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• EntityFramework 4.0: can you return different types depending on data in the database?

  - by user200341

  I have a Media table in the database. I also have an IMedia interface. I have two different media types that implements the same interface: 1) AudioMedia 2) PictureMedia What I wonder here, is if I can use EntityFramework (I'm using an EDMX file but I have my models in a separate library, with automatic code generation turned off), and depending on the data in the database, select what type to get (AutioMedia or PictureMedia). Since they are both implementing the same interface (could be changed to an abstract class if needed I suppose), I'm thinking that somewhere along the way you could specify what class it should be. I should perhaps point out that I have a class that inherits from ObjectContext to access the objects. Perhaps there is something that that can be done?

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• F# equivalent of the C# typeof(IEnumerable<>)

  - by Rune FS

  I have a piece of code where I need to figure out if a given type implements IEnumerable (I don't care about the T) I've tried (t:System.Type in case you wonder) let interfaces = t.GetInterfaces() let enumerbale = interfaces.Any( fun t -> (t.GetGenericTypeDefinition() = typeof<IEnumerable<>>) however that wont compile (the compile don't like the <). I then tried let interfaces = t.GetInterfaces() let enumerbale = interfaces.Any( fun t -> (t.GetGenericTypeDefinition() = typeof<IEnumerable<'a>>) but get's a warning that 'a is constraint to obj. I Don't want to figure out if IEnumerable is implemented but IEnumerabl<. Any one know's the solution and btw feel free to comment on the code above as well. It's my first non-trivial F# program

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• "Remember" last three MySql queries; Cookie, passed variable or other method?

  - by Camran

  I have a classified website, with pretty sophisticated searching, and I am about to implement a function where the last three queries is displayed for the user, so that the user can go back easier through the queries. This because for each query the user has to provide a lot of input. I have four questions for you: I wonder, how can I save the actual query (SELECT * FROM etc etc)...? Do I need to add some form of encryption to be on the safe side? How will this affect performance? (I don't like the fact that cookies slow websites down) Anything else to think about? If you need more input, let me know... Btw, the website is PHP based. Thanks

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• if (self = [super init]) vs. if ((self = [super init]))

  - by JOM

  Was just doing a code review and started to wonder: I thought if (self = [super init]) checks whether assigning return value of [super init] to variable self was successful or not (value of operation). Thus (self = nil) would actually be TRUE. I thought if ((self = [super init])) checks what is the value of self after assignment (value of variable). Thus ((self = nil)) would be FALSE. Which one is the correct way to use when initializing your own classes? Apple documentation uses the former one (for example here), which style I'm actually using now.

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• What is the best, python or bash for selectively concatenating lots of files?

  - by Werner

  Hi, I have around 20000 files coming from the output of some program, and their names follow the format: data1.txt data2.txt ... data99.txt data100.txt ... data999.txt data1000.txt ... data20000.txt I would like to write a script that gets as input argument the number N. Then it makes blocks of N concatenated files, so if N=5, it would make the following new files: data_new_1.txt: it would contain (concatenated) data1.txt to data5.txt (like cat data1.txt data2.txt ... data_new_1.txt ) data_new_2.txt: it would contain (concatenated) data6.txt to data10.txt ..... I wonder what do you think would be the best approach to do this, whether bash, python or another one like awk, perl, etc. The best approach I mean in terms of simplest code. Thanks

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• Can I use breakpoints (as while debugging) while 'unit testing' ?

  - by Richard77

  Hello, I'm walking through the FrontStore series tutorial on TDD in MVC (Part 3 by Rob Conery/ASP.NET). The test I'm concerned with is the CatalogRepository_Each_Category_Contains_5_Products(). Until I get to that test, everything was working fine. Now, I've gone through every line that makes this test (including the test itself, the TestCatalogRepository, ...). I've also compared my code to that of Rob, but the test keeps failing. I also checked the source code from CodePlex, that test was not there. Now, I wonder if I can put a break point somewhere to check the local values as the test is being executed? If not, something similar? Thanks for helping.

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• Speedup C++ code

  - by Werner

  Hi, I am writing a C++ number crunching application, where the bottleneck is a function that has to calculate for double: template<class T> inline T sqr(const T& x){return x*x;} and another one that calculates Base dist2(const Point& p) const { return sqr(x-p.x) + sqr(y-p.y) + sqr(z-p.z); } These operations take 80% of the computation time. I wonder if you can suggest approaches to make it faster, even if there is some sort of accuracy loss Thanks

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• Subtype polymorphism and arrays

  - by user133466

  Computer[] labComputers = new Computer[10]; with public class Computer { ... void toString(){ // print computer specs } } public class Notebook extends Computer{ ... void toString(){ // print computer specs + laptop color } } each subscripted variable labComputers[i] can reference either a Computer object or a Notebook object because Notebook is a subclass of Computer. For the method call labComputers[i].toString(), polymorphism ensures that the correct toString method is called. I wonder what if we do Notebook[] labComputers = new Notebook[10]; what kind or error would I get if I reference with Computer object and a Notebook object

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• Can I distort a bitmap image in Flash?

  - by drpepper

  Hi, what I would like to do is to take a loaded GIF file as a Bitmap, and then distort it by stretching and shrinking parts of it, so it would look like it got squished up against the screen. I'm pretty sure that there's no easy way in Flash to go beyond scaling and shearing, but I wonder if there might be some simple techniques to accomplish this kind of effect. By the way, I've also thought of pre-deforming the images in GIMP and saving them there, but I can't find a simple way to do it without learning their scripting language. Thanks for your help!

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• Is there any difference in the implementation of these three validation methods?

  - by dontWatchMyProfile

  Core Data is calling these methods in certain situations: - (BOOL)validateForInsert:(NSError **)outError; - (BOOL)validateForUpdate:(NSError **)outError; - (BOOL)validateForDelete:(NSError **)outError; I wonder if they're doing anything different, or if they're essentially doing the exact same things. As far as I know, these methods call the -validateValue:forKey:error: method once for every property. The only difference I can imagine is in the .validateForDelete: method. I see no reason why to validate an object when it shall be deleted, except for applying delete rules, probably only in the case of the DENY rule.

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• wordpress: previous_post_link() / next_post_link() placeholder

  - by superUntitled

  I am having trouble with the previous_post_link() and next_post_link() functionality. When there is no previous post, the function previous_post_link() does not display a link, likewise for the next_post_link() and the last post. I would like to have a placeholder image so that the design stays consistent. Currently I have images of green arrows pointing left and right, I would like to place an image of a grey arrow if there are no more posts to go back to. Is there a way to use the next_post_link()/previous_post_link() functions but not have the link removed. I also wonder if there is a way for the links to cycle, so that if you come to the most recent post, the next post link would bring you back to the first post.

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• .NET Garbage Collection behavior (with DataTable)

  - by gmac

  I am wonder why after creating a very simple DataTable and then setting it to null why Garbage Collection does not clear out all the memory used by that DataTable. Here is an example. The variable Before should be equal to Removed but it is not. { long Before = 0, After = 0, Removed = 0, Collected = 0; Before = GC.GetTotalMemory(true); DataTable dt = GetSomeDataTableFromSql(); After = GC.GetTotalMemory(true); dt = null; Removed = GC.GetTotalMemory(true); GC.Collect(); Collected = GC.GetTotalMemory(true); } Gives the following results. Before = 388116 After = 731248 Removed = 530176 Collected = 530176

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• Use this. to access internal class members?

  - by Sam

  On the internet I see a lot of code which uses this. to access local members of a class, like this: private String _whatever; public String Whatever { get { return this._whatever; } set { this._whatever = value; } } public void DoSomething() { String s = this.Whatever; this.DoSomething(); } (don't expect the code to do something sensible. I just wanted to show a few different uses for "this.") I wonder why to do this? To add more clarity to the source? Or is it just a waste of space?

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• How to test if Scala combinator parser matches a string

  - by W.P. McNeill

  I have a Scala combinator parser that handles comma-delimited lists of decimal numbers. object NumberListParser extends RegexParsers { def number: Parser[Double] = """\d+(\.\d*)?""".r ^^ (_.toDouble) def numbers: Parser[List[Double]] = rep1sep(number, ",") def itMatches(s: String): Boolean = parseAll(numbers, s) match { case _: Success[_] => true case _ => false } } The itMatches function returns true when given a string that matches the pattern. For example: NumberListParser.itMatches("12.4,3.141") // returns true NumberListParser.itMatches("bogus") // returns false Is there a more terse way to do this? I couldn't find one in the documentation, but my function sees a bit verbose, so I wonder if I'm overlooking something.

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• Usage examples of binary search

  - by python dude

  I just realized that in my 4+ years of Java programming (mostly desktop apps) I never used the binary search methods in the Arrays class for anything practical. Not even once. Some reasons I can think of: 100% of the time you can get away with linear search, maps or something else that isn't binary search. The incoming data is almost never sorted, and making it sorted requires an extra sorting step. So I wonder if it's just me, or do a lot of people never use binary search? And what are some good, practical usage examples of binary search?

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• Is it possible to put a form control on its own thread?

  - by BVernon

  I'm using a DataGridView and some operations that I do cause it to become unresponsive for periods of time. Normally I would put data processing in its own thread to make the form more responsive, but in this case it's the DataGridView itself that's taking so long. This leads me to wonder whether it's possible to have the main form on one thread and the DataGridView on another thread so it doesn't prevent the main form from responding. I completely understand that doing so is probably not 'safe' and likely opens up a can of worms that makes it hardly worth trying and I fully expect this post will be getting down votes for merely suggesting such a ridiculous idea. Is this possible? And if so how would you go about it?

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• Why delegate types are derived from MulticastDelegate class why not it directly derive from Delegate class?

  - by Vijay

  I have a very basic question regarding delegate types. I compared the memebers of Delegate and MulticastDelegate classes in object browser and I couldn't find any new additional member present in MulticastDelegate. I also noticed that the Delegate class has GetInvocationList virtual method. So I assume that the Delegate class should have the capability to hold references to multiple methods. If my assumption is correct I wonder why not custom delegate types directly derive from the Delegate class instead of MulticastDelegate class. Not sure what I am missing here. Please help me understand the difference.

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• Best use of Jquery sliders and PHP

  - by Coronier

  Hello there, I have two questions: What's the best way to send sliders' values to a PHP page ? I'm associating each slider (several per page) with an hidden form so far, but I wonder if there's a "cleaner" way to do this. Related to the 1st question; I've some trouble with the script: var score = $(this).slider( "option", "value" ); $(this).closest("input[type=='hidden']").val(score); It doesn't set the value of the hidden input. Can somebody tells me what's wrong ? Thanks

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• When is it good to use FTP?

  - by Tom Duckering

  In my experience I see a lot of architecture diagrams which make extensive use of FTP as a medium for linking architectural components. As someone who doesn't make architectural decisions but tends to look at architecture diagrams could anyone explain what the value is of using FTP, where it's appropriate and when transferring data as files is a good idea. I get that there are often legacy systems that just need to work that way - although any historical insight would be interesting too I can see the attraction in transferring files (especially if that's what needs to be transferred) because of the simplicity and familiarity and wonder if the reasoning goes beyond this.

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• How to efficiently render different things at different times in a game?

  - by Baqjohanson

  Sorry for the ambiguous title. What I am wondering is what is an efficient way to alternate rendering between lets say a main menu, options menu, and "in the game." The only two ways I've come up with so far are to have 1 render function, with code for each part (menu, ...) and a variable to control what gets drawn, or to have multiple render functions, and use a function pointer to point to the appropriate one, and then just call the function pointer. I always wonder how more professional games do it.

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• number of methods in an interface.

  - by Jeow

  I know this might seem a controversial question but it really is not meant to be. is there an optimal number of methods in an interface. For example, I personally hate an interface with 20 methods. It is just difficult to implement. The contract seems to hard to maintain. Similarly if the number of methods is just 1. It makes me wonder if it is really a good abstraction. Any thoughts ?

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• is it a good idea to write tests for environments other than development?

  - by jcollum

  Let's say I have a (fairly typical) set of environments: PROD, UAT, QA, DEV. Is it a good idea to run your tests across all environments? Here's what I'm thinking of. I have a proc in SQL that my code depends on, I'll call it proc_getActiveCustomers. If that proc isn't present my app will go south real fast. So I write a test that checks for the existence of this proc in the database. Nothing new here. But when I then deploy my app to the QA environment, would I also want to have a test that checks that environment for the existence of proc_getActiveCustomers? I think this is a good idea but I've never heard much about testing in environments outside of development. Makes me wonder if there's some downside I'm not aware of. The direction that I'm going is to have a list of environments in code and then passing that environment into my unit test.

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• Serialization of a TChan String

  - by J Fritsch

  I have declared the following type KEY = (IPv4, Integer) type TPSQ = TVar (PSQ.PSQ KEY POSIXTime) type TMap = TVar (Map.Map KEY [String]) data Qcfg = Qcfg { qthresh :: Int, tdelay :: Rational, cwpsq :: TPSQ, cwmap :: TMap, cw chan :: TChan String } deriving (Show) and would like this to be serializable in a sense that Qcfg can either be written to disk or be sent over the network. When I compile this I get the error No instances for (Show TMap, Show TPSQ, Show (TChan String)) arising from the 'deriving' clause of a data type declaration Possible fix: add instance declarations for (Show TMap, Show TPSQ, Show (TChan String)) or use a standalone 'deriving instance' declaration, so you can specify the instance context yourself When deriving the instance for (Show Qcfg) I am now not quite sure whether there is a chance at all to serialize my TChan although all individual nodes in it are members of the show class. For TMap and TPSQ I wonder whether there are ways to show the values in the TVar directly (because it does not get changed, so there should no need to lock it) without having to declare an instance that does a readTVar ?

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• How to specify "PG-USERNAME" in pg_ident.conf so that it'll match any database user ?

  - by felace

  I need to restrict a specific unix user so that it can login with only a few select postgres usernames (with password prompt), but allowing every other user to use whatever pg username they want. Assuming restrUnixUser is the unix user name and restrUser is one of the postgres users it may use, and AllowedDB is the only database they should connect to : pg_hba.conf : local AllowedDB restrUser password local all restrUser reject local all all ident map=exceptrestrUser And pg_ident.conf : exceptrestrUser /^(?!restrUnixUser).*$ user1 exceptrestrUser /^(?!restrUnixUser).*$ user2 exceptrestrUser /^(?!restrUnixUser).*$ postgres does what I exactly want to do right now, however, I'll probably add a lot more users so I wonder if there is something like mapname unixuserpattern allpgusers that'll match with whatever username used to login by any unix user matching the pattern.

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• What control to use

  - by Tarscher

  Hi all, I have a list of devices that I need to filter on according to options selected by the user. One such option is cooling: when the user selects cooling only the devices with cooling are shown. If cooling is not selected then all devices (with or without cooling) are shown. I wonder what kind of control I best use for this. My feeling is thata checkbox is not a good control since it represents: No cooling (unchecked) / only cooling (checked) while I want cooling and no cooling (unchecked)/ only cooling (checked). What control is best used here? Thanks.

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