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• DAO design pattern and using it across multiple tables

  - by Casey

  I'm looking for feedback on the Data Access Object design pattern and using it when you have to access data across multiple tables. It seems like that pattern, which has a DAO for each table along with a Data Transfer Object (DTO) that represents a single row, isn't too useful for when dealing with data from multiple tables. I was thinking about creating a composite DAO and corresponding DTO that would return the result of, let's say performing a join on two tables. This way I can use SQL to grab all the data instead of first grabbing data from one using one DAO and than the second table using the second DAO, and than composing them together in Java. Is there a better solution? And no, I'm not able to move to Hibernate or another ORM tool at the moment. Just straight JDBC for this project.

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• Which design pattern is most appropriate?

  - by Anon

  Hello, I want to create a class that can use one of four algorithms (and the algorithm to use is only known at run-time). I was thinking that the Strategy design pattern sounds appropriate, but my problem is that each algorithm requires slightly different parameters. Would it be a bad design to use strategy, but pass in the relevant parameters into the constructor?. Here is an example (for simplicity, let's say there are only two possible algorithms) ... class Foo { private: // At run-time the correct algorithm is used, e.g. a = new Algorithm1(1); AlgorithmInterface* a; }; class AlgorithmInterface { public: virtual void DoSomething = 0; }; class Algorithm1 : public AlgorithmInterface { public: Algorithm1( int i ) : value(i) {} virtual void DoSomething(){ // Does something with int value }; int value; }; class Algorithm2 : public AlgorithmInterface { public: Algorithm2( bool b ) : value(b) {} virtual void DoSomething(){ // Do something with bool value }; bool value; };

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• .NET without use of DLL's

  - by Kieran

  Hi SO community I have been issued a problem with security. A bank will not allow use of DLL's in the project. What sort of structure would be needed to allow DataAccess and or the use of external services (like an email client mailchimp, icontct). has anyone else encountered this sort of problem before? If they have how should the project be structured (.net 3.5+). Thanks, KJ

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• c# object initializer complexity. best practice

  - by Andrew Florko

  I was too excited when object initializer appeared in C#. MyClass a = new MyClass(); a.Field1 = Value1; a.Field2 = Value2; can be rewritten shorter: MyClass a = new MyClass { Field1 = Value1, Field2 = Value2 } Object initializer code is more obvious but when properties number come to dozen and some of the assignment deals with nullable values it's hard to debug where the "null reference error" is. Studio shows the whole object initializer as error point. Nowadays I use object initializer for straightforward assignment only for error-free properties. How do you use object initializer for complex assignment or it's a bad practice to use dozen of assigments at all? Thank you in advance!

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• MVC (model-view-controller) - can it be explained in simple terms?

  - by DVK

  I need to explain to a not-very-technical manager the MVC (model-view-controller) concept and ran into trouble. The problem is that the explanation needs to be on a "your grandma will get it" level - e.g. even the fairly straightforward explanation offered on MVC Wiki page didn't work, at least with my commentary. Does anyone have a reference to a good MVC explanation in simple terms? It would ideally be done with non-techie metaphor examples (e.g. similar to "Decorator pattern is like glasses") - one reason I failed was that all MVC examples I could come up with were development related. I once saw a list of pattern explanations but to the best of my memory MVC was not on it. Thanks!

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• Equivalent of HTMLLoader class for an AS3 only project?

  - by eco_bach

  Hi I'm building an as3 only web application and want to be able to include external html content within a flash 'window'. In AIR there is the flash.html.HTMLLoader class which makes this possible. Can anyone point to an example of this being done in a flash as opposed to AIR application?

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• Search for a pattern in a list of strings - Python

  - by Holtz

  I have a list of strings containing filenames such as, file_names = ['filei.txt','filej.txt','filek.txt','file2i.txt','file2j.txt','file2k.txt','file3i.txt','file3j.txt','file3k.txt'] I then remove the .txt extension using: extension = os.path.commonprefix([n[::-1] for n in file_names])[::-1] file_names_strip = [n[:-len(extension)] for n in file_names] And then return the last character of each string in the list file_names_strip: h = [n[-1:] for n in file_names_strip] Which gives h = ['i', 'j', 'k', 'i', 'j', 'k', 'i', 'j', 'k'] How can i test for a pattern of strings in h? So if i,j,k occur sequentially it would return True and False if not. I need to know this because not all file names are formatted like they are in file_names. So: test_ijk_pattern(h) = True no_pattern = ['1','2','3','1','2','3','1','2','3'] test_ijk_pattern(no_pattern) = False

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• Is there a pattern that allows a constructor to be called only from a specific factory and from nowh

  - by willem

  We have a class, say LegacyUserSettingsService. LegacyUserSettingsService implements an interface, IUserSettingsService. You can get an instance of the IUserSettingsService by calling our ApplicationServicesFactory. The factory uses Spring.NET to construct the concrete LegacyUserSettingsService. The trouble is that new developers sometimes do their own thing and construct new instances of the LegacyUserSettingsService directly (instead of going via the factory). Is there a way to protect the constructor of the concrete class so it can only be called from the factory? A well-known pattern perhaps? Note that the concrete class resides in a different assembly (separate from the Factory's assembly, so the internal keyword is not a solution). The factory assembly references the other assembly that contains the concrete class. Any ideas?

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• HTTP_HOST vs. SERVER_NAME

  - by Emanuil

  When would you consider using one over the other and why?

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• Git Submodule or fork

  - by Eric

  I have a private repo in github that is the complete source code to my cms. Now I have a few local customers that I want to use the same code base on but with different themes. Is it better to fork the original project out into a repo for each one. Or use a submodule and create a new repo for each customer? After each site is complete I would imagine the theme files wouldn't change much but would need to pull in changes from the main repo when bugs are discovered.

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• .Net Compact Framework Tips, Tricks, and Gotchas

  - by Mat Nadrofsky

  Hey everyone, We work extensively in the .Net Compact Framework and Windows Mobile. I've seen plenty of questions come up regarding specifics to development of ASP.Net apps or other .Net based desktop apps but nothing CF specific. Anyone else a mobile developer out there that can share some things to start doing, stop doing, and avoid doing when developing in the Compact Framework?

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• Definitive method for sizing font in css

  - by David

  Hi there, I would like to know some opinions from experienced developers on what they think the definitive way to size fonts (in a base sense). I know that working with ems is considered best but im referring to the best way to set the base font size. There is the technique of setting font to 10px using 62.5 method but i think ie has an issue with rounding which throws this out slightly (perhaps not) YUI framework uses body { font:13px/1.231 arial,helvetica,clean,sans-serif; /* for IE6/7 */ *font-size:small; /* for IE Quirks Mode */ *font:x-small; } which really confuses me! Tripoli uses html { font-size:125%; } body { font-size:50%; } a list apart suggest something along the lines of : body { font-size: 16px; *font-size: 100%; } So which is the best either out of these methods or any alternatives. The best being the easiest to work with and the most reliable cross browser.

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• What turns away users/prospective users?

  - by Zach Johnson

  In your experience, what kinds of things have turned away users and prospective users from using your programs? Also, what kinds of things turn you away from using someone else's programs? For example, one thing that really bugs me is when someone provides free software, but requires you to enter your name and email address before you download it. Why do they need my name and email address? I just want to use the program! I understand that the developer(s) may want to get a feel for how many users they have, etc, but the extra work I have to do really makes me think twice about downloading their software, even if it does really great things.

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• Should I create protected constructor for my singleton classes?

  - by Vijay Shanker

  By design, in Singleton pattern the constructor should be marked private and provide a creational method retuning the private static member of the same type instance. I have created my singleton classes like this only. public class SingletonPattern {// singleton class private static SingletonPattern pattern = new SingletonPattern(); private SingletonPattern() { } public static SingletonPattern getInstance() { return pattern; } } Now, I have got to extend a singleton class to add new behaviors. But the private constructor is not letting be define the child class. I was thinking to change the default constructor to protected constructor for the singleton base class. What can be problems, if I define my constructors to be protected? Looking for expert views....

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• View artifacts leaking into the model of MVC

  - by Jono

  In an ASP.NET MVC application (which has very little chance of having its view technology ported to something non-HTML, but whose functional requirements evolve weekly,) how much HTML should ideally be allowed to be directly represented in the Model? I might come across as a design bigot for this, but I regard it as bad practice to allow any view constructs to "leak" into the model in an MVC application (and vice versa). For example, a Model that represents an item you're about to purchase should know nothing about the HTML check box that says "add giftwrap/message", nor should it know about any HTML drop down lists for payment card types. Conversely the View shouldn't be doing work like figuring out button text by translating keys into values (by looking in resource files.)

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• Which framework exceptions should every programmer know about ?

  - by Thibault Falise

  I've recently started a new project in C#, and, as I was coding some exception throw in a function, I figured out I didn't really know which exception I should use. Here are common exceptions that are often thrown in many programs : ArgumentException ArgumentNullException InvalidOperationException Are there any framework exceptions you often use in your programs ? Which exceptions should every .net programmer know about ? When do you use custom exception ?

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• How to write a good PHP database insert using an associative array

  - by Tom

  In PHP, I want to insert into a database using data contained in a associative array of field/value pairs. Example: $_fields = array('field1'=>'value1','field2'=>'value2','field3'=>'value3'); The resulting SQL insert should look as follows: INSERT INTO table (field1,field2,field3) VALUES ('value1','value2','value3'); I have come up with the following PHP one-liner: mysql_query("INSERT INTO table (".implode(',',array_keys($_fields)).") VALUES (".implode(',',array_values($_fields)).")"); It separates the keys and values of the the associative array and implodes to generate a comma-separated string . The problem is that it does not escape or quote the values that were inserted into the database. To illustrate the danger, Imagine if $_fields contained the following: $_fields = array('field1'=>"naustyvalue); drop table members; --"); The following SQL would be generated: INSERT INTO table (field1) VALUES (naustyvalue); drop table members; --; Luckily, multiple queries are not supported, nevertheless quoting and escaping are essential to prevent SQL injection vulnerabilities. How do you write your PHP Mysql Inserts? Note: PDO or mysqli prepared queries aren't currently an option for me because the codebase already uses mysql extensively - a change is planned but it'd take alot of resources to convert?

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• Is it best practice to try - catch my entire PHP code, or be as specific as possible?

  - by Itay Moav

  I do not have many kinds of Exceptions in my project. Right now,(we use MVC) I have the try catch encompassing my entire code: try{ fronController::dispatch($somthing...); }catch(Exception $E){ //handle errors } I wonder if there is a good reason to use the try-catch block in as specific as possible way as I can or just keep it general as it is now?

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• Immutable classes in C++

  - by ereOn

  Hi, In one of my projects, I have some classes that represent entities that cannot change once created, aka. immutable classes. Example : A class RSAKey that represent a RSA key which only has const methods. There is no point changing the existing instance: if you need another one, you just create one. My objects sometimes are heavy and I enforced the use of smart pointers to avoid copy. So far, I have the following pattern for my classes: class RSAKey : public boost::noncopyable, public boost::enable_shared_from_this<RSAKey> { public: /** * \brief Some factory. * \param member A member value. * \return An instance. */ static boost::shared_ptr<const RSAKey> createFromMember(int member); /** * \brief Get a member. * \return The member. */ int getMember() const; private: /** * \brief Constructor. * \param member A member. */ RSAKey(int member); /** * \brief Member. */ const int m_member; }; So you can only get a pointer (well, a smart pointer) to a const RSAKey. To me, it makes sense, because having a non-const reference to the instance is useless (it only has const methods). Do you guys see any issue regarding this pattern ? Are immutable classes something common in C++ or did I just created a monster ? Thank you for your advices !

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• Practical usings of "internal" keyword in C#

  - by Alexander Prokofyev

  Would you explain, please, what are practical usings of "internal" keyword in C#? I know what "internal" modifier limits access to the current assembly. But when could I need it? Thanks!

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• P/Invoke or C++/CLI for wrapping a C library

  - by Ian G

  Have a moderate size (40-odd function) C API that needs to be called from a C# project. The functions logically break up to form a few classes that will be API presented to the rest of the project. Are there any objective reasons to prefer P/Invoke or C++/CLI for the interoperability underneath that API, in terms of robustness, maintainability, deployment, ...? The issues I could think of that might be, but aren't problematic are: C++/CLI will require an separate assembly, the P/Invoke classes can be in the main assembly. (We've already got multiple assemblies and there'll be the C dlls anyway so not a major issue). Performance doesn't seem differ noticeable between the two methods. Issues that I'm not sure about are: My feeling is C++/CLI will be easier to debug if there's inter-op problem, is this true? Language familiarity enough people know C# and C++ but knowledge of details of C++/CLI are rarer here. Anything else?

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• distributing R package with optional S4 syntax sugar

  - by mariotomo

  I've written a small package for logging, I'm distributing it through r-forge, recently I received some very interesting feedback on how to make it easier to use, but this functionality is based on stuff (setRefClass) that was added to R in 2.12. I'd like to keep distributing the package also for R-2.9, so I'm looking for a way to include or exclude the S4 syntactical sugar automatically, and include it when the library is loaded on a R = 2.12 system. one other option I see, that is to write a small S4 package that needs 2.12, imports the simpler logging package and exports the syntactically sugared interface... I don't like it too much, as I'd need to choose a different name for the S4 package.

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• Including partial views when applying the Mode-View-ViewModel design pattern

  - by Filip Ekberg

  Consider that I have an application that just handles Messages and Users I want my Window to have a common Menu and an area where the current View is displayed. I can only work with either Messages or Users so I cannot work simultaniously with both Views. Therefore I have the following Controls MessageView.xaml UserView.xaml Just to make it a bit easier, both the Message Model and the User Model looks like this: Name Description Now, I have the following three ViewModels: MainWindowViewModel UsersViewModel MessagesViewModel The UsersViewModel and the MessagesViewModel both just fetch an ObserverableCollection<T> of its regarding Model which is bound in the corresponding View like this: <DataGrid ItemSource="{Binding ModelCollection}" /> The MainWindowViewModel hooks up two different Commands that have implemented ICommand that looks something like the following: public class ShowMessagesCommand : ICommand { private ViewModelBase ViewModel { get; set; } public ShowMessagesCommand (ViewModelBase viewModel) { ViewModel = viewModel; } public void Execute(object parameter) { var viewModel = new ProductsViewModel(); ViewModel.PartialViewModel = new MessageView { DataContext = viewModel }; } public bool CanExecute(object parameter) { return true; } public event EventHandler CanExecuteChanged; } And there is another one a like it that will show Users. Now this introduced ViewModelBase which only holds the following: public UIElement PartialViewModel { get { return (UIElement)GetValue(PartialViewModelProperty); } set { SetValue(PartialViewModelProperty, value); } } public static readonly DependencyProperty PartialViewModelProperty = DependencyProperty.Register("PartialViewModel", typeof(UIElement), typeof(ViewModelBase), new UIPropertyMetadata(null)); This dependency property is used in the MainWindow.xaml to display the User Control dynamicly like this: <UserControl Content="{Binding PartialViewModel}" /> There are also two buttons on this Window that fires the Commands: ShowMessagesCommand ShowUsersCommand And when these are fired, the UserControl changes because PartialViewModel is a dependency property. I want to know if this is bad practice? Should I not inject the User Control like this? Is there another "better" alternative that corresponds better with the design pattern? Or is this a nice way of including partial views?

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• What performance overhead do IoC containers involve?

  - by Sosh

  Hi, Loose coupling is wonderful of course, but I have often wondered what overhead wiring up dynamically using an IoC container (for example Castle Windsor) has over a tightly coupled system? I know that a detailed answer would depend on what the IoC was being used for, but I'm really just trying to get a feel for the magnitude of effort involved in the IoC work. Does anyone have any stats or other resources regarding this? Thanks

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

  - by Edward

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

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