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• CFHost DNS Resolution - When is it OK to use synchronous API?

  - by Jasarien

  I went to the iPhone Developer Tech Talk a few months ago and asked one of the gurus there about the lack of NSHost on the iPhone. Some code I was porting to the iPhone made significant use of NSHost throughout its networking code. I was told that NSHost is on the iPhone, but its private. I was also told that NSHost is a synchronous API and that I shouldn't use it anyway. (If anyone could elaborate on why it shouldn't be used, as a bonus, that'd be great.) I can see the caveats of using synchronous API's on the main thread in that they'll block until complete - and that's never a good thing with network code because there are so many factors that could cause the API to block the thread for a significant amount of time. My solution was to write a wrapper around CFHost's asynchronous resolution functions. The result works quite well, and I'm considering releasing it into the public domain. But my question is this: Say my app only resolves a hostname once per run, during the connecting phase, and then cache's it for the rest of the session. During the time it is resolving, a modal screen is shown telling the user "Connecting" with a nice spinner. Does it really matter whether or not the resolution is asynchronous?? The user has to wait to connect anyway, and the resolution is only done on the first connection. Subsequent connections use the cached result of the resolution. When is it OK to be synchronous and when should things be asynchronous?

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• Play and Stop in One button

  - by Ardi

  i'm newbie, i'm tried to make play audio play and stop for 1 button only, but i'm in trouble now. if i touch a button when audio is playing, it doesn't stop, even playing audio again and make a double sound. here's my code public class ProjectisengActivity extends Activity{ ImageButton mainkan; MediaPlayer mp; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.test2); mainkan=(ImageButton)findViewById(R.id.imageButton1); mainkan.setOnClickListener(new OnClickListener(){ @Override public void onClick(View v){ go(); } }); public void go(){ mp=MediaPlayer.create(ProjectisengActivity.this, R.raw.test); if(mp.isPlaying()){ mp.stop(); try { mp.prepare(); } catch (IllegalStateException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } mp.seekTo(0); } else { mp.start(); } i'm create for android 3.0 (HoneyComb) thanks for help

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• Java Concurrency : Synchronized(this) => and this.wait() and this.notify()

  - by jens

  Hello Experts, I would appreciate your help in understand a "Concurrency Example" from: http://forums.sun.com/thread.jspa?threadID=735386 Qute Start: public synchronized void enqueue(T obj) { // do addition to internal list and then... this.notify(); } public synchronized T dequeue() { while (this.size()==0) { this.wait(); } return // something from the queue } Quote End: My Question is: Why is this code valid? = When I synchronize a method like "public synchronized" = then I synchronize on the "Instance of the Object == this". However in the example above: Calling "dequeue" I will get the "lock/monitor" on this Now I am in the dequeue method. As the list is zero, the calling thread will be "waited" From my understanding I have now a deadlock situation, as I will have no chance of ever enquing an object (from an nother thread), as the "dequeue" method is not yet finised and the dequeue "method" holds the lock on this: So I will never ever get the possibility to call "enequeue" as I will not get the "this" lock. Backround: I have exactly the same problem: I have some kind of connection pool (List of Connections) and need to block if all connections are checked. What is the correct way to synchronize the List to block, if size exceeds a limit or is zero? Thank you very much Jens

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• NetBeans Tips and Tricks

  - by cdmckay

  I just saw an Eclipse tips & tricks post and was wondering if anyone had any tips & tricks for my IDE of choice: NetBeans. Here's a few I know and find to be useful: Removing a package: After you remove a package in NetBeans, it sticks around as a grayed-out package in your Project view. To get rid of that, switch to Files view and delete the directory. Alt-Insert (in Windows) opens up a Generate submenu at your cursor. A nice shortcut for quickly generating getters/setters (among other things). Selecting a chunk of code, right-clicking and then clicking "Refactor Introduce Method" will have NetBeans introduce a method, complete with arguments and return value. Of course you have to make sure the chunk of code only has one return value. Sometimes when you run a build and it crashes, the Java window sticks around at the bottom. I used to just click X until Windows let me End Task, but there's a nicer way to get rid of them. Click "Run Stop Build/Run" and NetBeans will close the window for you. It'll even let you close multiple applications at once. These may seem obvious to grizzled NetBeans developers, but I thought they might be useful for NetBeans newbs like me. Anyone else have any tips/tricks to share? Here are some from the comments: NetBeans allows for code templates. You can even add yours on the Code Templates tab under the Editor settings on the Options window. Some examples: Type sout and hit the tab key as a shorcut for System.out.println("") Type psvm and hit the tab key as a shorcut for public static void main(String args[]) {} Ctrl Shift C: Comments out the selected block of code. Alt Shift F: Formats the selected block of code. Ctrl E: Deletes current line. Ctrl Shift I: Fixes your imports, handy if you've just written a piece of code that needs a lot of packages imported.

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• Run a .java file using ProcessBuilder

  - by David K

  I'm a novice programmer working in Eclipse, and I need to get multiple processes running (this is going to be a simulation of a multi-computer system). My initial hackup used multiple threads to multiple classes, but now I'm trying to replace the threads with processes. From my reading, I've gleaned that ProcessBuilder is the way to go. I have tried many many versions of the input you see below, but cannot for the life of me figure out how to properly use it. I am trying to run the .java files I previously created as classes (which I have modified). I eventually just made a dummy test.java to make sure my process is working properly - its only function is to print that it ran. My code for the two files are below. Am I using ProcessBuilder correctly? Is this the correct way to read the output of my subprocess? Any help would be much appreciated. David primary process package Control; import java.io.*; import java.lang.*; public class runSPARmatch { /** * @param args */ public static void main(String args[]) { try { ProcessBuilder broker = new ProcessBuilder("javac.exe","test.java","src\\Broker\\"); Process runBroker = broker.start(); Reader reader = new InputStreamReader(runBroker.getInputStream()); int ch; while((ch = reader.read())!= -1) System.out.println((char)ch); reader.close(); runBroker.waitFor(); System.out.println("Program complete"); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } subprocess package Broker; public class test { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub System.out.println("This works"); } }

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• IUsable: controlling resources in a better way than IDisposable

  - by Ilya Ryzhenkov

  I wish we have "Usable" pattern in C#, when code block of using construct would be passed to a function as delegate: class Usable : IUsable { public void Use(Action action) // implements IUsable { // acquire resources action(); // release resources } } and in user code: using (new Usable()) { // this code block is converted to delegate and passed to Use method above } Pros: Controlled execution, exceptions The fact of using "Usable" is visible in call stack Cons: Cost of delegate Do you think it is feasible and useful, and if it doesn't have any problems from the language point of view? Are there any pitfalls you can see? EDIT: David Schmitt proposed the following using(new Usable(delegate() { // actions here }) {} It can work in the sample scenario like that, but usually you have resource already allocated and want it to look like this: using (Repository.GlobalResource) { // actions here } Where GlobalResource (yes, I know global resources are bad) implements IUsable. You can rewrite is as short as Repository.GlobalResource.Use(() => { // actions here }); But it looks a little bit weird (and more weird if you implement interface explicitly), and this is so often case in various flavours, that I thought it deserve to be new syntactic sugar in a language.

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• WPF and Prism View Overlay

  - by Zaheer

  Hi, I need some help with overlaying views using the prism framework.Its a little more complexed than that so let me explain.I could be over-thinking this as well :D i have shell (wpf window) and i have 2 views(A & B - both usercontrols) in a module. when the shell loads it loads view A. On view A i have a button to "popup" view B for some user input. so naturally i would think to some sort of modal window/control, maybe even a popup. however the problem i face with the popup is that when i move the shell the popup remains fixed and it doesnt block events in view A. I've tried disabling view A to stop events being fired and i've also tried to use a to get the view B move with the shell. Only the canvas works but i now need a way to block it tho'. Is there anyway i can overlay a view on top of another view with prism? or how does everyone else create modal popups with prism & wpf? any advise or pointers would be greatly appreciated.

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• Javascript: prototypeal inheritance and the prototype proprity

  - by JanD

  Hi, I have a simple code fragment in JS working with prototype inheritance. function object(o) { function F() {} F.prototype = o; return new F(); } //the following code block has a alternate version var mammal={ color: "brown", getColor: function(){ return this.color; } } var myCat = object(mammal); myCat.meow = function(){return "meow";} that worked fine but adding this: mammal.prototype.kindOf = "predator"; does not. ("mammal.prototype is undefined") Since I guessed that object maybe have no prototype I rewrote it, replacing the var mammal={... block with: function mammal(){ this.color="brown"; this.getColor = function(){return this.color;} } which gave me a bunch of other errors: "Function.prototype.toString called on incompatible object" and if I try to call _myCat.getColor() "myCat.getColor is not a function" Now I am totally confused. After reading Crockford, and Flanagan I did not get the solution for the errors. So it would be great if somebody knows... - why is the prototype undefined in the first example (which is foremost concern; I thought the prototype of explicitly set in the object() function) - why get I these strange errors trying to use the mammal function as prototype object in the object() function?

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• Javascript: prototypal inheritance and the prototype property

  - by JanD

  Hi, I have a simple code fragment in JS working with prototype inheritance. function object(o) { function F() {} F.prototype = o; return new F(); } //the following code block has a alternate version var mammal = { color: "brown", getColor: function() { return this.color; } } var myCat = object(mammal); myCat.meow = function(){return "meow";} that worked fine but adding this: mammal.prototype.kindOf = "predator"; does not. ("mammal.prototype is undefined") Since I guessed that object maybe have no prototype I rewrote it, replacing the var mammal={... block with: function mammal() { this.color = "brown"; this.getColor = function() { return this.color; } } which gave me a bunch of other errors: "Function.prototype.toString called on incompatible object" and if I try to call _myCat.getColor() "myCat.getColor is not a function" Now I am totally confused. After reading Crockford, and Flanagan I did not get the solution for the errors. So it would be great if somebody knows... - why is the prototype undefined in the first example (which is foremost concern; I thought the prototype of explicitly set in the object() function) - why get I these strange errors trying to use the mammal function as prototype object in the object() function? Edit by the Creator of the Question: These two links helped a lot too: Prototypes_in_JavaScript on the spheredev wiki explains the way the prototype property works relativily simple. What it lacks is some try-out code examples. Some good examples are provided by Morris John's Article. I personally find the explanations are not that easy as in the first link, but still very good. The most difficult part even after I actually got it is really not to confuse the .prototype propery with the internal [[Prototype]] of an object.

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• Unable to upload large files on FTP using Apache commons-net-3.1

  - by Nitin

  I am trying to upload the one large file ( more than 8 MB) using storeFile(remote, local) method of FTPClient but it results false.It get uploaded with some extra bytes.Following is the code with Output: public class Main { public static void main(String[] args) { FTPClient client = new FTPClient(); FileInputStream fis = null; try { client.connect("208.106.181.143"); client.setFileTransferMode(client.BINARY_FILE_TYPE); client.login("abc", "java"); int reply = client.getReplyCode(); System.out.println("Received Reply from FTP Connection:" + reply); if(FTPReply.isPositiveCompletion(reply)){ System.out.println("Connected Success"); } client.changeWorkingDirectory("/"+"Everbest"+"/"); client.makeDirectory("ETPSupplyChain5.3-EvbstSP3"); client.changeWorkingDirectory("/"+"Everbest"+"/"+"ETPSupplyChain5.3-EvbstSP3"+"/"); FTPFile[] names = client.listFiles(); String filename = "E:\\Nitin\\D-Drive\\Installer.rar"; fis = new FileInputStream(filename); boolean result = client.storeFile("Installer.rar", fis); int replyAfterupload = client.getReplyCode(); System.out.println("Received Reply from FTP Connection replyAfterupload:" + replyAfterupload); System.out.println("result:"+result); for (FTPFile name : names) { System.out.println("Name = " + name); } client.logout(); fis.close(); client.disconnect(); } catch (SocketException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } o/p: Received Reply from FTP Connection:230 Connected Success 32 /Everbest/ETPSupplyChain5.3-EvbstSP3 Received Reply from FTP Connection replyAfterupload:150 result:false

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• Squid handling of concurrent cache misses

  - by Oliver H-H

  We're using a Squid cache to off-load traffic from our web servers, ie. it's setup as a reverse-proxy responding to inbound requests before they hit our web servers. When we get blitzed with concurrent requests for the same request that's not in the cache, Squid proxies all the requests through to our web ("origin") servers. For us, this behavior isn't ideal: our origin servers gets bogged down trying to fulfill N identical requests concurrently. Instead, we'd like the first request to proxy through to the origin server, the rest of the requests to queue at the Squid layer, and then all be fulfilled by Squid when the origin server has responded to that first request. Does anyone know how to configure Squid to do this? We've read through the documentation multiple times and thoroughly web-searched the topic, but can't figure out how to do it. We use Akamai too and, interestingly, this is its default behavior. (However, Akamai has so many nodes that we still see lots of concurrent requests in certain traffic spike scenarios, even with Akamai's super-node feature enabled.) This behavior is clearly configurable for some other caches, eg. the Ehcache documentation offers the option "Concurrent Cache Misses: A cache miss will cause the filter chain, upstream of the caching filter to be processed. To avoid threads requesting the same key to do useless duplicate work, these threads block behind the first thread." Some folks call this behavior a "blocking cache," since the subsequent concurrent requests block behind the first request until it's fulfilled or timed-out. Thx for looking over my noob question! Oliver

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• Form values in a list item

  - by Tri

  Here is the site mock-up I'm working on for my job: http://dev.arm.gov/~noensie/dqhands/cgi-bin/explorer. I'm still a novice in web developing and I need help with placing form values in a list item to pass on to another page. I'd rather not go in great detail the purpose of this website, but in terms of its basic use, select the parameters in the middle column for a request and add it to the list on the right column by pressing on "add request" button when it appears. After the list have been populated, a user would submit the selected requests, which will direct them to another page based on the requests selected (or added to the list, same thing). That last sentence is where I'm having a problem. Right now, each of request in the list in the right column are <li> elements and I assign them attribute values that needed to be passed on to the next page. I tried inserting a hidden input with same values, but I'm still not sure how to utilize that; I'm not even sure using the hidden input is the correct way. Also the "submit request" button is located outside the <form> block. I was going to utilize javascript and jQuery to enable the button to serialize the values in the <form> block, but I don't know quite how to do that. Go ahead and take a look at my javascript code (index.js) and slay me, or, I mean, my code. It's still pretty elementary and short (~260 lines, that's short right?). I will take any help for this problem (as the matter of fact, if you see any other problems or a better way of implementation of something, go ahead and mention that too); tips, advice, code samples, or whatever else you can contribute, it will be greatly appreciated. Tri

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• Parsing basic math equations for children's educational software?

  - by Simucal

  Inspired by a recent TED talk, I want to write a small piece of educational software. The researcher created little miniature computers in the shape of blocks called "Siftables". [David Merril, inventor - with Siftables in the background.] There were many applications he used the blocks in but my favorite was when each block was a number or basic operation symbol. You could then re-arrange the blocks of numbers or operation symbols in a line, and it would display an answer on another siftable block. So, I've decided I wanted to implemented a software version of "Math Siftables" on a limited scale as my final project for a CS course I'm taking. What is the generally accepted way for parsing and interpreting a string of math expressions, and if they are valid, perform the operation? Is this a case where I should implement a full parser/lexer? I would imagine interpreting basic math expressions would be a semi-common problem in computer science so I'm looking for the right way to approach this. For example, if my Math Siftable blocks where arranged like: [1] [+] [2] This would be a valid sequence and I would perform the necessary operation to arrive at "3". However, if the child were to drag several operation blocks together such as: [2] [\] [\] [5] It would obviously be invalid. Ultimately, I want to be able to parse and interpret any number of chains of operations with the blocks that the user can drag together. Can anyone explain to me or point me to resources for parsing basic math expressions? I'd prefer as much of a language agnostic answer as possible.

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• Flexible CMS for non-programmers

  - by Bunkerbewohner

  Hello! I'm looking for a content management system that allows creating single pages out of predefined blocks flexibly. For example I have a "product" block that is used to show producs on a page and it may appear numerous times on one page with different contents. But I also might wanna use it on different pages. Also I have simply generic blocks like multiple column text blocks (1 col, 2 col etc.) where I just want to insert this kind of structure into the page and enter any text. So I'm looking for a cms with someething like a building block / module concept for contents. I'm already searching the web but there are so many CMSs that I can't look into every one. So if anyone knows a solution that might be right for me, please tell me! Technology-wise it just has to run on Linux. If it's OpenSource / free that's great, but I might also pay for it, if it offers the features I want. Thanks for any hints in advance!

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• Debug NAudio MP3 reading difference?

  - by Conrad Albrecht

  My code using NAudio to read one particular MP3 gets different results than several other commercial apps. Specifically: My NAudio-based code finds ~1.4 sec of silence at the beginning of this MP3 before "audible audio" (a drum pickup) starts, whereas other apps (Windows Media Player, RealPlayer, WavePad) show ~2.5 sec of silence before that same drum pickup. The particular MP3 is "Like A Rolling Stone" downloaded from Amazon.com. Tested several other MP3s and none show any similar difference between my code and other apps. Most MP3s don't start with such a long silence so I suspect that's the source of the difference. Debugging problems: I can't actually find a way to even prove that the other apps are right and NAudio/me is wrong, i.e. to compare block-by-block my code's results to a "known good reference implementation"; therefore I can't even precisely define the "error" I need to debug. Since my code reads thousands of samples during those 1.4 sec with no obvious errors, I can't think how to narrow down where/when in the input stream to look for a bug. The heart of the NAudio code is a P/Invoke call to acmStreamConvert(), which is a Windows "black box" call which I can't think how to error-check. Can anyone think of any tricks/techniques to debug this?

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• strategy for choosing proper object and proper method

  - by zerkms

  in the code below at first if statements block (there will be more than just "worker" condition, joined with else if) i select proper filter_object. After this in the same conditional block i select what filter should be applied by filter object. This code is silly. public class Filter { public static List<data.Issue> fetch(string type, string filter) { Filter_Base filter_object = new Filter_Base(filter); if (type == "worker") { filter_object = new Filter_Worker(filter); } else if (type == "dispatcher") { filter_object = new Filter_Dispatcher(filter); } List<data.Issue> result = new List<data.Issue>(); if (filter == "new") { result = filter_object.new_issues(); } else if (filter == "ended") { result = filter_object.ended_issues(); } return result; } } public class Filter_Base { protected string _filter; public Filter_Base(string filter) { _filter = filter; } public virtual List<data.Issue> new_issues() { return new List<data.Issue>(); } public virtual List<data.Issue> ended_issues() { return new List<data.Issue>(); } } public class Filter_Worker : Filter_Base { public Filter_Worker(string filter) : base(filter) { } public override List<data.Issue> new_issues() { return (from i in data.db.GetInstance().Issues where (new int[] { 4, 5 }).Contains(i.RequestStatusId) select i).Take(10).ToList(); } } public class Filter_Dispatcher : Filter_Base { public Filter_Dispatcher(string filter) : base(filter) { } } it will be used in some kind of: Filter.fetch("worker", "new"); this code means, that for user that belongs to role "worker" only "new" issues will be fetched (this is some kind of small and simple CRM). Or another: Filter.fetch("dispatcher", "ended"); // here we get finished issues for dispatcher role Any proposals on how to improve it?

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• CUDA: When to use shared memory and when to rely on L1 caching?

  - by Roger Dahl

  After Compute Capability 2.0 (Fermi) was released, I've wondered if there are any use cases left for shared memory. That is, when is it better to use shared memory than just let L1 perform its magic in the background? Is shared memory simply there to let algorithms designed for CC < 2.0 run efficiently without modifications? To collaborate via shared memory, threads in a block write to shared memory and synchronize with __syncthreads(). Why not simply write to global memory (through L1), and synchronize with __threadfence_block()? The latter option should be easier to implement since it doesn't have to relate to two different locations of values, and it should be faster because there is no explicit copying from global to shared memory. Since the data gets cached in L1, threads don't have to wait for data to actually make it all the way out to global memory. With shared memory, one is guaranteed that a value that was put there remains there throughout the duration of the block. This is as opposed to values in L1, which get evicted if they are not used often enough. Are there any cases where it's better too cache such rarely used data in shared memory than to let the L1 manage them based on the usage pattern that the algorithm actually has?

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• XSL-FO: Static content AND Flow content in Region-Body: Possible?

  - by Peterdk

  I have the following problem: I need to use XSLFO to generate a 2-column multipage document. Problem is: I need to have a vertical line between the 2 columns. Since XSLFO does not seem to specify a option for creating such a divider, I need to manually put it there. I was thinking of using a static rotated blockcontainer with a leader in it. However, it looks like it's not possible to use static-content on the same region as where the flow content comes. <fo:layout-master-set> <fo:simple-page-master page-width="170mm" page-height="222mm" master-name="page" > <fo:region-body region-name="xsl-region-body" margin-top="2mm" margin-bottom="2mm" margin-left="10mm" margin-right="10mm" column-count="2" column-gap="5mm" /> </fo:simple-page-master> </fo:layout-master-set> <fo:page-sequence master-reference="page"> <fo:static-content flow-name="xsl-region-body" ><!-- This gives a error --> <fo:block>test</fo:block> </fo:static-content> <fo:flow flow-name="xsl-region-body"> <xsl:apply-templates/> </fo:flow> </fo:page-sequence> Results in (XEP): [error] Duplicate identifier: flow-name="xsl-region-body". Property 'flow-name' should be unique within 'fo:page-sequence'. Are there any methods to place static content on the main region when also flow content is placed there? Or: Is there a way to define the divider that divides a 2-column layout?

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• DataTable won't DataBind with a DataTable.NewRow()

  - by David

  Is DataRow.NewRow() insufficient as the only row in a DataTable? I would expect this to work, but it doesn't. It's near the end of my Page_Load inside my If(!Postback) block. gridCPCP is GridView DataTable dt = new DataTable(); dt.Columns.Add("ID", int.MinValue.GetType()); dt.Columns.Add("Code", string.Empty.GetType()); dt.Columns.Add("Date", DateTime.MinValue.GetType()); dt.Columns.Add("Date2", DateTime.MinValue.GetType()); dt.Columns.Add("Filename", string.Empty.GetType()); //code to add rows if (dt.Rows.Count > 0) { gridCPCP.DataSource = dt; gridCPCP.DataBind(); } else { dt.Rows.Add(dt.NewRow()); gridCPCP.DataSource = dt; gridCPCP.DataBind(); //EXCEPTION int TotalColumns = gridCPCP.Rows[0].Cells.Count; gridCPCP.Rows[0].Cells.Clear(); gridCPCP.Rows[0].Cells.Add(new TableCell()); gridCPCP.Rows[0].Cells[0].ColumnSpan = TotalColumns; gridCPCP.Rows[0].Cells[0].Text = "No Record Found"; } The exception throws on gridCPCP.DataBind() and only when execution reaches the else block. If there were rows added above via dt.Rows.Add(new object[] { ... } binding works. System.ArgumentOutOfRangeException: Length cannot be less than zero. Parameter name: length

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• Singleton Issues in iOS http client

  - by Andrew Lauer Barinov

  I implemented an HTTP client is iOS that is meant to be a singleton. It is a subclass of AFNetworking's excellent AFHTTPClient My access method is pretty standard: + (LBHTTPClient*) sharedHTTPClient { static dispatch_once_t once = 0; static LBHTTPClient *sharedHTTPClient = nil; dispatch_once(&once, ^{ sharedHTTPClient = [[LBHTTPClient alloc] initHTTPClient]; }); return sharedHTTPClient; } // my init method - (id) initHTTPClient { self = [super initWithBaseURL:[NSURL URLWithString:kBaseURL]]; if (self) { // Sub class specific initializations } return self; } Super's init method is very long, and can be found here However the problem I experience is when the dispatch_once queue is run, the app locks and become unresponsive. When I step through code, I notice that it locks on dispatch_once and then remains frozen. Is this something to do with the main thread locking down? How come it stays locked like that? Also, none of the HTTP client methods fire. Stepping through the code some more, I find this line in dispatch/once.h is where the app locks down: DISPATCH_INLINE DISPATCH_ALWAYS_INLINE DISPATCH_NONNULL_ALL DISPATCH_NOTHROW void _dispatch_once(dispatch_once_t *predicate, dispatch_block_t block) { if (DISPATCH_EXPECT(*predicate, ~0l) != ~0l) { dispatch_once(predicate, block); // App locks here } }

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• Triple Quotes? How do I delimit a databound Javascript string parameter in ASP.NET?

  - by David HAust

  How do I delimit a Javascript databound string parameter in an anchor OnClick event? I have an anchor tag in an ASP.NET Repeater control. The OnClick event of the anchor contains a call to a Javascript function. The Javascript funciton takes a string for it's input parameter. The string parameter is populated with a databound value from the Repeater. I need the 'double quotes' for the Container.DataItem. I need the 'single quotes' for the OnClick. And I still need one more delimiter (triple quotes?) for the input string parameter of the Javascript function call. Since I can't use 'single quotes' again, how do I ensure the Javascript function knows the input parameter is a string and not an integer? Without the extra quotes around the input string parameter, the Javascript function thinks I'm passing in an integer. Cheers in advance for any knowledge you can drop. The anchor: <a id="aShowHide" onclick='ToggleDisplay(<%# DataBinder.Eval(Container.DataItem, "JobCode") %>);' >Show/Hide</a> and here is the Javascript: <script language="JavaScript" type="text/javascript">/* Shows/Hides the Jobs Div */ function ToggleDisplay(jobCode) { /* Each div has it's ID set dynamically ('d' plus the JobCode) */ var elem = document.getElementById('d' + jobCode); if (elem) { if (elem.style.display != 'block') { elem.style.display = 'block'; elem.style.visibility = 'visible'; } else { elem.style.display = 'none'; elem.style.visibility = 'hidden'; } } }</script>

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• Copy vector of values to vector of pairs in one line

  - by Kirill V. Lyadvinsky

  I have the following types: struct X { int x; X( int val ) : x(val) {} }; struct X2 { int x2; X2() : x2() {} }; typedef std::pair<X, X2> pair_t; typedef std::vector<pair_t> pairs_vec_t; typedef std::vector<X> X_vec_t; I need to initialize instance of pairs_vec_t with values from X_vec_t. I use the following code and it works as expected: int main() { pairs_vec_t ps; X_vec_t xs; // this is not empty in the production code ps.reserve( xs.size() ); { // I want to change this block to one line code. struct get_pair { pair_t operator()( const X& value ) { return std::make_pair( value, X2() ); } }; std::transform( xs.begin(), xs.end(), back_inserter(ps), get_pair() ); } return 0; } What I'm trying to do is to reduce my copying block to one line with using boost::bind. This code is not working: for_each( xs.begin(), xs.end(), boost::bind( &pairs_vec_t::push_back, ps, boost::bind( &std::make_pair, _1, X2() ) ) ); I know why it is not working, but I want to know how to make it working without declaring extra functions and structs?

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• In .NET when Aborting Thread, can this piece of code get corrupted?

  - by bosko

  Little intro: In complex multithreaded aplication (enterprise service bus EBS), I need to use Thread.Abort, because this EBS accepts user written modules which communicates with hardware security modules. So if this module gets deadlocked or hardware stops responding - i need to just unload this module and rest of this server aplication must keep runnnig. So there is abort sync mechanism which ensures that code can be aborted only in user section and this section must be marked as AbortAble. If this happen there is possibility that ThreadAbortException will be thrown in this pieace of code: public void StopAbortSection() { var id = Thread.CurrentThread.ManagedThreadId; lock (threadIdMap[id]) { .... } } If module is on AbortSection and Aplication decides to abort module, but after this decision but before actual Thread.Abort, module enters NonAbortableSection by calling this method, but lock is actualy taken on that locking object. So lock will block until Abort or abort can be executed before reaching this block by this code. But Object with this method is essential and i need to be sure that this pieace of code is safe to abort in any moment. Probably i have to mention that threadIdMap is Dictionary(int,ManualResetEvent), so locking object is instance of ManualResetEvent. I hope you now understad my question. Sorry for its largeness.

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• TransactionScope Prematurely Completed

  - by Chris

  I have a block of code that runs within a TransactionScope and within this block of code I make several calls to the DB. Selects, Updates, Creates, and Deletes, the whole gamut. When I execute my delete I execute it using an extension method of the SqlCommand that will automatically resubmit the query if it deadlocks as this query could potentially hit a deadlock. I believe the problem occurs when a deadlock is hit and the function tries to resubmit the query. This is the error I receive: The transaction associated with the current connection has completed but has not been disposed. The transaction must be disposed before the connection can be used to execute SQL statements. This is the simple code that executes the query (all of the code below executes within the using of the TransactionScope): using (sqlCommand.Connection = new SqlConnection(ConnectionStrings.App)) { sqlCommand.Connection.Open(); sqlCommand.ExecuteNonQueryWithDeadlockHandling(); } Here is the extension method that resubmits the deadlocked query: public static class SqlCommandExtender { private const int DEADLOCK_ERROR = 1205; private const int MAXIMUM_DEADLOCK_RETRIES = 5; private const int SLEEP_INCREMENT = 100; public static void ExecuteNonQueryWithDeadlockHandling(this SqlCommand sqlCommand) { int count = 0; SqlException deadlockException = null; do { if (count > 0) Thread.Sleep(count * SLEEP_INCREMENT); deadlockException = ExecuteNonQuery(sqlCommand); count++; } while (deadlockException != null && count < MAXIMUM_DEADLOCK_RETRIES); if (deadlockException != null) throw deadlockException; } private static SqlException ExecuteNonQuery(SqlCommand sqlCommand) { try { sqlCommand.ExecuteNonQuery(); } catch (SqlException exception) { if (exception.Number == DEADLOCK_ERROR) return exception; throw; } return null; } } The error occurs on the line that executes the nonquery: sqlCommand.ExecuteNonQuery();

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• Display: Custom Control

  - by pipelinecache

  Hi folks, I've made a simple custom control: base.Style[HtmlTextWriterStyle.Position] = "absolute"; if (this.Expanded) // If the Calendar is expanded. this.Style[HtmlTextWriterStyle.Display] = "block"; else this.Style[HtmlTextWriterStyle.Display] = "none"; //create the containing table Panel pnl = new Panel(); pnl.ID = "pnl_" + this.ClientID; pnl.Enabled = true; SherlockIIITextBox txtCalendar = new SherlockIIITextBox(); txtCalendar.ID = "Cal_" + this.ClientID; pnl.Controls.Add(txtCalendar); ImageButton imgButton = new ImageButton(); imgButton.ImageUrl = ""; imgButton.ID = "img_" + this.ClientID; imgButton.BorderStyle = BorderStyle.NotSet; imgButton.OnClientClick = "o = document.getElementById('" + this.ClientID + "');if (o.style.display=='none'){o.style.display='block';}else{o.style.display='none';}"; pnl.Controls.Add(imgButton); pnl.RenderControl(writer); When I click the ImageButton it should render the calendar. But when I click the ImageButton nothing happens. Anyone got an idea?

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