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  • ASP.NET MVC3 checkbox dropdownlist create [migrated]

    - by user95381
    i'm new in asp.net MVC and I/m use view model to poppulate the dropdown list and group of checkboxes. I use SQL Server 2012, where have many to many relationships between Students - Books; Student - Cities. I need collect StudentName, one city and many books for one student. I have next questions: 1. How can I get the values from database to my StudentBookCityViewModel? 2. How can I save the values to my database in [HttpPost] Create method? Here is the code: MODEL public class Student { public int StudentId { get; set; } public string StudentName { get; set; } public ICollection<Book> Books { get; set; } public ICollection<City> Cities { get; set; } } public class Book { public int BookId { get; set; } public string BookName { get; set; } public bool IsSelected { get; set; } public ICollection<Student> Students { get; set; } } public class City { public int CityId { get; set; } public string CityName { get; set; } public bool IsSelected { get; set; } public ICollection<Student> Students { get; set; } } VIEW MODEL public class StudentBookCityViewModel { public string StudentName { get; set; } public IList<Book> Books { get; set; } public StudentBookCityViewModel() { Books = new[] { new Book {BookName = "Title1", IsSelected = false}, new Book {BookName = "Title2", IsSelected = false}, new Book {BookName = "Title3", IsSelected = false} }.ToList(); } public string City { get; set; } public IEnumerable<SelectListItem> CityValues { get { return new[] { new SelectListItem {Value = "Value1", Text = "Text1"}, new SelectListItem {Value = "Value2", Text = "Text2"}, new SelectListItem {Value = "Value3", Text = "Text3"} }; } } } Context public class EFDbContext : DbContext{ public EFDbContext(string connectionString) { Database.Connection.ConnectionString = connectionString; } public DbSet<Book> Books { get; set; } public DbSet<Student> Students { get; set; } public DbSet<City> Cities { get; set; } protected override void OnModelCreating(DbModelBuilder modelBuilder) { modelBuilder.Entity<Book>() .HasMany(x => x.Students).WithMany(x => x.Books) .Map(x => x.MapLeftKey("BookId").MapRightKey("StudentId").ToTable("StudentBooks")); modelBuilder.Entity<City>() .HasMany(x => x.Students).WithMany(x => x.Cities) .Map(x => x.MapLeftKey("CityId").MapRightKey("StudentId").ToTable("StudentCities")); } } Controller public ActionResult Create() { return View(); } [HttpPost] public ActionResult Create() { //I don't understand how I can save values to db context.SaveChanges(); return RedirectToAction("Index"); } View @model UsingEFNew.ViewModels.StudentBookCityViewModel @using (Html.BeginForm()) { Your Name: @Html.TextBoxFor(model = model.StudentName) <div>Genre:</div> <div> @Html.DropDownListFor(model => model.City, Model.CityValues) </div> <div>Books:</div> <div> @for (int i = 0; i < Model.Books.Count; i++) { <div> @Html.HiddenFor(x => x.Books[i].BookId) @Html.CheckBoxFor(x => x.Books[i].IsSelected) @Html.LabelFor(x => x.Books[i].IsSelected, Model.Books[i].BookName) </div> } </div> <div> <input id="btnSubmit" type="submit" value="Submit" /> </div> </div> }

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  • Merge sort versus quick sort performance

    - by Giorgio
    I have implemented merge sort and quick sort using C (GCC 4.4.3 on Ubuntu 10.04 running on a 4 GB RAM laptop with an Intel DUO CPU at 2GHz) and I wanted to compare the performance of the two algorithms. The prototypes of the sorting functions are: void merge_sort(const char **lines, int start, int end); void quick_sort(const char **lines, int start, int end); i.e. both take an array of pointers to strings and sort the elements with index i : start <= i <= end. I have produced some files containing random strings with length on average 4.5 characters. The test files range from 100 lines to 10000000 lines. I was a bit surprised by the results because, even though I know that merge sort has complexity O(n log(n)) while quick sort is O(n^2), I have often read that on average quick sort should be as fast as merge sort. However, my results are the following. Up to 10000 strings, both algorithms perform equally well. For 10000 strings, both require about 0.007 seconds. For 100000 strings, merge sort is slightly faster with 0.095 s against 0.121 s. For 1000000 strings merge sort takes 1.287 s against 5.233 s of quick sort. For 5000000 strings merge sort takes 7.582 s against 118.240 s of quick sort. For 10000000 strings merge sort takes 16.305 s against 1202.918 s of quick sort. So my question is: are my results as expected, meaning that quick sort is comparable in speed to merge sort for small inputs but, as the size of the input data grows, the fact that its complexity is quadratic will become evident? Here is a sketch of what I did. In the merge sort implementation, the partitioning consists in calling merge sort recursively, i.e. merge_sort(lines, start, (start + end) / 2); merge_sort(lines, 1 + (start + end) / 2, end); Merging of the two sorted sub-array is performed by reading the data from the array lines and writing it to a global temporary array of pointers (this global array is allocate only once). After each merge the pointers are copied back to the original array. So the strings are stored once but I need twice as much memory for the pointers. For quick sort, the partition function chooses the last element of the array to sort as the pivot and scans the previous elements in one loop. After it has produced a partition of the type start ... {elements <= pivot} ... pivotIndex ... {elements > pivot} ... end it calls itself recursively: quick_sort(lines, start, pivotIndex - 1); quick_sort(lines, pivotIndex + 1, end); Note that this quick sort implementation sorts the array in-place and does not require additional memory, therefore it is more memory efficient than the merge sort implementation. So my question is: is there a better way to implement quick sort that is worthwhile trying out? If I improve the quick sort implementation and perform more tests on different data sets (computing the average of the running times on different data sets) can I expect a better performance of quick sort wrt merge sort? EDIT Thank you for your answers. My implementation is in-place and is based on the pseudo-code I have found on wikipedia in Section In-place version: function partition(array, 'left', 'right', 'pivotIndex') where I choose the last element in the range to be sorted as a pivot, i.e. pivotIndex := right. I have checked the code over and over again and it seems correct to me. In order to rule out the case that I am using the wrong implementation I have uploaded the source code on github (in case you would like to take a look at it). Your answers seem to suggest that I am using the wrong test data. I will look into it and try out different test data sets. I will report as soon as I have some results.

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  • What is so good about Linux? [closed]

    - by Chris Bridgett
    Self-explanatory question title. I've only ever used Windows OS's (except Mac OSX at friends etc, years ago occasionally) and when diving into the world of programming, Linux is a name that is coming up every other tutorial or article. All my web hosts run Linux and a lot of programming literature covers how to go about various tasks on Linux as well as Windows, but other than the odd raving I've read years ago about Linux being less resource-intensive, I haven't really given it much thought. Any article I read about Linux and whether it should be used for... 'regular' use, it's shunned since any windows applications I'm familiar with will usually require the windows API and there's no end of 'hacking' to get various programs working on Linux. As far as I understand a GUI is optional on Linux too? This all sounds very noobish I'm sure, but we all start somewhere, so: What is Linux good for? What should Linux be used for?

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  • Is there a distributed project management software like Redmine?

    - by Tobias Kienzler
    I am quite familiar with and love using git, among other reasons due to its distributed nature. Now I'd like to set up some similarly distributed (FOSS) Project Management software with features similar to what Redmine offers, such as Issue & time tracking, milestones Gantt charts, calendar git integration, maybe some automatic linking of commits and issues Wiki (preferably with Mathjax support) Forum, news, notifications Multiple Projects However, I am looking for a solution that does not require a permanently accesible server, i.e. like in git, each user should have their own copy which can be easily synchronized with others. However it should be possible to not have a copy of every Project on every machine. Since trac uses multiple instances for multiple projects anyway, I was considering using that, but I neither know how well it adapts to simply giting the database itself (which would be be easiest way to handle the distribution due to git being used anyway), nor does it include all of Redmine's feature. So, can you recommend me a distributed project management software? If your suggestion is a software that usually runs on a server please include a description of the distribution method (e.g. whether simply putting the data in a git repository would do the trick), and if it's e.g. trac, please mention plugins required to include the features mentioned.

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  • Architecting Python application consisting of many small scripts

    - by Duke Dougal
    I am building an application which, at the moment, consists of many small Python scripts. Each Python script processes items from one Amazon SQS queue. Emails come into an initial queue and are processed by a script and typically the script will do a small unit of processing (for example, parse email and store some database fields), then an item will be placed on the next queue for further processing, until eventually the email has finished going through the various scripts and queues. What I like about this approach is that it is very loosely coupled. However, I'm not sure how I should implement live. Should I make each script a daemon which is constantly polling it's inbound queue for things to do? Or should there be some overarching orchestration program or process? Or maybe I should not have lots of small Python scripts but one large application? Specific questions: How should I run each of these scripts - as a daemon with some sort or restart monitor to restart them in case they stop for any reason? If yes, should I have some program which orchestrates this? Or is the idea of many small script not a good one, would it make more sense to have a larger python program which contains all the functionality and does all the queue polling and execution of functionality for each queue? What is the current preferred approach to daemonising Python scripts? Broadly I would welcome any comments or opinions on any aspect of this. thanks

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  • Which points should be covered in basic Bachelors' level C++ course?

    - by Gulshan
    I have a young lecturer friend who is going to take the C++ course for the bachelors' degree in CS. He asked me for some suggestions regarding how the course should be organized. Now I am asking you. I have seen many trends in universities which leads to a nasty experience of C++. So, please suggest from a professional programmer's point of view. For your information, the students going to take the course, have taken course like "Introduction to programming with C" in previous semester.

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  • Is there any way to disable write-access to source code from within Xcode?

    - by Kapil Kapre
    Is there any easy solution to prevent Xcode from writing to source files in a project? I want to edit source files externally and only use Xcode for debugging and so I want to prevent any accidental modifications getting saved via xcode. (Obviously I want Xcode to pickup external changes to files when I build/debug) One possible solution that I thought of was to enable app sandbox entitlements on xcode and manually maintain a list of directories that it should not write to. Is this feasible? Any other ideas? On the sandboxing thing, I'm not sure if Xcode is disqualified as per Apple's Sandboxing Requirements.

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  • Documenting and enforcing programming standards and guidelines for shared library

    - by dreza
    Myself and another developer with the go ahead from our IT director have started a general purpose library in .NET with the intention that it will provide many common purpose classes that we use in our day to day development. During discussions and design of the library we have come up with a set of standards that we want the library to follow to ensure it is maintained and expanded on in a consistent manner. What is the best way to ensure these decisions we made for the library get feed to the other developers who might be using and adding to this library in the future. One of our decisions was to ensure we review all checked in code so we expect initially there to be some differences in coding styles of individuals not fitting in with the project standards. Some ideas I had were: Add a Read-me.txt to the project that outline the guidelines and standards Send an email out to everyone in the team to let them know about the project etc Call a team meeting to go through this new project and our expectations and standards we were aiming to follow Try and enforce the standards via Visual Studio (not sure if this would be possible or how just an idea) At the moment there is no general company programming standards so this would be a first really insofar as we are creating a standard that different project teams would need to adhere to.

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  • Large invoice database structure and rendering

    - by user132624
    Our client has a MS SQL database that has 1 million customer invoice records in it. Using the database, our client wants its customers to be able to log into a frontend web site and then be able to view, modify and download their company’s invoices. Given the size of the database and the large number of customers who may log into the web site at any time, we are concerned about data base engine performance and web page invoice rendering performance. The 1 million invoice database is for just 90 days sales, so we will remove invoices over 90 days old from the database. Most of the invoices have multiple line items. We can easily convert our invoices into various data formats so for example it is easy for us to convert to and from SQL to XML with related schema and XSLT. Any data conversion would be done on another server so as not to burden the web interface server. We have tentatively decided to run the web site on a .NET Framework IIS web server using MS SQL on MS Azure. How would you suggest we structure our database for best performance? For example, should we put all the invoices of all customers located within the same 5 digit or 6 digit zip codes into the same table? Or could we set up a separate home directory for each customer on IIS and place each customer’s invoices in each customer’s home directory in XML format? And secondly what would you suggest would be the best method to render customer invoices on a web page and allow customers to modify for best performance? The ADO.net XML Data Set looks intriguing to us as a method, but we have never used it.

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  • How to detect two moving shapes overlapped?

    - by user1389813
    Given a list of circles with its coordinates (x and y) that are moving every second in different direction (South-East, South-West, North-East and North-West), and the circle will change direction if it hits the wall sort of like bouncing, so how do we detect if any of them collide or overlap with each other ? I am not sure if we can use some data structures like a Binary Search Tree because since all the coordinates vary every seconds, so the tree will have to re-build accordingly. Or can we use Vertical Sweep Line Algorithm each time ? Any ideas on how to do this in a efficient way ?

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  • Can python and php work together?

    - by user71741
    I am having a mobile app created for ios. The developers built the app in php. The app requires an algorithm so I found another programmer to develop it. The algorithm programmer built the algorithm in python. The developers refuse to finish the app because they say it won't work with python, while the programmer insist it will. The programmer says put the algorithm in its on server and connect then over http. Will this work and I'd so how risky is it to future problems?

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  • 2 Servers 1 Database - Can I use Redis?

    - by Aust
    Ok I have a couple of questions here. First let me give you some background information. I'm starting a project where I have a node.js server running my application and my website running on another normal server. My application will allow multiple users simultaneous connections and updates to the database so Redis seemed like a good fit there because of its speed and atomic functions. For someone to access my application they have to login with an account. To get an account, they have to signup for one through my website. So my website needs a database, but its not important to have a database like Redis here because it doesn't need it. Which leads me to my first question: 1. Can Redis even be used without node.js? It seems like it would be convenient if both of my servers were using the same database to keep track of information. In some cases, they will keep track of the same information (as in user information) and in other cases, they will be keeping track of separate information. So even if the website wouldn't be taking full advantage of all that Redis has to offer it seems like it would be more convenient. So assuming Redis could be used in this situation that leads to my next question: 2. Since Redis is linked with JavaScript, how would I handle the security from my website users? What would be stopping my website users from opening firebug or chrome's inspector and making changes to the database? Maybe if I designed my site with the layout like this: apply.php-update.php-home.php. Where after they submitted their form it would redirect them to the update page where the JavaScript would run and then redirect them after the database updated to the home page. I don't really know I'm just taking shots in the dark at this point. :) Maybe a better alternative would be to have my node.js application access its own Redis database and also have access to another MySQL database that my website also has access to. Or maybe there is another database that would be better suited for this situation other than Redis. Anyways any direction on this matter would be greatly appreciated. :)

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  • Security programming jobs

    - by Mike Smith
    I am a student, about to finish my undergraduate in Computer Science in about a year. I am very interested in computer/network security, but I also love programming. Is there a job or subfield that is a fusion of both? I have programmed everything from games to barcode readers to web bots, and I know for sure that I want to do some kind of programming, but ideally I would like to do some kind of software development involving computer security. Any advice would be appreciated.

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  • I need books for procedural programming

    - by Student
    Please suggest books for procedural programming. I need to know the core principles/patterns of procedural programming. So it doesn't matter if the book using any language to convey the procedural programming principles, be it pure C or others languages. Nowadays it is difficult to find ones. Even google and amazon searches didn't give me a satisfactory books. You may vote to close this question but please recommend books in comment section.

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  • UI message passing programming paradigm

    - by Ronald Wildenberg
    I recently (about two months ago) read an article that explained some user interface paradigm that I can't remember the name of and I also can't find the article anymore. The paradigm allows for decoupling the user interface and backend through message passing (via some queueing implementation). So each user action results in a message being pased to the backend. The user interface is then updated to inform the user that his request is being processed. The assumption is that a user interface is stale by definition. When you read data from some store into memory, it is stale because another transaction may be updating the same data already. If you assume this, it makes no sense to try to represent the 'current' database state in the user interface (so the delay introduced by passing messages to a backend doesn't matter). If I remember correctly, the article also mentioned a read-optimized data store for rendering the user interface. The article assumed a high-traffic web application. A primary reason for using a message queue communicating with the backend is performance: returning control to the user as soon as possible. Updating backend stores is handled by another process and eventually these changes also become visible to the user. I hope I have explained accurately enough what I'm looking for. If someone can provide some pointers to what I'm looking for, thanks very much in advance.

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  • Selling your services when you use uncommon technologies

    - by speeder
    I took a look in Stackoverflow most popular profiles, and then I did the same in several other sites, and then I took a look in job postings in several boards, mostly out of curiosity, because I noticed this: If you work with Java, .NET or other managed languages, or you work with stuff that is popular for web development (Ruby, JavaScript, etc...) you can get lots of points on Stackoverflow, find lots of jobs and clients, find forums, friends, colleagues, etc... But how a programmer of uncommon languages (Lua, pure C, Lisp, D, ADA, Haskell, etc...) find information, sell his services, and so on? EDIT: This also applies to fields: You work with web, corporate software, database, etc... it is great... You dislike those previous 3, noone ever will hire your services...

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  • Recursion VS memory allocation

    - by Vladimir Kishlaly
    Which approach is most popular in real-world examples: recursion or iteration? For example, simple tree preorder traversal with recursion: void preorderTraversal( Node root ){ if( root == null ) return; root.printValue(); preorderTraversal( root.getLeft() ); preorderTraversal( root.getRight() ); } and with iteration (using stack): Push the root node on the stack While the stack is not empty Pop a node Print its value If right child exists, push the node's right child If left child exists, push the node's left child In the first example we have recursive method calls, but in the second - new ancillary data structure. Complexity is similar in both cases - O(n). So, the main question is memory footprint requirement?

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  • Is there a way communicate or measure levels of abstraction?

    - by hydroparadise
    I'll be the first to say that this question is a bit... out there. But here are a couple questions I bear in mind : Is abstraction continuous or discrete? Is there a single unit of abstraction? But I'm not sure those questions are truly answerable or even really makes sence. My naive answer would be something along the lines of abitrarily discrete but not necescarily having a single unit measure. Here's what I mean... Take a Black Labrador; an abstraction that could be made is that a Black Lab is a type of animal. [Animal]<--[Black Lab] A Black Lab is also a type of Dog. [Dog]<--[Black Lab] One way to establish a degree of abstraction is by comparing the two the abstractions. We could say that [Animal] is more abstract than [Dog] in respect to a Black Lab. It just so happens [Animal] can also be used as an abstraction of [Dog] So, we might end up with something like [Animal]<--[Dog]<--[Black Lab] With the model above, one might be inclined to say that there's two hops of abstraction to get from [Black Lab] to [Animal]. But you can't exactly tell somebody they need one level abstraction and reasonalby expect they will come up with [Dog] given they aren't explicity given the options above. If I needed to tell someobody in a single email that they needed an abstract class with out knowing what that abstract class is, is there a way to communaticate a degree of abstraction such that they might end up on Dog instead of Animal? As a side note, what area of study might this type of analysis fall under?

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  • Microsoft SDET position

    - by Mark
    I was curious about MS's SDET position. I've heard a lot of people speak negatively and positively about this position. I was wondering if any current or previous SDETs could comment on a couple of issues. 1) Is career development in any way hurt by this position within and outside of MS? 1.5) Is it harder to get hired as a developer at another company after being an SDET? 2) Within MS culture, how is the SDET position viewed with respect to PM or SDE? Is it respected or looked down upon? 3) If you worked as an SDET, did you like it?

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  • Is there a Javascript library for creating vintage photos?

    - by Nguyen Thanh Tu
    I'm working on a Canvas object in HTML5, and I am attempting to make some photos look "better". I tried VintageJS, an existing photo-retouching Javascript library, and Picozu, a web application cloning some Adobe Photoshop functionalities, but I'm still not happy. Can you help me with an algorithm or point to an existing Javascript library that would allow me to make my photos look like the following example? http://i46.photobucket.com/albums/f137/thanhtu_zx/Untitled-1.jpg

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  • What's the term for re-implementing an old API in terms of a newer API

    - by dodgy_coder
    The reason for doing it is to solve the case when a newer API is no longer backwards compatible with an older API. To explain, just say that there is an old API v1.0. The maker of this API decides it is broken and works on a new API v1.1 that intentionally breaks compatibility with the old API v1.0. Now, any programs written against the old API cannot be recompiled as-is with the new API. Then lets say there is a large app written against the old API and the developer doesn't have access to the source code. A solution would be to re-implement a "custom" old API v1.0 in terms of the new API v1.1 calls. So the "custom" v1.0 API is actually keeping the same interface/methods as the v1.0 API but inside its implementation it is actually making calls to the new API v1.1 methods. So the large app can be then compiled and linked against the "custom" v1.0 API and the new v1.1 API without any major source code changes. Is there a term for this practice? There's a recent example of this happening in Jamie Zawinski's port of XScreenSaver to the iPhone - he re-implemented the OpenGL 1.3 API in terms of the OpenGL ES 1.1 API. In this case, OpenGL 1.3 represents the "old" API and OpenGL ES 1.1 represents the "new" API.

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  • Why is Python slower than Java but faster than PHP

    - by good_computer
    I have many times seen various benchmarks that show how a bunch of languages perform on a given task. Always these benchmarks reveal that Python is slower then Java and faster than PHP. And I wonder why is that the case. Java, Python, and PHP run inside a virtual machine All three languages convert their programs into their custom byte codes that run on top of OS -- so none is running natively Both Java and Python can be "complied" (.pyc for Python) but the __main__ module for Python is not compiled Python and PHP are dynamically typed and Java statically -- is this the reason Java is faster, and if so, please explain how that affects speed. And, even if the dynamic-vs-static argument is correct, this does not explain why PHP is slower than Python -- because both are dynamic languages. You can see some benchmarks here and here, and here

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  • 32-bit / 64-bit processors - what is that feature officially called?

    - by JW01
    I see talk of CPU's being either 32-bit or 64-bit processors. Information which is often required on download pages But what is that feature officially called. i.e What's the inverse of saying "I have a 64-bit processor"? I want to say: The ??? of my processor is 64 bit What is the correct term to use for ??? I have looked at a random product on the Intel site and I suspect the correct word for this is "Instruction Set", but I'm not sure.

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  • when to introduce an application services tier in an n-tier application

    - by user20358
    I am developing a web based application whose primary objective is to fetch data from the database, display it on the UI, take in user inputs and write them back to the database. The application is not going to be doing any industrial strength algorithm crunching, but will be receiving a very high number of hits at peak times (described below) which will be changing thru the day. The layers are your typical Presentation, Business, Data. The data layer is taken care of by the database server. The business layer will contain the DAL component to access the database server over tcp. The choices I have to separate these layers into tiers are: The presentation and business layers can be either kept on the same tier. The presentation layer on a separate tier by itself and the business layer on a separate tier by itself. In the case of choice 2, the business layer will be accessed by the presentation layer using a WCF service either over http or tcp. I don't see any heavy processing being done on the Business layer, so I am leaning towards option 1 above. I also feel for the same reason, adding a new tier will only introduce the network latency. However, in terms of scalability in case I need to scale up or scale out, which is a better way to go? This application will need to be able to support up to 6 million users an hour. There will be a reasonable amount of data in each user session, storing user's preferences and other details. I will be using page level caching as well.

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  • How do you differentiate between "box," "machine," "computer" and whatever else?

    - by Corey
    There seems to be a few terms for referring to a computer, especially in the tech world. Different terms seem to be used based on technical expertise. When talking with people with some technical knowledge, I'll refer to it as a machine. When talking to non-technical people (family, friends) I'll call it a computer. On the rare occasion I'm talking about servers, I might call it a box, but even then I'll probably still call it a machine. Is that just me, or do there exist rules already for what to call a computer?

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