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• Newbie database index question

  - by RenderIn

  I have a table with multiple indexes, several of which duplicate the same columns: Index 1 columns: X, B, C, D Index 2 columns: Y, B, C, D Index 3 columns: Z, B, C, D I'm not very knowledgeable on indexing in practice, so I'm wondering if somebody can explain why X, Y and Z were paired with these same columns. B is an effective date. C is a semi-unique key ID for this table for a specific effective date B. D is a sequence that identifies the priority of this record for the identifier C. Why not just create 6 indexes, one for each X, Y, Z, B, C, D? I want to add an index to another column T, but in some contexts I'll only be querying on T alone while in others I will also be specifying the B, C and D columns... so should I create just one index like above or should I create one for T and one for (T, B, C, D)? I've not had as much luck as expected when googling for comprehensive coverage of indexing. Any resources where I can get a through explanation and lots of examples of B-tree indexing?

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• Abusing the word "library"

  - by William Pursell

  I see a lot of questions, both here on SO and elsewhere, about "maintaining common libraries in a VCS". That is, projects foo and bar both depend on libbaz, and the questioner is wondering how they should import the source for libbaz into the VCS for each project. My question is: WTF? If libbaz is a library, then foo doesn't need its source code at all. There are some libraries that are reasonably designed to be used in this manner (eg gnulib), but for the most part foo and bar ought to just link against the library. I guess my thinking is: if you cut-and-paste source for a library into your own source tree, then you obviously don't care about future updates to the library. If you care about updates, then just link against the library and trust the library maintainers to maintain a stable API. If you don't trust the API to remain stable, then you can't blindly update your own copy of the source anyway, so what is gained? To summarize the question: why would anyone want to maintain a copy of a library in the source code for a project rather than just linking against that library and requiring it as a dependency? If the only answer is "don't want the dependency", then why not just distribute a copy of the library along with your app, but keep them totally separate?

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• Please explain JSONP

  - by Cheeso

  I don't understand jsonp. I understand JSON. I don't understand JSONP. Wikipedia is the top search result for JSONP. It says JSONP or "JSON with padding" is a JSON extension wherein a prefix is specified as an input argument of the call itself. Huh? What call? That doesn't make any sense to me. JSON is a data format. There's no call. The 2nd search result is from some guy named Remy, who writes JSONP is script tag injection, passing the response from the server in to a user specified function. I can sort of understand that, but it's still not making any sense. What is JSONP, why was it created (what problem does it solve), and why would I use it? Addendum: I've updated Wikipedia with a clearer and more thorough description of JSONP, based on jvenema's answer. Thanks, all.

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• Login failed when a web service tries to communicate with SharePoint 2007

  - by tata9999

  Hi, I created a very simple webservice in ASP.NET 2.0 to query a list in SharePoint 2007 like this: namespace WebService1 { /// <summary> /// Summary description for Service1 /// </summary> [WebService(Namespace = "http://tempuri.org/")] [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)] [System.ComponentModel.ToolboxItem(false)] // To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line. // [System.Web.Script.Services.ScriptService] public class Service1 : System.Web.Services.WebService { [WebMethod] public string HelloWorld() { return "Hello World"; } [WebMethod] public string ShowSPMyList() { string username = this.User.Identity.Name; return GetList(); } private string GetList() { string resutl = ""; SPSite siteCollection = new SPSite("http://localhost:89"); using (SPWeb web = siteCollection.OpenWeb()) { SPList mylist = web.Lists["MySPList"]; SPQuery query = new SPQuery(); query.Query = "<Where><Eq><FieldRef Name=\"AssignedTo\"/><Value Type=\"Text\">Ramprasad</Value></Eq></Where>"; SPListItemCollection items = mylist.GetItems(query); foreach (SPListItem item in items) { resutl = resutl + SPEncode.HtmlEncode(item["Title"].ToString()); } } return resutl; } } } This web service runs well when tested using the built-in server of Visual Studio 2008. The username indicates exactly my domain account (domain\myusername). However when I create a virtual folder to host and launch this web service (still located in the same machine with SP2007), I got the following error when invoking ShowSPMyList() method, at the line to execute OpenWeb(). These are the details of the error: System.Data.SqlClient.SqlException: Cannot open database "WSS_Content_8887ac57951146a290ca134778ddc3f8" requested by the login. The login failed. Login failed for user 'NT AUTHORITY\NETWORK SERVICE'. Does anyone have any idea why this error happens? Why does the web service run fine inside Visual Studio 2008, but not when running stand-alone? I checked and in both cases, the username variable has the same value (domain\myusername). Thank you very much.

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• Securely erasing a file using simple methods?

  - by Jason

  Hello, I am using C# .NET Framework 2.0. I have a question relating to file shredding. My target operating systems are Windows 7, Windows Vista, and Windows XP. Possibly Windows Server 2003 or 2008 but I'm guessing they should be the same as the first three. My goal is to securely erase a file. I don't believe using File.Delete is secure at all. I read somewhere that the operating system simply marks the raw hard-disk data for deletion when you delete a file - the data is not erased at all. That's why there exists so many working methods to recover supposedly "deleted" files. I also read, that's why it's much more useful to overwrite the file, because then the data on disk actually has to be changed. Is this true? Is this generally what's needed? If so, I believe I can simply write the file full of 1's and 0's a few times. I've read: http://www.codeproject.com/KB/files/NShred.aspx http://blogs.computerworld.com/node/5756 http://blogs.computerworld.com/node/5687 http://stackoverflow.com/questions/4147775/securely-deleting-a-file-in-c-net

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• When should I be cautious using about data binding in .NET?

  - by Ben McCormack

  I just started working on a small team of .NET programmers about a month ago and recently got in a discussion with our team lead regarding why we don't use databinding at all in our code. Every time we work with a data grid, we iterate through a data table and populate the grid row by row; the code usually looks something like this: Dim dt as DataTable = FuncLib.GetData("spGetTheData ...") Dim i As Integer For i = 0 To dt.Rows.Length - 1 '(not sure why we do not use a for each here)' gridRow = grid.Rows.Add() gridRow(constantProductID).Value = dt("ProductID").Value gridRow(constantProductDesc).Value = dt("ProductDescription").Value Next '(I am probably missing something in the code, but that is basically it)' Our team lead was saying that he got burned using data binding when working with Sheridan Grid controls, VB6, and ADO recordsets back in the nineties. He's not sure what the exact problem was, but he remembers that binding didn't work as expected and caused him some major problems. Since then, they haven't trusted data binding and load the data for all their controls by hand. The reason the conversation even came up was because I found data binding to be very simple and really liked separating the data presentation (in this case, the data grid) from the in-memory data source (in this case, the data table). "Loading" the data row by row into the grid seemed to break this distinction. I also observed that with the advent of XAML in WPF and Silverlight, data-binding seems like a must-have in order to be able to cleanly wire up a designer's XAML code with your data. When should I be cautious of using data-binding in .NET?

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• Error 1053: the service did not respond to the start or control request in a timely fashion

  - by deejjaayy

  i know this is very much a "how long is a piece of string" type of question, however i have recently inherited a couple of applications that run as windows services, and i am having problems providing a gui (accessible from a context menu in system tray) with both of them. before you ask, the reason why we need a gui for a windows service is in order to be able to re-configure the behaviour of the windows service(s) without resorting to stopping/re-starting. my code works fine in debug mode, and i get the context menu come up, and everything behaves correctly etc. when i install the service via "installutil" using a named account (i.e., not Local System Account), the service runs fine, but doesn't display the icon in the system tray (i know this is normal behaviour because i don't have the "interact with desktop" option). here is the problem though - when i choose the "LocalSystemAccount" option, and check the "interact with desktop" option, the service takes AGES to start up for no obvious reason, and i just keep getting "Could not start the ... service on Local Computer. Error 1053: the service did not respond to the start or control request in a timely fashion". incidentally, i increased the windows service timeout from the default 30 seconds to 2 minutes via a registry hack (see http://support.microsoft.com/kb/824344, search for TimeoutPeriod in section 3), however the service start up still times out. my first question is - why might the "Local System Account" login takes SOOOOO MUCH LONGER than when the service logs in with the non-LocalSystemAccount, causing the windows service time-out? what's could the difference be between these two to cause such different behaviour at start up? secondly - taking a step back, all i'm trying to achieve, is simply a windows service that provides a gui for configuration - I'd be quite happy to run using the non-Local System Account (with named user/pwd), if I could get the service to interact with the desktop (that is, have a context menu available from the system tray). is this possible, and if so how? any pointers to the above questions would be very much appreciated! thanks in advance for your help.

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• Trouble getting started with Spring Roo and GWT

  - by Abdel Olakara

  Hi all, I am trying to get started with SpringRoo and GWT after seeing the keynote.. unfortunately I am stuck at this issue. I successfully created the project using Roo and added the persistence, the entities and when I perform the command "perform package" I get this error: 23/5/10 12:10:13 AM AST: [ERROR] ApplicationEntityTypesProcessor cannot be resolved 23/5/10 12:10:13 AM AST: [ERROR] ApplicationEntityTypesProcessor cannot be resolved to a type 23/5/10 12:10:13 AM AST: [WARN] advice defined in org.springframework.mock.staticmock.AnnotationDrivenStaticEntityMockingControl has not been applied [Xlint:adviceDidNotMatch] 23/5/10 12:10:13 AM AST: [WARN] advice defined in org.springframework.mock.staticmock.AbstractMethodMockingControl has not been applied [Xlint:adviceDidNotMatch] 23/5/10 12:10:13 AM AST: Build errors for helloroo; org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.codehaus.mojo:aspectj-maven-plugin:1.0:compile (default) on project helloroo: Compiler errors : error at import tp.gwt.request.ApplicationEntityTypesProcessor; I see this in the Maven console and cannot complete the build..I know there is some jar missing but how and why? because I downloaded all the latest version including GWT milestone release. Any idea why this error is occurring? How do I resolve this issue? Thanks in Advance, Abdel Olakara

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• Should we have a database independent SQL like query language in Django? [closed]

  - by Yugal Jindle

  Note : I know we have Django ORM already that keeps things database independent and converts to the database specific SQL queries. Once things starts getting complicated it is preferred to write raw SQL queries for better efficiency. When you write raw sql queries your code gets trapped with the database you are using. I also understand its important to use the full power of your database that can-not be achieved with the django orm alone. My Question : Until I use any database specific feature, why should one be trapped with the database. For instance : We have a query with multiple joins and we decided to write a raw sql query. Now, that makes my website postgres specific. Even when I have not used any postgres specific feature. I feel there should be some fake sql language which can translate to any database's sql query. Even Django's ORM can be built over it. So, that if you go out of ORM but not database specific - you can still remain database independent. I asked the same question to Jacob Kaplan Moss (In person) : He advised me to stay with the database that I like and endure its whole power, to which I agree. But my point was not that we should be database independent. My point is we should be database independent until we use a database specific feature. Please explain, why should be there a fake sql layer over the actual sql ?

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• what the difference between break with label and without label in javascript

  - by dramasea

  <script type="text/javascript"> var num = 0; for(var i = 0; i < 10; i++){ for(var j = 0; j < 10 ; j++){ if(i == 5 && j == 5){ break; } num++; } } alert(num); </script> In the above code,i expect the result to be 55 but why the result is 95. But why if i added that the label, the result become 55?Can someone tell me thanks!! <script type="text/javascript"> var num = 0; outermost: for(var i = 0; i < 10; i++){ for(var j = 0; j < 10 ; j++){ if(i == 5 && j == 5){ break outermost; } num++; } } alert(num); </script>

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• how to insert multiple rows using cakephp

  - by Paul

  In the cakePHP project I'm building, I want to insert a defined number of identical records. These will serve as placeholders records that will have additional data added later. Each record will insert the IDs taken from two belongs_to relationships as well as two other string values. What I want to do is be able to enter a value for the number of records I want created, which would equate to how many times the data is looped during save. What I don't know is: 1) how to setup a loop to handle a set number of inserts 2) how to define a form field in cakePHP that only sets the number of records to create. What I've tried is the following: function massAdd() { $inserts_required = 1; while ($inserts_required <= 10) { $this->Match->create(); $this->Match->save($this->data); echo $inserts_required++; } $brackets = $this->Match->Bracket->find('list'); $this->set(compact('brackets')); } What happens is: 1) at the top of the screen, above the doc type, the string 12345678910 is displayed, this is displayed on screen 2) a total of 11 records are created, and only the last record has the values passed in the form. I don't know why 11 records as opposed to 10 are created, and why only the last records has the entered form data? As always, your help and direction is appreciated. -Paul

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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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• Getting error: "This webpage is not available" for my chrome app's options page

  - by Don Rhummy

  My CRX had the proper html page options.html in it, the manifest declares it properly (it shows up as a link on the chrome://extensions page) but when I click that link, Chrome gives the error: This webpage is not available The webpage at chrome-extension://invalid/ might be temporarily down or it may have moved permanently to a new web address. It says "invalid" but the app runs perfectly well (all the content scripts run, the background created a database and saved to it). Why would it show as invalid? Why doesn't it have the extensions' id? Here's the manifest: { "manifest_version": 2, "name": "MyAPP", "description": "My App", "version": "0.0.0.32", "minimum_chrome_version": "27", "offline_enabled": true, "options_page": "options.html", "icons": { "16": "images/icon16.png", "48": "images/icon48.png", "128": "images/icon128.png" }, "app": { "background": { "scripts": [ "scripts/background.js" ] } }, "permissions": [ "unlimitedStorage", "fullscreen", { "fileSystem": [ "write" ] }, "background", "<all_urls>", "tabs" ] } Does it need to be declared in "web_accessible_resources"? Any idea what's wrong? Update Adding to "web_accessible_resources" does not fix the issue. I added everything on that page too. update 2 It looks like it might be a Chrome bug for packaged apps. When I remove the "app" section in the manifest, it works! This is a bug since the Chrome app documentation states that apps can have options pages: https://developer.chrome.com/apps/options.html

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• Cannot spawn an erlang supervisor from the shell.

  - by drfloob

  I've implemented a gen_server and supervisor: test_server and test_sup. I want to test them from the shell/CLI. I've written their start_link functions such that their names are registered locally. I've found that I can spawn the test_server from the command line just fine, but a spawned test_sup does nothing whatsoever. Why is this? For example, I can spawn a test_server by executing: 1> spawn(test_server, start_link, []). <0.39.0> 2> registered(). [...,test_server,...] I can interact with the server, and everything appears fine. However, if I try to do the same thing with test_sup, no new names/Pids are registered, and it looks like my test_server was not spawned at all. I'd assume I coded an error in my supervisor, but this method of starting my supervisor works perfectly fine: 1> {ok, Pid}= test_sup:start_link([]). {ok, <0.39.0>} 2> unlink(Pid). true 3> registered(). [...,test_server,test_sup,...] Why is it that I can spawn a gen_server but not a supervisor?

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• Linq2sql code generator misbehaving

  - by Martin

  Sometime the linq2sql just makes its mind up about things. I've been pulling my hair for the past hours trying to work out what I'm doing differently from all the other times when I don't get ForeignKeyReferenceAlreadyHasValueException. Turns out that if (this._Activity.HasLoadedOrAssignedValue) { throw new System.Data.Linq.ForeignKeyReferenceAlreadyHasValueException(); } is present on my primary key in this particular table, and in no other. No matter what I do with the association, I've even tried deleting and dragging the thing back to the designer, it's still there and I'm sure it's not supposed to be. I know why, of course, but I don't know why, so to speak. A while back the association went the other way. Whereas I've left that era behind me, the code generator seems to exhibit phantom pains. The same phenomenon, is responsible for me having to change the namespace in the designer.cs everytime I make changes in the designer. I made the mistake of renaming my namespace and the code generator just doesn't get it. Somebody please help this poor boy out.

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• jQuery Animate Inconsistencies between Browsers

  - by silent1mezzo

  I'm trying to figure out why this works in FireFox, Chrome but not in IE and not properly in Safari and Opera (you can view it working at http://41six.com/about/) HTML: <div id="menu"> <ul> <li> <a href="/" class="home" title="Home" alt="fortyonesix">&nbsp;</a> <div id='home-hover'>Home Page</div> </li> </ul> </div> CSS: #menu .home { display:block; height:24px; width:24px; background-image: url('../images/Home.png'); } #home-hover { position:fixed; padding: 3px 0 3px 10px; left:40px; top:125px; width: 100px; height: 20px; background-color:#000; color: #fff; z-index:9999; opacity: .9; filter: alpha(opacity=90); -ms-filter:"progid:DXImageTransform.Microsoft.Alpha(Opacity=90)"; -moz-border-radius-topright: 5px; -webkit-border-top-right-radius: 5px; -moz-border-radius-bottomright: 5px; -webkit-border-top-bottom-radius: 5px; display:none; } JQuery: $('.home').hover(function() { $('#home-hover').animate({width:'toggle'},200); }, function() { $('#home-hover').animate({width:'toggle'},200); }); It's definitely not pretty but I'm not sure why its not working for Safari, Opera and IE

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• Fastest Method to Learn Web Design for a Developer

  - by hekevintran

  I am a Web developer and in my projects I have noticed that my weakest point is not being good at the front-end design. Relying on other designers can be annoying if they are not able to produce as quickly as I want. My perspective on HTML/CSS is that it is basically a big hack that amazingly works. There are too many CSS and browser specific bugs/quirks to learn and remember them all without spending extreme amounts of time trying to untangle everything. Is there a fast track route to getting CSS into my brain? I have looked at some CSS books, but to me they really read as long lists of how to render things correctly in IE6 and how to make corners rounded. (Seriously why does it require so many tricks to make a sharp corner round? On any platform but the Web this would be called a major oversight.) Does there exist something that does the analogous to CSS that jQuery does for JavaScript? Using jQuery you don't need to know JavaScript well to make things that work. I am not interested in learning why IE6 does things in weird ways because I don't care about supporting it at all. I am more interested in a method of learning how to use CSS to do what I want without spending hours and hours reading obscure blogs.

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• ASP.NET MVC and NHibernate coupling

  - by Ben

  I have just started learning NHibernate. Over the past few months I have been using IoC / DI (structuremap) and the repository pattern and it has made my applications much more loosely coupled and easier to test. When switching my persistence layer to NHibernate I decided to stick with my repositories. Currently I am creating a new session on each method call but of course this means that I can not benefit from lazy loading. Therefore I wish to implement session-per-request but in doing so this will make my web project dependent on NHibernate (perhaps this is not such a bad thing?). I was planning to inject ISession into my repositories and create and dispose sessions on beginrequest/endrequest events (see http://ayende.com/Blog/archive/2009/08/05/do-you-need-a-framework.aspx) Is this a good approach? Presumably I cannot use session-per-request without having a reference to NHibernate in my web project? Having the web project dependent on NHibernate prompts my next (few) questions - why even bother with the repository? Since my web app is calling services that talk to the repositories, why not ditch the repositories and just add my NHibernate persistance code inside the services? And finally, is there really any need to split out into so many projects. Is a web project and an infrastructure project sufficient? I realise that I have veered off a bit from my original question but it seems that everyone seems to have their own opinion on these topics. Some people use the repository pattern with NHibernate, some don't. Some people stick their mapping files with the related classes, others have a separate project for this. Many thanks, Ben

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• How to make designer generated .Net application settings portable

  - by Ville Koskinen

  Hello, I've been looking at modifying the source of the Doppler podcast aggregator with the goal of being able to run the program directly from my mp3 player. Doppler stores application settings using a Visual Studio designer generated Settings class, which by default serializes user settings to the user's home directory. I'd like to change this so that all settings would be stored in the same directory as the exe. It seems that this would be possible by creating a custom provider class which inherits the SettingsProvider class. Has anyone created such a provider and would like to share code? Update: I was able to get a custom settings provider nearly working by using this MSDN sample, i.e. with simple inheritance. I was initially confused as Windows Forms designer stopped working until I did this trick suggested at Codeproject: internal sealed partial class Settings { private MySettingsProvider settingsprovider = new MySettingsProvider(); public Settings() { foreach (SettingsProperty property in this.Properties) { property.Provider = settingsprovider; } ... The program still starts with window size 0;0 though. Anyone with any insight to this? Why the need to assing the provider in runtime---instead of using attributes as suggested by MSDN? Why the changes in how the default settings are passed to the application with the default settings provider vs. the custom one?

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• phpmyadmin shows numbers or blob for mysql's utf8_bin callation columns?

  - by marc40000

  Hi ! I have a table with a varchar column. Its collation is set to utf8_bin. My software using this table and column works perfectly. But when I look at the content in phpmyadmin, I only see some hex values or [Blob xB]. Can I make phpmyadmin show the content correctly? Besides, when I set the collation to utf8_general_ci or utf8_unicode_ci, the phpmyadmin shows the content correctly. Thx Marc [edit]Hah, I found out, there is a small "+Options" link above every table in phpmyadmin. It opens several options including "Show BLOB contents" - which makes the [blob] to readable text when enabled and "Show binary contents as HEX" which shows the hex codes as text when disabled. No idea why there are two options though and why sometimes there is a [Blob] and sometimes hex values. Well. Now I'm still wondering: Setting these options get lost when I go to another table. I have to set them every time I go there. Is there a way to save those options? [/edit]

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• "<" operator error

  - by Nona Urbiz

  Why is the ( i < UniqueWords.Count ) expression valid in the for loop, but returns "CS0019 Operator '<' cannot be applied to operands of type 'int' and 'method group'" error when placed in my if? They are both string arrays, previously declared. for (int i = 0;i<UniqueWords.Count;i++){ Occurrences[i] = Words.Where(x => x.Equals(UniqueWords[i])).Count(); Keywords[i] = UniqueWords[i]; if (i<UniqueURLs.Count) {rURLs[i] = UniqueURLs[i];} } EDITED to add declarations: List<string> Words = new List<string>(); List<string> URLs = new List<string>(); //elements added like so. . . . Words.Add (referringWords); //these are strings URLs.Add (referringURL); UniqueWords = Words.Distinct().ToList(); UniqueURLs = URLs.Distinct().ToList(); SOLVED. thank you, parentheses were needed for method .Count() I still do not fully understand why they are not always necessary. Jon Skeet, thanks, I guess I don't understand what exactly the declarations are either then? You wanted the actual values assigned? They are pulled from an external source, but are strings. I get it! Thanks. (the ()'s at least.)

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• android : bluetooth support

  - by Puneet kaur

  i have coded for bluetooth via defining a user task ,which will search the devices in background and set the list on foreground after finishing the search . but sometimes i am getting the data in adapter as "nodevice" "device1" "device2" ...... the problem here is why it is always filling the no device in the list and after that fill the device in list .. private BroadcastReceiver mBlueToothInfoDiscoveryListener = new BroadcastReceiver() { /** * This is an overridden function called by the framework whenever there * is some broadcast message for Bluetooth info discovery listener */ @Override public void onReceive(Context context, Intent intent) { String action = intent.getAction(); // When discovery finds a device if (BluetoothDevice.ACTION_FOUND.equals(action)) { // Get the BluetoothDevice object from the Intent BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE); // If it's already paired, skip it, because it's been listed // already if (device.getBondState() != BluetoothDevice.BOND_BONDED) { mNewBtDevicesArrayAdapter.add(device.getName() + "\n" + device.getAddress()); } // When discovery is finished, change the Activity title } else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) { setProgressBarIndeterminateVisibility(false); setTitle("device list"); if (mNewBtDevicesArrayAdapter.getCount() == 0) { String noDevices = "No devices found"; mNewBtDevicesArrayAdapter.add(noDevices); } } } }; but here why it is sometimes going into else option on start and filling the list with no device then to if part again ... when devices are already on .

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• "Ambigous type variable" error when defining custom "read" function

  - by Tener

  While trying to compile the following code, which is enhanced version of read build on readMay from Safe package. readI :: (Typeable a, Read a) => String -> a readI str = case readMay str of Just x -> x Nothing -> error ("Prelude.read failed, expected type: " ++ (show (typeOf > (undefined :: a))) ++ "String was: " ++ str) I get an error from GHC: WavefrontSimple.hs:54:81: Ambiguous type variable `a' in the constraint: `Typeable a' arising from a use of `typeOf' at src/WavefrontSimple.hs:54:81-103 Probable fix: add a type signature that fixes these type variable(s)` I don't understand why. What should be fixed to get what I meant? EDIT: Ok, so the solution to use ScopedTypeVariables and forall a in type signature works. But why the following produces very similar error to the one above? The compiler should infer the right type since there is asTypeOf :: a -> a -> a used. readI :: (Typeable a, Read a) => String -> a readI str = let xx = undefined in case readMay str of Just x -> x `asTypeOf` xx Nothing -> error ("Prelude.read failed, expected type: " ++ (show (typeOf xx)) ++ "String was: " ++ str)

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• how to know location of return address on stack c/c++

  - by Dr Deo

  i have been reading about a function that can overwrite its return address. void foo(const char* input) { char buf[10]; //What? No extra arguments supplied to printf? //It's a cheap trick to view the stack 8-) //We'll see this trick again when we look at format strings. printf("My stack looks like:\n%p\n%p\n%p\n%p\n%p\n% p\n\n"); //%p ie expect pointers //Pass the user input straight to secure code public enemy #1. strcpy(buf, input); printf("%s\n", buf); printf("Now the stack looks like:\n%p\n%p\n%p\n%p\n%p\n%p\n\n"); } It was sugggested that this is how the stack would look like Address of foo = 00401000 My stack looks like: 00000000 00000000 7FFDF000 0012FF80 0040108A <-- We want to overwrite the return address for foo. 00410EDE Question: -. Why did the author arbitrarily choose the second last value as the return address of foo()? -. Are values added to the stack from the bottom or from the top? apart from the function return address, what are the other values i apparently see on the stack? ie why isn't it filled with zeros Thanks.

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• COM AddIn for Outlook Tries to Install Self on Startup

  - by Ben

  Hi, I have an outlook addin that I have been developing for some time now, and am experiencing a problem. If I have a computer with two 'administrator' users (call them User A and User B), the addin installs and runs just fine as long as the same user tries to run it. In other words, if User A installs the addin, then User A has no problem using. The strange behavior comes in when we see the following scenario: User A installs the addin (for all users), User B launches outlook and observes that the addin is trying to install itself yet again. If User B cancels out of the 'install', he can then go and use the addin just fine. Right now, I use office's registry key propagation to do an 'all users' install, and I inspected the registry for any duplications and found none. I even used the officeins tool to try and detect if there was any duplication going on, and found none. I'm really bewildered as to why the addin would try to install itself over and over again. Does anyone know why this might be happening?

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