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• C#, Manage concurrency in database access

  - by Goul

  Hi there, I have written a while ago an application used by multiple users to handle trades creation. I haven't done development for some time now and can't remember how I managed the concurrency between the users and so would have liked your advices in term of design. The application was as follow: - One heavy client per user - A single database - Access to the database for each user to insert/update/delete trades - A grid in the application reflecting the trades table. That grid being updated each time someone changes a deal. My questions: 1- Do you confirm I shouldn't care about the connection to the database for each application. Considering that there is a singleton in each, I would expect on connexion per client with no issue. 2- How preventing the concurrency of the accesses? I guess I should lock when modifying the data, however don't remember how to. 3- How to have the grid automatically updated whenever the database is (by another user for example)? Thank you in advance for your help!

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• require user to login in at login screen before giving access to iPhone app that accesses secure web

  - by MikeN

  On iPhone, how do I show a login screen to get username and password before giving access to iPhone app? Also, does the iPhone store a cookie to the secure website like a web browser? I was thinking of giving users to my website a long API key to store in the settings of their iPhone instead of asking them to login with a username/password (seems to be the Slicehost iPhone app approach.) Which is the best way to get a user to login securely? I have full control over the design of the iPhone app and website so have a lot of flexibility.

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• Sphinx without using an auto_increment id

  - by squeeks

  I am current in planning on creating a big database (2+ million rows) with a variety of data from separate sources. I would like to avoid structuring the database around auto_increment ids to help prevent against sync issues with replication, and also because each item inserted will have a alphanumeric product code that is guaranteed to be unique - it seems to me more sense to use that instead. I am looking at a search engine to index this database with Sphinx looking rather appealing due to its design around indexing relational databases. However, looking at various tutorials and documentation seems to show database designs being dependent on an auto_increment field in one form or another and a rather bold statement in the documentation saying that document ids must be 32/64bit integers only or things break. Is there a way to have a database indexed by Sphinx without auto_increment fields as the id?

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• Is it possible to align an element with the bottom of the window, yet make it scrollable, with CSS o

  - by last-child

  I have a design going on where I want to align the bottom of an intro paragraph with the bottom of the window, yet make it scroll with the rest of the page. So when the page opens, the visitor sees only the first paragraph (and a full screen background image, which is what I want to focus their attention on), but as they scroll they see the paragraph and the rest of the text. The height of the intro element can vary. Right now I think I have to introduce some javascript to do this - meassure the height of the window, the height of the paragraph, and adjust top: or margin-top of the paragraph to the difference between the two values. If there is a way to make a div have a height that corresponds exactly to the window height, and position the paragraph absolutely inside of this div, the let the rest of the text sit outside of the div, it could work... but I can't seem to make that happen with css. Any suggestions?

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• How to detect that a process is started using C# code[windows service]

  - by infant programmer

  I am trying to design a windows-service which monitors a process namely "Gtalk", if the process is started then, the browser Internet-explorer (process iexplore) should be closed. This should happen only when the process "Gtalk" is started, [not when running] The code I have written and implemented, doesn't allow to open IExplore when Gtalk is running. That is certainly what not I am trying for. The process Gtalk should close browser only at its start-up, After the process is started, it should allow to open IExplore. Is it possible with Windows service or is it must be the part of Gtalk process itself? This is my code: while (true) { if (Process.GetProcessesByName("Gtalk").Length > 0) { foreach (Process prc in Process.GetProcessesByName("IExplore")) { prc.Kill(); } } }

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• What is the best way to start building a Web 2.0 / Start up?

  - by spyhunterx

  I'm planning on developing my own web 2.0 application from scratch, using Yii Framework, JQuery, and HTML5 Boilerplate or Boots Strap. But I have huge dilemma. To begin this web 2.0, where is it best to start ? I've already completed flowcharts, diagrams and descriptions sheets for my project; However, i'm stuck programming and design wise. Should I start with the CSS of the the website, Photoshop, or functionality ( Php ) ? Where should I start ? I would really love this start up to be a success. I will greatly appreciate some responses.

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• Declaring two classes that contain instance variables of each others' types.

  - by Benji XVI

  Let’s say you wish to have two classes like so, each declaring an instance variable that is of the other’s class. @interface A : NSObject { B *something; } @end @interface B : NSObject { A *something; } @end It seems to be impossible to declare these classes with these instance variables. In order for A to include an IV of class B, B must already be compiled, and so its @interface must come before A’s. But A’s must be put before B’s for the same reason. Putting the two class declarations in separate files, and #import-ing each other’s .h doesn’t work either, for obvious reasons. So, what is the solution? Or is this either (1) impossible or (2) indicative of a bad design anyway?

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• Neural network for aproximation function for board game

  - by Pax0r

  I am trying to make a neural network for aproximation of some unkown function (for my neural network course). The problem is that this function has very many variables but many of them are not important (for example in [f(x,y,z) = x+y] z is not important). How could I design (and learn) network for this kind of problem? To be more specific the function is an evaluation function for some board game with unkown rules and I need to somehow learn this rules by experience of the agent. After each move the score is given to the agent so actually it needs to find how to get max score. I tried to pass the neighborhood of the agent to the network but there are too many variables which are not important for the score and agent is finding very local solutions.

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• jQuery plugin to style objects

  - by Alex

  Hi. I've been looking at the various JavaScript UI libraries and am wondering if there's one that can add some styling to page elements. I'm currently adding rounded corners, shadows, borders, and gradients via my own CSS + hacks to get it working on IE. I'm using jQuery for a number of tasks and wondered if there's a plugin that can add these design flairs more easily to DIVs. Not that you want to go overboard with this stuff, but when you need to use it, you'd like to depend on cross-browser and tried-and-tested solutions. Thanks.

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• multi directional scrolling site

  - by user557318

  Ive been asked if i am able to program a multi directional scrolling site like this- COS only using wordpress. Initially i thought i may be flash but the source seems like it could be simple, possibly with elements of jquery. . . . . I am unable to find any themes that even come close to it. And initially i wanted to know how it has been achieved to see if i am able to start the design work any ideas how this has been achieved. More to the point if the multi scrolling could be applied on wordpress

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• "Volkswagen Passat" Navigation

  - by joe_midi

  http://web.vw.com/all-new-passat-experience/ The navigation on this .swf is very impressive, and I was wondering how I would go about replicating it. The way each of the sections Design / Technology / Safety / Performance I want to know how each section can expand and still fit together. I've started with MOUSE_OVER events, but I'm not entirely sure how to order them so each section is the right size for every mouse over Event. This is the code I have for each "Section", I have created a movie clip with a Mask that expands on mouse over and brings the selected clip to the highest depth. this.firstButton01.addEventListener(MouseEvent.MOUSE_OVER, firstButton01OVER) function firstButton01OVER(e:Event):void { this.firstButton01.gotoAndPlay(2); this.setChildIndex(firstButton01,this.numChildren-1); }

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• including .h files.

  - by Max

  Suppose I have two .h files: A.h and B.h. Moreover, A.h includes B.h itself: B.h - declares class B. class B { ... }; A.h - declares class A, which uses class B. #include B.h class A { void SomeFunction(const B& b); }; Now, I have some .cpp file, that uses both A and B classes (B class maybe used not only in A::SomeFunction(B)) What are the pluses to include both A.h and B.h (instead of only A.h) from the perspective of design-patterns and coding style.

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• C++: String and unions

  - by sub

  I'm having a (design) problem: I'm building an interpreter and I need some storage for variables. There are basically two types of content a variable here can have: string or int. I'm using a simple class for the variables, all variables are then stored in a vector. However, as a variable can hold a number or a string, I don't want C++ to allocate both and consume memory for no reason. That's why I wanted to use unions: union { string StringValue; int IntValue; } However, strings don't work with unions. Is there any workaround so no memory gets eaten for no reason?

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• Delphi: what are the 8 mystery components on my form?

  - by mawg

  When I iterate of the controls on my form, I see those which I placed there at design time or run time. They are all of type TEdit, Tmemo, TComboBox, etc ... However, there are always exactly eight which I do not recognize. I can skip over them, since they are not of a type which interests me, but I am curios. I am guessing system controls like min/max/close. Their Name property is empty. Is there any way I can determine what type they are (without explicitly testing for every standard component derived from TWinControl) ? I am curious - but not yellow ;-)

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• .NET security mechanism to restrict access between two Types in the same Website project?

  - by jdk

  Question: Is there a mechanism in the .NET Framework to hide one custom Type from another without using separate projects/assemblies? I'm using C# with ASP.NET in a Website project (Note: Not a Web Application). Obviously there's not a way to enforce this restriction using language-specific OO keywords so I am looking for something else, for example: maybe a permission framework or code access mechanism, maybe something that uses meta data like Attributes. I'm unsure. I don't really care whether the solution actually hides classes from each other or just makes them inaccessible, etc. A runtime or design time answer will suffice. Looking for something easy to implement otherwise it's not worth the effort ... Background: I'm working in an ASP.NET Website project and the team has decided not to use separate project assemblies for different software layers. Therefore I'm looking for a way to have, for example, a DataAccess/ folder of which I disallow its classes to access other Types in the ASP.NET Website project.

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• Best way to handle different panels occupying same area

  - by gmnnn

  I have this application: I want to change the marked area when the user is clicked one of the navBarItems (like Microsoft OUTLOOK). I've been doing some research and a lot of people said that I can add several panels and show/hide them when user is clicked a navBarItem. But the area will contain a lot of gridviews and a lot of other controls. I don't know if I want to initialize all of them when application starts because it's gonna be hard on the cpu and memory to keep all the controls running at the same time. And I don't think it's an elegant solution for this kind of situation. But if I choose to initialize controls when user is clicked to corresponding navBarItem, it's gonna be laggy for the user. What is the best design approach for this situation? PS: I can use commercial libraries too. Thank you.

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• ASP.net PreInit() Vs Init()

  - by ASP.netBeginner

  From local forum i understood that PreInit can be used to handle the following PreInit() >Master pages can be called dynamically >Themes can be set dynamically >Programatically add controls to controls collection and i read Init() is for Init() In this event, we can read the controls properties (set at design time). We cannot read control values changed by the user because that changed value will get loaded after LoadPostData() event fires. Question I am not getting the point "We cannot read control values changed by the user".Where do users change the value of control?.Example would help me to understand the point.

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• WCF: Is there a way to return an object that is able to execute on the server?

  - by mafutrct

  Coming from a Java background, this is the way I'm thinking: The server provides an object to the client. This object should be able to execute on the server. Server: private string _S = "A"; public interface IFoo { void Bar(); } private class Foo : IFoo { void Bar() { _S = "B";} } public IFoo GetFoo() { return new Foo(); } Client: IFoo foo = serverChannel.GetFoo(); foo.Bar(); Is this possible? Or is my understanding wrong and this is not how it works in WCF? What would be a better design?

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• OpenGL performance on rendering "virtual gallery" (textures)

  - by maticus

  I have a considerable (120-240) amount of 640x480 images that will be displayed as textured flat surfaces (4 vertex polygons) in a 3D environment. About 30-50% of them will be visible in a given frame. It is possible for them to crossover. Nothing else will be present in the environment. The question is - will the modern and/or few-years-old (lets say Radeon 9550) GPU cope with that, and what frame rate can I expect? I aim for 20FPS, but 30-40 would be nice. Would changing the resolution to 320x240 make it more probable to happen? I do not have any previous experience with performance issues of 3D graphics on modern GPUs, and unfortunately I must make a design choice. I don't want to waste time on doing something that couldn't have worked :-)

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• Optimal strategy to make a C++ hash table, thread safe

  - by Ajeet

  (I am interested in design of implementation NOT a readymade construct that will do it all.) Suppose we have a class HashTable (not hash-map implemented as a tree but hash-table) and say there are eight threads. Suppose read to write ratio is about 100:1 or even better 1000:1. Case A) Only one thread is a writer and others including writer can read from HashTable(they may simply iterate over entire hash table) Case B) All threads are identical and all could read/write. Can someone suggest best strategy to make the class thread safe with following consideration 1. Top priority to least lock contention 2. Second priority to least number of locks My understanding so far is thus : One BIG reader-writer lock(semaphore). Specialize the semaphore so that there could be eight instances writer-resource for case B, where each each writer resource locks one row(or range for that matter). (so i guess 1+8 mutexes) Please let me know if I am thinking on the correct line, and how could we improve on this solution.

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• Concurrency handling

  - by Lijo

  Hi, Suppose, I am about to start a project using ASP.NET and SQL Server 2005. I have to design the concurrency requirement for this application. I am planning to add a TimeStamp column in each table. While updating the tables I will check that the TimeStamp column is same, as it was selected. Will this approach be suffice? Or is there any shortcomings for this approach under any circumstances? Please advice. Thanks Lijo

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• AS3 - Can I have access to the object (or function) who call me?

  - by lk

  I've asked this same question with Python. Now I like to know if this can be done in AS3. If I have something like this: package { public class SomeClass { private function A():void { C() } private function B():void { C() } private function C():void { // who is the caller, A or B ??? } public function SomeClass() { A() B() } } } Despite the design or other issues, this is only a question of an inquiring mind. Note: This has to be done without changing C signature Note 2: I like to have an access to an instance of the caller function so I can call that caller function (if I want to)

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• New datatype which can have numbers upto 100 digits.

  - by ckv

  Note: This was an interview question and may not have an actual use case currently The question was to design a class that can store numbers which are very very large say each number can have 100 digits. This new class is a datatype like int. What are the different types of constructors, overloads and other functions that you would write. How can this be further extended to support really large floating point numbers. How this can be given to others so that they can reuse the same component with their own additional functionality. My answer consisted of 2 approaches 1. using array of integers to store every say 10 digits 2. using string itself to store the number and perform operations on individual numbers. What would be the best approach?

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• Why is it called NoSQL?

  - by beef jerky

  I've recently worked with MongoDB and learned about its schemaless design. However, I'm confused with the term NoSQL? Why is it called that? Doesn't it use SQL or SQL-like queries? I've also read from an article that the main difference lies in how data is stored. In the case of MongoDB, it's stored like JSON documents. Is this true? Also, I'm confused why I always see 'NoSQL vs relational databases'. Aren't NoSQL databases relational? I believe documents in MongoDB are still related/linked through some keys (please correct me if I'm wrong). So why is it labeled as non-relational? Thanks in advance!

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• How to turn one server into many servers? (Virtualization/VMWare)

  - by user1229962

  I'm hoping for a high level discussion of this problem I know is quickly approaching my application. I have a server that binds on a specific port and manages TCP Sockets from my clients. I know that it is common practice to use VMWare to virtualize servers and run multiple servers at once. How can a single server design be changed to support multiple servers? Multiple servers can't bind to the same port. If I had to guess I would say a proxy server binds to the port and then sends connections off to the other servers to be handled as if it was still a single server application. I'm wondering what options there are and what are the common practices for solving this problem? Thanks in advance!

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