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• Integrating with a payment provider; Proper and robust OOP approach

  - by ExternalUse

  History We are currently using a so called redirect model for our online payments (where you send the payer to a payment gateway, where he inputs his payment details - the gateway will then return him to a success/failure callback page). That's easy and straight-forward, but unfortunately quite inconvenient and at times confusing for our customers (leaving the site, changing their credit card details with an additional login on another site etc). Intention & Problem description We are now intending to switch to an integrated approach using an exchange of XML requests and responses. My problem is on how to cater with all (or rather most) of the things that may happen during processing - bearing in mind that normally simplicity is robust whereas complexity is fragile. Examples User abort: The user inputs Credit Card details and hits submit. An XML message to the provider's gateway is sent and waiting for response. The user hits "stop" in his browser or closes the window. ignore_user_abort() in PHP may be an option - but is that reliable? might it be better to redirect the user to a "please wait"-page, that in turn opens an AJAX or other request to the actual processor that does not rely on the connection? Database goes away sounds over-complicated, but with e.g. a webserver in the States and a DB in the UK, it has happened and will happen again: User clicks together his order, payment request has been sent to the provider but the response cannot be stored in the database. What approach could I use, using PHP to sort of start an SQL like "Transaction" that only at the very end gets committed or rolled back, depending on the individual steps? Should then neither commit or roll back have happened, I could sort of "lock" the user to prevent him from paying again or to improperly account for payments - but how? And what else do I need to consider technically? None of the integration examples of e.g. Worldpay, Realex or SagePay offer any insight, and neither Google or my search terms were good enough to find somebody else's thoughts on this. Thank you very much for any insight on how you would approach this!

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• Validation and authorization in layered architecture

  - by SonOfPirate

  I know you are thinking (or maybe yelling), "not another question asking where validation belongs in a layered architecture?!?" Well, yes, but hopefully this will be a little bit of a different take on the subject. I am a firm believer that validation takes many forms, is context-based and varies at each level of the architecture. That is the basis for the post - helping to identify what type of validation should be performed in each layer. In addition, a question that often comes up is where authorization checks belong. The example scenario comes from an application for a catering business. Periodically during the day, a driver may turn in to the office any excess cash they've accumulated while taking the truck from site to site. The application allows a user to record the 'cash drop' by collecting the driver's ID, and the amount. Here's some skeleton code to illustrate the layers involved: public class CashDropApi // This is in the Service Facade Layer { [WebInvoke(Method = "POST")] public void AddCashDrop(NewCashDropContract contract) { // 1 Service.AddCashDrop(contract.Amount, contract.DriverId); } } public class CashDropService // This is the Application Service in the Domain Layer { public void AddCashDrop(Decimal amount, Int32 driverId) { // 2 CommandBus.Send(new AddCashDropCommand(amount, driverId)); } } internal class AddCashDropCommand // This is a command object in Domain Layer { public AddCashDropCommand(Decimal amount, Int32 driverId) { // 3 Amount = amount; DriverId = driverId; } public Decimal Amount { get; private set; } public Int32 DriverId { get; private set; } } internal class AddCashDropCommandHandler : IHandle<AddCashDropCommand> { internal ICashDropFactory Factory { get; set; } // Set by IoC container internal ICashDropRepository CashDrops { get; set; } // Set by IoC container internal IEmployeeRepository Employees { get; set; } // Set by IoC container public void Handle(AddCashDropCommand command) { // 4 var driver = Employees.GetById(command.DriverId); // 5 var authorizedBy = CurrentUser as Employee; // 6 var cashDrop = Factory.CreateCashDrop(command.Amount, driver, authorizedBy); // 7 CashDrops.Add(cashDrop); } } public class CashDropFactory { public CashDrop CreateCashDrop(Decimal amount, Employee driver, Employee authorizedBy) { // 8 return new CashDrop(amount, driver, authorizedBy, DateTime.Now); } } public class CashDrop // The domain object (entity) { public CashDrop(Decimal amount, Employee driver, Employee authorizedBy, DateTime at) { // 9 ... } } public class CashDropRepository // The implementation is in the Data Access Layer { public void Add(CashDrop item) { // 10 ... } } I've indicated 10 locations where I've seen validation checks placed in code. My question is what checks you would, if any, be performing at each given the following business rules (along with standard checks for length, range, format, type, etc): The amount of the cash drop must be greater than zero. The cash drop must have a valid Driver. The current user must be authorized to add cash drops (current user is not the driver). Please share your thoughts, how you have or would approach this scenario and the reasons for your choices.

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• Proper library for enums

  - by Bobson

  I'm trying to refactor some code such that the display is separate from the implementation, and I'm not sure where to put the existing enums. My project is currently structured as follows: Utilities RemoteData (Depends on: Utilities) LocalData (Depends on: RemoteData, Utilities) RemoteWeb (Depends on: RemoteData, Utilities) LocalWeb (Depends on: RemoteData, LocalData, Utilities) I'm now trying to add "ViewLibrary (Depends on: Utilities)" to this list, and then adding it as a new dependency to both RemoteWeb and LocalWeb. It will contain a set of interfaces which the other two projects will implement, use to populate the view, and then consume the result. There's an enum which is currently used in all the projects except Utilities. It thus lives in the RemoteData project, because everything else depends on it. But this new ViewLibrary won't depend on either data project. So how will it know about this enum? Some options I see: Create a new project just for shared enum values. Add it to Utilities, even though it is related to data. Define it a second time in ViewLibrary, and require both RemoteWeb and LocalWeb to convert the one type into the other when they access the shared views. Add a dependency on RemoteData to the ViewLibrary, even though it's supposed to be independent of data-source. Are there any better options? Is this structure flawed to begin with?

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• Should i continue my self-taught coding practice or learn how to do coding professionally?

  - by G1i1ch

  Lately I've been getting professional work, hanging out with other programmers, and making friends in the industry. The only thing is I'm 100% self-taught. It's caused my style to extremely deviate from the style of those that are properly trained. It's the techniques and organization of my code that's different. It's a mixture of several things I do. I tend to blend several programming paradigms together. Like Functional and OO. I lean to the Functional side more than OO, but I see the use of OO when something would make more sense as an abstract entity. Like a game object. Next I also go the simple route when doing something. When in contrast, it seems like sometimes the code I see from professional programmers is complicated for the sake of it! I use lots of closures. And lastly, I'm not the best commenter. I find it easier just to read through my code than reading the comment. And most cases I just end up reading the code even if there are comments. Plus I've been told that, because of how simply I write my code, it's very easy to read it. I hear professionally trained programmers go on and on about things like unit tests. Something I've never used before so I haven't even the faintest idea of what they are or how they work. Lots and lots of underscores "_", which aren't really my taste. Most of the techniques I use are straight from me, or a few books I've read. Don't know anything about MVC, I've heard a lot about it though with things like backbone.js. I think it's a way to organize an application. It just confuses me though because by now I've made my own organizational structures. It's a bit of a pain. I can't use template applications at all when learning something new like with Ubuntu's Quickly. I have trouble understanding code that I can tell is from someone trained. Complete OO programming really leaves a bad taste in my mouth, yet that seems to be what EVERYONE else is strictly using. It's left me not that confident in the look of my code, or wondering whether I'll cause sparks when joining a company or maybe contributing to open source projects. In fact I'm rather scared of the fact that people will eventually be checking out my code. Is this just something normal any programmer goes through or should I really look to change up my techniques?

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• Storing revisions of a document

  - by dev.e.loper

  This is a follow up question to my original question. I'm thinking of going with generating diffs and storing those diffs in the database 'History' table. I'm using diff-match-patch library to generate what is called a 'patch'. On every save, I compare previous and new version and generate this patch. The patch could be used to generate a document at specific point in time. My dilemma is how to store this data. Should I: a Insert a new database record for every patch? b. Store these patches in javascript array and store that array in history table. So there is only one db History record for document with an array of all the patches. Concerns with: a. Too many db records generated. Will be slow and CPU intensive to query. b. Only one record. If record is somehow corrupted/deleted. Entire revision history is gone. I'm looking for suggestions, concerns with either approach.

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• Too complex/too many objects?

  - by Mike Fairhurst

  I know that this will be a difficult question to answer without context, but hopefully there are at least some good guidelines to share on this. The questions are at the bottom if you want to skip the details. Most are about OOP in general. Begin context. I am a jr dev on a PHP application, and in general the devs I work with consider themselves to use many more OO concepts than most PHP devs. Still, in my research on clean code I have read about so many ways of using OO features to make code flexible, powerful, expressive, testable, etc. that is just plain not in use here. The current strongly OO API that I've proposed is being called too complex, even though it is trivial to implement. The problem I'm solving is that our permission checks are done via a message object (my API, they wanted to use arrays of constants) and the message object does not hold the validation object accountable for checking all provided data. Metaphorically, if your perm containing 'allowable' and 'rare but disallowed' is sent into a validator, the validator may not know to look for 'rare but disallowed', but approve 'allowable', which will actually approve the whole perm check. We have like 11 validators, too many to easily track at such minute detail. So I proposed an AtomicPermission class. To fix the previous example, the perm would instead contain two atomic permissions, one wrapping 'allowable' and the other wrapping 'rare but disallowed'. Where previously the validator would say 'the check is OK because it contains allowable,' now it would instead say '"allowable" is ok', at which point the check ends...and the check fails, because 'rare but disallowed' was not specifically okay-ed. The implementation is just 4 trivial objects, and rewriting a 10 line function into a 15 line function. abstract class PermissionAtom { public function allow(); // maybe deny() as well public function wasAllowed(); } class PermissionField extends PermissionAtom { public function getName(); public function getValue(); } class PermissionIdentifier extends PermissionAtom { public function getIdentifier(); } class PermissionAction extends PermissionAtom { public function getType(); } They say that this is 'not going to get us anything important' and it is 'too complex' and 'will be difficult for new developers to pick up.' I respectfully disagree, and there I end my context to begin the broader questions. So the question is about my OOP, are there any guidelines I should know: is this too complicated/too much OOP? Not that I expect to get more than 'it depends, I'd have to see if...' when is OO abstraction too much? when is OO abstraction too little? how can I determine when I am overthinking a problem vs fixing one? how can I determine when I am adding bad code to a bad project? how can I pitch these APIs? I feel the other devs would just rather say 'its too complicated' than ask 'can you explain it?' whenever I suggest a new class.

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• Logic or Algorithm to solve this problem [closed]

  - by jade

  I have two lists. List1 {a,b,c,d,e} and List2 {f,g,h,i,j} The relation between the two list is as follows a->g,a->h,h->c,h->d,d->i,d->j Now I have these two lists displayed. Based on the relation above on selecting element a from List1, List2 shows g,h. On selecting h from List2, in List1 c,d are shown in List1. On selecting d from List1 it shows i,j in List2. How to trace back to initial state by deselecting the elements in reverse order in which they have been selected?

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• 3D mobile game development [on hold]

  - by SCM

  I am not a developer or programmer and, I am planning an educative project that will involve having students to develop a cross-platform, 3D mobile game, similar to the SimCity concept. I need to write a project requirement and I'd like to pick someone's brain to understand what's involved in developing such a project: -Is it realistic to have one or two students to do it? and along their other modules at uni? - How much time can it take to develop from scratch? - what are the different skills required? Thank you All SCM

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• Combinatorial explosion of interfaces: How many is too many?

  - by mga

  I'm a relative newcomer to OOP, and I'm having a bit of trouble creating good designs when it comes to interfaces. Consider a class A with N public methods. There are a number of other classes, B, C, ..., each of which interacts with A in a different way, that is, accesses some subset (<= N) of A's methods. The maximum degree of encapsulation is achieved by implementing an interface of A for each other class, i.e. AInterfaceForB, AInterfaceForC, etc. However, if B, C, ... etc. also interact with A and with each other, then there will be a combinatorial explosion of interfaces (a maximum of n(n-1), to be precise), and the benefit of encapsulation becomes outweighed by a code-bloat. What is the best practice in this scenario? Is the whole idea of restricting access to a class's public functions in different ways for other different classes just silly altogether? One could imagine a language that explicitly allows for this sort of encapsulation (e.g. instead of declaring a function public, one could specify exactly which classes it is visible to); Since this is not a feature of C++, maybe it's misguided to try to do it through the back door with interaces?

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• What are the advantages of storing xml in a relational database?

  - by Chris

  I was poking around the AdventureWorks database today and I noticed that a number of tables (HumanResources.JobCandidate and Sales.Individual for example) have a column which is storing xml data. What I would to know is, what is the advantage of storing basically a database table row's worth of data in another table's column? Doesn't this make it difficult to query off of this information? Or is the assumption that the data won't need to be queried and just needs to be stored?

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• What kind of graphics would you like better? [ pictures ] [closed]

  - by Roger Travis

  I am looking forward to make an android game, something angrybirds style. I've already made my own engine and now have to decide what kind of graphics should I make. It could be either realistic, like that or a doodle-style like this Right now the first one looks more appealing to me... on the other hand, doodle-graphics are very easy to draw and their transparency doesn't seem to slow down the engine much. What do you think?

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• Question about creating a sprite based 2-D Side Scroller with scaling/zooming

  - by Arthur

  I'm just wondering if anyone can offer any advice on how best to go about creating a 2-D game with zooming/scaling features akin to the early Samurai Showdown games. In this case it would be a side scroller a la Metal Slug, the zooming would come in as more enemy sprites entered the screen, or when facing a large sized boss. A feature that would be both cosmetic as well as functional to the game. I've done some reading and noticed a few suggestions that included drawing different sized sprites, a standard size and zoomed out size. Any thoughts? Thanks for your time.

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• Image slider not working when website is hosted on remote server [on hold]

  - by Tushar Khatiwada

  I'm having a different problem. I made a html website and it contains Nivo Slider in the index page. The site is working perfectly when viewed locally. I uploaded the site to remote server but the slider is not being displayed and the photo from the gallery is not working as expected ( popups on the local pc). The url of the site is: http://d138444.u24.elitehostingwizard.com/ The screenshot from the local pc: http://postimg.org/image/lxiqzx7br/ Thanks

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• Summary of usage policies for website integration of various social media networks?

  - by Dallas

  To cut to the chase... I look at Twitter's usage policy and see limitations on what can and can't be done with their logo. I also see examples of websites that use icons that have been integrated with the look and feel of their own site. Given Twitter's policy, for example, it would appear that legal conversations/agreements would need to take place to do this, especially on a commercial site. I believe it is perfectly acceptable to have a plain text button that simply has the word "Tweet" on it, that has the same functionality. My question is if anyone can provide online (or other) references that attempt to summarize what can and can't be done when integrating various social networks into your own work? The answer I will mark as the correct one will be the one which provides the best resource(s) giving the best summaries of what can and can't be done with specific logos/icons, with a secondary factor being that a variety of social networking sites are addressed in your answer. Before people point to specific questions, I am looking for a well-rounded approach that considers a breadth of networks and considerations. Background: I would like to incorporate social media icons and functionality, but would like to consider what type of modifications can be done without needing to involve lawyers. For example, can I bring in a standard Facebook logo, but incorporate my site color into the logo? Would the answer differ if I maintained their color, but add in a few pixels of another color to transition? I am not saying I want to do this, but rather using it as an example.

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• Designing a user-defined list to be stored in a relational database - Should I include user index?

  - by Zaemz

  By index, I mean, as the user creates the list, each item receives an integer index for its place in that particular list. Since there will be a table of ListItems, I'd prefer to avoid using the name "Index" for the field. Then I was thinking - should I even include the list index in the database? I figured I would because the list would be created in the same fashion every time, then. Or I could order the list for the user based on its actual primary key, since the list items are created in succession anyway... What should I do?

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• How to run around another football player

  - by Lumis

  I have finished a simple 2D one-on-one indoor football Android game. The thing that it seemed so simple to me, a human being, turned out to be difficult for a computer: how to go around the opponent … At the moment the game logic of the computer player is that if it hits into the human player will step back few points on the pixel greed and then try again to go towards the ball. The problem is if the human player is in-between then the computer player will oscillate in one place, which does not look very nice and the human opponent can use this weakness to control the game. You can see this in the photo – at the moment the computer will go along the red line indefinitely. I tried few ideas but it proved not easy to do it when both the human player and the ball are constantly moving so at each step computer would change directions and “oscillate” again. Once when the computer player reaches the ball it will kick it with certain amount of random strength and direction towards the human’s goal. The question here is how to formulate the logic of going around the ever moving human opponent and how to translate it into the co-ordinate system and frame by frame animation… any suggestions welcome.

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• How can I designed multi-threaded application for larger user base

  - by rokonoid

  Here's my scenario, I need to develop a scalable application. My user base may be over 100K, every user has 10 or more small tasks. Tasks check every minute with a third party application through web services, retrieving data which is written in the database, then the data is forwarded to it's original destination. So here's the processing of a small task: while(true){ Boolean isNewInformationAvailable = checkWhetherInformationIsAvailableOrNot(); If(isNewInformationAvailable ==true){ fetchTheData(); writeToDatabase(); findTheDestination(); deliverTheData(); isAvailable =false; } } Here is the question: as the application is large, how should I approach designing this. I'm going to use Java to write it. Should I use concurrency, and how would you manage the concurrency?

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• Maya and Game Engines (i.e. Environment Testing)

  - by DiscreteGenius

  What does it mean if I'm designing an environment and I want to test it in the game engine, to see what its like to "run" [or fly] around my environment? I heard an instructor say that exact thing in a Maya training video and I'd like to know more about "How Game Engines and Maya are related to each other." He stated this would be done to see how things look in "size" (e.g. I assume he meant: 'How big is the cathedral, bridge, wall, building, etc.'). I've tried to research such information but it's too complicated, and detailed. I just want a simplistic response to my query. Thanks to everyone willing to help and not criticize my question.

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• Footer not showing in website depending on which item is loaded [on hold]

  - by samyb8

  I designed a website which is having an issue, but I checked the html tagging very well and cannot fix it. If you go to this item: http://www.tahara.es/store/headbands/11/Ivory-Turquoise-headband You will see the FOOTER display normally. However if you go to this other item: http://www.tahara.es/store/headscarves/15/Grey-and-ivory-with-stoned-flower-Headscarf The footer does not show. Any clue of what I am missing or adding? The footer DIV is like this: <div id="footer">

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• Is there any CSS selector to reach an element outside of the current container?

  - by acidrums4

  (And excuse me for my bad english, for starters...) Sorry if this is a noob question, but I really don't know if the following is possible. I'm doing a html5 portfolio. I'm following a tuto from codrops to visually filter works with only css3 (http://tympanus.net/codrops/2012/01/09/filter-functionality-with-css3/). There, user can select which category want to see with some <input type="radio">'s. But those selectors are under the same container (a <section>) and give visibility for the elements via CSS using a general sibling combinator (~). So in that example, the CSS code goes like this: .ff-container input.ff-selector-type-all:checked ~ label.ff-label-type-all, .ff-container input.ff-selector-type-1:checked ~ label.ff-label-type-1, .ff-container input.ff-selector-type-2:checked ~ label.ff-label-type-2, .ff-container input.ff-selector-type-3:checked ~ label.ff-label-type-3{ background: linear-gradient(top, #646d93 0%,#7c87ad 100%); color: #424d71; text-shadow: 0px 1px 1px rgba(255,255,255,0.3); box-shadow: 0px 0px 0px 1px #40496e, 0 1px 2px rgba(0,0,0,0.1) inset; } The thing is I want to put those <input type="radio">'s on the <head> section of my portfolio, but obviously the ~ selector won't work there. So my question is that is there any selector, hack or something that can do that? Something like .ff-container input.ff-selector-type-all:checked $ header > label.ff-label-type-all { awesomeness:100%; } I really don't want to use Javascript/Jquery for that... Thank you so much in advance!

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• Is there an industry standard for systems registered user permissions in terms of database model?

  - by EASI

  I developed many applications with registered user access for my enterprise clients. In many years I have changed my way of doing it, specially because I used many programming languages and database types along time. Some of them not very simple as view, create and/or edit permissions for each module in the application, or light as access or can't access certain module. But now that I am developing a very extensive application with many modules and many kinds of users to access them, I was wondering if there is an standard model for doing it, because I already see that's the simple or the light way won't be enough.

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• Should I make up my own HTTP status codes? (a la Twitter 420: Enhance Your Calm)

  - by Max Bucknell

  I'm currently implementing an HTTP API, my first ever. I've been spending a lot of time looking at the Wikipedia page for HTTP status codes, because I'm determined to implement the right codes for the right situations. Listed on that page is a code with number 420, which is a custom code that Twitter used to use for rate limiting. There is already a code for rate limiting, though. It's 429. This led me to wonder why they would set a custom one, when there is already a use case. Is that just being cute? And if so, then which circumstances would make it acceptable to return a different status code, and what, if any problems may clients have with it? I read somewhere that Mozilla doesn't implement the joke 418: I’m a teapot response, which makes me think that clients choose which status codes they implement. If that's true, then I can imagine Twitter's funny little enhance your calm code being problematic. Unless I'm mistaken, and we can appropriate any code number to mean whatever we like, and that only convention dictates that 404 means not found, and 429 means take it easy.

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• Set modified date = created date or null on record creation?

  - by User

  I've been following the convention of adding created and modified columns to most of my database tables. I also have been leaving the modified column as null on record creation and only setting a value on actual modification. The other alternative is to set the modified date to be equal to created date on record creation. I've been doing it the former way but I recent ran into one con which is seriously making me think of switching. I needed to set a database cache dependency to find out if any existing data has been changed or new data added. Instead of being able to do the following: SELECT MAX(modified) FROM customer I have to do this: SELECT GREATEST(MAX(created), MAX(modified)) FROM customer The negative being that it's a more complicated query and slower. Another thing is in file systems I believe they usually use the second convention of setting modified date = created date on creation. What are the pros and cons of the different methods? That is, what are the issues to consider?

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• What is a normalized Vector?

  - by draiden

  Can someone explain the following code? I need to learn what each part means so I can turn it into enemy movement in a space shoot-em-up Vec2d playerPos; Vec2d direction; // always normalized float velocity; I get the above is naming two 2d Vector objects, and creating a variable called velocity. I'm not sure what the normalized comment is about, though. update() { direction = normalize(playerPos - enemyPos); playerPos = playerPos + direction * velocity; }

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• Are null references really a bad thing?

  - by Tim Goodman

  I've heard it said that the inclusion of null references in programming languages is the "billion dollar mistake". But why? Sure, they can cause NullReferenceExceptions, but so what? Any element of the language can be a source of errors if used improperly. And what's the alternative? I suppose instead of saying this: Customer c = Customer.GetByLastName("Goodman"); // returns null if not found if (c != null) { Console.WriteLine(c.FirstName + " " + c.LastName + " is awesome!"); } else { Console.WriteLine("There was no customer named Goodman. How lame!"); } You could say this: if (Customer.ExistsWithLastName("Goodman")) { Customer c = Customer.GetByLastName("Goodman") // throws error if not found Console.WriteLine(c.FirstName + " " + c.LastName + " is awesome!"); } else { Console.WriteLine("There was no customer named Goodman. How lame!"); } But how is that better? Either way, if you forget to check that the customer exists, you get an exception. I suppose that a CustomerNotFoundException is a bit easier to debug than a NullReferenceException by virtue of being more descriptive. Is that all there is to it?

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