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• Questions every good .NET developer should be able to answer?

  - by splattne

  My company is about to hire .NET developers. We work on a variety of .NET platforms: ASP.NET, Compact Framework, Windowsforms, Web Services. I'd like to compile a list/catalog of good questions, a kind of minimum standard to see if the applicants are experienced. So, my question is: What questions do you think should a good .NET programmer be able to respond? I'd also see it as a checklist for myself, in order to see where my own deficits are (there are many...). *UPDATE: It want to make clear that we're not testing only for .NET knowledge, and that problem solving capabilities and general programming skills are even more important to us.

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• How to improve INSERT INTO ... SELECT locking behavior

  - by Artem

  In our production database, we ran the following pseudo-code SQL batch query running every hour: INSERT INTO TemporaryTable (SELECT FROM HighlyContentiousTableInInnoDb WHERE allKindsOfComplexConditions are true) Now this query itself does not need to be fast, but I noticed it was locking up HighlyContentiousTableInInnoDb, even though it was just reading from it. Which was making some other very simple queries take ~25 seconds (that's how long that other query takes). Then I discovered that InnoDB tables in such a case are actually locked by a SELECT! http://www.mysqlperformanceblog.com/2006/07/12/insert-into-select-performance-with-innodb-tables/ But I don't really like the solution in the article of selecting into an OUTFILE, it seems like a hack (temporary files on filesystem seem sucky). Any other ideas? Is there a way to make a full copy of an InnoDB table without locking it in this way during the copy. Then I could just copy the HighlyContentiousTable to another table and do the query there.

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• What is the best approach towards styling GWT applications?

  - by Ashwin

  General approach in GWT is to use Panels and then apply custom CSS themes to get a customized look. While I can achieve a certain extent of personalization of my GWT app through CSS tinkering, I was wondering how others generally approach styling. Some of the suggestions I came across the web were to manage layout with plain HTML, through use of HTMLPanel's. This way one can straightaway use the HTML mock-up within the application without having to code all the layout. So what in your opinion is the best and least painful way to approach layout and custom styling of GWT application?

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• CakePHP dynamic element

  - by Logic Artist

  I am trying to create a message-board type element in a CakePHP app. This element will be displayed on all pages and views that use a particular layout. I want it to display all the messages in the model, then show the add form when a link is clicked, then return to the updated message list when submitted. All this without affecting the current view/page. I have my message model/controller/index set up, with a message board element that requests the index action. This works fine. However I am perplexed about how to return back to the original page/action from which the link was clicked. I can't use $this-referer() because that will link back to the add() action; what I want rather is to link to the page/view before that. Any general pointers on how to achieve something like this?

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• nHibernate multiple classes pointing to same table?

  - by Amitabh

  Is it a good idea to create a lighter version of an Entity in some cases just for performance reason pointing to same table but with fewer columns mapped. E.g If I have a Contact Table which has 50 Columns and in few of the related entities I might be interested in FirstName and LastName property is it a good idea to create a lightweight version of Contact table. E.g. public class LightContact { public int Id {get; set;} public string FirstName {get; set;} public string LastName {get; set;} } Also is it possible to map multiple classes to same table?

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• Min/Max across an array of objects

  - by graham.reeds

  It has been done to death pretty much, here on SO and around the 'Net. However I was wondering if there was a way to leverage the standard min/max functions of: Array.max = function(array) { return Math.max.apply(Math, array); }; Array.min = function(array) { return Math.min.apply(Math, array); }; So I can search across an array of objects of say: function Vector(x, y, z) { this.x = x; this.y = y; this.z = z; } var ArrayVector = [ /* lots of data */ ]; var min_x = ArrayVector.x.min(); // or var max_y = ArrayVector["y"].max(); Currently I have to loop through the array and compare the object values manually and craft each one to the particular need of the loop. A more general purpose way would be nice (if slightly slower).

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• ASP.NET Download All Files as Zip

  - by Ronnie Overby

  I have a folder on my web server that has hundreds of mp3 files in it. I would like to provide the option for a user to download a zipped archive of every mp3 in the directory from a web page. I want to compress the files programmatically only when needed. Because the zip file will be quite large, I am thinking that I will need to send the zip file to the response stream as it is being zipped, for performance reasons. Is this possible? How can I do it?

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• Trying to build automatic audio-conferencing capability into a WebApp

  - by Keller

  Hey all, I'm working with a team of relatively novice programmers, and we are trying to create a site that will have audio-conferencing capabilities such that whenever someone visits the page, they will immediately have audio-conferencing capabilities with everyone else on the page (5 people max). Can anyone point us in a general direction? Should we be looking into building a custom app, leveraging audio conferencing software, or trying to mimic a webex program? Would Adobe Stratus be useful in getting this kind of functionality? Does anyone have any ideas about how we would design something like this on a macro level? Sorry for the noobish question, but any guidance would be deeply appreciated. Thanks, Keller

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• Emulating HTTP POST via httpclient 3.x for multi options

  - by Frankie Ribery

  I want to emulate a HTTP POST using application/x-www-form-urlencoded encoding to send a option group that allows multiple selections. <select name="groups" multiple="multiple" size="4"> <option value="2">Administration</option> <option value="1">General</option> </select> Does adding 2 NameValuePairs (NVP) with the same name work ? My serverside log shows that only the first NVP was received. e.g PostMethod method = ...; NameValuePair[] nvpairs = { new NameValuePair( "groups", "2" ); new NameValuePair( "groups", "1" ); }; method.addParameter( nvpairs ); Only the groups=1 parameter was received. Thanks

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• C++ Win32 Unhandled Exception Handler

  - by uray

  currently I used SetUnhandledExceptionFilter() to provide callback to get information when an unhandled exception was occurred, that callback will provides me with EXCEPTION_RECORD which provides ExceptionAddress. [1]what is actually ExceptionAddress is? does it the address of function / code that gives exception, or the memory address that some function tried to access? [2]is there any better mechanism that could give me better information when unhandled exception occured? (I can't use debug mode or add any code that affect runtime performance, since crash is rare and only on release build when code run as fast as possible) [3]is there any way for me to get several callstack address when unhandled exception occured. [4]suppose ExceptionAddress has address A, and I have DLL X loaded and executed at base address A-x, and some other DLL Y at A+y, is it good to assume that crash was PROBABLY caused by code on DLL X?

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• Variable 'app' in url-pattern for servlet mapping

  - by Brian

  I'm learning Spring MVC (and servlets in general) and following springsource's mvc-ajax example, which uses annotated controller methods. It appears that there is only one url-pattern (in web.xml) mapped to a servlet in that example: /app/* I've deployed the app as a WAR file, and the actual, ugly URL I'm requesting is http://127.0.0.1:8080/org.springframework.samples.mvc.ajax-1.0.0-20100407.233245-1/account. So, it appears that 'app' in '/app/*' is a variable corresponding to 'org.springframework.samples.mvc.ajax-1.0.0-20100407.233245-1', however, it isn't universal because it isn't usable in my own app, and it contradicts my understanding that url-pattern contains the portion of the URL after the app name. So, what is 'app'? Where is it configured?

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• do I need to use partial?

  - by wiso

  I've a general function, for example (only a simplified example): def do_operation(operation, a, b, name): print name do_something_more(a,b,name, operation(a,b)) def operation_x(a,b): return a**2 + b def operation_y(a,b): return a**10 - b/2. and some data: data = {"first": {"name": "first summation", "a": 10, "b": 20, "operation": operation_x}, "second": {"name": "second summation", "a": 20, "b": 50, "operation": operation_y}, "third": {"name": "third summation", "a": 20, "b": 50, "operation": operation_x}, # <-- operation_x again } now I can do: what_to_do = ("first", "third") # this comes from command line for sum_id in what_to_do: do_operation(data["operation"], data["a"], data["b"], data["name"]) or maybe it's better if I use functools.partial? from functools import partial do_operation_one = do_operation(name=data["first"]["name"], operation=data["first"]["operation"], a=data["first"]["a"], b=data["first"]["b"]) do_operation_two = do_operation(name=data["second"]["name"], operation=data["second"]["operation"] a=data["second"]["a"], b=data["second"]["b"]) do_operation_three = do_operation(name=data["third"]["name"], operation=data["third"]["operation"] a=data["third"]["a"], b=data["third"]["b"]) do_dictionary = { "first": do_operation_one, "second": do_operation_two, "third": do_operation_three } for what in what_to_do: do_dictionary[what]()

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• Choosing between ExtJS and YUI based on application parameters.

  - by Kabeer

  Hello. I need help in taking call to choose between Ext JS and YUI libraries. Here are the key factors I have derived from my application requirements & development process: Complex, windows forms like controls Widgets, Layouts, Utilities Inter widget communication Easy to extend Easy to learn Intuitive & concise coding Strong exception handling Active support / community To update with upcoming technologies (HTML5, etc.) Skins & Themes to be easy to change Skins & Themes to support variety (a text box for different context to appear differently) Support & Utilities for standard protocols (XmlHttp, JSON) Good performance (responsive) Cost is not crucial, but I don't mind saving :)

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• Tomcat - virtualhosting - name / ip / port - based

  - by lisak

  Hey, what are the usage scenarios for these kinds of virtual hosting ? Name Based - typical tomcat virtual hosting, one HOME instance with many contexts, each as an individual host IP based / port based - multiple instances of tomcat ( how is it with performance and memory consuption?) running on IP aliases (virtual IPs) for one network adapter, usually behind http apache server that can run name based virtual hostings. Otherwise I can't figure out how would I forward requests in iptables/firewall based on IP address, which is just one. How is IP based virtual hosting done as to Tomcat and multiple instances ? I'd like to hear some usage scenarios from your experience. How are you running your applications. Cause there are applications having it's own modified classloader and they are developed in a way to run alone withing a tomcat instance. Then there are trivial applications which can run within one instance without problems. Many thanks

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• Are we asking too much of transactional memory?

  - by Carl Seleborg

  I've been reading up a lot about transactional memory lately. There is a bit of hype around TM, so a lot of people are enthusiastic about it, and it does provide solutions for painful problems with locking, but you regularly also see complaints: You can't do I/O You have to write your atomic sections so they can run several times (be careful with your local variables!) Software transactional memory offers poor performance [Insert your pet peeve here] I understand these concerns: more often than not, you find articles about STMs that only run on some particular hardware that supports some really nifty atomic operation (like LL/SC), or it has to be supported by some imaginary compiler, or it requires that all accesses to memory be transactional, it introduces type constraints monad-style, etc. And above all: these are real problems. This has lead me to ask myself: what speaks against local use of transactional memory as a replacement for locks? Would this already bring enough value, or must transactional memory be used all over the place if used at all?

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• [OpenGL] I'm having an issue to use GLshort for representing Vertex, and Normal.

  - by Xylopia

  As my project gets close to optimization stage, I notice that reducing Vertex Metadata could vastly improve the performance of 3D rendering. Eventually, I've dearly searched around and have found following advices from stackoverflow. Using GL_SHORT instead of GL_FLOAT in an OpenGL ES vertex array How do you represent a normal or texture coordinate using GLshorts? Advice on speeding up OpenGL ES 1.1 on the iPhone Simple experiments show that switching from "FLOAT" to "SHORT" for vertex and normal isn't tough, but what troubles me is when you're to scale back verticies to their original size (with glScalef), normals are multiplied by the reciprocal of the scale. Then how do you use "short" for both vertex and normal at the same time? I've been trying this and that for about a full day, but I could only go for "float vertex w/ byte normal" or "short vertex w/ float normal" so far. Your help would be truly appreciated.

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• Using one sqlconnection/sqlcommand through 2 DB-bound methods

  - by dotnetdev

  I have a class with a method which gets data from a database through a SELECT stored proc. This method uses a SqlDbReader by returning ExecuteReader() on a SqlCommand. The connection and everything is made in this method, with fields (such as connection string) set as class level fields. I now need to populate an array based on the results of this query (so the columns of each row will go into the array with its own index). However, this query will not select all of the data from one table which is involved. I can write the queries to get what I need, but how can I use one connection throughout the class? If I instantiate the connection object and call Open() in the constructor, I get an exception @ runtime. I'm hoping for something like this: // At class level: sqlconn.Open(); // sqlcommand set up Method() { // Fire stored proc // Insert results in a collection } Method2() { // Pass same collection in (use same one), // Add new row columns into same collection } How can I do this with strict performance in mind? Thanks

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• GPU YUV to RGB. Worth the effort?

  - by Jaime Pardos

  Hello, I have to convert several full PAL videos (720x576@25) from YUV 4:2:2 to RGB, in real time, and probably a custom resize for each. I have thought of using the GPU, as I have seen some example that does just this (except that it's 4:4:4 so the bpp is the same in source and destiny)-- http://www.fourcc.org/source/YUV420P-OpenGL-GLSLang.c However, I don't have any experience with using GPU's and I'm not sure of what can be done. The example, as I understand it, just converts the video frame to YUV and displays it in the screen. Is it possible to get the processed frame instead? Would it be worth the effort to send it to the GPU, get it transformed, and sending it again to main memory, or would it kill performance? Being a bit platform-specific, assuming I work on windows, is it possible to get an OpenGL or DirectDraw surface from a window so the GPU can draw directly to it?

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• Tables with no Primary Key

  - by Matt Hamilton

  I have several tables whose only unique data is a uniqueidentifier (a Guid) column. Because guids are non-sequential (and they're client-side generated so I can't use newsequentialid()), I have made a non-primary, non-clustered index on this ID field rather than giving the tables a clustered primary key. I'm wondering what the performance implications are for this approach. I've seen some people suggest that tables should have an auto-incrementing ("identity") int as a clustered primary key even if it doesn't have any meaning, as it means that the database engine itself can use that value to quickly look up a row instead of having to use a bookmark. My database is merge-replicated across a bunch of servers, so I've shied away from identity int columns as they're a bit hairy to get right in replication. What are your thoughts? Should tables have primary keys? Or is it ok to not have any clustered indexes if there are no sensible columns to index that way?

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• How to achieve a palette effect on iPhone using OpenGL

  - by Joe

  I'm porting a 2d retro game to iPhone that has the following properties: targets OpenGL ES 1.1 entire screen is filled with tiles (textured triangle strip tile textured using a single 256x256 RGBA texture image the texture is passed to OpenGL once at the start of the game only 4 displayed colours are used one of the displayed colours is black The original game flashed the screen when time starts to run out by toggling the black pixels to white using an indexed palette. What is the best (i.e. most efficient) way to achieve this in OpenGL ES 1.1? My thoughts so far: Generate an alternative texture with white instead of black pixels, and pass to OpenGL when the screen is flashing Render a white poly underneath the background and render the texture with alpha on to display it Try and render a poly on top with some blending that achieves the effect (not sure this is possible) I'm fairly new to OpenGL so I'm not sure what the performance drawbacks of each of these are, or if there's a better way of doing this.

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• Using Windows media foundation

  - by Martin Beckett

  Ok so my new gig is high performance video (think Google streetview but movies) - the hard work is all embedded capture and image processing but: I was looking at the new MS video offerings to display content = Windows Media Foundation. Is anyone actually using this ? There are no books on the topic. The only documentation is a developer team blog with a single entry 9 months old. I thought we had got past having to learn an MS api by spying on the com control messages! Is it just another wrapper around the same old activeX control?

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• Portable C++ library for IPC (processes and shared memory), Boost vs ACE vs Poco?

  - by user363778

  Hi, I need a portable C++ library for doing IPC. I used fork() and SysV shared memory until now but this limits me to Linux/Unix. I found out that there are 3 major C++ libraries that offer a portable solution (including Windows and Mac OS X). I really like Boost, and would like to use it but I need processes and it seems like that this is only an experimental branch until now!? I have never heard of ACE or POCO before and thus I am stuck I do not know which one to choose. I need fork(), sleep() (usleep() would be great) and shared memory of course. Performance and documentation are also important criteria. Thanks, for your Help!

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• How to SET ARITHABORT ON for connections in Linq To SQL

  - by Laurence

  By default, the SQL connection option ARITHABORT is OFF for OLEDB connections, which I assume Linq To SQL is using. However I need it to be ON. The reason is that my DB contains some indexed views, and any insert/update/delete operations against tables that are part of an indexed view fail if the connection does not have ARITHABORT ON. Even selects against the indexed view itself fail if the WITH(NOEXPAND) hint is used (which you have to use in SQL Standard Edition to get the performance benefit of the indexed view). Is there somewhere in the data context I can specify I want this option ON? Or somewhere in code I can do it?? I have managed a clumsy workaround, but I don't like it .... I have to create a stored procedure for every select/insert/update/delete operation, and in this proc first run SET ARITHABORT ON, then exec another proc which contains the actual select/insert/update/delete. In other words the first proc is just a wrapper for the second. It doesn't work to just put SET ARITHABORT ON above the select/insert/update/delete code.

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• Is it a good idea to create an STL iterator which is noncopyable?

  - by BillyONeal

  Most of the time, STL iterators are CopyConstructable, because several STL algorithms require this to improve performance, such as std::sort. However, I've been working on a pet project to wrap the FindXFile API (previously asked about), but the problem is it's impossible to implement a copyable iterator around this API. A find handle cannot be duplicated by any means -- DuplicateHandle specifically forbids passing handles to it. And if you just maintain a reference count to the find handle, then a single increment by any copy results in an increment of all copies -- clearly that is not what a copy constructed iterator is supposed to do. Since I can't satisfy the traditional copy constructible requirement for iterators here, is it even worth trying to create an "STL style" iterator? On one hand, creating some other enumeration method is going to not fall into normal STL conventions, but on the other, following STL conventions are going to confuse users of this iterator if they try to CopyConstruct it later. Which is the lesser of two evils?

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• Best way to store large dataset in SQL Server?

  - by gary

  I have a dataset which contains a string key field and up to 50 keywords associated with that information. Once the data has been inserted into the database there will be very few writes (INSERTS) but mostly queries for one or more keywords. I have read "Tagsystems: performance tests" which is MySQL based and it seems 2NF appears to be a good method for implementing this, however I was wondering if anyone had experience with doing this with SQL Server 2008 and very large datasets. I am likely to initially have 1 million key fields which could have up to 50 keywords each. Would a structure of keyfield, keyword1, keyword2, ... , keyword50 be the best solution or two tables keyid keyfield | 1 | | M keyid keyword Be a better idea if my queries are mostly going to be looking for results that have one or more keywords?

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