth the switching cost of time to learn new services / implementing the change? Edit: After educating myself further on the options it appears DVCS offer powerful benefits that may be worth investing in now as opposed to later in the company's lifetime when the switching cost is higher: I'm a Subversion geek, why I should consider or not consider Mercurial or Git or any other DVCS?

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  • Inheritance Mapping Strategies with Entity Framework Code First CTP5 Part 1: Table per Hierarchy (TPH)

    - by mortezam
    A simple strategy for mapping classes to database tables might be “one table for every entity persistent class.” This approach sounds simple enough and, indeed, works well until we encounter inheritance. Inheritance is such a visible structural mismatch between the object-oriented and relational worlds because object-oriented systems model both “is a” and “has a” relationships. SQL-based models provide only "has a" relationships between entities; SQL database management systems don’t support type inheritance—and even when it’s available, it’s usually proprietary or incomplete. There are three different approaches to representing an inheritance hierarchy: Table per Hierarchy (TPH): Enable polymorphism by denormalizing the SQL schema, and utilize a type discriminator column that holds type information. Table per Type (TPT): Represent "is a" (inheritance) relationships as "has a" (foreign key) relationships. Table per Concrete class (TPC): Discard polymorphism and inheritance relationships completely from the SQL schema.I will explain each of these strategies in a series of posts and this one is dedicated to TPH. In this series we'll deeply dig into each of these strategies and will learn about "why" to choose them as well as "how" to implement them. Hopefully it will give you a better idea about which strategy to choose in a particular scenario. Inheritance Mapping with Entity Framework Code FirstAll of the inheritance mapping strategies that we discuss in this series will be implemented by EF Code First CTP5. The CTP5 build of the new EF Code First library has been released by ADO.NET team earlier this month. EF Code-First enables a pretty powerful code-centric development workflow for working with data. I’m a big fan of the EF Code First approach, and I’m pretty excited about a lot of productivity and power that it brings. When it comes to inheritance mapping, not only Code First fully supports all the strategies but also gives you ultimate flexibility to work with domain models that involves inheritance. The fluent API for inheritance mapping in CTP5 has been improved a lot and now it's more intuitive and concise in compare to CTP4. A Note For Those Who Follow Other Entity Framework ApproachesIf you are following EF's "Database First" or "Model First" approaches, I still recommend to read this series since although the implementation is Code First specific but the explanations around each of the strategies is perfectly applied to all approaches be it Code First or others. A Note For Those Who are New to Entity Framework and Code-FirstIf you choose to learn EF you've chosen well. If you choose to learn EF with Code First you've done even better. To get started, you can find a great walkthrough by Scott Guthrie here and another one by ADO.NET team here. In this post, I assume you already setup your machine to do Code First development and also that you are familiar with Code First fundamentals and basic concepts. You might also want to check out my other posts on EF Code First like Complex Types and Shared Primary Key Associations. A Top Down Development ScenarioThese posts take a top-down approach; it assumes that you’re starting with a domain model and trying to derive a new SQL schema. Therefore, we start with an existing domain model, implement it in C# and then let Code First create the database schema for us. However, the mapping strategies described are just as relevant if you’re working bottom up, starting with existing database tables. I’ll show some tricks along the way that help you dealing with nonperfect table layouts. Let’s start with the mapping of entity inheritance. -- The Domain ModelIn our domain model, we have a BillingDetail base class which is abstract (note the italic font on the UML class diagram below). We do allow various billing types and represent them as subclasses of BillingDetail class. As for now, we support CreditCard and BankAccount: Implement the Object Model with Code First As always, we start with the POCO classes. Note that in our DbContext, I only define one DbSet for the base class which is BillingDetail. Code First will find the other classes in the hierarchy based on Reachability Convention. public abstract class BillingDetail  {     public int BillingDetailId { get; set; }     public string Owner { get; set; }             public string Number { get; set; } } public class BankAccount : BillingDetail {     public string BankName { get; set; }     public string Swift { get; set; } } public class CreditCard : BillingDetail {     public int CardType { get; set; }                     public string ExpiryMonth { get; set; }     public string ExpiryYear { get; set; } } public class InheritanceMappingContext : DbContext {     public DbSet<BillingDetail> BillingDetails { get; set; } } This object model is all that is needed to enable inheritance with Code First. If you put this in your application you would be able to immediately start working with the database and do CRUD operations. Before going into details about how EF Code First maps this object model to the database, we need to learn about one of the core concepts of inheritance mapping: polymorphic and non-polymorphic queries. Polymorphic Queries LINQ to Entities and EntitySQL, as object-oriented query languages, both support polymorphic queries—that is, queries for instances of a class and all instances of its subclasses, respectively. For example, consider the following query: IQueryable<BillingDetail> linqQuery = from b in context.BillingDetails select b; List<BillingDetail> billingDetails = linqQuery.ToList(); Or the same query in EntitySQL: string eSqlQuery = @"SELECT VAlUE b FROM BillingDetails AS b"; ObjectQuery<BillingDetail> objectQuery = ((IObjectContextAdapter)context).ObjectContext                                                                          .CreateQuery<BillingDetail>(eSqlQuery); List<BillingDetail> billingDetails = objectQuery.ToList(); linqQuery and eSqlQuery are both polymorphic and return a list of objects of the type BillingDetail, which is an abstract class but the actual concrete objects in the list are of the subtypes of BillingDetail: CreditCard and BankAccount. Non-polymorphic QueriesAll LINQ to Entities and EntitySQL queries are polymorphic which return not only instances of the specific entity class to which it refers, but all subclasses of that class as well. On the other hand, Non-polymorphic queries are queries whose polymorphism is restricted and only returns instances of a particular subclass. In LINQ to Entities, this can be specified by using OfType<T>() Method. For example, the following query returns only instances of BankAccount: IQueryable<BankAccount> query = from b in context.BillingDetails.OfType<BankAccount>() select b; EntitySQL has OFTYPE operator that does the same thing: string eSqlQuery = @"SELECT VAlUE b FROM OFTYPE(BillingDetails, Model.BankAccount) AS b"; In fact, the above query with OFTYPE operator is a short form of the following query expression that uses TREAT and IS OF operators: string eSqlQuery = @"SELECT VAlUE TREAT(b as Model.BankAccount)                       FROM BillingDetails AS b                       WHERE b IS OF(Model.BankAccount)"; (Note that in the above query, Model.BankAccount is the fully qualified name for BankAccount class. You need to change "Model" with your own namespace name.) Table per Class Hierarchy (TPH)An entire class hierarchy can be mapped to a single table. This table includes columns for all properties of all classes in the hierarchy. The concrete subclass represented by a particular row is identified by the value of a type discriminator column. You don’t have to do anything special in Code First to enable TPH. It's the default inheritance mapping strategy: This mapping strategy is a winner in terms of both performance and simplicity. It’s the best-performing way to represent polymorphism—both polymorphic and nonpolymorphic queries perform well—and it’s even easy to implement by hand. Ad-hoc reporting is possible without complex joins or unions. Schema evolution is straightforward. Discriminator Column As you can see in the DB schema above, Code First has to add a special column to distinguish between persistent classes: the discriminator. This isn’t a property of the persistent class in our object model; it’s used internally by EF Code First. By default, the column name is "Discriminator", and its type is string. The values defaults to the persistent class names —in this case, “BankAccount” or “CreditCard”. EF Code First automatically sets and retrieves the discriminator values. TPH Requires Properties in SubClasses to be Nullable in the Database TPH has one major problem: Columns for properties declared by subclasses will be nullable in the database. For example, Code First created an (INT, NULL) column to map CardType property in CreditCard class. However, in a typical mapping scenario, Code First always creates an (INT, NOT NULL) column in the database for an int property in persistent class. But in this case, since BankAccount instance won’t have a CardType property, the CardType field must be NULL for that row so Code First creates an (INT, NULL) instead. If your subclasses each define several non-nullable properties, the loss of NOT NULL constraints may be a serious problem from the point of view of data integrity. TPH Violates the Third Normal FormAnother important issue is normalization. We’ve created functional dependencies between nonkey columns, violating the third normal form. Basically, the value of Discriminator column determines the corresponding values of the columns that belong to the subclasses (e.g. BankName) but Discriminator is not part of the primary key for the table. As always, denormalization for performance can be misleading, because it sacrifices long-term stability, maintainability, and the integrity of data for immediate gains that may be also achieved by proper optimization of the SQL execution plans (in other words, ask your DBA). Generated SQL QueryLet's take a look at the SQL statements that EF Code First sends to the database when we write queries in LINQ to Entities or EntitySQL. For example, the polymorphic query for BillingDetails that you saw, generates the following SQL statement: SELECT  [Extent1].[Discriminator] AS [Discriminator],  [Extent1].[BillingDetailId] AS [BillingDetailId],  [Extent1].[Owner] AS [Owner],  [Extent1].[Number] AS [Number],  [Extent1].[BankName] AS [BankName],  [Extent1].[Swift] AS [Swift],  [Extent1].[CardType] AS [CardType],  [Extent1].[ExpiryMonth] AS [ExpiryMonth],  [Extent1].[ExpiryYear] AS [ExpiryYear] FROM [dbo].[BillingDetails] AS [Extent1] WHERE [Extent1].[Discriminator] IN ('BankAccount','CreditCard') Or the non-polymorphic query for the BankAccount subclass generates this SQL statement: SELECT  [Extent1].[BillingDetailId] AS [BillingDetailId],  [Extent1].[Owner] AS [Owner],  [Extent1].[Number] AS [Number],  [Extent1].[BankName] AS [BankName],  [Extent1].[Swift] AS [Swift] FROM [dbo].[BillingDetails] AS [Extent1] WHERE [Extent1].[Discriminator] = 'BankAccount' Note how Code First adds a restriction on the discriminator column and also how it only selects those columns that belong to BankAccount entity. Change Discriminator Column Data Type and Values With Fluent API Sometimes, especially in legacy schemas, you need to override the conventions for the discriminator column so that Code First can work with the schema. The following fluent API code will change the discriminator column name to "BillingDetailType" and the values to "BA" and "CC" for BankAccount and CreditCard respectively: protected override void OnModelCreating(System.Data.Entity.ModelConfiguration.ModelBuilder modelBuilder) {     modelBuilder.Entity<BillingDetail>()                 .Map<BankAccount>(m => m.Requires("BillingDetailType").HasValue("BA"))                 .Map<CreditCard>(m => m.Requires("BillingDetailType").HasValue("CC")); } Also, changing the data type of discriminator column is interesting. In the above code, we passed strings to HasValue method but this method has been defined to accepts a type of object: public void HasValue(object value); Therefore, if for example we pass a value of type int to it then Code First not only use our desired values (i.e. 1 & 2) in the discriminator column but also changes the column type to be (INT, NOT NULL): modelBuilder.Entity<BillingDetail>()             .Map<BankAccount>(m => m.Requires("BillingDetailType").HasValue(1))             .Map<CreditCard>(m => m.Requires("BillingDetailType").HasValue(2)); SummaryIn this post we learned about Table per Hierarchy as the default mapping strategy in Code First. The disadvantages of the TPH strategy may be too serious for your design—after all, denormalized schemas can become a major burden in the long run. Your DBA may not like it at all. In the next post, we will learn about Table per Type (TPT) strategy that doesn’t expose you to this problem. References ADO.NET team blog Java Persistence with Hibernate book a { text-decoration: none; } a:visited { color: Blue; } .title { padding-bottom: 5px; font-family: Segoe UI; font-size: 11pt; font-weight: bold; padding-top: 15px; } .code, .typeName { font-family: consolas; } .typeName { color: #2b91af; } .padTop5 { padding-top: 5px; } .padTop10 { padding-top: 10px; } p.MsoNormal { margin-top: 0in; margin-right: 0in; margin-bottom: 10.0pt; margin-left: 0in; line-height: 115%; font-size: 11.0pt; font-family: "Calibri" , "sans-serif"; }

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  • MS Grad Student Project

    - by Bernie Perez
    I'm a computer science grad student at UCLA specializing in security and/or mobile devices. I'm looking for ideas for my M.S. Project. Something with research and experimenting or testing. I have a few in mind, just wondering if the community has some good thoughts. I'm currently working on a project that deals with offload security related operations to a grid-powered/cloud server to improve battery life on phones or tablets, aka Security-Aware software on mobile devices. I might be able to expand on this for my project... but I'm open to any new types of ideas. I have another idea about secure communications with a peer-2-peer ad-hoc network, but its seems a little dull. Hope this questions is not off topic for this StackExchange. I look forward to hearing your thoughts and ideas.

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  • Getting overwhelmed after starting a new project

    - by Kian Mayne
    I started a project (a Windows based timetable program that helps you stay organised with your subjects and assignments). The problem is that I'm not sure how I should manage this project and what order to build things. I.e. Should I build all the different interface elements then write the code or should I make an interface, code it, make another interface then code that? So my question is; how do I split up this longish project into small, ordered pieces to complete; and how should I order this?

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  • Community to discuss project ideas

    - by Auxiliary
    Although I already predict the down votes but the question has stuck in my throat for a while now. I think this has happened to many of us. Sometimes we find a great idea for a project and obviously think this is THE GREATEST idea ever but then one of the following things will happen: The project is a small one, so you might actually give it a try and see how it goes. The project is a big one, even a risk, and you just need a good programmer's community that you could just discuss your idea with them and see what they say and even get some help to make it happen. And there's always the possibility of others stealing your idea which is really bad. So could anyone suggest an online community or place or even method of talking about ideas and the ways of developing them? and do you think it's a good thing to tell others about your idea?

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  • What makes for the ideal project? [closed]

    - by Hans Westerbeek
    I try to be careful when accepting assignments, to avoid mutual disappointment. So, I started to come up with a list of things that I consider ingredients for The Ideal Project: (in no particular order) What did I miss? What did I get wrong? Team size < 6 persons to avoid having too many meetings Team members must be dedicated to the project Gut-feeling-estimate (made by developers) of running period does not exceed 4 months. Projects longer than that tend to become open-ended, and are therefore not projects. Has a Product Owner who has mandate and is well-respected at their own company and who has a real interest in the long-term success of the project. Has no technical involvement from people that are not on the team. (yes that's you, Mr Architect That Doesn't Code) All the usual about quiet working conditions Exciting subject matter. Content management is just not as cool as controlling robots :)

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  • Letting go of a project

    - by SkyOrg
    I've been the sole developer of a niche product for my company for nearly 6 years. I've grown quite attached to the project and I enjoy working on it. However, it was the decision of management to take the project out of my hands and move it under the wings of another team. Unfortunately, I'm having a hard time letting go of the project. I'm sad to see it leave my hands since I've put so much time into it and enjoyed working on it, but it also allows me to work on new things. I've even caught myself being a bit hostile to the other team, which is poor on my part. How can I convince myself to just let it go?

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  • Android Application for Final Year Project [closed]

    - by user1070241
    I hope this is the right place to post this question. Basically, I'm about to choose a Final Year Project for my third and final year in BSc Computer Science. I have worked with different apps and therefore I do have some experience with the Android SDK Platform in general. However, my question is this, how do you think an Android based project would go down with potential employers? I personally don't think the complexity of this project is lower than other projects proposed by my university. Please let me know what you think, and do share any experiences that you have had with this, if any. Thank you very much.

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  • How do I start a personal programming project?

    - by Pureferret
    I've just started a programming job where I'm applying my 'How to code' knowledge to what I'm being taught of 'How to Program' (They are different!). As well of this I'm taught how to capture requirements from clients, so as to start a new project. How do I do this for a nebulous personal project? I say nebulous, as I often find halfway through programming something, I want to expand what my program will do, or alter the result. Eventually I'm tangled in code, and have to restart. This can be frustrating and off putting. Conversely when given a fixed task, and fixed requirements, it's much easier to programme from a - b. So how do I plan a personal programming project?

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  • Thou shalt not put code on a piedestal - Code is a tool, no more, no less

    - by Ralf Westphal
    “Write great code and everything else becomes easier” is what Paul Pagel believes in. That´s his version of an adage by Brian Marick he cites: “treat code as an end, not just a means.” And he concludes: “My post-Agile world is software craftsmanship.” I wonder, if that´s really the way to go. Will “simply” writing great code lead the software industry into the light? He´s alluding to the philosopher Kant who proposed, a human beings should never be treated as a means, but always as an end. But should we transfer this ethical statement into the world of software? I doubt it.   Reason #1: Human beings are categorially different from code. They are autonomous entities who need to find a way of living happily together. To Kant it seemed this goal could only be reached if nobody (ab)used a human being for his/her purposes. Because using a human being, i.e. treating it as a means, would contradict the fundamental autonomy and freedom of human beings. People should hold up a symmetric view of their relationships: Since nobody wants to be (ab)used, nobody should (ab)use anybody else. If you want to be treated decently, with respect, in accordance with your own free will - which means as an end - then do the same to other people. Code is dead, it´s a product, it´s a tool for people to reach their goals. No company spends any money on code other than to save money or earn money in the long run. Code is not a puppy. Enterprises do not commission software development to just feel good in its company. Code is not a buddy. Code is a slave, if you will. A mechanical slave, a non-tangible robot. Code is a tool, is a tool. And if we start to treat it differently, if we elevate its status unduely… I guess that will contort our relationship in a contraproductive way. Please get me right: Just because something is “just a tool”, “just a product” does not mean we should not be careful while designing, building, using it. Right to the contrary. We should be very careful when writing code – but not for the code´s sake! We should be careful because we respect our customers who are fellow human beings who should be treated as an end. If we are careless, neglectful, ignorant when producing code on their behalf, then we´re using them. Being sloppy means you´re caring more for yourself that for your customer. You´re then treating the customer as a means to fulfill some of your own needs. That´s plain unethical behavior.   Reason #2: The focus should always be on your purpose, not on any tool. But if code is treated as an end, then the focus is on the code. That might sound right, because where else should be your focus as a software developer? But, well, I´d say, your focus should be on delivering value to your customer. Because in the end your customer does not care if you write a single line of code. She just wants her problem to be solved. Solving problems is the purpose of any contractor. Code must be treated just as a means, a tool we know how to handle very well. But if we´re really trying to be craftsmen then we should be conscious about exactly that and act ethically. That means we must never be so focused on our tool as to be unable to suggest better solutions to the problems of our customers than code.   I´m all with Paul when he urges us to “Write great code”. Sure, if you need to write code, then by all means do so. Write the best code you can think of – and then try to improve it. Paul has all the best intentions when he signs Brians “treat code as an end” - but as we all know: “The road to hell is paved with best intentions” ;-) Yes, I can imagine a “hell of code focus”. In fact, I don´t need to imagine it, I´m seeing it quite often. Because code hell is whereever two developers stand together and are so immersed in talking about all sorts of coding tricks, design patterns, code smells, technologies, platforms, tools that they lose sight of the big picture. Talking about TDD or SOLID or refactoring is a sign of consciousness – relative to the “cowboy coders” view of the world. But from yet another point of view TDD, SOLID, and refactoring are just cures for ailments within a system. And I fear, if “Writing great code” is the only focus or the main focus of software development, then we as an industry lose the ability to see that. Focus draws a line around something, it defines a horizon for perceptions and thinking. So if we focus on code our horizon ends where “the land of code” ends. I don´t think that should be our professional attitude.   So what about Software Craftsmanship as the next big thing after Agility? I think Software Craftsmanship has an important message for all software developers and beyond. But to make it the successor of the Agility movement seems to miss a point. Agility never claimed to solve all software development problems, I´d say. So to blame it for having missed out on certain aspects of it is wrong. If I had to summarize Agility in one word I´d say “Value”. Agility put value for the customer back in software development. Focus on delivering value early and often – that´s Agility´s mantra. All else follows from that. And I ask you: Is that obsolete? Is delivering value not hip anymore? No, sure not. That´s our very purpose as software developers. So how can Agility become obsolete and need to be replaced? We need to do away with this “either/or”-thinking. It´s either Agility or Lean or Software Craftsmanship or whatnot. Instead we should start integrating concepts and movements. Think “both/and”. Think Agility plus Software Craftsmanship plus Lean plus whatnot. We don´t neet to tear down anything from a piedestal and replace it with a new idol. Instead we should do away with piedestals and arrange whatever is helpful is a circle. Then we can turn to concepts, movements for whatever they are best. After 10 years of Agility we should be able to identify what it was good at – and keep that. Keep Agility around and add whatever Agility was lacking or never concerned with. Add whatever is at the core of Software Craftsmanship. Add whatever is at the core of Lean etc. But don´t call out the age of Post-Agility. Because it better never will end. Because once we start to lose Agility´s core we´re losing focus of the customer.

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