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• "Special case" records for foreign key constraints

  - by keithjgrant

  Let's say I have a mysql table, called foo with a foreign key option_id constrained to the option table. When I create a foo record, the user may or may not have selected an option, and 'no option' is a viable selection. What is the best way to differentiate between 'null' (i.e. the user hasn't made a selection yet) and 'no option' (i.e. the user selected 'no option')? Right now, my plan is to insert a special record into the option table. Let's say that winds up with an id of 227 (this table already has a number of records at this point, so '1' isn't available). I have no need to access this record at a database level, and it would act as nothing more than a placeholder that the foreign key in the foo table can reference. So do I just hard-code '227' in my codebase when I'm creating 'foo' records where the user has selected 'no option'? The hard-coded id seems sloppy, and leaves room for error as the code is maintained down the road, but I'm not really sure of another approach.

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• how to merge ecommerce transaction data between two databases

  - by yamspog

  We currently run an ecommerce solution for a leisure and travel company. Everytime we have a release, we must bring the ecommerce site down as we update database schema and the data access code. We are using a custom built ORM where each data entity is responsible for their own CRUD operations. This is accomplished by dynamically generating the SQL based on attributes in the data entity. For example, the data entity for an address would be... [tableName="address"] public class address : dataEntity { [column="address1"] public string address1; [column="city"] public string city; } So, if we add a new column to the database, we must update the schema of the database and also update the data entity. As you can expect, the business people are not too happy about this outage as it puts a crimp in their cash-flow. The operations people are not happy as they have to deal with a high-pressure time when database and applications are upgraded. The programmers are upset as they are constantly getting in trouble for the legacy system that they inherited. Do any of you smart people out there have some suggestions?

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• overflow-x AND Middle Mouse Button Moving

  - by Rad The Mad

  My Page is 980px in Width, but I have a few design elements (which belong with the background). I positioned them with position: absolute;. This creates a horizontal scrollbar for those who have a =< 1024 resolution. I disabled that scrollbar with overflow-x:hidden on (and for IE7 and etc). However, when I hold my middle mouse button,(i think this applies to laptop touchpads as well) it let's me move around to the right, is it possible to fix this with anything? (javascript, css)? Tested this issues in Chrome, IE, Firefox.

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• Applying the Decorator Pattern to Forms

  - by devoured elysium

  I am trying to apply the Decorator Design Pattern to the following situation: I have 3 different kind of forms: Green, Yellow, Red. Now, each of those forms can have different set of attributes. They can have a minimize box disabled, a maximized box disabled and they can be always on top. I tried to model this the following way: Form <---------------------------------------FormDecorator /\ /\ |---------|-----------| |----------------------|-----------------| GreenForm YellowForm RedForm MinimizeButtonDisabled MaximizedButtonDisabled AlwaysOnTop Here is my GreenForm code: public class GreenForm : Form { public GreenForm() { this.BackColor = Color.GreenYellow; } public override sealed Color BackColor { get { return base.BackColor; } set { base.BackColor = value; } } } FormDecorator: public abstract class FormDecorator : Form { private Form _decoratorForm; protected FormDecorator(Form decoratorForm) { this._decoratorForm = decoratorForm; } } and finally NoMaximizeDecorator: public class NoMaximizeDecorator : FormDecorator { public NoMaximizeDecorator(Form decoratorForm) : base(decoratorForm) { this.MaximizeBox = false; } } So here is the running code: static void Main() { Application.EnableVisualStyles(); Application.SetCompatibleTextRenderingDefault(false); Application.Run(CreateForm()); } static Form CreateForm() { Form form = new GreenForm(); form = new NoMaximizeDecorator(form); form = new NoMinimizeDecorator(form); return form; } The problem is that I get a form that isn't green and that still allows me to maximize it. It is only taking in consideration the NoMinimizeDecorator form. I do comprehend why this happens but I'm having trouble understanding how to make this work with this Pattern. I know probably there are better ways of achieving what I want. I made this example as an attempt to apply the Decorator Pattern to something. Maybe this wasn't the best pattern I could have used(if one, at all) to this kind of scenario. Is there any other pattern more suitable than the Decorator to accomplish this? Am I doing something wrong when trying to implement the Decorator Pattern? Thanks

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• Self-Configuring Classes W/ Command Line Args: Pattern or Anti-Pattern?

  - by dsimcha

  I've got a program where a lot of classes have really complicated configuration requirements. I've adopted the pattern of decentralizing the configuration and allowing each class to take and parse the command line/configuration file arguments in its c'tor and do whatever it needs with them. (These are very coarse-grained classes that are only instantiated a few times, so there is absolutely no performance issue here.) This avoids having to do shotgun surgery to plumb new options I add through all the levels they need to be passed through. It also avoids having to specify each configuration option in multiple places (where it's parsed and where it's used). What are some advantages/disadvantages of this style of programming? It seems to reduce separation of concerns in that every class is now doing configuration stuff, and to make programs less self-documenting because what parameters a class takes becomes less explicit. OTOH, it seems to increase encapsulation in that it makes each class more self-contained because no other part of the program needs to know exactly what configuration parameters a class might need.

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• syntax for binding multiple variables within text

  - by danke

  When binding multiple variables value1 value2 value3 in the same text field, do I do this: text="{some text value1 other text value2 and other text value3}" or text="some text {value1} other text {value2} and other text {value3}" I noticed both work, but which is the right way to do it and will work all the time.

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• Advice on a simple Windows Form

  - by Austin Hyde

  I have a VERY simple windows form that the user uses to manage "Stores". Each store has a name and number, and is kept in a corresponding DB table. The form has a listbox of stores, an add button that creates a new store, a delete button, and an edit button. Beside those I have text boxes for the name and number, and save/cancel buttons. When the user chooses a store from the list box, and clicks 'edit', the textboxes become populated and save/cancel become active. When the user clicks 'add', I create a new Store, add it to the listbox, activate the textboxes and save/cancel buttons, then commit it to the database when the user clicks 'save', or discards it when the user clicks 'cancel'. Right now, my event system looks like this (in psuedo-code. It's just shorter that way.) add->click: store = new Store() listbox.add(store) populateAndEdit(store) delete->click: store = listbox.selectedItem db.deleteOnSubmit(store) listbox.remove(store) db.submit() edit->click: populateAndEdit(listbox.selectedItem) save->click: parseAndSave(listbox.selectedItem) db.submit() disableTexts() cancel->click: disableTexts() The problem is in how I determine if we are inserting a new Store, or updating an existing one. The obvious solution to me would be to make it a "modal" process - that is, when I click edit, I go into edit mode, and the save button does things differently than if I were in add mode. I know I could make this more MVC-like, but I don't really think this simple form merits the added complexity. I'm not very experienced with winforms, so I'm not sure if I even have the right idea for how to tackle this. Is there a better way to do this? I would like to keep it simple, but usable.

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• What is a good practice to access class attributes in class methods?

  - by Clem

  I always wonder about the best way to access a class attribute from a class method in Java. Could you quickly convince me about which one of the 3 solutions below (or a totally different one :P) is a good practice? public class Test { String a; public String getA(){ return this.a; } public setA(String a){ this.a = a; } // Using Getter public void display(){ // Solution 1 System.out.println(this.a); // Solution 2 System.out.println(getA()); // Solution 3 System.out.println(this.getA()); } // Using Setter public void myMethod(String b, String c){ // Solution 1 this.a = b + c; // Solution 2 setA(b + c); // Solution 3 this.setA(b + c); } }

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• SQL Server 2008 Optimization

  - by hgulyan

  I've learned today, if you append to your query OPTION (MAXDOP 0) your query will run on multiple processors and if it's huge query, query will perform faster. I know general guidelines on query optimizations (using indexes, selecting only needed fields etc.), my question is about SQL Server optimization. Maybe changing some options in configurations or anything else. What guidelines are there for SQL Server Optimization? Thank you.

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• Best practice to include log4Net external config file in ASP.NET

  - by Martin Buberl

  I have seen at least two ways to include an external log4net config file in an ASP.NET web application: Having the following attribute in your AssemblyInfo.cs file: [assembly: log4net.Config.XmlConfigurator(ConfigFile = "Log.config", Watch = true)] Calling the XmlConfigurator in the Global.asax.cs: protected void Application_Start() { XmlConfigurator.Configure(new FileInfo("Log.config")); } What would be the best practice to do it?

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• Should I use IDisposable for purely managed resources?

  - by John Gietzen

  Here is the scenario: I have an object called a Transaction that needs to make sure that only one entity has permission to edit it at any given time. In order to facilitate a long-lived lock, I have the class generating a token object that can be used to make the edits. You would use it like this: var transaction = new Transaction(); using (var tlock = transaction.Lock()) { transaction.Update(data, tlock); } Now, I want the TransactionLock class to implement IDisposable so that its usage can be clear. But, I don't have any unmanaged resources to dispose. however, the TransctionLock object itself is a sort of "unmanaged resource" in the sense that the CLR doesn't know how to properly finalize it. All of this would be fine and dandy, I would just use IDisposable and be done with it. However, my issue comes when I try to do this in the finalizer: ~TransactionLock() { this.Dispose(false); } I want the finalizer to release the transaction from the lock, if possible. How, in the finalizer, do I detect if the parent transaction (this.transaction) has already been finalized? Is there a better pattern I should be using? The Transaction class looks something like this: public sealed class Transaction { private readonly object lockMutex = new object(); private TransactionLock currentLock; public TransactionLock Lock() { lock (this.lockMutex) { if (this.currentLock != null) throw new InvalidOperationException(/* ... */); this.currentLock = new TransactionLock(this); return this.currentLock; } } public void Update(object data, TransactionLock tlock) { lock (this.lockMutex) { this.ValidateLock(tlock); // ... } } internal void ValidateLock(TransactionLock tlock) { if (this.currentLock == null) throw new InvalidOperationException(/* ... */); if (this.currentLock != tlock) throw new InvalidOperationException(/* ... */); } internal void Unlock(TransactionLock tlock) { lock (this.lockMutex) { this.ValidateLock(tlock); this.currentLock = null; } } }

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• Efficiently Serving Dynamic Content in Google App Engine

  - by awegawef

  My app on google app engine returns content items (just text) and comments on them. It works like this (pseudo-ish code): query: get keys of latest content #query to datastore for each item in content if item_dict in memcache: use item_dict else: build_item_dict(item) #by fetching from datastore store item_dict in memcache send all item_dicts to template Sorry if the code isn't understandable. I get all of the content dictionaries and send them to the template, which uses them to create the webpage. My problem is that if the memcache has expired, for each item I want to display, I have to (1) lookup item in memcache, (2) since no memcache exists I must fetch item from the datastore, and (3) store the item in memcache. These calls build up quickly. I don't set an expire time for the entries to the memcache, so this really only happens once in the morning, but the webpage takes long enough to load (~1 sec) that the browser reports it as not existing. Regularly, my webpages take about 50ms to load. This approach works decently for frequent visits, but it has its flaws as shown above. How can I remedy this? The entries are dynamic enough that I don't think it would be in my best interest to cache my initial request. Thanks in advance

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• What are the reasons for casting a void pointer?

  - by Maulrus

  I'm learning C++ from scratch, and as such I don't have an expert understanding of C. In C++, you can't cast a void pointer to whatever, and I understand the reasons behind that. However, I know that in C, you can. What are the possible reasons for this? It just seems like it's be a huge hole in type safety, which (to me) seems like a bad thing.

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• Handling input from a keyboard wedge

  - by JDibble

  Following on from the question asked by Mykroft Best way to handle input from a keyboard “wedge” http://stackoverflow.com/questions/42437/best-way-to-handle-input-from-a-keyboard-wedge. I need to write a class that intercepts key strokes, if the input is determined to be from the keyboard wedge (as described in the above post) the data will be directed to POS classes to handle, otherwise they keystrokes must be passed on to be handled in windows in the normal manner. This raises two questions How can I intercept key strokes when not in a WinForm. How can I pass on the keypresses to windows. Thanks JDibble

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• Some good websites to learn about JavaScript and programming architecture?

  - by Jack Roscoe

  I'm not sure if 'architecture' is the correct term, but I've been looking for some articles online which talk about programming design and more about how best to use languages such as JavaScript in a code design sense rather than the actual syntax itself. I have found many websites but a lot seem to be very out dated, and I'm not sure what developments have taken place with JavaScript over the years so do not know how old is too old. If anybody could suggest some great websites, or maybe specific articles you think would be useful, that would be highly appreciated. I am a beginner programmer currently using JavaScript with XML and of course HTML & CSS, and I'm currently trying to get further into and learn more about web development.

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• Does C# allow method overloading, PHP style (__call)?

  - by mr.b

  In PHP, there is a special method named __call($calledMethodName, $arguments), which allows class to catch calls to non-existing methods, and do something about it. Since most of classic languages are strongly typed, compiler won't allow calling a method that does not exist, I'm clear with that part. What I want to accomplish (and I figured this is how I would do it in PHP, but C# is something else) is to proxy calls to a class methods and log each of these calls. Right now, I have code similar to this: class ProxyClass { static logger; public AnotherClass inner { get; private set; } public ProxyClass() { inner = new AnotherClass(); } } class AnotherClass { public void A() {} public void B() {} public void C() {} // ... } // meanwhile, in happyCodeLandia... ProxyClass pc = new ProxyClass(); pc.inner.A(); pc.inner.B(); // ... So, how can I proxy calls to an object instance in extensible way? Extensible, meaning that I don't have to modify ProxyClass whenever AnotherClass changes. In my case, AnotherClass can have any number of methods, so it wouldn't be appropriate to overload or wrap all methods to add logging. I am aware that this might not be the best approach for this kind of problem, so if anyone has idea what approach to use, shoot. Thanks!

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• Pattern for null settings

  - by user21243

  Hi, I would like to hear your thoughts and ideas about this one. in my application i have controls that are binded to objects properties. but.. the controls always looks like that: a check box, label that explain the settings and then the edited control (for ex: text box) when unchecking the checkbox i disable the text box (using binding) when the checkbox is unchecked i want the property to contain null, and when it is checked i would like the property to contain the text box's text. Of course text box can be NumericUpDown, ComboBox, DatePicker etc.. Do you have any smart way of doing it using binding or do i have to do everything on code; I really would like to a build a control that supports that and re-use it all over Ideas? Thanks,

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• ASP.Net MVC: User messages stack implementations

  - by SDReyes

  How would you implement a user message stack in ASP.Net MVC (you set messages for the user in any place inside your app. and they are shown as hints of your app to the user anywhere inside the app) Example:

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• Standard Workflow when working with JPA

  - by jschoen

  I am currently trying to wrap my head around working with JPA. I can't help but feel like I am missing something or doing it the wrong way. It just seems forced so far. What I think I know so far is that their are couple of ways to work with JPA and tools to support this. You can do everything in Java using annotations, and let JPA (whatever implementation you decide to use) create your schema and update it when changes are made. You can use a tool to reverse engineer you database and generate the entity classes for you. When the schema is updated you have to regenerate these classes, or manually update them. There seems to be drawbacks to both, and benefits to both (as with all things). My question is in an ideal situation what is the standard workflow with JPA? Most schemas will require updates during the maintenance phase and especially during the development phase, so how is this handled?

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• What is the best method to convert to an Integer in JavaScript?

  - by Mathew Byrne

  There are several different methods for converting floating point numbers to Integers in JavaScript. My question is what method gives the best performance, is most compatible, or is considered the best practice? Here are a few methods that I know of: var a = 2.5; window.parseInt(a); // 2 Math.floor(a); // 2 a | 0; // 2 I'm sure there are others out there. Suggestions?

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• Multiple Actions (Forms) on one Page - How not to lose master data, after editing detail data?

  - by nWorx

  Hello all, I've got a form where users can edit members of a group. So they have the possibilty to add members or remove existing members. So the Url goes like ".../Group/Edit/4" Where 4 is the id of the group. the view looks like this <% using (Html.BeginForm("AddUser", "Group")) %> <%{%> <label for="newUser">User</label> <%=Html.TextBox("username")%> <input type="submit" value="Add"/> </div> <%}%> <% using (Html.BeginForm("RemoveUser", "Group")) %> <%{%> <div class="inputItem"> <label for="groupMember">Bestehende Mitglieder</label> <%= Html.ListBox("groupMember", from g in Model.GetMembers() select new SelectListItem(){Text = g}) %> <input type="submit" value="Remove" /> </div> <%}%> The problem is that after adding or removing one user i lose the id of the group. What is the best solution for solving this kind of problem? Should I use hidden fields to save the group id? Thanks in advance.

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• C++ visitor pattern handling templated string types?

  - by Steve the Plant

  I'm trying to use the visitor pattern to serialize the contents of objects. However one snag I'm hitting is when I'm visiting strings. My strings are of a templated type, similar to STL's basic_string. So something like: basic_string<char_type, memory_allocator, other_possible_stuff> \\ many variations possible! Since I can have very many different templated string types, I can't go and add them to my visitor interface. It would be ridiculous. But I can't add templates to my VisitString method because C++ prevents using templates parameters in virtual methods. So what are my options to work around this?

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• What is a the 'best practice' for location of windows service logfiles?

  - by rupello

  A lot of windows services write daily log files to their application installation directory under "program files". Windows system apps (eg IIS) use %SystemRoot%\System32\LogFiles. Is something I should do for my service?

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• Why should GoTos be bad?

  - by lisn

  I'm using gotos and a lot of them. C++, PHP or COBOL - I use them on nearly all occasions where everybody else would use functions or even classes. Yet my code is Clear Maintainable Bug-free Fast So why does everybody I meet tell me about how bad gotos are? Are there any facts that show that they are "bad"?

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• Designing different Factory classes (and what to use as argument to the factories!)

  - by devoured elysium

  Let's say we have the following piece of code: public class Event { } public class SportEvent1 : Event { } public class SportEvent2 : Event { } public class MedicalEvent1 : Event { } public class MedicalEvent2 : Event { } public interface IEventFactory { bool AcceptsInputString(string inputString); Event CreateEvent(string inputString); } public class EventFactory { private List<IEventFactory> factories = new List<IEventFactory>(); public void AddFactory(IEventFactory factory) { factories.Add(factory); } //I don't see a point in defining a RemoveFactory() so I won't. public Event CreateEvent(string inputString) { try { //iterate through all factories. If one and only one of them accepts //the string, generate the event. Otherwise, throw an exception. return factories.Single(factory => factory.AcceptsInputString(inputString)).CreateEvent(inputString); } catch (InvalidOperationException e) { throw new InvalidOperationException("No valid factory found to generate this kind of Event!", e); } } } public class SportEvent1Factory : IEventFactory { public bool AcceptsInputString(string inputString) { return inputString.StartsWith("SportEvent1"); } public Event CreateEvent(string inputString) { return new SportEvent1(); } } public class MedicalEvent1Factory : IEventFactory { public bool AcceptsInputString(string inputString) { return inputString.StartsWith("MedicalEvent1"); } public Event CreateEvent(string inputString) { return new MedicalEvent1(); } } And here is the code that runs it: static void Main(string[] args) { EventFactory medicalEventFactory = new EventFactory(); medicalEventFactory.AddFactory(new MedicalEvent1Factory()); medicalEventFactory.AddFactory(new MedicalEvent2Factory()); EventFactory sportsEventFactory = new EventFactory(); sportsEventFactory.AddFactory(new SportEvent1Factory()); sportsEventFactory.AddFactory(new SportEvent2Factory()); } I have a couple of questions: Instead of having to add factories here in the main method of my application, should I try to redesign my EventFactory class so it is an abstract factory? It'd be better if I had a way of not having to manually add EventFactories every time I want to use them. So I could just instantiate MedicalFactory and SportsFactory. Should I make a Factory of factories? Maybe that'd be over-engineering? As you have probably noticed, I am using a inputString string as argument to feed the factories. I have an application that lets the user create his own events but also to load/save them from text files. Later, I might want to add other kinds of files, XML, sql connections, whatever. The only way I can think of that would allow me to make this work is having an internal format (I choose a string, as it's easy to understand). How would you make this? I assume this is a recurrent situation, probably most of you know of any other more intelligent approach to this. I am then only looping in the EventFactory for all the factories in its list to check if any of them accepts the input string. If one does, then it asks it to generate the Event. If you find there is something wrong or awkward with the method I'm using to make this happen, I'd be happy to hear about different implementations. Thanks! PS: Although I don't show it in here, all the different kind of events have different properties, so I have to generate them with different arguments (SportEvent1 might have SportName and Duration properties, that have to be put in the inputString as argument).

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