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  • What is a NullReferenceException in .NET?

    - by John Saunders
    (I'm creating this separate question and answer because every question we get on NullReferenceException is really the same) I have some code and when it executes, it throws a NullReferenceException, saying, "Object reference not set to an instance of an object.". What does this mean, and what can I do about it? Note again, that this is a question meant to focus answers to the canonical "what is a NullReferenceException and why did I get one" question. I do know what a NullReferenceException is, as my answer below demonstrates.

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  • Coding guidelines + Best Practises?

    - by Chathuranga Chandrasekara
    I couldn't find any question that directly applies to my query so I am posting this as a new question. If there is any existing discussion that may help me, please point it out and close the question. Question: I am going to do a presentation on C# coding guidelines but it is not supposed to limit to coding standards. So I have a rough idea but I think I need to address good programing practices. So the contents will be something like this. Basic coding standards - Casing, Formatting etc. Good practices - Usage of Hashset over other data structures, String vs String Builder, String's immutability and using them effectively etc Really I would like to add more good practices (Especially to improve the performance.) So like to hear some more good practices to be used with C#. Any suggestions??? (No need of large descriptions :) Just the idea is sufficient.)

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  • Verify Authenticode signature as being from our company for automatic updater

    - by James Johnston
    I am implementing an automatic update feature and need some advice on how to do this securely using best practices. I would like to use the downloaded file's Authenticode signature to verify that it is safe to run (i.e. originates from our company and hasn't been tampered with). My question is very similar to question #2008519. The bottom-line question: what's the best, most secure way to check Authenticode signatures for an automatic update feature? What fields in the certificate should be checked? Requirements being: (1) check signature is valid, (2) check it's my signature, (3) old clients can still update when my certificate expires and I get a new one. Here's some background information / ideas from my research: I believe this could be broken into two steps: Verify that the signature is valid. I believe this should be easy using WinVerifyTrust as outlined in http://msdn.microsoft.com/en-us/library/aa382384(VS.85).aspx - I don't expect problems here. Verify that the signature corresponds to our company, and not another company. This seems to be a more difficult question to answer: One possibility is to check some of the strings in the signature. Could be obtained via code at MS KB article #323809, but this article doesn't make recommendations on what fields should be checked for this type of application (or any other, for that matter). Question #1072540 also illustrates how to get some certificate info, but again doesn't recommend what fields to actually check. My concern is that the strings might not be the best check: what if another person is able to obtain a certificate with the same name, for example? Or if there's a valid reason for us to change the strings in the future? The person at question #2008519 has a very similar requirement. His need for a "TrustedByUs" function is identical to mine. However, he goes about doing the check by comparing public keys. While this would work in the short-term, it seems like it won't work for an automatic update feature. This is because code signing certificates are only valid for 2 - 3 years max. Therefore, in the future, when we buy a new certificate in 2 years, the old clients wouldn't be able to update any more due to the change in public key.

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  • String Field Sizes for unicode database fields using different data access components

    - by Serg
    mjustin in his question 1 and question 2 says that TWideStringField.Size property for UTF8 fields in Delphi 2009 dbExpress is 4 times larger than the logical field size (max number of characters in the field). I inclined to consider this a dbExpress bug. That is what Delphi 2009 Help says: The interpretation of Size depends on the data type. The meaning of Size for data types that use it is given in the following table. For all other data types, Size is not used and its value is always 0. ftString - Size is the maximum number of characters in the string. I am using FibPlus 6.9.9 and it follows the above documentation - the string field size is the maximum number of characters, not bytes. So the question also implies the following question: Are DbExpress drivers in Delphi 2009 unusable for unicode databases?

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  • What is the best server side solution for a real-time GPS tracking system

    - by Ayman
    Well, I tried to ask this question as a comment on this question, but I thought that maybe no one will notice it, so I decided to ask it as a separate one. The question is about how to do real-time GPS tracking system things; if we have the following scenario: Rather than connecting a GPS receiver to a PC, the user will have a mobile device with an integrated GPS receiver. Location data will be sent over mobile network using GPRS data connection to a server side. The data will be processed and a KML path file will be created and updated on time intervals and used to track the user using Google Earth. The question is: what is the best method to accomplish this scenario for the server side; is it a web service, a web application, a windows service, a windows application or what exactly? Taking into account that the system will serve a number of users simultaneously, and that more users may use the system in the future(scalability issues). Thank you in advance and I highly appreciate any help :)

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  • Intermittent Internet Explorer Error whilst using Javascript to traverse XML Nodes

    - by Sykth
    Hi there all, Basically I use a javascript SOAP plugin to send and receive XML from a web service. Recently I've been experiencing intermittment (1 in every 20-30 times) errors in IE when trying to access data in the XML file. Bear with me on this, I'm going to try and go into a fair amount of detail to help anyone who is willing to read this: I have a html file, with an external javascript file attached. In the javascript file I include 5 global variables: var soapRes; var questionXML; var xRoot; var assessnode; var edStage = 0; Once the html file is at a readystate I request the XML file from the web service like this: function initNextStage(strA) { // Set pl Parameters here var pl = new SOAPClientParameters(); // soap call var r = SOAPClient.invoke(url, "LoadAssessment", pl, true, initStage_callBack); } function initStage_callBack(r, soapResponse) { soapRes = soapResponse; initvalues(); function initvalues(){ xRoot = soapRes.documentElement; assessnode = xRoot.getElementsByTagName("ed")[0]; questionXML = assessnode.getElementsByTagName("question")[edStage]; } } Once this is completed the XML should be loaded into memory via the global variable soapRes. I then save values to the XML before moving one node down the XML tree, and pulling the next set of values out of it. function submitAns1() { var objAns; var corElem; var corElemTxt; questionXML = assessnode.getElementsByTagName("question")[edStage]; objAns = questionXML.getElementsByTagName("item")[0].getAttribute("answer"); corElem = soapRes.createElement("correct"); corElemTxt = soapRes.createTextNode("value"); questionXML.appendChild(corElem); corElem.appendChild(corElemTxt); if(objAns == "t") { corElemTxt.nodeValue = "true"; } else { corElemTxt.nodeValue = "false"; } edStage++; questionXML = assessnode.getElementsByTagName("question")[edStage]; var inc1 = questionXML.getElementsByTagName("sentence")[0]; var inc2 = questionXML.getElementsByTagName("sentence")[1]; var edopt1 = questionXML.getElementsByTagName("item")[0]; var edopt2 = questionXML.getElementsByTagName("item")[1]; var edopt3 = questionXML.getElementsByTagName("item")[2]; var edopt4 = questionXML.getElementsByTagName("item")[3]; var edopt5 = questionXML.getElementsByTagName("item")[4]; var temp1 = edopt1.childNodes[0].nodeValue; var temp2 = edopt2.childNodes[0].nodeValue; var temp3 = edopt3.childNodes[0].nodeValue; var temp4 = edopt4.childNodes[0].nodeValue; var temp5 = edopt5.childNodes[0].nodeValue; } This is an example of our XML: <ed> <appid>Administrator</appid> <formid>ED009</formid> <question id="1"> <sentence id="1">[email protected]</sentence> <sentence id="2">[email protected]</sentence> <item id="0" answer="f" value="0">0</item> <item id="1" answer="f" value="1">1</item> <item id="2" answer="f" value="2">2</item> <item id="3" answer="t" value="3">3</item> <item id="4" answer="f" value="4">4</item> </question> <question id="2"> <sentence id="1">Beausdene 13</sentence> <sentence id="2">Beauscene 83</sentence> <item id="0" answer="f" value="0">0</item> <item id="1" answer="f" value="1">1</item> <item id="2" answer="t" value="2">2</item> <item id="3" answer="f" value="3">3</item> <item id="4" answer="f" value="4">4</item> </question> </ed> The error I receive intermittently is that "questionXML" is null or not an object. Specifically this line when I call on the submitAns1() method: questionXML = assessnode.getElementsByTagName("question")[edStage]; This solution works on FF, Opera, Chrome & Safari without any issues as far as I am aware. Am I accessing the XML nodes incorrectly? I've been toying with fixes for this bug for weeks now, I'd really appreciate any insight into what I'm doing wrong. On a side note, this is a personal project of mine - it's not university related - I'm much too old for that! Any help greatly appreciated. Regards, Sykth.

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  • Listing like appstore in firefox

    - by jenso
    A little question about the listing in iphone os and some other applications, and possibly in android market. When listing the apps, it fills the list in an automatic process, when reaching or is near to reach the end. My question is: How is that written in iphone applications. But the main question is: Is that possible to make for firefox users with javascript, ajax or possibly any other language? out

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  • Javascript InnerHTML Erases Data In Form Elements

    - by Jordan
    I have this form with a button that allows you to add fields to the form. <form id="contact" name="contactForm" action="newPoll.php" method="post"> <fieldset> <legend>Create A Poll</legend><br style="clear:both;"> <ol> <li><lable for=pollTitle>Poll Title:</lable><input name="pollTitle" id="pollTitle" type="text" size="66" /> </li> <li><lable for=question>1st Question:</lable><input name="question" id="question" type="text" size="66" /> </li> <li><lable for=answerType>Constrained:</lable><input name="answerType" id="answerType" value="Constrained" type="radio" size="66" /><span style="margin: 0 0 0 40px;"> Unconstrained: <input style="margin-right: 30px;" name="answerType" value="Unconstrained" id="question" type="radio" size="66" /></span>(Allow multiple answers) </li> <li><lable for=answer1>Answer:</lable><input name="answer1" id="answer1" type="text" size="66" /> </li> <li><lable for=answer2>Answer:</lable><input name="answer2" id="answer2" type="text" size="66" /> </li> <li><lable for=answer3>Answer:</lable><input name="answer3" id="answer3" type="text" size="66" /> </li> <li><lable for=answer4>Answer:</lable><input name="answer4" id="answer4" type="text" size="66" /> </li> </ol><br /> </fieldset> <input type="button" value="Add More Answers" name="addAnswer" onClick="generateRow()" /><input type="submit" name="submit" value="Add Another Question"> </form> And here is generateRow(): var count = 5; function generateRow() { var d=document.getElementById("contact"); var b = document.getElementById("answer4"); var c =b.name.charAt(0); var f = b.name.substr(0, 6); var y = f + count; count = count + 1; d.innerHTML+='<li><lable for=' + y + '>Answer:</lable><input name="' + y + '" id="' + y + '" type="text" size="66"/> </li>'; } The issue is whenever a new row is added, it erases any input that may have been typed in any of the un-original (added) text fields. It should leave the data in form elements

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  • Is ASP.NET MVC is really MVC? Or how to separate model from controller?

    - by Andrey
    Hi all, This question is a bit rhetorical. At some point i got a feeling that ASP.NET MVC is not that authentic implementation of MVC pattern. Or i didn't understood it. Consider following domain: electric bulb, switch and motion detector. They are connected together and when you enter the room motion detector switches on the bulb. If i want to represent them as MVC: switch is model, because it holds the state and contains logic bulb is view, because it presents the state of model to human motion detector is controller, because it converts user actions to generic model commands Switch has one private field (On/Off) as a State and two methods (PressOn, PressOff). If you call PressOn when it is Off it goes to On, if you call it again state doesn't change. Bulb can be replaced with buzzer, motion detector with timer or button, but the model still represent the same logic. Eventually system will have same behavior. This is how i understand classical MVC decomposition, please correct me if i am wrong. Now let's decompose it in ASP.Net MVC way. Bulb is still a view Controller will be switch + motion detector Model is some object that will just pass state to bulb. So the logic that defines behavior moves to controller. Question 1: Is my understanding of MVC and ASP.NET MVC correct? Question 2: If yes, do you agree that ASP.NET MVC is not 100% accurate implementation? And back to life. The final question is how to separate model from controller in case of ASP.NET MVC. There can be two extremes. Controller does basic stuff and call model to do all the logic. Another is controller does all the logic and model is just something like class with properties that is mapped to DB. Question 3: Where should i draw the line between this extremes? How to balance? Thanks, Andrey

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  • Detecting a Dispose() from an exception inside using block

    - by Augusto Radtke
    I have the following code in my application: using (var database = new Database()) { var poll = // Some database query code. foreach (Question question in poll.Questions) { foreach (Answer answer in question.Answers) { database.Remove(answer); } // This is a sample line that simulate an error. throw new Exception("deu pau"); database.Remove(question); } database.Remove(poll); } This code triggers the Database class Dispose() method as usual, and this method automatically commits the transaction to the database, but this leaves my database in an inconsistent state as the answers are erased but the question and the poll are not. There is any way that I can detect in the Dispose() method that it being called because of an exception instead of regular end of the closing block, so I can automate the rollback? I don´t want to manually add a try ... catch block, my objective is to use the using block as a logical safe transaction manager, so it commits to the database if the execution was clean or rollbacks if any exception occured. Do you have some thoughts on that?

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  • What's your most controversial programming opinion?

    - by Jon Skeet
    This is definitely subjective, but I'd like to try to avoid it becoming argumentative. I think it could be an interesting question if people treat it appropriately. The idea for this question came from the comment thread from my answer to the "What are five things you hate about your favorite language?" question. I contended that classes in C# should be sealed by default - I won't put my reasoning in the question, but I might write a fuller explanation as an answer to this question. I was surprised at the heat of the discussion in the comments (25 comments currently). So, what contentious opinions do you hold? I'd rather avoid the kind of thing which ends up being pretty religious with relatively little basis (e.g. brace placing) but examples might include things like "unit testing isn't actually terribly helpful" or "public fields are okay really". The important thing (to me, anyway) is that you've got reasons behind your opinions. Please present your opinion and reasoning - I would encourage people to vote for opinions which are well-argued and interesting, whether or not you happen to agree with them.

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  • Stand - alone application with JBoss or Tomcat

    - by sufoid
    Hallo, I have a more specific question about deploying a Java-application. I have created a Java application, it is a WAR file and can be installed on any Java application server. This works perfect. Now for users who do not have Java experience I want to package somehow my application together with the application server and distribute it as a stand-alone version. Question 1: Is this possible? Question 2: Which application server would be best for this? Question 3: Where should I start to learn how to do this? Do you have any experience you can share with me. Thanks.

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  • Are Symphony and CakePHP too slow to be usable?

    - by Aziz Light
    Until now, I have always said that CakePHP is too bloated and slow. I don't really know that, I just saw "some" benchmarks. What I really want to know, is that if those two frameworks (Symfony and CakePHP) are too slow to be usable in a way that the user will get frustrated. I already know that those frameworks are slower than other alternatives, but that's not the question. I ask the question because I want to create a project management web application and I still hesitate between a couple frameworks. I've had some trouble learning Zend, but imho I haven't tried hard enough. So in conclusion, in addition to the first question above, I would like to ask another question: If I want to create a project management tool (which is a pretty big project), which of the following should you suggest, considering the developement time, the speed of the resulting application, and the robustness of the final product: Symphony CakePHP Zend Framework Also I should mention that I don't know any of those frameworks, and that I want to learn one of them (at least).

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  • Function-Local Static Const variable Initialization semantics.

    - by Hassan Syed
    The questions are in bold, for those that cannot be bothered reading a question in depth. This is a followup to this question. It is to do with the initialization semantics of static variables in functions. Static variables should be initialized once, and their internal state might be altered later - as I (currently) do in the linked question. However, the code in question does not require the feature to change the state of the variable later. Let me clarrify my position, since I don't require the string object's internal state to change. The code is for a trait class for meta programming, and as such would would benifit from a const char * const ptr -- thus Ideally a local cost static const variable is needed. My educated guess is that in this case the string in question will be optimally placed in memory by the link-loader, and that the code is more secure and maps to the intended semantics. This leads to the semantics of such a variable "The C++ Programming language Third Edition -- Stroustrup" does not have anything (that I could find) to say about this matter. All that is said is that the variable is initialized once when the flow of control of the thread first reaches the code. This leads me to ponder if the following code would be sensible, and if not what are the intended semantics ?. #include <iostream> const char * const GetString(const char * x_in) { static const char * const x = x_in; return x; } int main() { const char * const temp = GetString("yahoo"); std::cout << temp << std::endl; const char * const temp2 = GetString("yahoo2"); std::cout << temp2 << std::endl; } The following compiles on GCC and prints "yahoo" twice. Which is what I want -- However it might not be standards compliant (which is why I post this question). It might be more elegant to have two functions, "SetString" and "String" where the latter forwards to the first. If it is standards compliant does someone know of a templates implementation in boost (or elsewhere) ?

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  • Most useful parallel programming algorithm?

    - by Zubair
    I recenty asked a question about parallel programming algorithms which was closed quite fast due to my bad ability to communicate my intent: http://stackoverflow.com/questions/2407631/what-is-the-most-useful-parallel-programming-algorithm-closed I had also recently asked another question, specifically: http://stackoverflow.com/questions/2407493/is-mapreduce-such-a-generalisation-of-another-programming-principle/2407570#2407570 The other question was specifically about map reduce and to see if mapreduce was a more specific version of some other concept in parallel programming. This question (about a useful parallel programming algorithm) is more about the whole series of algorithms for parallel programming. You will have to excuse me though as I am quite new to parallel programming, so maybe MapReduce or something that is a more general form of mapreduce is the "only" parallel programming construct which is available, in which case I apologise for my ignorance

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  • augment the factory pattern in java

    - by TP
    I am trying to use a factory pattern to create a QuestionTypeFactory where the instantiated classes will be like MultipleChoice, TrueFalseQuestion etc. The factory code looks something like this class QuestionFactory { public enum QuestionType { TrueFalse, MultipleChoice, Essay } public static Question createQuestion(QuestionType quesType) { switch (quesType) { case TrueFalse: return new TrueFalseQuestion(); case MultipleChoice: return new MultipleChoiceQuestion(); case Essay: return new EssayQuestion(); } throw new IllegalArgumentException("Not recognized."); } } This works ok for now. If I want to add another question type I will need to modify the factory class and I do not want to do that. How can I set it up so that each question class registers itself with the Factory so that when I add a new question type, I do not have to change the code for the factory? I am a bit new to java and am not sure how to do this.

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  • XML Node replacement in Actionscript 3

    - by Andreas
    Hi, A couple of days ago I asked a question about how to replace and edit values in an xml file with c#. The question got a great answer. Now I wonder how to do this in Actionscript and if there is an as simple way as in c#. The question can be found here: http://stackoverflow.com/questions/2856459/advanced-replace-in-c Thanks

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  • Shipping Integration into a Rails App

    - by MikeH
    I'm working on integrating a shipping solution into a Rails ecommerce app. We're only going to use one shipping provider. So the question is: Fedex or UPS? I'm wondering what Rails developers think about the tech side of this question. What do you think about the APIs, ease of integration, focus on developer's needs between Fedex and UPS? I was leaning towards Fedex, but from looking at the developers resources sections of both sites, it seems that UPS might be more developer friendly. Also, I'm going to be using Shopify's active_shipping gem: http://github.com/Shopify/active_shipping And I also based my app off the Spree Ecommerce solution, but I don't think that's particularly relevant to the question. Spree wrote a wrapper to integrate active_shipping with the Spree system. I gave away all my points, so SO wont' let me post another link in this question. But if you google "Spree active-shipping", their wrapper on github is the first result. Thanks.

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  • When using the getInstance() method of the abstract java.text.NumberFormat class, what is the actual

    - by iamchuckb
    This question expands upon the one at abstract-class-numberformat-very-confused-about-getinstance. I feel that this question is different enough to merit being asked on its own. In the answers to that question, it was stated that a code statement such as NumberFormat en = NumberFormat.getInstance(Locale.US); returns an object that is a subclass of the java.text.NumberFormat class. It makes sense to me why the return type can't be just an instance of NumberFormat since that is an abstract class. Rather, it was stated that the returned object is at least an instance of NumberFormat, but actually something else. My question is this: what specifically is the class of the object that is returned? In the Sun documentation the only subclasses I see are ChoicesFormat and DecimalFormat. Is there some sort of behind the scenes compiler voodoo going on here? Thanks in advance!

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  • Search and replace hundreds of strings in tens of thousands of files?

    - by C Johnson
    I am looking into changing the file name of hundreds of files in a (C/C++) project that I work on. The problem is our software has tens of thousands of files that including (i.e. #include) these hundreds of files that will get changed. This looks like a maintenance nightmare. If I do this I will be stuck in Ultra-Edit for weeks, rolling hundreds of regex's by hand like so: ^\#include.*["<\\/]stupid_name.*$ with #include <dir/new_name.h> Such drudgery would be worse than peeling hundreds of potatoes in a sunken submarine in the antarctic with a spoon. I think it would rather be ideal to put the inputs and outputs into a table like so: stupid_name.h <-> <dir/new_name.h> stupid_nameb.h <-> <dir/new_nameb.h> stupid_namec.h <-> <dir/new_namec.h> and feed this into a regular expression engine / tool / app / etc... My Ultimate Question: Is there a tool that will do that? Bonus Question: Is it multi-threaded? I looked at quite a few search and replace topics here on this website, and found lots of standard queries that asked a variant of the following question: standard question: Replace one term in N files. as opposed to: my question: Replace N terms in N files. Thanks in advance for any replies.

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