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• Programming tips for writing document editors?

  - by Tesserex

  I'm asking this because I'm in the process of writing two such editors for my Mega Man engine, one a tileset editor, and another a level editor. When I say document editor, I mean the superset application type for things like image editors and text editors. All of these share things like toolbars, menu options, and in the case of image editors, and my apps, tool panes. We all know there's tons of advice out there for interface design in these apps, but I'm wondering about programming advice. Specifically, I'm doubting my code designs with the following things: Many menu options toggle various behaviors. What's the proper way to reliably tie the checked state of the option with the status of the behavior? Sometimes it's more complicated, like options being disabled when there's no document loaded. More and more consensus seems to be against using MDI, but how should I control tool panes? For example, I can't figure out how to get the panels to minimize and maximize along with the main window, like Photoshop does. When tool panels are responsible for a particular part of the document, who actually owns that thing? The main window, or the panel class? How do you do communication between the tool panels and the main window? Currently mine is all event based but it seems like there could be a better way. This seems to be a common class of gui application, but I've never seen specific pointers on code design for them. Could you please offer whatever advice or experience you have for writing them?

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• Creating a window manager type overlay for Mac OS X

  - by zorg1379

  I want to make my own window manager for OS X, or at least give it the appearance of a new one. I have many designs written down in a book, and would like to implement them. These include altering, or even completely removing, menu bars, creating entirely new guis for switching applications, etc. I know that OS X does not have a window manager, and that basically the functions that an X11 window manager would perform are done by Carbon, Cocoa, the Dock application, and the window server. I've read that it would take an incredible amount of reverse engineering to write my own api, etc. at the hardware level. I am still not that good at programming though, and don't have that kind of time. That's why I was thinking of maybe running an application on top of OS X that will function like a separate window manager - and do everything that the normal OS GUI / window manager would do. Is this possible? For example: making a custom button that would appear upon a certain key combination, that could be clicked to access a document viewer, change the time, minimize a window, etc. Is there some way to access functionality to basic tasks / actions like this without using the default OS X button controls, and implementing them with my own GUI? I am talking about more than a simple theme change, I want to completely change the user experience. This means that this application would be run in a full screen mode that blocks out default OS X menu bars. I've heard something about using graphics architectures to plug in your own window manager? Would this be an option too? If so, how would I go about doing that? Thank you,

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• Synchronizing ASP.NET MVC action methods with ReaderWriterLockSlim

  - by James D

  Any obvious issues/problems/gotchas with synchronizing access (in an ASP.NET MVC blogging engine) to a shared object model (NHibernate, but it could be anything) at the Controller/Action level via ReaderWriterLockSlim? (Assume the object model is very large and expensive to build per-request, so we need to share it among requests.) Here's how a typical "Read Post" action would look. Enter the read lock, do some work, exit the read lock. public ActionResult ReadPost(int id) { // ReaderWriterLockSlim allows multiple concurrent writes; this method // only blocks in the unlikely event that some other client is currently // writing to the model, which would only happen if a comment were being // submitted or a new post were being saved. _lock.EnterReadLock(); try { // Access the model, fetch the post with specificied id // Pseudocode, etc. Post p = TheObjectModel.GetPostByID(id); ActionResult ar = View(p); return ar; } finally { // Under all code paths, we must release the read lock _lock.ExitReadLock(); } } Meanwhile, if a user submits a comment or an author authors a new post, they're going to need write access to the model, which is done roughly like so: [AcceptVerbs(HttpVerbs.Post)] public ActionResult SaveComment(/* some posted data */) { // try/finally omitted for brevity _lock.EnterWriteLock(); // Save the comment to the DB, update the model to include the comment, etc. _lock.ExitWriteLock(); } Of course, this could also be done by tagging those action methods with some sort of "synchronized" attribute... but however you do it, my question is is this a bad idea? ps. ReaderWriterLockSlim is optimized for multiple concurrent reads, and only blocks if the write lock is held. Since writes are so infrequent (1000s or 10,000s or 100,000s of reads for every 1 write), and since they're of such a short duration, the effect is that the model is synchronized , and almost nobody ever locks, and if they do, it's not for very long.

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• Changing customErrors in web.config semi-dynamically

  - by Tom Ritter

  The basic idea is we have a test enviroment which mimics Production so customErrors="RemoteOnly". We just built a test harness that runs against the Test enviroment and detects breaks. We would like it to be able to pull back the detailed error. But we don't want to turn customErrors="On" because then it doesn't mimic Production. I've looked around and thought a lot, and everything I've come up with isn't possible. Am I wrong about any of these points? We can't turn customErrors on at runtime because when you call configuration.Save() - it writes the web.config to disk and now it's Off for every request. We can't symlink the files into a new top level directory with it's own web.config because we're on windows and subversion on windows doesn't do symlinks. We can't use URL-Mapping to make an empty folder dir2 with its own web.config and make the files in dir1 appear to be in dir2 - the web.config doesn't apply We can't copy all the aspx files into dir2 with it's own web.config because none of the links would be consistent and it's a horrible hacky solution. We can't change customErrors in web.config based on hostname (e.g. add another dns entry to the test server) because it's not possible/supported We can't do any virtual directory shenanigans to make it work. If I'm not, is there a way to accomplish what I'm trying to do? Turn on customErrors site-wide under certain circumstances (dns name or even a querystring value)?

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• Prevent Ninject from calling Initialize multiple times when binding to several interfaces

  - by Ahe

  Hi We have a concrete singleton service which implements Ninject.IInitializable and 2 interfaces. Problem is that services Initialize-methdod is called 2 times, when only one is desired. We are using .NET 3.5 and Ninject 2.0.0.0. Is there a pattern in Ninject prevent this from happening. Neither of the interfaces implement Ninject.IInitializable. the service class is: public class ConcreteService : IService1, IService2, Ninject.IInitializable { public void Initialize() { // This is called twice! } } And module looks like this: public class ServiceModule : NinjectModule { public override void Load() { this.Singleton<Iservice1, Iservice2, ConcreteService>(); } } where Singleton is an extension method defined like this: public static void Singleton<K, T>(this NinjectModule module) where T : K { module.Bind<K>().To<T>().InSingletonScope(); } public static void Singleton<K, L, T>(this NinjectModule module) where T : K, L { Singleton<K, T>(module); module.Bind<L>().ToMethod(n => n.Kernel.Get<T>()); } Of course we could add bool initialized-member to ConcreteService and initialize only when it is false, but it seems quite a bit of a hack. And it would require repeating the same logic in every service that implements two or more interfaces. Thanks for all the answers! I learned something from all of them! (I am having a hard time to decide which one mark correct). We ended up creating IActivable interface and extending ninject kernel (it also removed nicely code level dependencies to ninject, allthough attributes still remain).

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• Organizing code, logical layout of segmented files

  - by David H

  I have known enough about programming to get me in trouble for about 10 years now. I have no formal education, though I've read many books on the subject for various languages. The language I am primarily focused on now would be php, atleast for the scale of things I am doing now. I have used some OOP classes for a while, but never took the dive into understanding principals behind the scenes. I am still not at the level I would like to be expression-wise...however my recent reading into a book titled The OOP Thought Process has me wanting to advance my programming skills. With motivation from the new concepts, I have started with a new project that I've coded some re-usable classes that deal with user auth, user profiles, database interfacing, and some other stuff I use regularly on most projects. Now having split my typical garbled spaghetti bowl mess of code into somewhat organized files, I've come into some problems when it comes to making sure files are all included when they need to be, and how to logically divide the scripts up into classes, aswell as how segmented I should be making each class. I guess I have rambled on enough about much of nothing, but what I am really asking for is advise from people, or suggested reading that focuses not on specific functions and formats of code, but the logical layout of projects that are larger than just a hobby project. I want to learn how to do things proper, and while I am still learning in some areas, this is something that I have no clue about other than just being creative, and trial/error. Mostly error. Thanks for any replies. This place is great.

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• Logging with Quartz.net

  - by Young Ninja

  I will shamelessly state that I have little experience with Log4Net... I only just installed it, but it won't capture log events from Quartz.net, which is a scheduling library. Apparently Quartz.net uses Commons Logging and that needs to be configured to point to my Log4Net settings. Unfortunately, it doesn't seem to work. Help is appreciated: <configSections> ... <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" /> <section name="quartz" type="System.Configuration.NameValueSectionHandler, System, Version=1.0.5000.0,Culture=neutral, PublicKeyToken=b77a5c561934e089" /> <section name="commonLogging" type="Common.Logging.ConfigurationSectionHandler, Common.Logging"/> </configSections> <!-- Log4net error handling --> <log4net> <appender name="LogFileAppender" type="log4net.Appender.FileAppender"> <param name="File" value="Admin/LabSlice.log" /> <param name="AppendToFile" value="true" /> <layout type="log4net.Layout.PatternLayout"> <param name="ConversionPattern" value="%d [%t] %-5p %c %m%n" /> </layout> </appender> <root> <level value="INFO" /> <appender-ref ref="LogFileAppender" /> </root> </log4net> <!-- Commons logging (Quart.net logs) --> <commonLogging> <logging> <factoryAdapter type="Common.Logging.Log4Net.Log4NetLoggerFactoryAdapter, Common.Logging.Log4net"> <arg key="configType" value="INLINE" /> </factoryAdapter> </logging> </commonLogging>

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• jackson failing to map empty array with No content to map to Object due to end of input

  - by ijabz

  I send a query to an api and map the json results to my classes using Jackson. When I get some results it works fine, but when there are no results it fails with java.io.EOFException: No content to map to Object due to end of input at org.codehaus.jackson.map.ObjectMapper._initForReading(ObjectMapper.java:2766) at org.codehaus.jackson.map.ObjectMapper._readMapAndClose(ObjectMapper.java:2709) at org.codehaus.jackson.map.ObjectMapper.readValue(ObjectMapper.java:1854) at com.jthink.discogs.query.DiscogsServerQuery.mapQuery(DiscogsServerQuery.java:382) at com.jthink.discogs.query.SearchQuery.mapQuery(SearchQuery.java:37)* But the thing is the api isn't returning nothing at all, so I dont see why it is failing. Here is the query: http://api.discogs.com/database/search?page=1&type=release&release_title=nude+and+rude+the+best+of+iggy+pop this is what I get back { "pagination": { "per_page": 50, "pages": 1, "page": 1, "urls": {}, "items": 0 }, "results": [] } and here is the top level object Im trying to map to public class Search { private Pagination pagination; private Result[] results; public Pagination getPagination() { return pagination; } public void setPagination(Pagination pagination) { this.pagination = pagination; } public Result[] getResults() { return results; } public void setResults(Result[] results) { this.results = results; } } Im guessing the problem is something to do with the results array being returned being blank, but cant see what Im doing wrong EDIT: The comment below was correct, although I usually receive { "pagination": { "per_page": 50, "pages": 1, "page": 1, "urls": {}, "items": 0 }, "results": [] } and in these cases there is no problem but sometimes I seem to just get an empty String. Now Im wondering if the problem is how I read from the inputstream if (responseCode == HttpURLConnection.HTTP_OK) InputStreamReader in= new InputStreamReader(uc.getInputStream()); BufferedReader br= new BufferedReader(in); while(br.ready()) { String next = br.readLine(); sb.append(next); } return sb.toString(); } although I dont read until I get the response code, is it possible that the first time I call br.ready() that I call it before it is ready, and therefore I don't read the input EDIT 2: Changing above code to simply String line; while ((line = br.readLine()) != null) { sb.append(line); } resolved the issue.

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• Converting an input text value to a decimal number

  - by vitto

  Hi, I'm trying to work with decimal data in my PHP and MySql practice and I'm not sure about how can I do for an acceptable level af accuracy. I've wrote a simple function which recives my input text value and converts it to a decimal number ready to be stored in the database. <?php function unit ($value, $decimal_point = 2) { return number_format (str_replace (",", ".", strip_tags (trim ($value))), $decimal_point); } ?> I've resolved something like AbdlBsF5%?nl with some jQuery code for replace and some regex to keep only numbers, dots and commas. In some country, people uses the comma , to send decimal numbers, so a number like 72.08 is wrote like 72,08. I'd like avoid to forcing people to change their usual chars and I've decided to use a jQuery to keep this too. Now every web developer knows the last validation must be handled by the dynamic page for security reasons. So my answer is should I use something like unit (); function to store data or shoul I also check if users inserts invalid chars like letters or something else? If I try this and send letters, the query works without save the invalid data, I think this isn't bad, but I could easily be wrong because I'm a rookie. What kind of method should I use if I want a number like 99999.99 for my query?

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• Understanding OOP Principles in passing around objects/values

  - by Hans

  I'm not quite grokking a couple of things in OOP and I'm going to use a fictional understanding of SO to see if I can get help understand. So, on this page we have a question. You can comment on the question. There are also answers. You can comment on the answers. Question - comment - comment - comment Answer -comment Answer -comment -comment -comment Answer -comment -comment So, I'm imagining a very high level understanding of this type of system (in PHP, not .Net as I am not yet familiar with .Net) would be like: $question = new Question; $question->load($this_question_id); // from the URL probably echo $question->getTitle(); To load the answers, I imagine it's something like this ("A"): $answers = new Answers; $answers->loadFromQuestion($question->getID()); // or $answers->loadFromQuestion($this_question_id); while($answer = $answers->getAnswer()) { echo $answer->showFormatted(); } Or, would you do ("B"): $answers->setQuestion($question); // inject the whole obj, so we have access to all the data and public methods in $question $answers->loadFromQuestion(); // the ID would be found via $this->question->getID() instead of from the argument passed in while($answer = $answers->getAnswer()) { echo $answer->showFormatted(); } I guess my problem is, I don't know when or if I should be passing in an entire object, and when I should just be passing in a value. Passing in the entire object gives me a lot of flexibility, but it's more memory and subject to change, I'd guess (like a property or method rename). If "A" style is better, why not just use a function? OOP seems pointless here. Thanks, Hans

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• Change Data Capture or Change Tracking - Same as Traditional Audit Trail Table?

  - by HardCode

  Before I delve into the abyss of Microsoft documentation any deeper, I'd like to know if someone experienced with Change Data Capture and Change Tracking know if one or both of these can be used to replace the traditional ... "Audit trail table copy of the 'real table' (all of the fields of the original table, plus date/time, user ID, and DML action field) inserted into by Triggers" ... setup for a database table audit trail, where the trigger populates the audit trail table (which is all manual work). The MSDN overview documentation explains at a high level what Change Data Capture and Change Tracking are, but it isn't clear enough to me, and doesn't state outright, that these tools can be used to replace the traditional audit trail tables we've made so often. Can someone with any experience using Change Data Capture and Change Tracking save me a lot of time, or confirm that I am spending time looking at the right tool? The critical part of our audit trail is capturing all changes to a table's fields (on INSERT, UPDATE, DELETE), when it happened, and who did it. These changes are commonly provided to an end user chronologically via an audit trail report. Which is another question ... Change Data Capture or Change Tracking is the solution, I'd assume that this data can be queried just like data from a normal table? EDIT: I need a permanent audit trail, irregardless of time. I see that Change Data Capture has to do with the transaction logs, so this sounds finite to me.

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• Application connection with database persist after sucessfull transaction also.

  - by anupam3m

  Hi , I am using Spring.Data.NHibernate12 on my database level.my application connection with database is not getting released. Underneath given is Dataconfiguration.xml < ?xml version="1.0" encoding="utf-8" ? < objects xmlns="http://www.springframework.net" xmlns:db="http://www.springframework.net/database" < object id="AuditLogger" type="Risco.Rsp.Ac.Audit.AuditLogger, Risco.Rsp.Ac.Audit" singleton="false" < property name="CacheSettings" ref="CacheSettings"/ < /object < object id="CacheSettings" type="Risco.Rsp.Ac.AMAC.CacheMgmt.Utilities.UpdateEntityCacheHelper, Risco.Rsp.Ac.AMAC.CacheMgmt.Utilities" singleton="false"/ < object type="Spring.Objects.Factory.Config.PropertyPlaceholderConfigurer, Spring.Core" < <property name="ConfigSections" value="databaseSettings"/> < < db:provider id="AMACDbProvider" provider="OracleClient-2.0" connectionString="Data Source=RISCODEVDB;User ID=amsbvt; Password=amsuser1234;"/ Risco.Rsp.Ac.AMAC.Mapping Risco.Rsp.Ac.Logging.Appenders Risco.Rsp.Ac.AMAC.CacheMappings --

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• Does this use of Monitor.Wait/Pulse have a race condition?

  - by jw

  I have a simple producer/consumer scenario, where there is only ever a single item being produced/consumed. Also, the producer waits for the worker thread to finish before continuing. I realize that kind of obviates the whole point of multithreading, but please just assume it really needs to be this way (: This code doesn't compile, but I hope you get the idea: // m_data is initially null // This could be called by any number of producer threads simultaneously void SetData(object foo) { lock(x) // Line A { assert(m_data == null); m_data = foo; Monitor.Pulse(x) // Line B while(m_data != null) Monitor.Wait(x) // Line C } } // This is only ever called by a single worker thread void UseData() { lock(x) // Line D { while(m_data == null) Monitor.Wait(x) // Line E // here, do something with m_data m_data = null; Monitor.Pulse(x) // Line F } } Here is the situation that I am not sure about: Suppose many threads call SetData() with different inputs. Only one of them will get inside the lock, and the rest will be blocked on Line A. Suppose the one that got inside the lock sets m_data and makes its way to Line C. Question: Could the Wait() on Line C allow another thread at Line A to obtain the lock and overwrite m_data before the worker thread even gets to it? Supposing that doesn't happen, and the worker thread processes the original m_data, and eventually makes its way to Line F, what happens when that Pulse() goes off? Will only the thread waiting on Line C be able to get the lock? Or will it be competing with all the other threads waiting on Line A as well? Essentially, I want to know if Pulse()/Wait() communicate with each other specially "under the hood" or if they are on the same level with lock(). The solution to these problems, if they exist, is obvious of course - just surround SetData() with another lock - say, lock(y). I'm just curious if it's even an issue to begin with.

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• Android App Build system differences between Eclipse and Ant?

  - by Amy Winarske

  The Eclipse build for my 1.6 application project is succeeding and the Ant build is failing. I'm looking for help on why they aren't behaving the same way. We are developing on Mac OSX 10.5.8 with Eclipse 3.5 against SDK 1.6 + Google APIs. There are no setting changes in Eclipse, either at workspace or project level. Similarly, our ant is also a vanilla- flavored unmodified installation of 1.7.1. JDK is 1.5.0_22. The CLASSPATH environment variable is not set. JAVA_HOME is /Library/Java/ Home The application was initially created by a team member using the Eclipse plugins. The application references two jar files, one of which has a dependency on javax.xml.bind.annotation.XmlSeeAlso, which is not defined anywhere in our code or in android.jar. The other jar file has an explicit dependency on android.jar. I generated the Ant build file using android update. The Eclipse project builds an apk and runs the application in the emulator. I think this is incorrect behavior. The Android ant project fails to build. I think this is correct behavior. MyClass.java:98: cannot access javax.xml.bind.annotation.XmlSeeAlso [javac] file javax/xml/bind/annotation/XmlSeeAlso.class not found Any ideas as to why the two build methods are behaving differently? I would expect them both to fail. Thanks! -Amy

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• Reference inherited class's <T>ype in a derived class

  - by DRapp

  I don't know if its possible or not, but here's what I need. I'm toying around with something and want to know if its possible since you can't create your own data type based on a sealed type such as int, Int32, Int64, etc. I want to create a top-level class that is defined of a given type with some common stuff. Then, derive this into two subclasses, but in this case, each class is based on either and int or Int64 type. From THAT instance, create an instance of either one and know its yped basis for parameter referenc / return settings. So when I need to create an instance of the "ThisClass", I don't have to know its type basis of either int or Int64, yet IT will know the type and be able to allow methods/functions to be called with the typed... This way, If I want to change my ThisClass definition from SubLevel1 to SubLevel2, I don't have to dance around all different data type definitions. Hope this makes sense.. public class TopLevel<T> { ... } pubic class SubLevel1 : TopLevel<int> { ... } public class SubLevel2 : TopLevel<Int64> { ... } public class ThisClass : SubLevel1 { ... public <based on the Int data type from SubLevel1> SomeFunc() { return <the Int value computed>; } }

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• chrome extension login security with iframe

  - by Weaver

  I should note, I'm not a chrome extension expert. However, I'm looking for some advice or high level solution to a security concern I have with my chrome extension. I've searched quite a bit but can't seem to find a concrete answer. The situation I have a chrome extension that needs to have the user login to our backend server. However, it was decided for design reasons that the default chrome popup balloon was undesirable. Thus I've used a modal dialog and jquery to make a styled popup that is injected with content scripts. Hence, the popup is injected into the DOM o the page you are visiting. The Problem Everything works, however now that I need to implement login functionality I've noticed a vulnerability: If the site we've injected our popup into knows the password fields ID they could run a script to continuously monitor the password and username field and store that data. Call me paranoid, but I see it as a risk. In fact,I wrote a mockup attack site that can correctly pull the user and password when entered into the given fields. My devised solution I took a look at some other chrome extensions, like Buffer, and noticed what they do is load their popup from their website and, instead, embed an iFrame which contains the popup in it. The popup would interact with the server inside the iframe. My understanding is iframes are subject to same-origin scripting policies as other websites, but I may be mistaken. As such, would doing the same thing be secure? TLDR To simplify, if I embedded an https login form from our server into a given DOM, via a chrome extension, are there security concerns to password sniffing? If this is not the best way to deal with chrome extension logins, do you have suggestions with what is? Perhaps there is a way to declare text fields that javascript can simply not interact with? Not too sure! Thank you so much for your time! I will happily clarify anything required.

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• Why does my Workflow Service (4.0) variable go null in a DoWhile Activity?

  - by jlafay

  I have a WF service that I'm trying to setup receive activities to "Subscribe" and "Unsubscribe". I'm using This WF Durable Duplex Tutorial as a basis because my service performs callbacks to clients. Basically, think of it as a chat service. I can make client calls to the two receive activities just fine. What happens is the callback address of the client is passed in to Subscribe() on the service. The address is stored as a variable in the WF service and everything looks like it would work as to be expected. When a client calls Unsubscribe(), my watch I have set on the address var during debugging shows it as null. So what gives? Here's the basic setup of my WF service layout... Everything is enveloped in a DoWhile activity. Inside of that is a Pick activity and two Pick branches. The first branch is for subscribing activities. It has a receive-sendreply activity that assigns the string passed by the client to the WF address var. The second branch handles unsubscribing. The trigger is the Request activity and the client address is again passed in. From there it goes into a sequence, starting with an If. It checks to see if the unsubscribeAddress equals the address already subscribed. If it does, then it sets the address to String.Empty and sends a success message back to the client. Why would a variable that's scoped to the enveloping DoWhile activity be implicitly assigned to null? I'm trying to get this to work so I can implement multiple client subscribers from there and work on triggers that invoke callbacks to multiple clients. CONCAT EDIT: I set a breakpoint at the DoWhile level and my var is null once Unsubscribe() is called. When Subscribe() is invoked, the watch shows a value in the var all the way through. Until I Unsubscribe() with a client. Should I be using a While Activity instead?

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• Log4net Logging Problem : Very simple file appender logging not working

  - by contactmatt

  Here's my web.config information <configSections> <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net"/> </configSections> <log4net> <root> <level value="ALL" /> </root> <appender name="RollingFileAppender" type="log4net.Appender.RollingFileAppender"> <file value="c:\temp\log-file.txt" /> <appendToFile value="true" /> <rollingStyle value="Size" /> <maxSizeRollBackups value="10" /> <maximumFileSize value="1MB" /> <staticLogFileName value="true" /> <layout type="log4net.Layout.SimpleLayout" /> </appender> </log4net> ... Here's the code that initalizes the logger protected void SendMessage() { log4net.Config.XmlConfigurator.Configure(); ILog log = LogManager.GetLogger(typeof(Contact)); ... log.Info("here we go!"); log.Debug("debug afasf"); ... } it doesn't work, no matter what I seem to do. I am referencing the 'log4net.dll' correctly, and by debugging the application i can see that the log object is getting initiated properly. This is a asp.net 3.5 framework web project. Any ideas/suggestions? I thought originally this error may be due to a file write permission constraint, but that doesn't seem to be the case (or so I think).

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• How to make comment reply query in MYSQL?

  - by Prashant

  I am having comment reply (only till one level) functionality. All comments can have as many as replies but no replies can have their further replies. So my database table structure is like below Id ParentId Comment 1 0 this is come sample comment text 2 0 this is come sample comment text 3 0 this is come sample comment text 4 1 this is come sample comment text 5 0 this is come sample comment text 6 3 this is come sample comment text 7 1 this is come sample comment text In the above structures, commentid, 1 (has 2 replies) and 3 (1 reply) has replies. So to fetch the comments and their replies, one simple method is first I fetch all the comments having ParentId as 0 and then by running a while loop fetch all the replies of that particular commentId. But that seems to be running hundreds of queries if I'll have around 200 comments on a particular record. So I want to make a query which will fetch Comments with their replies sequentially as following; Id ParentId Comment 1 0 this is come sample comment text 4 1 this is come sample comment text 7 1 this is come sample comment text 2 0 this is come sample comment text 3 0 this is come sample comment text 6 3 this is come sample comment text 5 0 this is come sample comment text I also have a comment date column in my comment table, if anyone wants to use this with comment query. So finally I want to fetch all the comments and their replies by using one single mysql query. Please tell me how I can do that? Thanks

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• WPF compile error "IDictionary must have a Key attribute"

  - by the empirical programmer

  I've created control styles I want to use among multiple xaml pages in my WPF app. To do this I created a Resources.xaml and added the styles there. Then in my pages I add this code <Grid.Resources> <ResourceDictionary> <ResourceDictionary.MergedDictionaries> <ResourceDictionary Source="pack://application:,,,/SampleEventTask;component/Resources.xaml" /> </ResourceDictionary.MergedDictionaries> </ResourceDictionary> </Grid.Resources> On two pages this works fine, but on the 3rd page I get a compile error that says: All objects added to an IDictionary must have a Key attribute or some other type of key associated with them. If I add a key to this, as such ResourceDictionary x:Key="x", then the compile error goes but on running the app it errors finding the style. I can make the compile error go away and have the app run by just moving original (no key specified) "ResourceDictionary" xaml from the top level Grid into a contained Grid on that page. But I don't understand what is going on here. Any suggestions as to what the problem is, I'm just missing something or doing something incorrectly. Is there a better way to share styles? thanks

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• Method binding to base method in external library can't handle new virtual methods "between"

  - by Berg

  Lets say I have a library, version 1.0.0, with the following contents: public class Class1 { public virtual void Test() { Console.WriteLine( "Library:Class1 - Test" ); Console.WriteLine( "" ); } } public class Class2 : Class1 { } and I reference this library in a console application with the following contents: class Program { static void Main( string[] args ) { var c3 = new Class3(); c3.Test(); Console.ReadKey(); } } public class Class3 : ClassLibrary1.Class2 { public override void Test() { Console.WriteLine("Console:Class3 - Test"); base.Test(); } } Running the program will output the following: Console:Class3 - Test Library:Class1 - Test If I build a new version of the library, version 2.0.0, looking like this: public class Class1 { public virtual void Test() { Console.WriteLine( "Library:Class1 - Test V2" ); Console.WriteLine( "" ); } } public class Class2 : Class1 { public override void Test() { Console.WriteLine("Library:Class2 - Test V2"); base.Test(); } } and copy this version to the bin folder containing my console program and run it, the results are: Console:Class3 - Test Library:Class1 - Test V2 I.e, the Class2.Test method is never executed, the base.Test call in Class3.Test seems to be bound to Class1.Test since Class2.Test didn't exist when the console program was compiled. This was very surprising to me and could be a big problem in situations where you deploy new versions of a library without recompiling applications. Does anyone else have experience with this? Are there any good solutions? This makes it tempting to add empty overrides that just calls base in case I need to add some code at that level in the future...

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• The Coolest Parts of Windows API

  - by Andreas Rejbrand

  I have noticed that there are quite a few community wikis about "Tips & Tricks" or "Hidden Features" in programming languages and APIs here at Stack Overflow. But I could not find any about my own personal favourites: Win32 API and Delphi. Therefore I start my "own" CW about Win32 API. There are (at least) two kinds of Win API users: those that have been brought up using Windows API in C/C++, and those that have been brought up using some level of abstraction above the Windows API. I belong to the latter category, being brought up using Delphi's VCL. But over the last five years, I have become increasingly interested in the underlaying API of the Windows operating system, and today I work a lot with it. Depending on which category a programmer belongs to, he (or possibly she) will think that different things are "cool" in the Windows API. For instance, whereas a VCL-brought up developer might think it it very cool to var errIcon: HICON; begin errIcon := LoadIcon(0, IDI_ERROR); DrawIcon(Canvas.Handle, 10, 10, errIcon), a programmer brought up using Windows API in C will not be as impressed. But no matter how you are "brought up": what are the coolest "tricks" in Windows API? I start by listing a few of my own favourites, some of which are more "cool" than "useful", though: LoadIcon and MessageBeep can load/play system default icons and sounds. Open the CD tray: mciSendString('Set cdaudio door open wait', nil, 0, 0); Fade out the screen (Windows Vista and later) and turn of the monitor: SendMessage(Application.Handle, WM_SYSCOMMAND, SC_MONITORPOWER, 2); GetWindowDC(GetDesktopWindow) returns the DC of the desktop.

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• Accessing class member variables inside a BackgroundWorker's DoWork event handler, and other Backgro

  - by Justin

  Question 1 In the DoWork event handler of a BackgroundWorker, is it safe to access (for both reading and writing) member variables of the class that contains the BackgroundWorker? Is it safe to access other variables that are not declared inside the DoWork event handler itself? Obviously DoWork should not be accessing any UI objects of, say, a WinForms application, as the UI should only be updated from the UI thread. But what about accessing other (not UI-related) member variables? The reason why I ask is that I've seen the occasional comment come up while Googling saying that accessing member variables is not allowed. The only example I can find at the moment is a comment on this MSDN page, which says: Note, that the BGW can cause exceptions if it attempts to access or modify class level variables. All data must be passed to it by delegates and events. And also: NEVER. NEVER. Never try to reference variables not declared inside of DoWork. It may seem to work at times, but in reality you are just getting lucky. As far as I know, MSDN itself does not document any restrictions of this kind (although if I'm wrong, I'd appreciate a link). But comments like these do seem to pop up every now and again. (Of course if DoWork does access/modify a member variable that could be accessed/modified by the main thread at the same time, it is necessary to synchronise access to that field, eg by using a locking object. But the above quotes seem to require a blanket ban of accessing member variables, rather than just synchronising access!) Question 2 To make this into a more general question, are there any other (not documented?) restrictions that users of the BackgroundWorker should be aware of, aside from the above? Any "best practices", perhaps?

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• Sorting by dates (including nil) with NSFetchedResultsController

  - by glorifiedHacker

  In my NSFetchedResultsController, I set a sortDescriptor that sorts based on the date property of my managed objects. The problem that I have encountered (along with several others according to Google) is that nil values are sorted at the earliest end rather than the latest end of the date spectrum. I want my list to be sorted earliest, earlier, now, later, latest, nil. As I understand it, this sorting is done at the database level in SQLite and so I cannot construct my own compare: method to provide the sorting I want. I don't want to manually sort in memory, because I would have to give up all of the benefits of NSFetchedResultsController. I can't do compound sorting because the sectionNameKeyPaths are tightly coupled to the date ranges. I could write a routine that redirects indexPath requests so that section 0 in the results controller gets mapped to the last section of the tableView, but I fear that would add a lot of overhead, severely increase the complexity of my code, and be very, very error-prone. The latest idea that I am considering is to map all nil dates to the furthest future date that NSDate supports. My left brain hates this idea, as it feels more like a hack. It will also take a bit of work to implement, since checking for nil factors heavily into how I process dates in my app. I don't want to go this route without first checking for better options. Can anyone think of a better way to get around this problem?

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• DIY intellisense on XPath - design approach? (WinForms app)

  - by Cheeso

  I read the DIY Intellisense article on code project, which was referenced from the Mimic Intellisense? question here on SO. I wanna do something similar, DIY intellisense, but for XPath not C#. The design approach used there makes sense to me: maintain a tree of terms, and when the "completion character" is pressed, in the case of C#, a dot, pop up the list of possible completions in a textfield. Then allow the user to select a term from the textfield either through typing, arrow keys, or double-click. How would you apply this to XPath autocompletion? should there be an autocomplete key? In XPath there is no obvious separator key like "dot" in C#. should the popup be triggered explicitly in some other way, let's say ctrl-. ? or should the parser try to autocomplete continuously? If I do the autocomplete continuously, how to scale it properly? There are 93 xpath functions, not counting overloads. I certainly don't want to popup a list of 93 choices. How do I decide when I've narrowed it enough to offer a useful lsit of possible completions? How to populate the tree of possible completions? For C#, it's easy: walk the type space via reflection. At a first level, the "syntax tree" for C# seems like a single tree, and the list of completions at any point depends on the graph of nodes you've traversed to that point. Typing System.Console. traverses to a certain node in that tree, and the list of completions is the set of child nodes available at that node in the tree. On the other hand, the xpath syntax seems like it is a "flatter" tree - function names, axis names, literals. Does this make sense? what have I not considered?

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