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  • What things to take into consideration when refactoring code?

    - by JustaPro
    Code refactoring is a "disciplined technique for restructuring an existing body of code, altering its internal structure without changing its external behavior" Could anyone explain this definition? I find it kind of blurry. Which is the best technique to do it? Are these the only ones? Which are the obstacles one would meet when refactoring code? What to take into consideration when switching between IDEs? Do tools which help refactoring exist? If yes, which one would you recommend using? Any references to links where I can find out more on this subject or to books that have been written are welcomed. The questions above are for any programming language, but specific examples are appreciated. Anything that would clarify this for me is.

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  • Does having a higher paid technical job mean you do not get to code any more?

    - by c_maker
    I work at a large company where technical people fall roughly in one of these categories: A developer on a scrum team who develops for a single product and maybe works with other teams that are closely related to the product. An architect who is more of a consultant on multiple teams (5-6) and tries to recognize commonalities between team efforts that could be abstracted into libraries (architects do not write the library code, however). This architect also attends many meetings with management and attempts to set technical direction. In my company the architect role is where most technical people move into as the next step in their career. My questions are: Do most companies work such a way that their highest paid technical people are far removed from writing code? Is this a natural tendency for a developer's career? Can a developer have it all (code AND set direction?)

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  • Action Script 3.0 datatype to match C++ iterator? (Code convertion)

    - by user919496
    I am developing a game with Action Script 3.0 using Starling Framework, converting it from C++ C++ Code : for (std::vector<MyObject*>::iterator i = m_listEnemy->begin();i!= m_listEnemy->end();) { (*i)->update(dt); if ( (*i)->m_Hp <=0 ) { (*i)->release(); i = m_listEnemy->erase(i); continue; } i++; } MyObject is the class. What Action Script 3.0 data type matches the C++ iterator? Also , how can I convert this C++ code to Action Script 3.0 code? Thanks in advance!

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  • Found a better solution to a problem at work - should I deter from posting the code snippet online?

    - by Calmarius
    I think most of us, programmers, used Stack Overflow to solve every day problems: looked for an efficient algorithm to do something. Now imagine a situation: you have a problem to solve. Googled a bit, found a StackOverflow question but you are not really satisfied with the answers so far. So you have to do your own research: you need to do it because you want it in the company's app. Eventually after some hours you have found the better solution. You're happy, you added it to the company's code base, then you want to submit your answer with a code snippet (just several lines) to the question you've found before to help others too. But wait: the company's software is closed source, and you worked on it on the clock. So does this mean I shouldn't post the answer neither at work nor at home to that question in the rest of my life, because I solved it at work, and the company owns that piece of code?

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  • C# code not take changes on server in asp.net MVC 4 ?

    - by Anirudha
    Originally posted on: http://geekswithblogs.net/anirugu/archive/2013/06/28/c-code-not-take-changes-on-server-in-asp.net-mvc.aspxToday I got a problem that When I make changes to My c# code and put them on FTP. The site still don’t take changes. I check the filesize of compile dll of my project in bin. Yes, File is uploaded but it’s not what my new code do.   If you ran into this problem Then I suggest you to delete old .pdb and .dll file of your project. for example your project namespace is xyz. delete the xyz.pdb and xyz.dll now upload your dll from bin to project bin on server. it will work

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  • Does low latency code sometimes have to be "ugly"?

    - by user997112
    (This is mainly aimed at those who have specific knowledge of low latency systems, to avoid people just answering with unsubstantiated opinions). Do you feel there is a trade-off between writing "nice" object orientated code and writing very fast low latency code? For instance, avoiding virtual functions in C++/the overhead of polymorphism etc- re-writing code which looks nasty, but is very fast etc? It stands to reason- who cares if it looks ugly (so long as its maintainable)- if you need speed, you need speed? I would be interested to hear from people who have worked in such areas.

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  • Recompiling an old fortran 2/4\66 program that was compiled for os\2 need it to run in dos

    - by Mike Hansen
    I am helping an old scientist with some problems and have 1 program that he found and modified about 20 yrs. ago, and runs fine as a 32 bit os\2 executable but i need it to run under dos! I am not a programmer but a good hardware & software man, so I'am pretty stupid about this problem, but here go's I have downloaded 6 different compilers watcom77,silverfrost ftn95,gfortran,2 versions of g77 and f80. Watcom says it is to old of program,find older compiler,silverfrost opens it,debugs, etc. but is changing all the subroutines from "real" to "complex" and vice-vesa,and the g77's seem to install perfectly (library links and etc.) but wont even compile the test.f programs.My problem is 1; to recompile "as is" or "upgrade" the code? PROGRAM xconvlv INTEGER N,N2,M PARAMETER (N=2048,N2=2048,M=128) INTEGER i,isign REAL data(n),respns(m),resp(n),ans(n2),t3(n),DUMMY OPEN(UNIT=1, FILE='C:\QKBAS20\FDATA1.DAT') DO 1 i=1,N READ(1,*) T3(i), data(i), DUMMY continue CLOSE(UNIT-1) do 12 i=1,N respns(i)=data(i) resp(i)=respns(i) continue isign=-1 call convlv(data,N,resp,M,isign,ans) OPEN(UNIT=1,FILE='C:\QKBAS20\FDATA9.DAT') DO 14 i=1,N WRITE(1,*) T3(i), ans(i) continue END SUBROUTINE CONVLV(data,n,respns,m,isign,ans) INTEGER isign,m,n,NMAX REAL data(n),respns(n) COMPLEX ans(n) PARAMETER (NMAX=4096) * uses realft, twofft INTEGER i,no2 COMPLEX fft (NMAX) do 11 i=1, (m-1)/2 respns(n+1-i)=respns(m+1-i) continue do 12 i=(m+3)/2,n-(m-1)/2 respns(i)=0.0 continue call twofft (data,respns,fft,ans,n) no2=n/2 do 13 i=1,no2+1 if (isign.eq.1) then ans(i)=fft(i)*ans(i)/no2 else if (isign.eq.-1) then if (abs(ans(i)) .eq.0.0) pause ans(i)=fft(i)/ans(i)/no2 else pause 'no meaning for isign in convlv' endif continue ans(1)=cmplx(real (ans(1)),real (ans(no2+1))) call realft(ans,n,-1) return END SUBROUTINE realft(data,n,isign) INTEGER isign,n REAL data(n) * uses four1 INTEGER i,i1,i2,i3,i4,n2p3 REAL c1,c2,hli,hir,h2i,h2r,wis,wrs DOUBLE PRECISION theta,wi,wpi,wpr,wr,wtemp theta=3.141592653589793d0/dble(n/2) cl=0.5 if (isign.eq.1) then c2=-0.5 call four1(data,n/2,+1) else c2=0.5 theta=-theta endif (etc.,etc., etc.) SUBROUTINE twofft(data,data2,fft1,fft2,n) INTEGER n REAL data1(n,data2(n) COMPLEX fft1(n), fft2(n) * uses four1 INTEGER j,n2 COMPLEX h1,h2,c1,c2 c1=cmplx(0.5,0.0) c2=cmplx(0.0,-0.5) do 11 j=1,n fft1(j)=cmplx(data1(j),data2(j) continue call four1 (fft1,n,1) fft2(1)=cmplx(aimag(fft1(1)),0.0) fft1(1)=cmplx(real(fft1(1)),0.0) n2=n+2 do 12 j=2,n/2+1 h1=c1*(fft1(j)+conjg(fft1(n2-j))) h2=c2*(fft1(j)-conjg(fft1(n2-j))) fft1(j)=h1 fft1(n2-j)=conjg(h1) fft2(j)=h2 fft2(n2-j)=conjg(h2) continue return END SUBROUTINE four1(data,nn,isign) INTEGER isign,nn REAL data(2*nn) INTEGER i,istep,j,m,mmax,n REAL tempi,tempr DOUBLE PRECISION theta, wi,wpi,wpr,wr,wtemp n=2*nn j=1 do 11 i=1,n,2 if(j.gt.i)then tempr=data(j) tempi=data(j+1) (etc.,etc.,etc.,) continue mmax=istep goto 2 endif return END There are 4 subroutines with this that are about 3 pages of code and whould be much easier to e-mail to someone if their able to help me with this.My e-mail is [email protected] , or if someone could tell me where to get a "working" compiler that could recompile this? THANK-YOU, THANK-YOU,and THANK-YOU for any help with this! The errors Iam getting are; 1.In a call to CONVLV from another procedure,the first argument was of a type REAL(kind=1), it is now a COMPLEX(kind=1) 2.In a call to REALFT from another procedure, ... COMPLEX(kind=1) it is now a REAL(kind=1) 3.In a call to TWOFFT from...COMPLEX(kind-1) it is now a REAL(kind=1) 4.In a previous call to FOUR1, the first argument was of a type REAL(kind=1) it is now a COMPLEX(kind=1).

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  • I've changed my URL schema. How do I tell Google to index the new schema and forget the old one?

    - by growse
    I had a site where the urls were constructed like this /index.php/Topic /index.php/AnotherTopic These were indexed in google, and search results returned that pointed to these. However, I've recently replatformed that site, and reconfigured it so the above urls would be: /index.php?title=Topic /index.php?title=AnotherTopic The original urls are returning 404s. The site is linking to the correct URL schema internally, but Google is retaining the original schema in its search results. I've updated and resubmitted the sitemap which only contains the new schema. Also, Google's webmasters tool is going slightly bananas at the fact there's now a spike in 404 errors in its crawl results. What would be the best approach to get Google to 'forget' about the old schema, and instead index the new schema? Should I try blocking /index.php/ in robots.txt? Should I be returning 301 codes instead of 404 for the original urls?

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  • JRuby wrong element type class java.lang.String(array contains char) related to JAVA_HOME

    - by Daryl
    I am on Ubuntu x64 bit running: java version "1.6.0_18" OpenJDK Runtime Environment (IcedTea6 1.8) (6b18-1.8-0ubuntu1) OpenJDK 64-Bit Server VM (build 14.0-b16, mixed mode) and jruby 1.4.0 (ruby 1.8.7 patchlevel 174) (2010-02-11 6586) (OpenJDK 64-Bit Server VM 1.6.0_18) [amd64-java] I have this code running on my Windows 7 computer at home. I recently copied over my whole folder over to Ubuntu, installed java, jruby, and associated gems but I get this error when I run my main file: jruby run.rb test =================Processing FREDERICKSBURG_1.1======================= ERROR IN TESTING wrong element type class java.lang.String(array contains char) /home/daryl/Desktop/work/Code/geografikos/lib/sentence_splitter/splitter.rb:21:in `to_java' /home/daryl/Desktop/work/Code/geografikos/lib/sentence_splitter/splitter.rb:21:in `split' /home/daryl/Desktop/work/Code/geografikos/lib/models/page.rb:103:in `sentences' /home/daryl/Desktop/work/Code/geografikos/lib/extractor/lingpipe_svm.rb:34:in `extract' /home/daryl/Desktop/work/Code/geografikos/lib/extractor/geo_controller.rb:9:in `process' /home/daryl/Desktop/work/Code/geografikos/lib/extractor/geo_controller.rb:8:in `each' /home/daryl/Desktop/work/Code/geografikos/lib/extractor/geo_controller.rb:8:in `process' /home/daryl/Desktop/work/Code/geografikos/lib/extractor/geo_controller.rb:6:in `each' /home/daryl/Desktop/work/Code/geografikos/lib/extractor/geo_controller.rb:6:in `process' /home/daryl/Desktop/work/Code/geografikos/lib/statistics.rb:111:in `generate_all' /home/daryl/Desktop/work/Code/geografikos/lib/statistics.rb:105:in `each' /home/daryl/Desktop/work/Code/geografikos/lib/statistics.rb:105:in `generate_all' run.rb:56 The focus of the error is: ERROR IN TESTING wrong element type class java.lang.String(array contains char) Everything works fine on my windows machine. I figured I was getting this error because I did not have JAVA_HOME set however I added this to bashrc as: export JAVA_HOME=/usr/lib/jvm/java-1.6.0-openjdk and have confirmed: echo $JAVA_HOME /usr/lib/jvm/java-1.6.0-openjdk I can produce a similar error by removing my JAVA_HOME variable on windows: =================Processing FREDERICKSBURG_1.3======================= ERROR IN TESTING cannot convert instance of class org.jruby.RubyString to char C:/work/Code/geografikos/lib/sentence_splitter/splitter.rb:21:in `to_java' C:/work/Code/geografikos/lib/sentence_splitter/splitter.rb:21:in `split' C:/work/Code/geografikos/lib/models/page.rb:103:in `sentences' C:/work/Code/geografikos/lib/extractor/lingpipe_svm.rb:34:in `extract' C:/work/Code/geografikos/lib/extractor/geo_controller.rb:9:in `process' C:/work/Code/geografikos/lib/extractor/geo_controller.rb:8:in `each' C:/work/Code/geografikos/lib/extractor/geo_controller.rb:8:in `process' C:/work/Code/geografikos/lib/extractor/geo_controller.rb:6:in `each' C:/work/Code/geografikos/lib/extractor/geo_controller.rb:6:in `process' C:/work/Code/geografikos/lib/statistics.rb:111:in `generate_all' C:/work/Code/geografikos/lib/statistics.rb:105:in `each' C:/work/Code/geografikos/lib/statistics.rb:105:in `generate_all' run.rb:56 It is obviously not exactly the same but I have a feeling this has to do with the java path. You can probably derive from the error that I am just trying to convert a ruby variable to java using to_java. This works fine on my windows machine and I have confirmed the gems are the same but I don't think this has to do with gems. I lied. I changed my JAVA_HOME back on my windows machine and this error still occurs. So now the code doesn't run on either machine. I recently installed git on my windows machine and added the code to a repository. But I haven't really done anything with it. All it said was it will convert all LF to CRLF...That shouldn't change anything though should it? Any ideas on why I am now getting these errors? I haven't changed anything on my windows machine in months except for installing git.

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  • How to use WINAPI from newer SDK but still using the old SDK in WindowsMobile.

    - by afriza
    Specifically, I want to use Point-to-point Message Queue but because I am still using legacy codes in eVC++ 4 and it only support until PocketPC 2003SE SDK, I cannot find CreateMsgQueue and friends in the headers (the port to newer VisualStudio is still in progess) I am using the Message Queue to do IPC with apps developed with WM-6.5-DTK (VS2005). Update: I am using the following code (taken from msgqueue.h) to store function pointers and load CoreDLL.dll using GetProcAddress() and LoadLibrary() respectively. HANDLE /*WINAPI*/ (*CreateMsgQueue)(LPCWSTR lpName, LPMSGQUEUEOPTIONS lpOptions); HANDLE /*WINAPI*/ (*OpenMsgQueue)(HANDLE hSrcProc, HANDLE hMsgQ , LPMSGQUEUEOPTIONS lpOptions); BOOL /*WINAPI*/ (*ReadMsgQueue)(HANDLE hMsgQ, /*__out_bcount(cbBufferSize)*/ LPVOID lpBuffer, DWORD cbBufferSize, LPDWORD lpNumberOfBytesRead, DWORD dwTimeout, DWORD *pdwFlags); BOOL /*WINAPI*/ (*WriteMsgQueue)(HANDLE hMsgQ, LPVOID lpBuffer, DWORD cbDataSize, DWORD dwTimeout, DWORD dwFlags); BOOL /*WINAPI*/ (*GetMsgQueueInfo)(HANDLE hMsgQ, LPMSGQUEUEINFO lpInfo); BOOL /*WINAPI*/ (*CloseMsgQueue)(HANDLE hMsgQ); Is the above code alright since I need to comment out WINAPI and __out_bcount(cbBufferSize) in order for them to compile.

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  • Which programming language is manageable by an 11 year old kid?

    - by tangens
    Possible Duplicates: What is the easiest language to start with? What are some recommended programming resources for pre-teens? My son is 11 years old and he would like to learn a programming language. Of course his primary goal is to develop some (simple) games. Do you know of a programming language that is suitable for this situation? Summary of languages recommended in the answers Snake Wrangling for Kids (answer) Scratch (answer) Small Basic (answer) (answer) Logo NXT-G for Lego Mindstorms (answer) Alice (answer) BlueJ (answer) Squeak Smalltalk (answer) (answer) (answer) Blender Game Engine (answer) PyGame (answer) (answer) (answer) Inform (answer) Phrogram (answer) Dr Scheme (answer) eToys (answer) runrev (answer) Karel Programming (answer) Hackety Hack (answer) Visual Basic (answer) (answer) Learn to Program (answer) QBasic (answer) (answer) Visual Basic Express (answer) Processing (answer) C# (answer) JavaScript (answer) (answer) Ruby (answer) ToonTalk (answer) Flash and ActionScript (answer) StarLogo (answer) Java (answer) Kodu (answer) XNA (answer) (answer) unity3D (answer) BlitzBasic (answer)(answer) Lua (answer)

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  • Ruby DEPRECATION WARNING: You are using the old router DSL which will be removed in Rails 3.1.

    - by user297221
    Hi guys. I am using rails 3 and at the moment i am writing tests for my application. I get this weird deprecation warning: DEPRECATION WARNING: You are using the old router DSL which will be removed in Rails 3.1. Please check how to update your routes file at: http://www.engineyard.com/blog/2010/the-lowdown-on-routes-in-rails-3/. (called from at /Users/jeljer/Dropbox/webCMS/config/environment.rb:6) Of course my routes file is this: WebCMS::Application.routes.draw do #... end but no luck. If I look at the place what it is pointing to in my enviroment.rb: WebCMS::Application.initialize! I did a gem cleanup without any luck. Does anybody have an idea? ps. i am using rvm with ruby 1.9.2

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  • Any serious problems when making an old java web app run on new IE 8 browser?

    - by pinichi
    I need make an quick estimation on project (not sure we got): It's an old banking CMS java web app: Server: jdk5, weblogic 9. Client: winXP, Ie6. It was design only for use with ie6 but now we need make it also run well on new client: ie8,ie7 on win7. I understand the most difference is the client: DOM and CSS. But my problem is we hasn't been worked with ie8, and I have not enough time to build an testing environment because our developing environment is not ready to make test (its remoting completely, and managed by another partner) Any experience or suggestion to help me weighing this task need will be welcomed.

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  • Want to improve my simple site/db backup script with auto removal of old backups.

    - by Robert Robb
    I have the following simple script for backing up my website files and db. The script is run each day via a cron job. #!/bin/sh NOW=$(date +"%Y-%m-%d") mysqldump --opt -h localhost -u username -p'password' dbname > /path/to/folder/backup/db-backup-$NOW.sql gzip -f /path/to/folder/backup/db-backup-$NOW.sql tar czf /path/to/folder/backup/web-backup-$NOW.tgz /path/to/folder/web/content/ It works great, but I don't want loads of old backups clogging my system. How can I modify the script to remove any backups older than a week when the script is run?

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  • Old Sony Digital Tape Handycam, imported Video is sped up?

    - by thatryan
    Friend gave me their OLD handycam and a bunch of tapes asking me to put them on a DVD. The model is Sony DCR-TVR103 and it records onto Hi8 Digital tapes. It has a firewire port also. I am trying to use import function in iMovie on OS X 10.6. Every import though the video is super fast, like playing in fast forward. Ever seen anything like this? How can I import this video? Thank you.

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  • How can I force a major upgrade to not switch to maintenance mode using the old installation package

    - by Brian
    I have an installer that I would like to use for a major upgrade. I have done the following: Increased the version number (from a.b.c to a.b.c+1) Changed the ProductCode Kept the same UpgradeCode Made the appropriate entry in the Upgrade table Changed the component ID of an existing component Changed the name of the installer package Changed the PackageCode Basically I've done everything I can think of to force MSI to treat this as a major upgrade. However, when I attempt to install this new package, the installer log says "Product registered: entering maintenance mode" and proceeds to try to find the old installer file (which fails, since the new installer is in a different folder than was used for the original installation, and wasn't even what I wanted to happen). What am I missing? Why does the installer switch to maintenance mode right away rather than perform the major upgrade? Thanks!

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  • How to keep an old VB6 application running in Windows Vista and Windows 7?

    - by MusiGenesis
    I have an old VB6 app which I'm still trying to support. A few users have reported weird crashes when running the app in Vista or Windows 7. The log files don't show anything after one of these crashes, but the customers report that the error message said "OLE something ...", if they saw anything at all. I've never been able to reproduce these crashes while running the program on my own Vista or Windows 7 boxes, so I have essentially no information on what the problem is. My suspicion is that it's a problem with their versions of one or more of the umpteen billion DLLs that a VB6 application is dependent on. The app also uses lame_enc.dll, which introduces a few more dependencies. I'm guessing this is a common problem with VB6 apps (although it's possible that I just sucked as a programmer 10 years ago). Is there some magical installer/updater out there that makes sure all the VB6 dependencies are what they need to be for a VB6 app to function properly?

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  • Skype Mac API - Use AppleScript or 5 year old API?

    - by Andrew
    I have a x86_64 app that I would like to have optionally read Skype status messages. However, the 5 year old skype mac framework is 32-bit, and if there is a way to have that compile within a 64-bit app, I haven't found it. My question is, basically, how should I go about doing this? I really only need to get and set the USERSTATUS AWAY/ONLINE string. Using AppleScript, a "Should Skype allow this" dialog pops up... every time. This is highly inefficient and downright irritating. Advice? I'm considering writing a 32-bit CLI wrapper, but that seems like overkill.

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  • AnkhSVN - How to remove old URLs from list of URLs in the "Open from Subversion" dialog box

    - by user2942597
    I work for a small company and am the sole developer using AnkhSVN to version my code. For the server side I am using VisualSVN v2.5.8. The server is installed on my own machine (on a different drive). I have a few repositories that I created about two years ago that have been working fine. We recently completed an Active Directory Domain Rename (that's another story) so the FQDN of my machine changed so the domain portion is no longer the same as what it was when the server portion was installed. I managed to get AnkhSVN to connect to the repositories so everything is working again but the URL list that comes up on the "Open from Subversion" dialog box still has all the old URLs. How can I remove them? I've searched everywhere I can think of looking for this list but can't seem to find it anywhere. Any suggestions would be greatly appreciated. Chuck R.

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  • What to beware of reading old Numarray tutorials and examples?

    - by DarenW
    Python currently uses Numpy for heavy duty math and image processing. The earlier Numeric and Numarray are obsolete, but still today there are many tutorials, notes, sample code and other documentation using them. Some of these cover special topics of interest, some are well written but haven't been updated or replaced, or are otherwise of use. Quite a bit is the same between Numeric, Numarray and Numpy, so I usually get good mileage out these older docs. Ocassionaly, though, I run into a line of code that results in error. Not often enough to remember how to get around it, but usually I figure it out at the cost of some time. What are the main things to watch out for when relying on such older documentation for current Numpy use? Is there a list of how to translate the differences that exist?

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  • How to install the new apk file without uninstall the old apk file on an Android device?

    - by naresh
    My apk file size is 2MB. First time installing the apk file in the device there is no problem. Suppose some changes in the application after that generated the new apk file. I am try to install the new apk file in the same device then it shows some message first uninstall the previous one(i.e. , same application) in the device. But small apk files, I am not facing this problem. Is it possible to install the new apk file without uninstall the old one?

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  • how to verify that an old session is really destroyed?

    - by jodeci
    Um, this might sound a bit weird. We were having some problems with a specific browser under a very specific condition, and finally narrowed down the problem to the fact that we were not properly destroying the old sessions after doing session_regenerate_id(). I believe I have solved this problem by doing session_regenerate_id(true) now, but how does one verify that the previous sessions really do not exist any more? Someone suggested cURL but I cannot find my way around their docs. Sadly(?) the boss does not take 'it just works' for an answer so I'd really appreciate any advice!

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  • Removing rows from MySQL table where the timestamp is over one day old?

    - by Rob
    I found the exact same question here. But it isn't working for me. I've modified it a bit, manipulated it, and I can't figure it out. I'm trying to remove rows that are over a day old. Here is my code: if (isset($_POST['prune'])) { $sql = "DELETE FROM logs WHERE time < date('now', '-1 days')"; mysql_query($sql); echo 'Logs older than one day removed.'; } Fairly simple question I suppose, but its bugging the hell out of me. I would appreciate any help. In case it makes a difference, the column is a TIMESTAMP type.

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  • The dynamic Type in C# Simplifies COM Member Access from Visual FoxPro

    - by Rick Strahl
    I’ve written quite a bit about Visual FoxPro interoperating with .NET in the past both for ASP.NET interacting with Visual FoxPro COM objects as well as Visual FoxPro calling into .NET code via COM Interop. COM Interop with Visual FoxPro has a number of problems but one of them at least got a lot easier with the introduction of dynamic type support in .NET. One of the biggest problems with COM interop has been that it’s been really difficult to pass dynamic objects from FoxPro to .NET and get them properly typed. The only way that any strong typing can occur in .NET for FoxPro components is via COM type library exports of Visual FoxPro components. Due to limitations in Visual FoxPro’s type library support as well as the dynamic nature of the Visual FoxPro language where few things are or can be described in the form of a COM type library, a lot of useful interaction between FoxPro and .NET required the use of messy Reflection code in .NET. Reflection is .NET’s base interface to runtime type discovery and dynamic execution of code without requiring strong typing. In FoxPro terms it’s similar to EVALUATE() functionality albeit with a much more complex API and corresponiding syntax. The Reflection APIs are fairly powerful, but they are rather awkward to use and require a lot of code. Even with the creation of wrapper utility classes for common EVAL() style Reflection functionality dynamically access COM objects passed to .NET often is pretty tedious and ugly. Let’s look at a simple example. In the following code I use some FoxPro code to dynamically create an object in code and then pass this object to .NET. An alternative to this might also be to create a new object on the fly by using SCATTER NAME on a database record. How the object is created is inconsequential, other than the fact that it’s not defined as a COM object – it’s a pure FoxPro object that is passed to .NET. Here’s the code: *** Create .NET COM InstanceloNet = CREATEOBJECT('DotNetCom.DotNetComPublisher') *** Create a Customer Object Instance (factory method) loCustomer = GetCustomer() loCustomer.Name = "Rick Strahl" loCustomer.Company = "West Wind Technologies" loCustomer.creditLimit = 9999999999.99 loCustomer.Address.StreetAddress = "32 Kaiea Place" loCustomer.Address.Phone = "808 579-8342" loCustomer.Address.Email = "[email protected]" *** Pass Fox Object and echo back values ? loNet.PassRecordObject(loObject) RETURN FUNCTION GetCustomer LOCAL loCustomer, loAddress loCustomer = CREATEOBJECT("EMPTY") ADDPROPERTY(loCustomer,"Name","") ADDPROPERTY(loCustomer,"Company","") ADDPROPERTY(loCUstomer,"CreditLimit",0.00) ADDPROPERTY(loCustomer,"Entered",DATETIME()) loAddress = CREATEOBJECT("Empty") ADDPROPERTY(loAddress,"StreetAddress","") ADDPROPERTY(loAddress,"Phone","") ADDPROPERTY(loAddress,"Email","") ADDPROPERTY(loCustomer,"Address",loAddress) RETURN loCustomer ENDFUNC Now prior to .NET 4.0 you’d have to access this object passed to .NET via Reflection and the method code to do this would looks something like this in the .NET component: public string PassRecordObject(object FoxObject) { // *** using raw Reflection string Company = (string) FoxObject.GetType().InvokeMember( "Company", BindingFlags.GetProperty,null, FoxObject,null); // using the easier ComUtils wrappers string Name = (string) ComUtils.GetProperty(FoxObject,"Name"); // Getting Address object – then getting child properties object Address = ComUtils.GetProperty(FoxObject,"Address");    string Street = (string) ComUtils.GetProperty(FoxObject,"StreetAddress"); // using ComUtils 'Ex' functions you can use . Syntax     string StreetAddress = (string) ComUtils.GetPropertyEx(FoxObject,"AddressStreetAddress"); return Name + Environment.NewLine + Company + Environment.NewLine + StreetAddress + Environment.NewLine + " FOX"; } Note that the FoxObject is passed in as type object which has no specific type. Since the object doesn’t exist in .NET as a type signature the object is passed without any specific type information as plain non-descript object. To retrieve a property the Reflection APIs like Type.InvokeMember or Type.GetProperty().GetValue() etc. need to be used. I made this code a little simpler by using the Reflection Wrappers I mentioned earlier but even with those ComUtils calls the code is pretty ugly requiring passing the objects for each call and casting each element. Using .NET 4.0 Dynamic Typing makes this Code a lot cleaner Enter .NET 4.0 and the dynamic type. Replacing the input parameter to the .NET method from type object to dynamic makes the code to access the FoxPro component inside of .NET much more natural: public string PassRecordObjectDynamic(dynamic FoxObject) { // *** using raw Reflection string Company = FoxObject.Company; // *** using the easier ComUtils class string Name = FoxObject.Name; // *** using ComUtils 'ex' functions to use . Syntax string Address = FoxObject.Address.StreetAddress; return Name + Environment.NewLine + Company + Environment.NewLine + Address + Environment.NewLine + " FOX"; } As you can see the parameter is of type dynamic which as the name implies performs Reflection lookups and evaluation on the fly so all the Reflection code in the last example goes away. The code can use regular object ‘.’ syntax to reference each of the members of the object. You can access properties and call methods this way using natural object language. Also note that all the type casts that were required in the Reflection code go away – dynamic types like var can infer the type to cast to based on the target assignment. As long as the type can be inferred by the compiler at compile time (ie. the left side of the expression is strongly typed) no explicit casts are required. Note that although you get to use plain object syntax in the code above you don’t get Intellisense in Visual Studio because the type is dynamic and thus has no hard type definition in .NET . The above example calls a .NET Component from VFP, but it also works the other way around. Another frequent scenario is an .NET code calling into a FoxPro COM object that returns a dynamic result. Assume you have a FoxPro COM object returns a FoxPro Cursor Record as an object: DEFINE CLASS FoxData AS SESSION OlePublic cAppStartPath = "" FUNCTION INIT THIS.cAppStartPath = ADDBS( JustPath(Application.ServerName) ) SET PATH TO ( THIS.cAppStartpath ) ENDFUNC FUNCTION GetRecord(lnPk) LOCAL loCustomer SELECT * FROM tt_Cust WHERE pk = lnPk ; INTO CURSOR TCustomer IF _TALLY < 1 RETURN NULL ENDIF SCATTER NAME loCustomer MEMO RETURN loCustomer ENDFUNC ENDDEFINE If you call this from a .NET application you can now retrieve this data via COM Interop and cast the result as dynamic to simplify the data access of the dynamic FoxPro type that was created on the fly: int pk = 0; int.TryParse(Request.QueryString["id"],out pk); // Create Fox COM Object with Com Callable Wrapper FoxData foxData = new FoxData(); dynamic foxRecord = foxData.GetRecord(pk); string company = foxRecord.Company; DateTime entered = foxRecord.Entered; This code looks simple and natural as it should be – heck you could write code like this in days long gone by in scripting languages like ASP classic for example. Compared to the Reflection code that previously was necessary to run similar code this is much easier to write, understand and maintain. For COM interop and Visual FoxPro operation dynamic type support in .NET 4.0 is a huge improvement and certainly makes it much easier to deal with FoxPro code that calls into .NET. Regardless of whether you’re using COM for calling Visual FoxPro objects from .NET (ASP.NET calling a COM component and getting a dynamic result returned) or whether FoxPro code is calling into a .NET COM component from a FoxPro desktop application. At one point or another FoxPro likely ends up passing complex dynamic data to .NET and for this the dynamic typing makes coding much cleaner and more readable without having to create custom Reflection wrappers. As a bonus the dynamic runtime that underlies the dynamic type is fairly efficient in terms of making Reflection calls especially if members are repeatedly accessed. © Rick Strahl, West Wind Technologies, 2005-2010Posted in COM  FoxPro  .NET  CSharp  

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  • How to find and fix performance problems in ORM powered applications

    - by FransBouma
    Once in a while we get requests about how to fix performance problems with our framework. As it comes down to following the same steps and looking into the same things every single time, I decided to write a blogpost about it instead, so more people can learn from this and solve performance problems in their O/R mapper powered applications. In some parts it's focused on LLBLGen Pro but it's also usable for other O/R mapping frameworks, as the vast majority of performance problems in O/R mapper powered applications are not specific for a certain O/R mapper framework. Too often, the developer looks at the wrong part of the application, trying to fix what isn't a problem in that part, and getting frustrated that 'things are so slow with <insert your favorite framework X here>'. I'm in the O/R mapper business for a long time now (almost 10 years, full time) and as it's a small world, we O/R mapper developers know almost all tricks to pull off by now: we all know what to do to make task ABC faster and what compromises (because there are almost always compromises) to deal with if we decide to make ABC faster that way. Some O/R mapper frameworks are faster in X, others in Y, but you can be sure the difference is mainly a result of a compromise some developers are willing to deal with and others aren't. That's why the O/R mapper frameworks on the market today are different in many ways, even though they all fetch and save entities from and to a database. I'm not suggesting there's no room for improvement in today's O/R mapper frameworks, there always is, but it's not a matter of 'the slowness of the application is caused by the O/R mapper' anymore. Perhaps query generation can be optimized a bit here, row materialization can be optimized a bit there, but it's mainly coming down to milliseconds. Still worth it if you're a framework developer, but it's not much compared to the time spend inside databases and in user code: if a complete fetch takes 40ms or 50ms (from call to entity object collection), it won't make a difference for your application as that 10ms difference won't be noticed. That's why it's very important to find the real locations of the problems so developers can fix them properly and don't get frustrated because their quest to get a fast, performing application failed. Performance tuning basics and rules Finding and fixing performance problems in any application is a strict procedure with four prescribed steps: isolate, analyze, interpret and fix, in that order. It's key that you don't skip a step nor make assumptions: these steps help you find the reason of a problem which seems to be there, and how to fix it or leave it as-is. Skipping a step, or when you assume things will be bad/slow without doing analysis will lead to the path of premature optimization and won't actually solve your problems, only create new ones. The most important rule of finding and fixing performance problems in software is that you have to understand what 'performance problem' actually means. Most developers will say "when a piece of software / code is slow, you have a performance problem". But is that actually the case? If I write a Linq query which will aggregate, group and sort 5 million rows from several tables to produce a resultset of 10 rows, it might take more than a couple of milliseconds before that resultset is ready to be consumed by other logic. If I solely look at the Linq query, the code consuming the resultset of the 10 rows and then look at the time it takes to complete the whole procedure, it will appear to me to be slow: all that time taken to produce and consume 10 rows? But if you look closer, if you analyze and interpret the situation, you'll see it does a tremendous amount of work, and in that light it might even be extremely fast. With every performance problem you encounter, always do realize that what you're trying to solve is perhaps not a technical problem at all, but a perception problem. The second most important rule you have to understand is based on the old saying "Penny wise, Pound Foolish": the part which takes e.g. 5% of the total time T for a given task isn't worth optimizing if you have another part which takes a much larger part of the total time T for that same given task. Optimizing parts which are relatively insignificant for the total time taken is not going to bring you better results overall, even if you totally optimize that part away. This is the core reason why analysis of the complete set of application parts which participate in a given task is key to being successful in solving performance problems: No analysis -> no problem -> no solution. One warning up front: hunting for performance will always include making compromises. Fast software can be made maintainable, but if you want to squeeze as much performance out of your software, you will inevitably be faced with the dilemma of compromising one or more from the group {readability, maintainability, features} for the extra performance you think you'll gain. It's then up to you to decide whether it's worth it. In almost all cases it's not. The reason for this is simple: the vast majority of performance problems can be solved by implementing the proper algorithms, the ones with proven Big O-characteristics so you know the performance you'll get plus you know the algorithm will work. The time taken by the algorithm implementing code is inevitable: you already implemented the best algorithm. You might find some optimizations on the technical level but in general these are minor. Let's look at the four steps to see how they guide us through the quest to find and fix performance problems. Isolate The first thing you need to do is to isolate the areas in your application which are assumed to be slow. For example, if your application is a web application and a given page is taking several seconds or even minutes to load, it's a good candidate to check out. It's important to start with the isolate step because it allows you to focus on a single code path per area with a clear begin and end and ignore the rest. The rest of the steps are taken per identified problematic area. Keep in mind that isolation focuses on tasks in an application, not code snippets. A task is something that's started in your application by either another task or the user, or another program, and has a beginning and an end. You can see a task as a piece of functionality offered by your application.  Analyze Once you've determined the problem areas, you have to perform analysis on the code paths of each area, to see where the performance problems occur and which areas are not the problem. This is a multi-layered effort: an application which uses an O/R mapper typically consists of multiple parts: there's likely some kind of interface (web, webservice, windows etc.), a part which controls the interface and business logic, the O/R mapper part and the RDBMS, all connected with either a network or inter-process connections provided by the OS or other means. Each of these parts, including the connectivity plumbing, eat up a part of the total time it takes to complete a task, e.g. load a webpage with all orders of a given customer X. To understand which parts participate in the task / area we're investigating and how much they contribute to the total time taken to complete the task, analysis of each participating task is essential. Start with the code you wrote which starts the task, analyze the code and track the path it follows through your application. What does the code do along the way, verify whether it's correct or not. Analyze whether you have implemented the right algorithms in your code for this particular area. Remember we're looking at one area at a time, which means we're ignoring all other code paths, just the code path of the current problematic area, from begin to end and back. Don't dig in and start optimizing at the code level just yet. We're just analyzing. If your analysis reveals big architectural stupidity, it's perhaps a good idea to rethink the architecture at this point. For the rest, we're analyzing which means we collect data about what could be wrong, for each participating part of the complete application. Reviewing the code you wrote is a good tool to get deeper understanding of what is going on for a given task but ultimately it lacks precision and overview what really happens: humans aren't good code interpreters, computers are. We therefore need to utilize tools to get deeper understanding about which parts contribute how much time to the total task, triggered by which other parts and for example how many times are they called. There are two different kind of tools which are necessary: .NET profilers and O/R mapper / RDBMS profilers. .NET profiling .NET profilers (e.g. dotTrace by JetBrains or Ants by Red Gate software) show exactly which pieces of code are called, how many times they're called, and the time it took to run that piece of code, at the method level and sometimes even at the line level. The .NET profilers are essential tools for understanding whether the time taken to complete a given task / area in your application is consumed by .NET code, where exactly in your code, the path to that code, how many times that code was called by other code and thus reveals where hotspots are located: the areas where a solution can be found. Importantly, they also reveal which areas can be left alone: remember our penny wise pound foolish saying: if a profiler reveals that a group of methods are fast, or don't contribute much to the total time taken for a given task, ignore them. Even if the code in them is perhaps complex and looks like a candidate for optimization: you can work all day on that, it won't matter.  As we're focusing on a single area of the application, it's best to start profiling right before you actually activate the task/area. Most .NET profilers support this by starting the application without starting the profiling procedure just yet. You navigate to the particular part which is slow, start profiling in the profiler, in your application you perform the actions which are considered slow, and afterwards you get a snapshot in the profiler. The snapshot contains the data collected by the profiler during the slow action, so most data is produced by code in the area to investigate. This is important, because it allows you to stay focused on a single area. O/R mapper and RDBMS profiling .NET profilers give you a good insight in the .NET side of things, but not in the RDBMS side of the application. As this article is about O/R mapper powered applications, we're also looking at databases, and the software making it possible to consume the database in your application: the O/R mapper. To understand which parts of the O/R mapper and database participate how much to the total time taken for task T, we need different tools. There are two kind of tools focusing on O/R mappers and database performance profiling: O/R mapper profilers and RDBMS profilers. For O/R mapper profilers, you can look at LLBLGen Prof by hibernating rhinos or the Linq to Sql/LLBLGen Pro profiler by Huagati. Hibernating rhinos also have profilers for other O/R mappers like NHibernate (NHProf) and Entity Framework (EFProf) and work the same as LLBLGen Prof. For RDBMS profilers, you have to look whether the RDBMS vendor has a profiler. For example for SQL Server, the profiler is shipped with SQL Server, for Oracle it's build into the RDBMS, however there are also 3rd party tools. Which tool you're using isn't really important, what's important is that you get insight in which queries are executed during the task / area we're currently focused on and how long they took. Here, the O/R mapper profilers have an advantage as they collect the time it took to execute the query from the application's perspective so they also collect the time it took to transport data across the network. This is important because a query which returns a massive resultset or a resultset with large blob/clob/ntext/image fields takes more time to get transported across the network than a small resultset and a database profiler doesn't take this into account most of the time. Another tool to use in this case, which is more low level and not all O/R mappers support it (though LLBLGen Pro and NHibernate as well do) is tracing: most O/R mappers offer some form of tracing or logging system which you can use to collect the SQL generated and executed and often also other activity behind the scenes. While tracing can produce a tremendous amount of data in some cases, it also gives insight in what's going on. Interpret After we've completed the analysis step it's time to look at the data we've collected. We've done code reviews to see whether we've done anything stupid and which parts actually take place and if the proper algorithms have been implemented. We've done .NET profiling to see which parts are choke points and how much time they contribute to the total time taken to complete the task we're investigating. We've performed O/R mapper profiling and RDBMS profiling to see which queries were executed during the task, how many queries were generated and executed and how long they took to complete, including network transportation. All this data reveals two things: which parts are big contributors to the total time taken and which parts are irrelevant. Both aspects are very important. The parts which are irrelevant (i.e. don't contribute significantly to the total time taken) can be ignored from now on, we won't look at them. The parts which contribute a lot to the total time taken are important to look at. We now have to first look at the .NET profiler results, to see whether the time taken is consumed in our own code, in .NET framework code, in the O/R mapper itself or somewhere else. For example if most of the time is consumed by DbCommand.ExecuteReader, the time it took to complete the task is depending on the time the data is fetched from the database. If there was just 1 query executed, according to tracing or O/R mapper profilers / RDBMS profilers, check whether that query is optimal, uses indexes or has to deal with a lot of data. Interpret means that you follow the path from begin to end through the data collected and determine where, along the path, the most time is contributed. It also means that you have to check whether this was expected or is totally unexpected. My previous example of the 10 row resultset of a query which groups millions of rows will likely reveal that a long time is spend inside the database and almost no time is spend in the .NET code, meaning the RDBMS part contributes the most to the total time taken, the rest is compared to that time, irrelevant. Considering the vastness of the source data set, it's expected this will take some time. However, does it need tweaking? Perhaps all possible tweaks are already in place. In the interpret step you then have to decide that further action in this area is necessary or not, based on what the analysis results show: if the analysis results were unexpected and in the area where the most time is contributed to the total time taken is room for improvement, action should be taken. If not, you can only accept the situation and move on. In all cases, document your decision together with the analysis you've done. If you decide that the perceived performance problem is actually expected due to the nature of the task performed, it's essential that in the future when someone else looks at the application and starts asking questions you can answer them properly and new analysis is only necessary if situations changed. Fix After interpreting the analysis results you've concluded that some areas need adjustment. This is the fix step: you're actively correcting the performance problem with proper action targeted at the real cause. In many cases related to O/R mapper powered applications it means you'll use different features of the O/R mapper to achieve the same goal, or apply optimizations at the RDBMS level. It could also mean you apply caching inside your application (compromise memory consumption over performance) to avoid unnecessary re-querying data and re-consuming the results. After applying a change, it's key you re-do the analysis and interpretation steps: compare the results and expectations with what you had before, to see whether your actions had any effect or whether it moved the problem to a different part of the application. Don't fall into the trap to do partly analysis: do the full analysis again: .NET profiling and O/R mapper / RDBMS profiling. It might very well be that the changes you've made make one part faster but another part significantly slower, in such a way that the overall problem hasn't changed at all. Performance tuning is dealing with compromises and making choices: to use one feature over the other, to accept a higher memory footprint, to go away from the strict-OO path and execute queries directly onto the RDBMS, these are choices and compromises which will cross your path if you want to fix performance problems with respect to O/R mappers or data-access and databases in general. In most cases it's not a big issue: alternatives are often good choices too and the compromises aren't that hard to deal with. What is important is that you document why you made a choice, a compromise: which analysis data, which interpretation led you to the choice made. This is key for good maintainability in the years to come. Most common performance problems with O/R mappers Below is an incomplete list of common performance problems related to data-access / O/R mappers / RDBMS code. It will help you with fixing the hotspots you found in the interpretation step. SELECT N+1: (Lazy-loading specific). Lazy loading triggered performance bottlenecks. Consider a list of Orders bound to a grid. You have a Field mapped onto a related field in Order, Customer.CompanyName. Showing this column in the grid will make the grid fetch (indirectly) for each row the Customer row. This means you'll get for the single list not 1 query (for the orders) but 1+(the number of orders shown) queries. To solve this: use eager loading using a prefetch path to fetch the customers with the orders. SELECT N+1 is easy to spot with an O/R mapper profiler or RDBMS profiler: if you see a lot of identical queries executed at once, you have this problem. Prefetch paths using many path nodes or sorting, or limiting. Eager loading problem. Prefetch paths can help with performance, but as 1 query is fetched per node, it can be the number of data fetched in a child node is bigger than you think. Also consider that data in every node is merged on the client within the parent. This is fast, but it also can take some time if you fetch massive amounts of entities. If you keep fetches small, you can use tuning parameters like the ParameterizedPrefetchPathThreshold setting to get more optimal queries. Deep inheritance hierarchies of type Target Per Entity/Type. If you use inheritance of type Target per Entity / Type (each type in the inheritance hierarchy is mapped onto its own table/view), fetches will join subtype- and supertype tables in many cases, which can lead to a lot of performance problems if the hierarchy has many types. With this problem, keep inheritance to a minimum if possible, or switch to a hierarchy of type Target Per Hierarchy, which means all entities in the inheritance hierarchy are mapped onto the same table/view. Of course this has its own set of drawbacks, but it's a compromise you might want to take. Fetching massive amounts of data by fetching large lists of entities. LLBLGen Pro supports paging (and limiting the # of rows returned), which is often key to process through large sets of data. Use paging on the RDBMS if possible (so a query is executed which returns only the rows in the page requested). When using paging in a web application, be sure that you switch server-side paging on on the datasourcecontrol used. In this case, paging on the grid alone is not enough: this can lead to fetching a lot of data which is then loaded into the grid and paged there. Keep note that analyzing queries for paging could lead to the false assumption that paging doesn't occur, e.g. when the query contains a field of type ntext/image/clob/blob and DISTINCT can't be applied while it should have (e.g. due to a join): the datareader will do DISTINCT filtering on the client. this is a little slower but it does perform paging functionality on the data-reader so it won't fetch all rows even if the query suggests it does. Fetch massive amounts of data because blob/clob/ntext/image fields aren't excluded. LLBLGen Pro supports field exclusion for queries. You can exclude fields (also in prefetch paths) per query to avoid fetching all fields of an entity, e.g. when you don't need them for the logic consuming the resultset. Excluding fields can greatly reduce the amount of time spend on data-transport across the network. Use this optimization if you see that there's a big difference between query execution time on the RDBMS and the time reported by the .NET profiler for the ExecuteReader method call. Doing client-side aggregates/scalar calculations by consuming a lot of data. If possible, try to formulate a scalar query or group by query using the projection system or GetScalar functionality of LLBLGen Pro to do data consumption on the RDBMS server. It's far more efficient to process data on the RDBMS server than to first load it all in memory, then traverse the data in-memory to calculate a value. Using .ToList() constructs inside linq queries. It might be you use .ToList() somewhere in a Linq query which makes the query be run partially in-memory. Example: var q = from c in metaData.Customers.ToList() where c.Country=="Norway" select c; This will actually fetch all customers in-memory and do an in-memory filtering, as the linq query is defined on an IEnumerable<T>, and not on the IQueryable<T>. Linq is nice, but it can often be a bit unclear where some parts of a Linq query might run. Fetching all entities to delete into memory first. To delete a set of entities it's rather inefficient to first fetch them all into memory and then delete them one by one. It's more efficient to execute a DELETE FROM ... WHERE query on the database directly to delete the entities in one go. LLBLGen Pro supports this feature, and so do some other O/R mappers. It's not always possible to do this operation in the context of an O/R mapper however: if an O/R mapper relies on a cache, these kind of operations are likely not supported because they make it impossible to track whether an entity is actually removed from the DB and thus can be removed from the cache. Fetching all entities to update with an expression into memory first. Similar to the previous point: it is more efficient to update a set of entities directly with a single UPDATE query using an expression instead of fetching the entities into memory first and then updating the entities in a loop, and afterwards saving them. It might however be a compromise you don't want to take as it is working around the idea of having an object graph in memory which is manipulated and instead makes the code fully aware there's a RDBMS somewhere. Conclusion Performance tuning is almost always about compromises and making choices. It's also about knowing where to look and how the systems in play behave and should behave. The four steps I provided should help you stay focused on the real problem and lead you towards the solution. Knowing how to optimally use the systems participating in your own code (.NET framework, O/R mapper, RDBMS, network/services) is key for success as well as knowing what's going on inside the application you built. I hope you'll find this guide useful in tracking down performance problems and dealing with them in a useful way.  

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