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• How to implement a syndication receiver? (multi-client / single server)

  - by LeonixSolutions

  I have to come up with a system architecture. A few hundred remote devices will be communicating over internet with a central server which will receive data and store it in a database. I could write my own TCP/IP based protocol use SOAP use AJAX use RSS anything else? This is currently seen as one way (telemetry, as opposed to SCADA). Would it make a difference if we make it bi-directional. There are no plans to do so, but Murphy's law makes me wary of a uni-directional solution (on the data plane; I imagine that the control plane is bi-directional in all solutions (?)). I hope that this is not too subjective. I would like a solution which is quick and easy to implement and for others to support and where the general "communications pipeline" from remote deceives to database server can be re-used as the core of future projects. I have a strong background in telecomms protocols, in C/C++ and PHP.

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• Differences between query using LINQ and IQueryable interface directly?

  - by JohnMetta

  Using Entity Framework 4, and given: ObjectSet<Thing> AllThings = Context.CreateObjectSet<Thing>; public IQueryable<Thing> ByNameA(String name) { IQueryable<Thing> query = from o in AllThings where o.Name == name select o; return query; } public IQueryable<Thing> ByNameB(String name) { return AllThings.Where((o) => o.Name == name); } Both return IQueryable< instances, and thus the query doesn't hit the server until something like ToList() is called, right? Is it purely readability that is the difference, or are the using fundamentally different technologies on the back-end?

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• Thread vs ThreadPool - .Net 2.0

  - by NLV

  Hello I'm not able to understand the difference between Thread vs ThreadPool. Consider i've to manipulate 50,000 records using threads. In case of threads i need to either predefine no of threads or no of records per threads. Either of them has to be constant. In case of threadpool we dont need to set any of them theoretically. But practically we need to assign the number of records per thread, because the no of threads may grow extremely large if the input no of records is huge. Any insights on this?

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• SMS war continues, ideas welcome

  - by Pavel Radzivilovsky

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

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• Chaning coding style due to Android GC performance, how far is too far?

  - by Benju

  I keep hearing that Android applications should try to limit the number of objects created in order to reduce the workload on the garbage collector. It makes sense that you may not want to created massive numbers of objects to track on a limited memory footprint, for example on a traditional server application created 100,000 objects within a few seconds would not be unheard of. The problem is how far should I take this? I've seen tons of examples of Android applications relying on static state in order supposedly "speed things up". Does increasing the number of instances that need to be garbage collected from dozens to hundreds really make that big of a difference? I can imagine changing my coding style to now created hundreds of thousands of objects like you might have on a full-blown Java-EE server but relying on a bunch of static state to (supposedly) reduce the number of objects to be garbage collected seems odd. How much is it really necessary to change your coding style in order to create performance Android apps?

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• Are there plans to make a non-programming general version of StackOverFlow like Yahoo Answer! [close

  - by RoboShop

  Firstly, I would like to say I think StackOverflow is a really great website, not just from a content perspective, but from a design perspective. The UI is designed in a way that makes it easy to use and the points are great incentives to be a productive part of the community. I was wondering, is there a part of the site, or maybe is there plans to make a new site, which is not programming driven. Like a general knowledge site but with StackOverflow as the engine. I use sites like Yahoo Answer! and they can be useful. But I think the main difference between Stack Overflow and Yahoo Answer is that Yahoo Answer encourages content indiscriminately, whereas Stack Overflow is disciplined enough that it only encourages content that are helpful or useful. I find it great that I can load up a question and the best answer pops up immediately, and the bad answers are voted down. Thanks

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• Auto-Implemented Properties c#

  - by user311130

  Hi all, could someone explain me what's the idea behind using Auto-Implemented Properties c#? public class Customer { public int ID { get; set; } public string Name { get; set; } } I get the motivation to use properties for private field, so we can determine how one can access a private field. But here - it's just like defining the field to be public from the first place. no? Is there a difference between defining a field to be "public const" or define it to have a get-only property ? Thanks Elad

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• Is it possible that __doPostBack() would ever send a GET request?

  - by Galilyou

  I'm having a problem with telerik RadGrid, I want to enable multiple row selection. I also want to go to the server whenever a row is selected or deselected. I created a javascript function to handle the Grid's client side events (OnRowSelected, and OnRowDeSelected). The functions look like this: function onOperationRowSelected(sender, eventArgs) { __doPostBack("<%=myControl.ClientID %>", "rowSelected:" + eventArgs.get_itemIndexHierarchical()); } The other function is very similar, the only difference is that it sends the string "rowDeselcted" instead of "rowSelected". On Page_Load I check to see if the request is a Post request using "IsPostBack" and if so, I check to see if it's a rowSelected or rowdeselected. My problem is when I select a first raw on my grid, a Post request happens (which is expected), however, when I select the second row, a GET request is issued, which (obviously) will result in IsPostBack returning false. What am I missing here?

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• Sharing a mex64 file across computers

  - by Shaihi

  I have a mex64 dll compiled on my machine. I used Matlab 2009b with VS2008 Pro to compile the dll. The dll works fine on my Matlab installation. I want a colleague to use the dll so I sent it to him and he gets the following error message when trying to use the dll: ??? Invalid MEX-file 'filename.mexw64': The specified module could not be found. My current assumption is that this is caused because he uses an older Matlab version or missing a dll that I have. I ran dependency checker and asked him to check that he has all the listed dlls. I am still waiting for him to confirm his Matlab version. What other reasons can cause this and can the Matlab version make a difference? (I mean R2009a when I have R2009B and not a huge version diff)

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• CouchDB Map/Reduce raises execption in reduce function?

  - by fuzzy lollipop

  my view generates keys in this format ["job_id:1234567890", 1271430291000] where the first key element is a unique key and the second is a timestamp in milliseconds. I run my view with this elapsed_time?startkey=["123"]&endkey=["123",{}]&group=true&group_level=1 and here is my reduce function, the intention is to reduce the output to get the earliest and latest timestamps and return the difference between them and now function(keys,values,rereduce) { var now = new Date().valueOf(); var first = Number.MIN_VALUE; var last = Number.MAX_VALUE; if (rereduce) { first = Math.max(first,values[0].first); last = Math.min(last,values[0].last); } else { first = keys[0][0][1]; last = keys[keys.length-1][0][1]; } return {first:now - first, last:now - last}; } and when processing a query it constantly raises the following execption: function raised exception (new TypeError("keys has no properties", "", 1)) I am making sure not to reference keys inside my rereduce block. Why does this function constantly raise this exception?

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• CSS dropdowns on touch-based clients. Are pure CSS dropdowns going to become extinct?

  - by Galen

  My company is starting to move toward adding the iPad as a browser i have to test my work on. This got me thinking... Since touch-based clients don't have a :hover state are pure CSS dropdowns going to go away? Then i thought even if you add some javascript to make the menus popup on click... What happens when the menu item (that expands to another menu) is also a link. How do you tell the difference between a click to see the menu or a click to go to that link?

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• How to make scipy.interpolate give a an extrapolated result beyond the input range?

  - by Salim Fadhley

  I'm trying to port a program which uses a hand-rolled interpolator (developed by a mathematitian colleage) over to use the interpolators provided by scipy. I'd like to use or wrap the scipy interpolator so that it has as close as possible behavior to the old interpolator. A key difference between the two functions is that in our original interpolator - if the input value is above or below the input range, our original interpolator will extrapolate the result. If you try this with the scipy interpolator it raises a ValueError. Consider this program as an example: import numpy as np from scipy import interpolate x = np.arange(0,10) y = np.exp(-x/3.0) f = interpolate.interp1d(x, y) print f(9) print f(11) # Causes ValueError, because it's greater than max(x) Is there a sensible way to make it so that instead of crashing, the final line will simply do a linear extrapolate, continuing the gradients defined by the first and last two pouints to infinity. Note, that in the real software I'm not actually using the exp function - that's here for illustration only!

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• Visual Studio 2005 - VC++ compiler C1001 on Windows 7

  - by Fritz H

  When I try to build a simple "Hello World" C++ app on Windows 7 Beta, using Visual Studio 2005 (VC++2005) I get a rather generic error C1001 error (Internal compiler error) The compiler seems to just crash, and Windows pops up its (un)helpful This program has stopped working dialog. The file it complains about is mcp1.cpp. Has anyone come across this before? Cheers, Fritz EDIT: The code is: #include <iostream> int main(int argc, char** argv) { std::cout << "Hello!"; return 0; } EDIT 2: I have installed SP1 as well as SP1 for Vista. VS popped up a warning saying it needs SP1 for Vista, but installing it makes no difference. No ideas about what I can possibly do to fix this?

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• Rails 4.2: "Assets should not be requested directly without their digests"

  - by Nowaker

  On Rails 4.2.0.beta1 I get an error: Assets should not be requested directly without their digests: Use the helpers in ActionView::Helpers to request fonts/source-sans-pro.woff The stylesheet: @font-face { font-family: 'Source Sans Pro'; font-style: normal; font-weight: 400; src: local('Source Sans Pro'), local('SourceSansPro-Regular'), url(/assets/source-sans-pro.woff) format('woff'); } The configuration is: config.serve_static_assets = true config.assets.js_compressor = :uglifier config.assets.compile = true config.assets.digest = true config.assets.version = '1.0' config.assets.paths << Rails.root.join('app', 'assets', 'fonts') config.assets.precompile += %w(.svg .eot .woff .ttf) Sure I can disable digests and it works again, but I'm interested in using them. Therefore, how do I make use of digests when I need to request source-sans-pro.woff? Please note that I place the fonts in assets/fonts directory, not the public/ directory. I don't see a difference between images and fonts, so I want to keep them under the same directory - app/assets.

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• is there a downside to putting N in front of strings in scripts? Is it considered a "best practice"?

  - by jcollum

  Let's say I have a table that has a varchar field. If I do an insert like this: INSERT MyTable SELECT N'the string goes here' Is there any fundamental difference between that and: INSERT MyTable SELECT 'the string goes here' My understanding was that you'd only have a problem if the string contained a Unicode character and the target column wasn't unicode. Other than that, SQL deals with it just fine and converts the string with the N'' into a varchar field (basically ignores the N). I was under the impression that N in front of strings was a good practice, but I'm unable to find any discussion of it that I'd consider definitive. Title may need improvement, feel free.

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• performance of parameterized queries for different db's

  - by tuinstoel

  A lot of people know that it is important to use parameterized queries to prevent sql injection attacks. Parameterized queries are also much faster in sqlite and oracle when doing online transaction processing because the query optimizer doesn't have to reparse every parameterized sql statement before executing. I've seen sqlite becoming 3 times faster when you use parameterized queries, oracle can become 10 times faster when you use parameterized queries in some extreme cases with a lot of concurrency. How about other db's like mysql, ms sql, db2 and postgresql? Is there an equal difference in performance between parameterized queries and literal queries?

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• Entity Framework How to specify paramter type in generated SQL (SQLServer 2005) Nvarchar vs Varchar

  - by Gratzy

  In entity framework I have an Entity 'Client' that was generated from a database. There is a property called 'Account' it is defined in the storage model as: <Property Name="Account" Type="char" Nullable="false" MaxLength="6" /> And in the Conceptual Model as: <Property Name="Account" Type="String" Nullable="false" /> When select statements are generated using a variable for Account i.e. where m.Account == myAccount... Entity Framework generates a paramaterized query with a paramater of type NVarchar(6). The problem is that the column in the table is data type of char(6). When this is executed there is a large performance hit because of the data type difference. Account is an index on the table and instead of using the index I believe an Index scan is done. Anyone know how to force EF to not use Unicode for the paramater and use Varchar(6) instead?

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• Adding WCF service reference adds DataContract types too

  - by Avi Shilon

  Hi everybody, I've used Visual Studio's Add Service Reference feature to add a service (actually it is a workflow service, created in WF4 RC1, but I don't think this makes any difference), and it also added the DataContracts that the service uses. At first this seemed fine, because All I've had in the DataContracts was simply properties, with no implementations. But now I've added code in the constructor of one data contracts that initializes creates an instance of one of the properties that exposes a list of other DCs, and when I've updated the service reference via VS (2010 RC1), the implementation was not updated. What should I do? Should I use my DCs instead of the ones created by VS or should I use the ones VS created? I've noticed that the properties in the VS-generated DCs contain some additional logic for checking equality in the setters and they also implement some interfaces too (like IExtensibleDataObject and INotifyPropertyChanged) which might get handy I guess in the future (I'm not knowledgeable at WCF). Thank you for your time folks, Avi

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• Do controls need to be defined in a web app or will .NET do it for you

  - by Chris

  I always thought that when you dropped a control onto an .aspx page that a declaration of that control ended up being generated for you (either in a designer file, or within your code behind). All of the apps I have worked on have worked this way. A coworker of mine was installing resharper and it was showing that all her code behind pages would not build. Turned out that resharper could not find a definition for any control that she has dropped onto her markup. She has no designer files, and no declarations in markup. Do they get automatically built when putting together the partial classes? Is there an option at that page/project level to instruct .NET to do this for you? Is this a difference between web app and web site? This is a a .NET 3.5 site, C#, and it is running in a production environment. Thanks in advance

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• SilverLight WebApp Calling Webservice in the same solution

  - by Ben

  Hi, I have a website solution that is composed of a SilverLight Project and an ASP Site that contains an asmx Webservice. The SilverLight project calls various methods in the Webservice, and this works fine on my home PC. When i publish the site (using 123-Reg if that makes a difference), it appears that the SilverLight app is no longer able to call the webservice. I have tried debugging the app by pointing my local version of the site to my published webservice and i get a "policy" issue. I know that 123 Reg have .Net 3.5 running on their servers, so i would assume that the site should "just work" when i publish it. Am i making a hugely stupid assumption there? Is there anything that i can do to change the "policies" within my app? Or is there another way around what i am trying to do ( i need to keep the webservice, as i want for it to be used from other places, and dont really want to duplicate code and create the same methods within the SilverLight project). Thanks

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• Ajax Post Request Returns JSON but Deferred Fails

  - by imrane

  I have a cross-domain POST request to http://api.local/user/auth - my API endpoint. I allow Cross Domain requests in my api with CORS. Using Chrome if that makes a difference. I get a valid server JSON response with 200 Status Code but I am using deferreds from a backbone model like so: @model.save() .fail(-> console.log 'sync fail') .success -> console.log 'sync OK' And I consistently get a 'sync fail' instead of the expected 'sync OK' Thoughts?

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• Returning IEnumerable<T> vs IQueryable<T>

  - by stackoverflowuser

  what is the difference between returning iqueryable vs ienumerable. IQueryable<Customer> custs = from c in db.Customers where c.City == "<City>" select c; IEnumerable<Customer> custs = from c in db.Customers where c.City == "<City>" select c; Will both be deferred execution? When should one be preferred over the other?

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• Fetch main model and translations in one query with globalize2

  - by J. Pablo Fernández

  Is there a way to fetch the model and the translations in one query when using globalize2? For example, having a model called Language which have two fields, code and name of which the second is translatable I do the following: en = Language.find_by_code("en") and it runs this query: SELECT SQL_NO_CACHE * FROM `languages` WHERE (`languages`.`code` = 'en') LIMIT 1 and when I do: en.name it runs: SELECT SQL_NO_CACHE * FROM `language_translations` WHERE (`language_translations`.language_id = 123 AND (`language_translations`.`locale` IN ('en','root'))) and if I do it again it'll re-run the query. Is there a way to fetch all the translated data in the first query? I've tried: en = Language.find_by_code("en", :joins => "JOIN language_translations ON language_translations.language_id = languages.id") but it made no difference. UPDATE: this is being discussed as an issue in globalize2: http://github.com/joshmh/globalize2/issues/#issue/33

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• Cursors vs Procedures in SQL

  - by CogitoErgoSum

  So, I just learned about CURSORS but still don't exactly grasp them. What is the difference between a cursor and procedure or even a function? So far from the various examples (DECLARE CURSOR ... SELECT ... FROM ...) It seems at most its a variable to hold a query. Is the data real time, or a snapshot of when the cursor was declared? i.e. I have a table with one row and one col with a value of 2. I do DECLARE CURSOR ... SELECT * FROM table1 I then insert a new row with a value of 3. When I run the cursor, would I Just get the one row from before the cursor was declared, or both rows? Thanks

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• Linux, how to capture screen, and simulate mouse movements.

  - by 2di

  Hi All I need to capture screen (as print screen) in the way so I can access pixel color data, to do some image recognition, after that I will need to generate mouse events on the screen such as left click, drag and drop (moving mouse while button is pressed, and then release it). Once its done, image will be deleted. Note: I need to capture whole screen everything that user can see, and I need to simulate clicks outside window of my program (if it makes any difference) Spec: Linux ubuntu Language: C++ Performance is not very important,"print screen" function will be executed once every ~10 sec. Duration of the process can be up to 24 hours so method needs to be stable and memory leaks free (as usuall :) I was able to do in windows with win GDI and some windows events, but I'ev no idea how to do it in Linux. Thanks a lot

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