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  • Design question for WinForms (C#) app, using Entity Framework

    - by cdotlister
    I am planning on writing a small home budget application for myself, as a learning excercise. I have built my database (SQL Server), and written a small console application to interact with it, and test out scenarios on my database. Once I am happy, my next step would be to start building the application - but I am already wondering what the best/standard design would be. I am palnning on using Entity Framework for handling my database entities... then linq to sql/objects for getting the data, all running under a WinForms (for now) application. My plan (I've never used EF... and most of my development background is Web apps) is to have my database... with Entity Framework in it's own project.. which has the connection to the database. This project would expose methods such as 'GetAccount()', 'GetAccount(int accountId)' etc. I'd then have a service project that references my EF project. And on top of that, my GUI project, which makes the calls to my service project. But I am stuck. Lets say I have a screen that displays a list of Account types (Debit, Credit, Loan...). Once I have selected one, the next drop down shows a list of accounts I have that suite that account type. So, my OnChange event on my DropDown on the account type control will make a call to the serviceLayer project, 'GetAccountTypes()', and I would expect back a List< of Account Types. However, the AccountType object ... what is that? That can't be the AccountType object from my EF project, as my GUI project doesn't have reference to it. Would I have to have some sort of Shared Library, shared between my GUI and my Service project, with a custom built AccountType object? The GUI can then expect back a list of these. So my service layer would have a method: public List<AccountType> GetAccountTypes() That would then make a call to a custom method in my EF project, which would probably be the same as the above method, except, it returns an list of EF.Data.AccountType (The Entity Framework generated Account Type object). The method would then have the linq code to get the data as I want it. Then my service layer will get that object, and transform it unto my custom AccountType object, and return it to the GUI. Does that sound at all like a good plan?

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  • Design Patters in Rails

    - by Winston
    I remember, I have a GoF book back in college about design patterns which helped me a lot with my C and C++ programming, since my jump ship to Rails I was trying to use those design patterns I learned previously, Rails is a relatively new paradigm to me, plurals, verbs, REST, DRY.. Can you give me a recommended book for Rails that I can easily understand what I previously learned back in College. P.S. I suspect Matz knew about the GoF book, and applied it on Ruby... :-)

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  • How to design shape class

    - by Tomek Tarczynski
    I want to design shape class. I need to distinguish several different shapes: -Point -Line -Triangle -Circle -Polygons The main purpose of this class is to calculate distance between two shapes. I've all methods for calculating those distances, but I want to have a single method that can be used, it should looks like this: float Distance(Shape a, Shape b) Simplest way to do it is to put a lot of if statements and then invoke proper method but this is deffinitely not OOP. How to design such class in OOP style?

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  • C# - Name the Design Pattern

    - by nettguy
    Using Fluent Interface design here if i call something like dog.Train("Running").Train("Eating").Do("Running").Do("Eating"); what is the name of this pattern ? is it chain-of-responsibility or there any specific design pattern name associated with it?

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  • C# ProgressBar design pattern

    - by MadSeb
    Hi, I'm working on a database upgrader application. The upgrader updates the schema of a database ( adds new columns, renames columns , adds new tables, new views to an existing database by executing SQL statements ). When a user wants to upgrade from version 1.0 to 2.0 , "Upgrader" objects are taken from an object factory and the "Execute" method of each "Upgrader" is called. The GUI of the application has a progress bar and each time an upgrader object performs a SQL statement the progress bar gets incremented. while (!version.Equal(CurrentVersion)) { IUpgrader myUpgrader = UpgraderFactory.GetUpgrader(version); myUpgrader.Execute(UpgradedFile,progressbar); version.Increment(); } My question is very simple : how should the upgrader object communicate with the progressbar. In the code above, the upgrader object is given direct access to the progressbar but I'm wondering if some better way of doing this or better design pattern exists. Regards, Seb

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  • Java design flaws that are unlikely to change due to backward compatibility

    - by koppernickus
    What are the Java language and standard library design flaws you are aware of? I ask only for flaws that: cannot be changed or are unlikely to change due to backward compatibility, are NOT controversial, i.e. most of programmers would agree that "this is a bug not a feature" (for example checked exceptions seem to be controversial language feature, so I wouldn't classify them as "design flaw").

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  • Simple database design and LINQ

    - by Anders Svensson
    I have very little experience designing databases, and now I want to create a very simple database that does the same thing I have previously had in xml. Here's the xml: <services> <service type="writing"> <small>125</small> <medium>100</medium> <large>60</large> <xlarge>30</xlarge> </service> <service type="analysis"> <small>56</small> <medium>104</medium> <large>200</large> <xlarge>250</xlarge> </service> </services> Now, I wanted to create the same thing in a SQL database, and started doing this ( hope this formats ok, but you'll get the gist, four columns and two rows): > ServiceType Small Medium Large > > Writing 125 100 60 > > Analysis 56 104 200 This didn't work too well, since I then wanted to use LINQ to select, say, the Large value for Writing (60). But I couldn't use LINQ for this (as far as I know) and use a variable for the size (see parameters in the method below). I could only do that if I had a column like "Size" where Small, Medium, and Large would be the values. But that doesn't feel right either, because then I would get several rows with ServiceType = Writing (3 in this case, one for each size), and the same for Analysis. And if I were to add more servicetypes I would have to do the same. Simply repetitive... Is there any smart way to do this using relationships or something? Using the second design above (although not good), I could use the following LINQ to select a value with parameters sent to the method: protected int GetHourRateDB(string serviceType, Size size) { CalculatorLinqDataContext context = new CalculatorLinqDataContext(); var data = (from calculatorData in context.CalculatorDatas where calculatorData.Service == serviceType && calculatorData.Size == size.ToString() select calculatorData).Single(); return data.Hours; } But if there is another better design, could you please also describe how to do the same selection using LINQ with that design? Please keep in mind that I am a rookie at database design, so please be as explicit and pedagogical as possible :-) Thanks! Anders

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  • Is factory method proper design for my problem?

    - by metdos
    Hello Everyone, here is my problem and I'm considering to use factory method in C++, what are your opinions ? There are a Base Class and a lot of Subclasses. I need to transfer objects on network via TCP. I will create objects in first side, and using this object I will create a byte array TCP message, and send it to other side. On the other side I will decompose TCP message, I will create object and I will add this object to a polymorphic queue.

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  • Resources on technical GUI design

    - by Thomas Lötzer
    Hi, I am looking for recommendations on resources (both books and websites) on designing GUI applications. By designing I mean the technical design (when and how to use data binding, when should MVC/MVP be used, what functionality should go into the model, the view, the controller/presenter, how can different parts of the UI best be kept in sync ...), not the screen design of which button goes where or how the interaction with the user should take place. Thanks, Thomas

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  • Could the cause of recent Toyota computing problems be an interface mismatch ?

    - by Spux
    Any ideas if the recent Toyota computing errors had something to do with the fact they where using an object orintated approach then took a data orientated approach thus causing user interface errors ? Studying programming languages with in interface robotic design and wondered if the car computing glitch Toyota has been having could have something to do with using a different programming approach with out reprogramming the whole system from scratch.

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  • view handler design pattern

    - by Mark Roberts
    I'm trying to figure out the origin of the view handler design pattern in software engineering. Many of the design patterns in software engineering were inspired by things which pre-date computers, and I was wondering if anybody had any insights on the origin of this particular pattern.

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  • Looking for design help

    - by jess
    I have this scenario in most of the WindowsForms having grids I have a sequence of code which is similar - AddNewRow(in grid),CreateNewEntity,notifyUser,few other steps Now, I want to use a template kind of pattern.But,my issue is with CreateEntity method since sometimes it is passed a parameter which is different depending on the type of object being created.Should I make createentity accept an "object" type,and cast when the parameter is to be used.What other way can I tackle this design issue? Also,CreateEntity returns the object being created.

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  • Design Patterns : Question about "Types"

    - by contactmatt
    Would someone please explain to me what the below paragraph means? This is a snippet from "Design Patterns: Elements of Reusable OO software" Part of an object's interface may be characterized by one type, and other parts by other types. Two objects of the same type need only share parts of their interfaces. Interfaces can contain other interfaces as subsets. - Design Patterns - Elements of Reusable OO software, pg 13

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  • Free GUI-like web design tool for Java?

    - by Peter C.
    Our company needs to build web solution and we're somewhat short on time. We use Java and do not have a design yet. We're looking for some tools/plugins for: GUI-like web design (drag and drop components) WYSIWYG The tools must be *free We like GWT but any other UI framework is fine. Plugins for NetBeans or Eclipse would be great. Any ideas?

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  • Multiple operations depending on the type of the object passed

    - by mixm
    Assuming I create a method which is passed an object and that method would perform an action depending on the object passed. How should I identify the object? I thought of using the class name to identify the object, but that may be impractical since I could easily change the class name of objects, and generate headaches during future development. Am I right? edit: for example, i have objects ball and bomb. if i have another object called wall, and the wall has the method to resolve collisions with the wall (e.g. the coordinates of the colliding ball and bomb) but have different logic depending on the colliding object (i.e. ball and bomb)

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  • Request for advice about class design, inheritance/aggregation

    - by Lasse V. Karlsen
    I have started writing my own WebDAV server class in .NET, and the first class I'm starting with is a WebDAVListener class, modelled after how the HttpListener class works. Since I don't want to reimplement the core http protocol handling, I will use HttpListener for all its worth, and thus I have a question. What would the suggested way be to handle this: Implement all the methods and properties found inside HttpListener, just changing the class types where it matters (ie. the GetContext + EndGetContext methods would return a different class for WebDAV contexts), and storing and using a HttpListener object internally Construct WebDAVListener by passing it a HttpListener class to use? Create a wrapper for HttpListener with an interface, and constrct WebDAVListener by passing it an object implementing this interface? If going the route of passing a HttpListener (disguised or otherwise) to the WebDAVListener, would you expose the underlying listener object through a property, or would you expect the program that used the class to keep a reference to the underlying HttpListener? Also, in this case, would you expose some of the methods of HttpListener through the WebDAVListener, like Start and Stop, or would you again expect the program that used it to keep the HttpListener reference around for all those things? My initial reaction tells me that I want a combination. For one thing, I would like my WebDAVListener class to look like a complete implementation, hiding the fact that there is a HttpListener object beneath it. On the other hand, I would like to build unit-tests without actually spinning up a networked server, so some kind of mocking ability would be nice to have as well, which suggests I would like the interface-wrapper way. One way I could solve this would be this: public WebDAVListener() : WebDAVListener(new HttpListenerWrapper()) { } public WebDAVListener(IHttpListenerWrapper listener) { } And then I would implement all the methods of HttpListener (at least all those that makes sense) in my own class, by mostly just chaining the call to the underlying HttpListener object. What do you think? Final question: If I go the way of the interface, assuming the interface maps 1-to-1 onto the HttpListener class, and written just to add support for mocking, is such an interface called a wrapper or an adapter?

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