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• Methods for ensuring security between users in multi-user applications

  - by Emilio

  I'm writing a multiuser application (.NET - C#) in which each user's data is separated from the others and there is no data that's common between users. It's critical to ensure that no user has access to another user's data. What are some approaches for implementing security at the database level and/or in the application architecture to to accomplish this? For example (and this is totally made up - I'm not suggesting it's a good or bad approach) including a userID column in all data tables might be an approach. I'm developing the app in C# (asp.net) and SQL Server 2008. I'm looking for options that are are either native in the tools I'm using or general patterns.

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• Global find object references in NHibernate

  - by Miral

  Is it possible to perform a global reversed-find on NHibernate-managed objects? Specifically, I have a persistent class called "Io". There are a huge number of fields across multiple tables which can potentially contain an object of that type. Is there a way (given a specific instance of an Io object), to retrieve a list of objects (of any type) that actually do reference that specific object? (Bonus points if it can identify which specific fields actually contain the reference, but that's not critical.) Since the NHibernate mappings define all the links (and the underlying database has corresponding foreign key links), there ought to be some way to do it.

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• Struct in C, are they efficient?

  - by pygabriel

  I'm reading some C code like that: double function( int lena,double xa,double ya, double za, double *acoefs, ..., int lenb,double xb,double yb, double zb, double *bcoefs, ..., same for c, same for d ) This function is called in the code mor than 100.000 times so it's performance-critical. I'm trying to extend this code but I want to know if it's efficient or not (and how much this influences the speed) to encapsulate all the parameters in a struct like this struct PGTO { int len; double x,y,z ; double *acoefs } and then access the parameters in the function.

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• Use of var keyword in C#

  - by kronoz

  After discussion with colleagues regarding the use of the 'var' keyword in C# 3 I wondered what people's opinions were on the appropriate uses of type inference via var? For example I rather lazily used var in questionable circumstances, e.g.:- foreach(var item in someList) { // ... } // Type of 'item' not clear. var something = someObject.SomeProperty; // Type of 'something' not clear. var something = someMethod(); // Type of 'something' not clear. More legitimate uses of var are as follows:- var l = new List<string>(); // Obvious what l will be. var s = new SomeClass(); // Obvious what s will be. Interestingly LINQ seems to be a bit of a grey area, e.g.:- var results = from r in dataContext.SomeTable select r; // Not *entirely clear* what results will be here. It's clear what results will be in that it will be a type which implements IEnumerable, however it isn't entirely obvious in the same way a var declaring a new object is. It's even worse when it comes to LINQ to objects, e.g.:- var results = from item in someList where item != 3 select item; This is no better than the equivilent foreach(var item in someList) { // ... } equivilent. There is a real concern about type safety here - for example if we were to place the results of that query into an overloaded method that accepted IEnumerable<int> and IEnumerable<double> the caller might inadvertently pass in the wrong type. Edit - var does maintain strong typing but the question is really whether it's dangerous for the type to not be immediately apparent on definition, something which is magnified when overloads mean compiler errors might not be issued when you unintentionally pass the wrong type to a method. Related Question: http://stackoverflow.com/questions/633474/c-do-you-use-var

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• JQUERY POST, UI to show if status is "saving" "still saving" "error" "complete"

  - by nobosh

  I have a JQUERY Post call which is posting critical data to the server. Which if isn't posted successfully, results in a huge loss of important data. I have a save banner UI show on the page before the JQUERY POST, after the JQUERY Post it has the Save Banner go away. I'd like an inbetween state, where if the save is taking longer than 1 second, it updates from "saving" to "saving..." but if it doesn't save within 4 seconds, it says "error, try again" something like that. Any ideas on how to accomplish this with JQUERY?

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• Java/Swing: the fast/slow UI binding problem

  - by Jason S

  I need a way to bind UI indicators to rapidly-changing values. I have a class NumberCruncher which does a bunch of heavy processing in a critical non-UI thread, thousands of iterations of a loop per second, and some number of those result in changes to a set of parameters I care about. (think of them as a key-value store) I want to display those at a slower rate in the UI thread; 10-20Hz would be fine. How can I add MVC-style notification so that my NumberCruncher code doesn't need to know about the UI code/binding?

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• allowDefinition='MachineToApplication' error when publishing from VS2010 (but only after a previous

  - by burnt_hand

  I can run my Asp.Net MVC 2 application without an issue on my local computer. Just Run / Debug. But if I have already built it, I can't publish it! I have to clean the solution and publish it again. I know this is not system critical, but it's really annoying. "One Click Publish" is not "Clean solution and then One click publish" The exact error is as follows: Error 11 It is an error to use a section registered as allowDefinition='MachineToApplication' beyond application level. This error can be caused by a virtual directory not being configured as an application in IIS. I suspect it's something to do with the Web.Config in the Views folder, but then why only after I build once previously. And just to note, the app works fine once published.

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• What to implement today to help yourself fixing bugs in the future?

  - by Heinrich Ulbricht

  Assume you are in the process of developing some really cool software. It will be deployed to a lot of customers. They will need this software and they will use it in time-critical situations. So if something goes wrong they will call (you). And you or your team will be the ones who have to resolve the issue. Fast. You know out of experience this will happen. Now if you could decide what to implement to aid your future self - what would that be?

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• What is a TFS Agile Issue?

  - by Jaxidian

  With TFS2010 using the "MSF for Agile Software Development v5" process template, I'm having some difficulty in understanding exactly what an Issue is. The most specific documentation I've been able to find is this. Is an Issue a higher-level item for which we will probably generate a Bug for after some investigation in code/requirements? Or is an Issue something different than a Bug because it has not actually a mistake in code but is more of a critical oversight in design (for example, there was never an attempt to create a datepicker for all date fields and this is a UX issue but not really a bug) and therefore a change request of sorts? Or is it something different?

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• How can I reuse my javascript code between client and server?

  - by Chris Farmer

  I have some javascript code that includes an ANTLR-generated lexer and parser, and some associated syntax tree evaluation functionality. This code runs in the browser in my web app to support users who author code snippets which process scientific data. Now I'd like to do some additional background processing on the server using the same generated parser. I would prefer not to have to re-implement this stuff in C# and have multiple bits of code that did the exact same thing. Performance isn't as critical to me as eliminating duplication, since this is a background process. So, how can I call into my javascript code from C#? And how can I format my script so that it plays nicely with my .NET web app?

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• .NET Thread.Abort again

  - by hoodoos

  Again I want to talk about safety of the Thread.Abort function. I was interested to have some way to abort operations which I can't control really and don't want actually, but I want to have my threads free as soon as possible to prevent thread thirsty of my application. So I wrote some test code to see if it's possible to use Thread.Abort and have the aborting thread clean up resources propertly. Here's code: int threadRunCount = 0; int threadAbortCount = 0; int threadFinallyCount = 0; int iterations = 0; while( true ) { Thread t = new Thread( () => { threadRunCount++; try { Thread.Sleep( Random.Next( 45, 55 ) ); } catch( ThreadAbortException ) { threadAbortCount++; } finally { threadFinallyCount++; } } ); t.Start(); Thread.Sleep( 45 ); t.Abort(); iterations++; } So, so far this code worked for about 5 mins, and threadRunCount was always equal to threadFinally and threadAbort was somewhat lower in number, because some threads completed with no abort or probably got aborted in finally. So the question is, do I miss something?

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• SQL Query to delete oldest rows over a certain row count?

  - by Casey

  I have a table that contains log entries for a program I'm writing. I'm looking for ideas on an SQL query (I'm using SQL Server Express 2005) that will keep the newest X number of records, and delete the rest. I have a datetime column that is a timestamp for the log entry. I figure something like the following would work, but I'm not sure of the performance with the IN clause for larger numbers of records. Performance isn't critical, but I might as well do the best I can the first time. DELETE FROM MyTable WHERE PrimaryKey NOT IN (SELECT TOP 10,000 PrimaryKey FROM MyTable ORDER BY TimeStamp DESC)

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• Representing a schedule in a database

  - by David Pfeffer

  I have the interesting problem of representing complex schedule data in a database. I need to be able to represent the entirety of what the iCalendar (ics) format can represent, but in my database. I don't care about insertion efficiency but query efficiency is critical. The operation I will be doing most often is providing either a single date/time or a date/time range, and trying to determine if the defined schedule matches any part of the date/time range. Other operations can be slower. For those unfamiliar, ics allows representation of a single event or a reoccuring event based on multiple times per day, days of the week, week of a month, month, year, or some combination of those. For example, the third Thursday in November, or the 25th of December, or every two weeks starting November 2nd and continuing until September the following year. Any suggestions?

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• Python: create a function to modify a list by reference not value

  - by Jonathan

  Hey all- I'm doing some performance-critical Python work and want to create a function that removes a few elements from a list if they meet certain criteria. I'd rather not create any copies of the list because it's filled with a lot of really large objects. Functionality I want to implement: def listCleanup(listOfElements): i = 0 for element in listOfElements: if(element.meetsCriteria()): del(listOfElements[i]) i += 1 return listOfElements myList = range(10000) myList = listCleanup(listOfElements) I'm not familiar with the low-level workings of Python. Is myList being passed by value or by reference? How can I make this faster? Is it possible to somehow extend the list class and implement listCleanup() within that? myList = range(10000) myList.listCleanup() Thanks- Jonathan

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• Raising C# events with an extension method - is it bad?

  - by Kyralessa

  We're all familiar with the horror that is C# event declaration. To ensure thread-safety, the standard is to write something like this: public event EventHandler SomethingHappened; protected virtual void OnSomethingHappened(EventArgs e) { var handler = SomethingHappened; if (handler != null) handler(this, e); } Recently in some other question on this board (which I can't find now), someone pointed out that extension methods could be used nicely in this scenario. Here's one way to do it: static public class EventExtensions { static public void RaiseEvent(this EventHandler @event, object sender, EventArgs e) { var handler = @event; if (handler != null) handler(sender, e); } static public void RaiseEvent<T>(this EventHandler<T> @event, object sender, T e) where T : EventArgs { var handler = @event; if (handler != null) handler(sender, e); } } With these extension methods in place, all you need to declare and raise an event is something like this: public event EventHandler SomethingHappened; void SomeMethod() { this.SomethingHappened.RaiseEvent(this, EventArgs.Empty); } My question: Is this a good idea? Are we missing anything by not having the standard On method? (One thing I notice is that it doesn't work with events that have explicit add/remove code.)

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• Unsuccessful error detection of improperly declared method in GCC 4.2 compiler

  - by sam

  I am using C++ compiler GCC 4.2 in XCode 3.2.2. I have noted that the compiler will successfully compile a method foo even though there are no ellipses. The header and method are properly declared as foo(), but when I do a find and replace either by file or by program-wide it will miss approximately 2-3% of the changes [foo to foo(). This would not be critical if the compiler did not give an erroneous successful build. I have not found that this to occur with: foo(any parameter). Does anyone have any solution? Thank you.

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• Methods and properties in scheme - is object oriented programming possible in scheme?

  - by incrediman

  I will use a simple example to illustrate my question. In Java, C, or any other OOP language, I could create a pie class in a way similar to this: class Apple{ public String flavor; public int pieces; private int tastiness; public goodness(){ return tastiness*pieces; } } What's the best way to do that with Scheme? I suppose I could do with something like this: (define make-pie (lambda (flavor pieces tastiness) (list flavor pieces tastiness))) (define pie-goodness (lambda (pie) (* (list-ref pie 1) (list-ref pie 2)))) (pie-goodness (make-pie 'cherry 2 5)) ;output: 10 ...where cherry is the flavor, 2 is the pieces, and 5 is the tastiness. However then there's no type-safety or visibility, and everything's just shoved in an unlabeled list. How can I improve that? Sidenote: The make-pie procedure expects 3 arguments. If I want to make some of them optional (like I'd be able to in curly-brace languages like Java or C), is it good practice to just take the arguments in as a list (that is treat the arguments as a list - not require one argument which is a list) and deal with them that way?

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• Performance optimization strategies of last resort?

  - by jerryjvl

  There are plenty of performance questions on this site already, but it occurs to me that almost all are very problem-specific and fairly narrow. And almost all repeat the advice to avoid premature optimization. Let's assume: the code already is working correctly the algorithms chosen are already optimal for the circumstances of the problem the code has been measured, and the offending routines have been isolated all attempts to optimize will also be measured to ensure they do not make matters worse What I am looking for here is strategies and tricks to squeeze out up to the last few percent in a critical algorithm when there is nothing else left to do but whatever it takes. Ideally, try to make answers language agnostic, and indicate any down-sides to the suggested strategies where applicable. I'll add a reply with my own initial suggestions, and look forward to whatever else the SO community can think of.

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• Recovering transaction log from corrupt SQL database

  - by Don Kirkham

  We have a database that is backed up weekly in simple mode. Yesterday, we had a crc error corrupt the mdf file and we were unable to save it. I restored the backup from last week, but now we have a gap from the time of the backup to the time of the restore. Since I have the ldf file from that database, is there any way to "replay" that transaction log to fill in the gap? I have tried reattaching the ldf file to the recovered mdf file, but SQL will not allow me to do that. (It just creates a new ldf file with a different name when I reattach the database.) Any ideas would help. This is a lot of data to lose and although it is not critical data, I'd like to get it back (as well as learn as well as learn how to do it.)

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• SMS war continues, ideas welcome

  - by Pavel Radzivilovsky

  I am trying to make U9 telit modem send SMS messages. I think I handle protocol correctly, at least, I manage to send them, but only under these circumstances: the native application was executed beforehand, and killed by task manager (without giving it a chance to initialize things). It looks like the supplied application is good at doing certain initialization/deinitialization which is critical. I also see the difference between the two states in output of AT+CIND command. When I am trying to do things on my own, it returns zeroes (including signal quality), but when I run the same command after killing the native application, the output looks reasonable. I am out nearly of ideas. I have tried many things, including attempts to spy at modem's COM ports (didn't work). Haven't tried setting windows hooks to see what the application is trying to get thru. Perhaps you have encountered a similar situation?

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• Examples of how to visualize a versioning system?

  - by Alex Gilbert

  My shop is trying to formalize the release management process for an OSS product we maintain. It's a sort of a web development framework/CMS kind of thing, as in it's a product that other projects are built on top of. This makes clear communication about the versioning system especially critical for developers that are using the tool. I'm hoping to find some examples of how best to graph this system so we can communicate it better internally and with outside developers. I know there are lots of standards and best practices around versioning, so I'm hoping this extends to some sort of visual vocabulary as well. As one example, there is a nifty graph at http://en.wikipedia.org/wiki/Versioning#Software_Versioning_schemes. Are there any guides out there on how these sorts of things should be designed?

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• How do I draw an ESB on a SoaML diagram?

  - by dave

  I've recently had to draw some architectural diagrams that feature the use of an Enterprise Service Bus. The ESB is critical, so everyone wants it to show up on the diagram. But since it's the center of what everything is connected to, it really of gets in the way. I settled on trying to use SoaML. I color-coded the request points blue and service points green, to help then stand out. The text names on the ports give you a sense of what talks to what, and it's incredibly obvious that everything goes through the ESB. Can anyone comment on my approach? Any suggestions on something better?

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• C# Process Binary File, Multi-Thread Processing

  - by washtik

  I have the following code that processes a binary file. I want to split the processing workload by using threads and assigning each line of the binary file to threads in the ThreadPool. Processing time for each line is only small but when dealing with files that might contain hundreds of lines, it makes sense to split the workload. My question is regarding the BinaryReader and thread safety. First of all, is what I am doing below acceptable. I have a feeling it would be better to pass only the binary for each line to the PROCESS_Binary_Return_lineData method. Please note the code below is conceptual. I looking for a but of guidance on this as my knowledge of multi-threading is in its infancy. Perhaps there is a better way to achieve the same result, i.e. split processing of each binary line. var dic = new Dictionary<DateTime, Data>(); var resetEvent = new ManualResetEvent(false); using (var b = new BinaryReader(File.Open(Constants.dataFile, FileMode.Open, FileAccess.Read, FileShare.Read))) { var lByte = b.BaseStream.Length; var toProcess = 0; while (lByte >= DATALENGTH) { b.BaseStream.Position = lByte; lByte = lByte - AB_DATALENGTH; ThreadPool.QueueUserWorkItem(delegate { Interlocked.Increment(ref toProcess); var lineData = PROCESS_Binary_Return_lineData(b); lock(dic) { if (!dic.ContainsKey(lineData.DateTime)) { dic.Add(lineData.DateTime, lineData); } } if (Interlocked.Decrement(ref toProcess) == 0) resetEvent.Set(); }, null); } } resetEvent.WaitOne();

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• Method hiding with interfaces

  - by fearofawhackplanet

  interface IFoo { int MyReadOnlyVar { get; } } class Foo : IFoo { int MyReadOnlyVar { get; set; } } public IFoo GetFoo() { return new Foo { MyReadOnlyVar = 1 }; } Is the above an acceptable way of implementing a readonly/immutable object? The immutability of IFoo can be broken with a temporary cast to Foo. In general (non-critical) cases, is hiding functionality through interfaces a common pattern? Or is it considered lazy coding? Or even an anti-pattern?

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• Taming the malloc/free beast -- tips & tricks

  - by roufamatic

  I've been using C on some projects for a master's degree but have never built production software with it. (.NET & Javascript are my bread and butter.) Obviously, the need to free() memory that you malloc() is critical in C. This is fine, well and good if you can do both in one routine. But as programs grow, and structs deepen, keeping track of what's been malloc'd where and what's appropriate to free gets harder and harder. I've looked around on the interwebs and only found a few generic recommendations for this. What I suspect is that some of you long-time C coders have come up with your own patterns and practices to simplify this process and keep the evil in front of you. So: how do you recommend structuring your C programs to keep dynamic allocations from becoming memory leaks?

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