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  • why is the address bar black in Google chrome so you cannot see what you're typing ? [closed]

    - by Tim
    The address bar background color in Google Chrome is black. I cannot see what I'm typing. What's going on? This is a problem when you're typing in a URL you've never used before (so there's no matching history). Type in a URL you've never used before. Imagine someone is giving it to you over the phone. Make a typo somewhere. Use the back arrow to go back and correct it. You cannot see where the cursor is. This just started happening yesterday. I'm on WinXP Pro.

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  • Most optimal way to detect if black (or any color pixels) exist in an image file?

    - by Zando
    What's the best and most flexible algorithm to detect any black (or colored pixel) in a given image file? Say I'm given an image file that could, say, have a blue background. And any non blue pixel, including a white pixel, is counted as a "mark". The function returns true if there are X number of pixels that deviate from each other at a certain threshold. I thought it'd be fastest to just simply iterate through every pixel and see if its color matches the last. But if it's the case that pixel (0,0) is deviant, and every other pixel is the same color (and I want to allow at least a couple deviated pixels before considering an image to be "marked), this won't work or be terribly efficient.

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  • PHP invalid image's and error handling

    - by Emdiesse
    Using PHP's Image and GD functions you can use the following method to finally output the php image imagepng($image); Sometimes, for whatever reason the image may not be displayed typically the error is not with the image but with the actual php functions not executing successfully. However this causes a blank image to be returned which doesn't help me. What I want to know is, is there a way to detect a blank or an invalid image and create a new image, write the errors to the new image using imagestring() and then display this new (debug) image instead. for example, a successfully displayed image with no errors: $image = imagecreate(256, 256); //create image imagecolortransparent($image, $BLUE); //set transparent imagefilledrectangle($image, 0, 0, 256, 256, $BLUE); //fill with 'transparent colour' //Draw a border round the image imageline($image, 0, 0, 0, 255, $Black); imageline($image, 0, 0, 255, 0, $Black); imageline($image, 255, 0, 255, 255, $Black); imageline($image, 0, 255, 255, 255, $Black); imagestring($image, 1, 10, 10, "I am an image!", $Black); imagepng($image); imagedestroy($image); but if I then introduce some errors in the php script that may or may not be to do with the actual image creation then the php script fails and the image will not be visible... $image = imagecreate(256, 256); //create image imagecolortransparent($image, $BLUE); //set transparent imagefilledrectangle($image, 0, 0, 256, 256, $BLUE); //fill with 'transparent colour' //Draw a border round the image imageline($image, 0, 0, 0, 255, $Black); imageline($image, 0, 0, 255, 0, $Black); imageline($image, 255, 0, 255, 255, $Black); imageline($image, 0, 255, 255, 255, $Black); imagestring($image, 1, 10, 10, "I am an image!", $Black); /* I am here to cause problems with the php script ** and cause the execution to fail, I am a function ** that does't exist... ** ** and I am missing a semi colon! ;)*/ non_existant_function() imagepng($image); imagedestroy($image); At this point I want to create a new image like above but in replacement of the I am an image! text I would put the actual error that has occured.

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  • Bargain Hunter Round Up – Kicking Off The E-Commerce Holiday Season

    - by Jeri Kelley
    Everyone has a different way to tackle holiday shopping – Black Friday, Small Business Saturday, Cyber Monday, some have it done months in advance, and others wait until the very last minute.   For me, I’m not big into massive crowds so online shopping to the rescue.   Others thrive on the energy of being in the stores on the busiest shopping day of the year.  With last weekend marking the official kick-off to the holiday season, I thought I’d provide a round up of what’s trending:   Online numbers are looking up: According to comScore, for the holiday season-to-date, $16.4 billion has been spent online, marking a 16-percent increase versus the corresponding days last year. Thanksgiving Day – Why wait until Black Friday or Cyber Monday: Online shopping on Thanksgiving Day also increased, totaling $633 million in receipts, a 32 percent increase over Thanksgiving 2011 Black Friday – More than just in-store: Bargain hunters spent $1.042 billion online the day after Thanksgiving, a 26 percent increase of last year's Black Friday, according to new figures released today by market analyst ComScore Cyber Monday Week: Cyber Monday reached $1.465 billion in online spending, up 17 percent versus year ago, representing the heaviest online spending day in history and the second day this season (in addition to Black Friday) to surpass $1 billion in sales                 Cyber Monday is now being dubbed Cyber Week:  “The annual event is increasingly becoming Cyber Week instead of a one-day event as retailers open their arms for Americans who prefer to avoid crowds and compare prices online.” But, Cyber Monday continues its importance, driving a nearly 22% increase in year-over-year (YoY) online sales. Monday sales beat Sunday, the next highest day by a margin of 26.7%. Mobile shopping continues to rise: ChannelAdvisor that said mobile shopping made up 32% of all online spending over the Black Friday weekend Mobile devices were a key part of the online shopping craziness that was November 26th.  Sales from smartphones and tablets doubled this year. I n tablets the growth was 110% and in smartphones - 100% Mobile bar code scans on Black Friday increased 50 percent, according to a report from ScanLife For more on how you can be ready for the holiday season, check out my blog post on commerce strategies for the holidays.

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  • Windows boots to Black Screen of Death — Is my HDD faulty?

    - by Flynn1179
    My wife's PC suddenly stopped booting up properly. It gets as far as the Windows 'loading' screen with the bar scrolling away, but that's as far as it gets for some time, then suddenly flashes up a BSoD barely long enough to see, then the display cuts out. We've got identical PCs, and after swapping components, I established that my PC suffers the same problem if I swap in the HDD. Even if I plug hers in as a second HDD on my machine, it still does the same thing, even though it's booting from mine. I can't even boot her machine from CD or DVD either, so I couldn't even use a recovery disc. I did manage to partially boot my PC into safe mode with the other HDD attached, and it got as far as loading 'crcdisk.sys' and froze. Anybody know what could be wrong with it, or at least how I can get the data off the disk? I'm assuming there's still data on the disk, given that it at least shows me the vista 'loading' screen.

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  • Unlocking AMD Phenom II X2 550 Black Edition cores - what are the risks?

    - by Vilx-
    I've got the above mentioned CPU and a GigaByte GA-MA790XT-UD4P motherboard, which should be capable of unlocking the extra two cores - if I'm lucky and they're not faulty. The Internet is full of instructions on how to do that. What I don't have is spare money to buy new hardware if I brick something. What are the risks when attempting to do this? Is it completely safe, or can I be left with an expensive pile of junk? What should I keep in mind when doing so? Bigger cooler maybe (I'm running with the default box cooler)? Should I lower the frequencies too? I've never done any OC before.

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  • ubuntu 11.10 foreman error

    - by user1060759
    Like this post I am also trying to complete this heroku tutorial I have installed and used everything (node.js, npm, express) successfully until I got to Foreman. I installed Foreman by first installing Ruby: alex@ubuntu:~$ sudo apt-get install ruby1.9.1 then installing Foreman. I am a newbie to Unix so I "sudo" perhaps unnecessarily here, but I got confirmation in the terminal that it had installed but also some errors: alex@ubuntu:~/NodeHelloWorld$ sudo gem install foreman Invalid gemspec in [/var/lib/gems/1.8/specifications/foreman-0.26.1.gemspec]: invalid date format in specification: "2011-11-10 00:00:00.000000000Z" Invalid gemspec in [/var/lib/gems/1.8/specifications/term-ansicolor-1.0.7.gemspec]: invalid date format in specification: "2011-10-13 00:00:00.000000000Z" Invalid gemspec in [/var/lib/gems/1.8/specifications/foreman-0.26.1.gemspec]: invalid date format in specification: "2011-11-10 00:00:00.000000000Z" Invalid gemspec in [/var/lib/gems/1.8/specifications/term-ansicolor-1.0.7.gemspec]: invalid date format in specification: "2011-10-13 00:00:00.000000000Z" Successfully installed term-ansicolor-1.0.7 Successfully installed foreman-0.26.1 Then when I try to start foreman I get similar: alex@ubuntu:~/NodeHelloWorld$ foreman start Invalid gemspec in [/var/lib/gems/1.8/specifications/foreman-0.26.1.gemspec]: invalid date format in specification: "2011-11-10 00:00:00.000000000Z" Invalid gemspec in [/var/lib/gems/1.8/specifications/term-ansicolor-1.0.7.gemspec]: invalid date format in specification: "2011-10-13 00:00:00.000000000Z" /usr/lib/ruby/vendor_ruby/1.8/rubygems.rb:926:in `report_activate_error': Could not find RubyGem foreman (>= 0) (Gem::LoadError) from /usr/lib/ruby/vendor_ruby/1.8/rubygems.rb:244:in `activate_dep' from /usr/lib/ruby/vendor_ruby/1.8/rubygems.rb:236:in `activate' from /usr/lib/ruby/vendor_ruby/1.8/rubygems.rb:1307:in `gem' from /usr/local/bin/foreman:18 Can anyone help me? I am a newbie to Unix after finally dumping windows as I found I could not get foreman-windows to work for me either I have found this post from someone with apparently the same issue. Does this mean my version of ruby could be wrong? I am running 1.9.1, though again new to ruby as well; alex@ubuntu:~/NodeHelloWorld$ ruby1.9.1 -v ruby 1.9.2p290 (2011-07-09 revision 32553) [i686-linux] Thanks

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  • Is there an high quality natural text reader for the mac?

    - by Another Registered User
    I'm reading about 150 pages of text on screen, every day. I will have to read about 15.000 in the next upcoming months. No joke. Well, the problem is this: I suffer from a sort of attention deficit hyperactivity disorder which forces me to read every sentence up to 10 times until I really get it. Mac OS X Snow Leopard has a built-in text reader with the name "Alex". Although it is already pretty good quality, I know there are far better natural sounding voices out there. I have heard already voices that are absolutely amazing compared to Alex. They're so good, that you can't tell anymore the difference between a real person or a computer. Alex still has this "metal factor" in its voice, which makes my ears hurt after 8 hours of listening. The next problem with Alex is, that he never makes a break after a sentence. Also, it's not possible to think about a sentence and then continue reading. It's also not possible to have him repeat a sentence, without tedious text selection and shortcut usage. Actually, the best tool I can imagine would have the option to read a sentence and move on to the next one after pressing a special key, OR repeating the previously one after pressing a special key. That would help so much! And if that's even with one of those bell lab / AT&T / whatever super-natural voices, even better! But it would be already a great relief if there was just a better tool to control Alex. To let him make breaks after sentences or let him speak big chunks of text sentence-by-sentence with fine-grained control over repetition and moving on. Is there anything?

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  • Convert color photos of documents to good black-and-white images?

    - by Norman Ramsey
    Since I don't have a copier or scanner, I'm using an 8 megapixel camera to copy documents. This works pretty well except they need a lot of processing afterward. I'd like to get from a photo to a bitmap, but using djpeg -grayscale -pnm photo.jpg | pgmtopbm -threshold -value XXX does not work so well, for two reasons: It's hard to guess what XXX should be, and XXX is different for different photos. Illumination varies, and sometimes a single threshold isn't what's right for the image. How can I do better? The ideal solution will be fully automatic command-line program that I can run on Linux. (I have already written a program to remove dark pixels from the edges of images.)

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  • Postfix SMTP-relay server against Gmail on CentOS 6.4

    - by Alex
    I'm currently trying to setup an SMTP-relay server to Gmail with Postfix on a CentOS 6.4 machine, so I can send e-mails from my PHP scripts. I followed this tutorial but I get this error output when trying to do a sendmail alex[email protected] Output: tail -f /var/log/maillog Apr 16 01:25:54 ext-server-dev01 postfix/cleanup[3646]: 86C2D3C05B0: message-id=<[email protected]> Apr 16 01:25:54 ext-server-dev01 postfix/qmgr[3643]: 86C2D3C05B0: from=<[email protected]>, size=297, nrcpt=1 (queue active) Apr 16 01:25:56 ext-server-dev01 postfix/smtp[3648]: 86C2D3C05B0: to=<[email protected]>, relay=smtp.gmail.com[173.194.79.108]:587, delay=4.8, delays=3.1/0.04/1.5/0.23, dsn=5.5.1, status=bounced (host smtp.gmail.com[173.194.79.108] said: 530-5.5.1 Authentication Required. Learn more at 530 5.5.1 http://support.google.com/mail/bin/answer.py?answer=14257 qh4sm3305629pac.8 - gsmtp (in reply to MAIL FROM command)) Here is my main.cf configuration, I tried a number of different options but nothing seems to work: alias_database = hash:/etc/aliases alias_maps = hash:/etc/aliases command_directory = /usr/sbin config_directory = /etc/postfix daemon_directory = /usr/libexec/postfix data_directory = /var/lib/postfix debug_peer_level = 2 html_directory = no inet_interfaces = localhost inet_protocols = ipv4 mail_owner = postfix mailq_path = /usr/bin/mailq.postfix manpage_directory = /usr/share/man mydestination = $myhostname, localhost.$mydomain, localhost myhostname = host.local.domain myorigin = $myhostname newaliases_path = /usr/bin/newaliases.postfix queue_directory = /var/spool/postfix readme_directory = /usr/share/doc/postfix-2.6.6/README_FILES relayhost = [smtp.gmail.com]:587 sample_directory = /usr/share/doc/postfix-2.6.6/samples sendmail_path = /usr/sbin/sendmail.postfix setgid_group = postdrop smtp_sasl_auth_enable = yes smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd smtp_sasl_security_options = noanonymous smtp_sasl_tls_security_options = noanonymous smtp_sasl_type = cyrus smtp_tls_CAfile = /etc/ssl/certs/ca-bundle.crt smtp_use_tls = yes smtpd_sasl_path = smtpd unknown_local_recipient_reject_code = 550 In the /etc/postfix/sasl_passwd files (sasl_passwd & sasl_passwd.db) I got the following (removed the real password, and replaced it with "password"): [smtp.google.com]:587 [email protected]:password To create the sasl_passwd.db file, I did that by running this command: postmap hash:/etc/postfix/sasl_passwd Do anybody got an idea why I can't seem to send an e-mail from the server? Kind Regards Alex

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  • Ubuntu 14.04 stalling. Problem with LightDM. Plymouth (and logging out) switches over to a black screen w/ white cursor

    - by Kage
    if its a duplicate, sorry. Couldn't find anything that fits my issue, much less that was on 14.04. I changed a few things recently. Switched to the Numix theme (from PPA), installed lm-sensors and psensor (ran all the I/O probes), Ubuntu Tweak, Pinta, and well, Team Fortress 2 on Steam. :P The system will get to the Plymouth 'ubuntu' screen, load load, all dots filled, switches over to LightDM, but wait! No LightDM. :I Just a blank screen with that white cursor. Can't switch out to tty1-6 - not sure if the Ctrl-Alt-F1 is disabled in 14.04 or if its literally just locked down. If I change any files, I have access to the filesystem from my Windows 8 partition. That's it. :/ I'm pretty familiar with Linux, especially Ubuntu, but I think I'm still at the point I know just enough to break things and not always how to fix 'em. Any help would be greatly appreciated. Thanks! UPDATE I was just able to get into my desktop briefly. I booted Ubuntu. When the black screen froze, I hit Ctrl-Alt-Del. When it started switching off, I hit Ctrl-Alt-Backspace. It rebooted. I plugged the second monitor in I had been using before the issue ever came about. Plymouth displayed on both. LightDM came up, displayed on both (it used to show only the ubuntu logo on the unfocused monitor though). I logged in just fine. Even ran some pending software updates. I logged out of the desktop though, and LightDM refused to show again. xP

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  • Emails not arriving to client's inbox. Server not on black list.

    - by EBroker
    Hi, I'm sending emails to my clients who are hosted on GoDaddy for both their website and email. For some reason, my system's emails are no longer reaching their inbox. My email server sends them alerts when an action is completed. These alerts are posted in my system and my email server is sending these out, but there are no bounceback emails. There have been no issues in the past year, but in the past two weeks the problem started cropping up. My clients were forced to switched to a web-based email provider like Gmail, Hotmail, Yahoo to receive their alerts. This is a temporary solution that works in the interim. I contacted GoDaddy and they are indicating that I am not being blocked. I also have a GoDaddy account and can confirm that my alerts aren't arriving in the inbox regardless of whatever safe sender items I employ in the webmail interface. I even switched all the system's outbound emails to Plain Text, no luck. Can anyone provide some insight and point me in the right direction? Thank you in advance.

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  • Is a red-black tree my ideal data structure?

    - by Hugo van der Sanden
    I have a collection of items (big rationals) that I'll be processing. In each case, processing will consist of removing the smallest item in the collection, doing some work, and then adding 0-2 new items (which will always be larger than the removed item). The collection will be initialised with one item, and work will continue until it is empty. I'm not sure what size the collection is likely to reach, but I'd expect in the range 1M-100M items. I will not need to locate any item other than the smallest. I'm currently planning to use a red-black tree, possibly tweaked to keep a pointer to the smallest item. However I've never used one before, and I'm unsure whether my pattern of use fits its characteristics well. 1) Is there a danger the pattern of deletion from the left + random insertion will affect performance, eg by requiring a significantly higher number of rotations than random deletion would? Or will delete and insert operations still be O(log n) with this pattern of use? 2) Would some other data structure give me better performance, either because of the deletion pattern or taking advantage of the fact I only ever need to find the smallest item? Update: glad I asked, the binary heap is clearly a better solution for this case, and as promised turned out to be very easy to implement. Hugo

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  • Editting CSS in iframe that sets Select tag's text color to black?

    - by Corey Ogburn
    This is a very specific question for a Google Chrome extension. http://www.meebo.com/mobile/ This page is where you're kicked to when you go to Meebo.com on an iPhone or Droid phone. But if you notice, the Status box where you can set yourself away or what you want your status to be has white text on a white background. In order to get a website to appear in a Google Chrome extension's popup window (the one that drops down when you click the icon next to the address bar) that isn't an included html file in the extension, I need to use an iFrame. I know that there's security measures about Cross-Site stuff like javascript and I'm not surprised I'm having trouble accessing the CSS. But there's a class, status, and it's color is white and I need to change that to black. I've tested it with Chrome's Inspect Element window and if I change that, I'll be fine. I've tried changing the manifest.json file to inject a CSS file using Content-Scripts, but nothing... I'm new to Chrome Extensions but I have experience doing web development.

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  • Converting image to Black & White image on iPhone SDK issues.

    - by KfirS
    Hello, I've used a familiar code to convert image to Black & White which I've founded on several forums. The code is: CGColorSpaceRef colorSapce = CGColorSpaceCreateDeviceGray(); CGContextRef context = CGBitmapContextCreate(nil, originalImage.size.width, originalImage.size.height, 8, originalImage.size.width, colorSapce, kCGImageAlphaNone); CGContextSetInterpolationQuality(context, kCGInterpolationHigh); CGContextSetShouldAntialias(context, NO); CGContextDrawImage(context, CGRectMake(0, 0, originalImage.size.width, originalImage.size.height), [originalImage CGImage]); CGImageRef bwImage = CGBitmapContextCreateImage(context); CGContextRelease(context); CGColorSpaceRelease(colorSapce); UIImage *resultImage = [UIImage imageWithCGImage:bwImage]; // This is result B/W image. CGImageRelease(bwImage); return resultImage; When I'm using this code with on Horizontal image it's work fine, but when I'm trying a to use this code on Vertical image, the result is disproportionate image and rotate 90 degree left. Can anyone know what could be the problem? Thanks, Kfir.

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  • How to have screen revert to BLACK between pages?

    - by user340667
    0 Hi - I tried out the Background Image Scaling script and with Cybr's update it works like magic. It SCALES the image perfectly. No distortion. BUT, my image isn't "computer friendly". I.e.: Not 1024 X 768 or even close to that. (Heck, my monitor has a wide screen, so it isn't 1024 X 768 either! Is anybody's anymore?) Anyhow, this creates a problem inasmuch as, unless I size the window from the bottom up it ends up with a white "stripe" beneath it. What I would REALLY like for it to do is have that white to be BLACK. My "usual" BG color/text etc. code is like: ""body bgcolor="#000000" text="#fcba1e" link="#0000ff" vlink="#800080" alink="#ff0000"" (Site won't let me add the arrows here.) I've tried inserting this in various places with no success. Any ideas for a workaround would surely be appreciated ! Thanks ! Bill

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  • ASP.NET Web API Exception Handling

    - by Fredrik N
    When I talk about exceptions in my product team I often talk about two kind of exceptions, business and critical exceptions. Business exceptions are exceptions thrown based on “business rules”, for example if you aren’t allowed to do a purchase. Business exceptions in most case aren’t important to log into a log file, they can directly be shown to the user. An example of a business exception could be "DeniedToPurchaseException”, or some validation exceptions such as “FirstNameIsMissingException” etc. Critical Exceptions are all other kind of exceptions such as the SQL server is down etc. Those kind of exception message need to be logged and should not reach the user, because they can contain information that can be harmful if it reach out to wrong kind of users. I often distinguish business exceptions from critical exceptions by creating a base class called BusinessException, then in my error handling code I catch on the type BusinessException and all other exceptions will be handled as critical exceptions. This blog post will be about different ways to handle exceptions and how Business and Critical Exceptions could be handled. Web API and Exceptions the basics When an exception is thrown in a ApiController a response message will be returned with a status code set to 500 and a response formatted by the formatters based on the “Accept” or “Content-Type” HTTP header, for example JSON or XML. Here is an example:   public IEnumerable<string> Get() { throw new ApplicationException("Error!!!!!"); return new string[] { "value1", "value2" }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The response message will be: HTTP/1.1 500 Internal Server Error Content-Length: 860 Content-Type: application/json; charset=utf-8 { "ExceptionType":"System.ApplicationException","Message":"Error!!!!!","StackTrace":" at ..."} .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   The stack trace will be returned to the client, this is because of making it easier to debug. Be careful so you don’t leak out some sensitive information to the client. So as long as you are developing your API, this is not harmful. In a production environment it can be better to log exceptions and return a user friendly exception instead of the original exception. There is a specific exception shipped with ASP.NET Web API that will not use the formatters based on the “Accept” or “Content-Type” HTTP header, it is the exception is the HttpResponseException class. Here is an example where the HttpReponseExcetpion is used: // GET api/values [ExceptionHandling] public IEnumerable<string> Get() { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError)); return new string[] { "value1", "value2" }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The response will not contain any content, only header information and the status code based on the HttpStatusCode passed as an argument to the HttpResponseMessage. Because the HttpResponsException takes a HttpResponseMessage as an argument, we can give the response a content: public IEnumerable<string> Get() { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent("My Error Message"), ReasonPhrase = "Critical Exception" }); return new string[] { "value1", "value2" }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   The code above will have the following response:   HTTP/1.1 500 Critical Exception Content-Length: 5 Content-Type: text/plain; charset=utf-8 My Error Message .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The Content property of the HttpResponseMessage doesn’t need to be just plain text, it can also be other formats, for example JSON, XML etc. By using the HttpResponseException we can for example catch an exception and throw a user friendly exception instead: public IEnumerable<string> Get() { try { DoSomething(); return new string[] { "value1", "value2" }; } catch (Exception e) { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent("An error occurred, please try again or contact the administrator."), ReasonPhrase = "Critical Exception" }); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   Adding a try catch to every ApiController methods will only end in duplication of code, by using a custom ExceptionFilterAttribute or our own custom ApiController base class we can reduce code duplicationof code and also have a more general exception handler for our ApiControllers . By creating a custom ApiController’s and override the ExecuteAsync method, we can add a try catch around the base.ExecuteAsync method, but I prefer to skip the creation of a own custom ApiController, better to use a solution that require few files to be modified. The ExceptionFilterAttribute has a OnException method that we can override and add our exception handling. Here is an example: using System; using System.Diagnostics; using System.Net; using System.Net.Http; using System.Web.Http; using System.Web.Http.Filters; public class ExceptionHandlingAttribute : ExceptionFilterAttribute { public override void OnException(HttpActionExecutedContext context) { if (context.Exception is BusinessException) { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent(context.Exception.Message), ReasonPhrase = "Exception" }); } //Log Critical errors Debug.WriteLine(context.Exception); throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent("An error occurred, please try again or contact the administrator."), ReasonPhrase = "Critical Exception" }); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   Note: Something to have in mind is that the ExceptionFilterAttribute will be ignored if the ApiController action method throws a HttpResponseException. The code above will always make sure a HttpResponseExceptions will be returned, it will also make sure the critical exceptions will show a more user friendly message. The OnException method can also be used to log exceptions. By using a ExceptionFilterAttribute the Get() method in the previous example can now look like this: public IEnumerable<string> Get() { DoSomething(); return new string[] { "value1", "value2" }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } To use the an ExceptionFilterAttribute, we can for example add the ExceptionFilterAttribute to our ApiControllers methods or to the ApiController class definition, or register it globally for all ApiControllers. You can read more about is here. Note: If something goes wrong in the ExceptionFilterAttribute and an exception is thrown that is not of type HttpResponseException, a formatted exception will be thrown with stack trace etc to the client. How about using a custom IHttpActionInvoker? We can create our own IHTTPActionInvoker and add Exception handling to the invoker. The IHttpActionInvoker will be used to invoke the ApiController’s ExecuteAsync method. Here is an example where the default IHttpActionInvoker, ApiControllerActionInvoker, is used to add exception handling: public class MyApiControllerActionInvoker : ApiControllerActionInvoker { public override Task<HttpResponseMessage> InvokeActionAsync(HttpActionContext actionContext, System.Threading.CancellationToken cancellationToken) { var result = base.InvokeActionAsync(actionContext, cancellationToken); if (result.Exception != null && result.Exception.GetBaseException() != null) { var baseException = result.Exception.GetBaseException(); if (baseException is BusinessException) { return Task.Run<HttpResponseMessage>(() => new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent(baseException.Message), ReasonPhrase = "Error" }); } else { //Log critical error Debug.WriteLine(baseException); return Task.Run<HttpResponseMessage>(() => new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent(baseException.Message), ReasonPhrase = "Critical Error" }); } } return result; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You can register the IHttpActionInvoker with your own IoC to resolve the MyApiContollerActionInvoker, or add it in the Global.asax: GlobalConfiguration.Configuration.Services.Remove(typeof(IHttpActionInvoker), GlobalConfiguration.Configuration.Services.GetActionInvoker()); GlobalConfiguration.Configuration.Services.Add(typeof(IHttpActionInvoker), new MyApiControllerActionInvoker()); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   How about using a Message Handler for Exception Handling? By creating a custom Message Handler, we can handle error after the ApiController and the ExceptionFilterAttribute is invoked and in that way create a global exception handler, BUT, the only thing we can take a look at is the HttpResponseMessage, we can’t add a try catch around the Message Handler’s SendAsync method. The last Message Handler that will be used in the Wep API pipe-line is the HttpControllerDispatcher and this Message Handler is added to the HttpServer in an early stage. The HttpControllerDispatcher will use the IHttpActionInvoker to invoke the ApiController method. The HttpControllerDipatcher has a try catch that will turn ALL exceptions into a HttpResponseMessage, so that is the reason why a try catch around the SendAsync in a custom Message Handler want help us. If we create our own Host for the Wep API we could create our own custom HttpControllerDispatcher and add or exception handler to that class, but that would be little tricky but is possible. We can in a Message Handler take a look at the HttpResponseMessage’s IsSuccessStatusCode property to see if the request has failed and if we throw the HttpResponseException in our ApiControllers, we could use the HttpResponseException and give it a Reason Phrase and use that to identify business exceptions or critical exceptions. I wouldn’t add an exception handler into a Message Handler, instead I should use the ExceptionFilterAttribute and register it globally for all ApiControllers. BUT, now to another interesting issue. What will happen if we have a Message Handler that throws an exception?  Those exceptions will not be catch and handled by the ExceptionFilterAttribute. I found a  bug in my previews blog post about “Log message Request and Response in ASP.NET WebAPI” in the MessageHandler I use to log incoming and outgoing messages. Here is the code from my blog before I fixed the bug:   public abstract class MessageHandler : DelegatingHandler { protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) { var corrId = string.Format("{0}{1}", DateTime.Now.Ticks, Thread.CurrentThread.ManagedThreadId); var requestInfo = string.Format("{0} {1}", request.Method, request.RequestUri); var requestMessage = await request.Content.ReadAsByteArrayAsync(); await IncommingMessageAsync(corrId, requestInfo, requestMessage); var response = await base.SendAsync(request, cancellationToken); var responseMessage = await response.Content.ReadAsByteArrayAsync(); await OutgoingMessageAsync(corrId, requestInfo, responseMessage); return response; } protected abstract Task IncommingMessageAsync(string correlationId, string requestInfo, byte[] message); protected abstract Task OutgoingMessageAsync(string correlationId, string requestInfo, byte[] message); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   If a ApiController throws a HttpResponseException, the Content property of the HttpResponseMessage from the SendAsync will be NULL. So a null reference exception is thrown within the MessageHandler. The yellow screen of death will be returned to the client, and the content is HTML and the Http status code is 500. The bug in the MessageHandler was solved by adding a check against the HttpResponseMessage’s IsSuccessStatusCode property: public abstract class MessageHandler : DelegatingHandler { protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) { var corrId = string.Format("{0}{1}", DateTime.Now.Ticks, Thread.CurrentThread.ManagedThreadId); var requestInfo = string.Format("{0} {1}", request.Method, request.RequestUri); var requestMessage = await request.Content.ReadAsByteArrayAsync(); await IncommingMessageAsync(corrId, requestInfo, requestMessage); var response = await base.SendAsync(request, cancellationToken); byte[] responseMessage; if (response.IsSuccessStatusCode) responseMessage = await response.Content.ReadAsByteArrayAsync(); else responseMessage = Encoding.UTF8.GetBytes(response.ReasonPhrase); await OutgoingMessageAsync(corrId, requestInfo, responseMessage); return response; } protected abstract Task IncommingMessageAsync(string correlationId, string requestInfo, byte[] message); protected abstract Task OutgoingMessageAsync(string correlationId, string requestInfo, byte[] message); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } If we don’t handle the exceptions that can occur in a custom Message Handler, we can have a hard time to find the problem causing the exception. The savior in this case is the Global.asax’s Application_Error: protected void Application_Error() { var exception = Server.GetLastError(); Debug.WriteLine(exception); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } I would recommend you to add the Application_Error to the Global.asax and log all exceptions to make sure all kind of exception is handled. Summary There are different ways we could add Exception Handling to the Wep API, we can use a custom ApiController, ExceptionFilterAttribute, IHttpActionInvoker or Message Handler. The ExceptionFilterAttribute would be a good place to add a global exception handling, require very few modification, just register it globally for all ApiControllers, even the IHttpActionInvoker can be used to minimize the modifications of files. Adding the Application_Error to the global.asax is a good way to catch all unhandled exception that can occur, for example exception thrown in a Message Handler.   If you want to know when I have posted a blog post, you can follow me on twitter @fredrikn

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  • Use Extension method to write cleaner code

    - by Fredrik N
    This blog post will show you step by step to refactoring some code to be more readable (at least what I think). Patrik Löwnedahl gave me some of the ideas when we where talking about making code much cleaner. The following is an simple application that will have a list of movies (Normal and Transfer). The task of the application is to calculate the total sum of each movie and also display the price of each movie. class Program { enum MovieType { Normal, Transfer } static void Main(string[] args) { var movies = GetMovies(); int totalPriceOfNormalMovie = 0; int totalPriceOfTransferMovie = 0; foreach (var movie in movies) { if (movie == MovieType.Normal) { totalPriceOfNormalMovie += 2; Console.WriteLine("$2"); } else if (movie == MovieType.Transfer) { totalPriceOfTransferMovie += 3; Console.WriteLine("$3"); } } } private static IEnumerable<MovieType> GetMovies() { return new List<MovieType>() { MovieType.Normal, MovieType.Transfer, MovieType.Normal }; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } In the code above I’m using an enum, a good way to add types (isn’t it ;)). I also use one foreach loop to calculate the price, the loop has a condition statement to check what kind of movie is added to the list of movies. I want to reuse the foreach only to increase performance and let it do two things (isn’t that smart of me?! ;)). First of all I can admit, I’m not a big fan of enum. Enum often results in ugly condition statements and can be hard to maintain (if a new type is added we need to check all the code in our app to see if we use the enum somewhere else). I don’t often care about pre-optimizations when it comes to write code (of course I have performance in mind). I rather prefer to use two foreach to let them do one things instead of two. So based on what I don’t like and Martin Fowler’s Refactoring catalog, I’m going to refactoring this code to what I will call a more elegant and cleaner code. First of all I’m going to use Split Loop to make sure the foreach will do one thing not two, it will results in two foreach (Don’t care about performance here, if the results will results in bad performance, you can refactoring later, but computers are so fast to day, so iterating through a list is not often so time consuming.) Note: The foreach actually do four things, will come to is later. var movies = GetMovies(); int totalPriceOfNormalMovie = 0; int totalPriceOfTransferMovie = 0; foreach (var movie in movies) { if (movie == MovieType.Normal) { totalPriceOfNormalMovie += 2; Console.WriteLine("$2"); } } foreach (var movie in movies) { if (movie == MovieType.Transfer) { totalPriceOfTransferMovie += 3; Console.WriteLine("$3"); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } To remove the condition statement we can use the Where extension method added to the IEnumerable<T> and is located in the System.Linq namespace: foreach (var movie in movies.Where( m => m == MovieType.Normal)) { totalPriceOfNormalMovie += 2; Console.WriteLine("$2"); } foreach (var movie in movies.Where( m => m == MovieType.Transfer)) { totalPriceOfTransferMovie += 3; Console.WriteLine("$3"); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The above code will still do two things, calculate the total price, and display the price of the movie. I will not take care of it at the moment, instead I will focus on the enum and try to remove them. One way to remove enum is by using the Replace Conditional with Polymorphism. So I will create two classes, one base class called Movie, and one called MovieTransfer. The Movie class will have a property called Price, the Movie will now hold the price:   public class Movie { public virtual int Price { get { return 2; } } } public class MovieTransfer : Movie { public override int Price { get { return 3; } } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The following code has no enum and will use the new Movie classes instead: class Program { static void Main(string[] args) { var movies = GetMovies(); int totalPriceOfNormalMovie = 0; int totalPriceOfTransferMovie = 0; foreach (var movie in movies.Where( m => m is Movie)) { totalPriceOfNormalMovie += movie.Price; Console.WriteLine(movie.Price); } foreach (var movie in movies.Where( m => m is MovieTransfer)) { totalPriceOfTransferMovie += movie.Price; Console.WriteLine(movie.Price); } } private static IEnumerable<Movie> GetMovies() { return new List<Movie>() { new Movie(), new MovieTransfer(), new Movie() }; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   If you take a look at the foreach now, you can see it still actually do two things, calculate the price and display the price. We can do some more refactoring here by using the Sum extension method to calculate the total price of the movies:   static void Main(string[] args) { var movies = GetMovies(); int totalPriceOfNormalMovie = movies.Where(m => m is Movie) .Sum(m => m.Price); int totalPriceOfTransferMovie = movies.Where(m => m is MovieTransfer) .Sum(m => m.Price); foreach (var movie in movies.Where( m => m is Movie)) Console.WriteLine(movie.Price); foreach (var movie in movies.Where( m => m is MovieTransfer)) Console.WriteLine(movie.Price); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Now when the Movie object will hold the price, there is no need to use two separate foreach to display the price of the movies in the list, so we can use only one instead: foreach (var movie in movies) Console.WriteLine(movie.Price); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } If we want to increase the Maintainability index we can use the Extract Method to move the Sum of the prices into two separate methods. The name of the method will explain what we are doing: static void Main(string[] args) { var movies = GetMovies(); int totalPriceOfMovie = TotalPriceOfMovie(movies); int totalPriceOfTransferMovie = TotalPriceOfMovieTransfer(movies); foreach (var movie in movies) Console.WriteLine(movie.Price); } private static int TotalPriceOfMovieTransfer(IEnumerable<Movie> movies) { return movies.Where(m => m is MovieTransfer) .Sum(m => m.Price); } private static int TotalPriceOfMovie(IEnumerable<Movie> movies) { return movies.Where(m => m is Movie) .Sum(m => m.Price); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Now to the last thing, I love the ForEach method of the List<T>, but the IEnumerable<T> doesn’t have it, so I created my own ForEach extension, here is the code of the ForEach extension method: public static class LoopExtensions { public static void ForEach<T>(this IEnumerable<T> values, Action<T> action) { Contract.Requires(values != null); Contract.Requires(action != null); foreach (var v in values) action(v); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } I will now replace the foreach by using this ForEach method: static void Main(string[] args) { var movies = GetMovies(); int totalPriceOfMovie = TotalPriceOfMovie(movies); int totalPriceOfTransferMovie = TotalPriceOfMovieTransfer(movies); movies.ForEach(m => Console.WriteLine(m.Price)); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The ForEach on the movies will now display the price of the movie, but maybe we want to display the name of the movie etc, so we can use Extract Method by moving the lamdba expression into a method instead, and let the method explains what we are displaying: movies.ForEach(DisplayMovieInfo); private static void DisplayMovieInfo(Movie movie) { Console.WriteLine(movie.Price); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Now the refactoring is done! Here is the complete code:   class Program { static void Main(string[] args) { var movies = GetMovies(); int totalPriceOfMovie = TotalPriceOfMovie(movies); int totalPriceOfTransferMovie = TotalPriceOfMovieTransfer(movies); movies.ForEach(DisplayMovieInfo); } private static void DisplayMovieInfo(Movie movie) { Console.WriteLine(movie.Price); } private static int TotalPriceOfMovieTransfer(IEnumerable<Movie> movies) { return movies.Where(m => m is MovieTransfer) .Sum(m => m.Price); } private static int TotalPriceOfMovie(IEnumerable<Movie> movies) { return movies.Where(m => m is Movie) .Sum(m => m.Price); } private static IEnumerable<Movie> GetMovies() { return new List<Movie>() { new Movie(), new MovieTransfer(), new Movie() }; } } public class Movie { public virtual int Price { get { return 2; } } } public class MovieTransfer : Movie { public override int Price { get { return 3; } } } pulbic static class LoopExtensions { public static void ForEach<T>(this IEnumerable<T> values, Action<T> action) { Contract.Requires(values != null); Contract.Requires(action != null); foreach (var v in values) action(v); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } I think the new code is much cleaner than the first one, and I love the ForEach extension on the IEnumerable<T>, I can use it for different kind of things, for example: movies.Where(m => m is Movie) .ForEach(DoSomething); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } By using the Where and ForEach extension method, some if statements can be removed and will make the code much cleaner. But the beauty is in the eye of the beholder. What would you have done different, what do you think will make the first example in the blog post look much cleaner than my results, comments are welcome! If you want to know when I will publish a new blog post, you can follow me on twitter: http://www.twitter.com/fredrikn

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  • Global name not defined

    - by anteater7171
    I wrote a CPU monitoring program in Python. For some reason sometimes the the program will run without any problem. Then other times the program won't even start because of the following error. Traceback (most recent call last): File "", line 244, in run_nodebug File "C:\Python26\CPUR1.7.pyw", line 601, in app = simpleapp_tk(None) File "C:\Python26\CPUR1.7.pyw", line 26, in init self.initialize() File "C:\Python26\CPUR1.7.pyw", line 107, in initialize self.F() File "C:\Python26\CPUR1.7.pyw", line 517, in F S2 = TL.entryVariableS.get() NameError: global name 'TL' is not defined I can't seem to find the problem, maybe someone more experienced may assist me? Here is a snippet of the part giving me trouble: (The second to last line in the snippet is what's giving me trouble) def E(self): if self.selectedM.get() =='Options...': Setup global TL TL = Tkinter.Toplevel(self) menu = Tkinter.Menu(TL) TL.config(menu=menu) filemenu = Tkinter.Menu(menu) menu.add_cascade(label="| Menu |", menu=filemenu) filemenu.add_command(label="Instruction Manual...", command=self.helpmenu) filemenu.add_command(label="About...", command=self.aboutmenu) filemenu.add_separator() filemenu.add_command(label="Exit Options", command=TL.destroy) filemenu.add_command(label="Exit", command=self.destroy) helpmenu = Tkinter.Menu(menu) menu.add_cascade(label="| Help |", menu=helpmenu) helpmenu.add_command(label="Instruction Manual...", command=self.helpmenu) helpmenu.add_separator() helpmenu.add_command(label="Quick Help...", command=self.helpmenu) Title TL.label5 = Tkinter.Label(TL,text="CPU Usage: Options",anchor="center",fg="black",bg="lightgreen",relief="ridge",borderwidth=5,font=('Arial', 18, 'bold')) TL.label5.pack(padx=15,ipadx=5) X Y scale TL.separator = Tkinter.Frame(TL,height=7, bd=1, relief='ridge', bg='grey95') TL.separator.pack(pady=5,padx=5) # TL.sclX = Tkinter.Scale(TL.separator, from_=0, to=1500, orient='horizontal', resolution=1, command=self.A) TL.sclX.grid(column=1,row=0,ipadx=27, sticky='w') TL.label1 = Tkinter.Label(TL.separator,text="X",anchor="s",fg="black",bg="grey95",font=('Arial', 8 ,'bold')) TL.label1.grid(column=0,row=0, pady=1, sticky='S') TL.sclY = Tkinter.Scale(TL.separator, from_=0, to=1500, resolution=1, command=self.A) TL.sclY.grid(column=2,row=1,rowspan=2,sticky='e', padx=4) TL.label3 = Tkinter.Label(TL.separator,text="Y",fg="black",bg="grey95",font=('Arial', 8 ,'bold')) TL.label3.grid(column=2,row=0, padx=10, sticky='e') TL.entryVariable2 = Tkinter.StringVar() TL.entry2 = Tkinter.Entry(TL.separator,textvariable=TL.entryVariable2, fg="grey15",bg="grey90",relief="sunken",insertbackground="black",borderwidth=5,font=('Arial', 10)) TL.entry2.grid(column=1,row=1,ipadx=20, pady=10,sticky='EW') TL.entry2.bind("<Return>", self.B) TL.label2 = Tkinter.Label(TL.separator,text="X:",fg="black",bg="grey95",font=('Arial', 8 ,'bold')) TL.label2.grid(column=0,row=1, ipadx=4, sticky='W') TL.entryVariable1 = Tkinter.StringVar() TL.entry1 = Tkinter.Entry(TL.separator,textvariable=TL.entryVariable1, fg="grey15",bg="grey90",relief="sunken",insertbackground="black",borderwidth=5,font=('Arial', 10)) TL.entry1.grid(column=1,row=2,sticky='EW') TL.entry1.bind("<Return>", self.B) TL.label4 = Tkinter.Label(TL.separator,text="Y:", anchor="center",fg="black",bg="grey95",font=('Arial', 8 ,'bold')) TL.label4.grid(column=0,row=2, ipadx=4, sticky='W') TL.label7 = Tkinter.Label(TL.separator,text="Text Colour:",fg="black",bg="grey95",font=('Arial', 8 ,'bold'),justify='left') TL.label7.grid(column=1,row=3, sticky='W',padx=10,ipady=10,ipadx=30) TL.selectedP = Tkinter.StringVar() TL.opt1 = Tkinter.OptionMenu(TL.separator, TL.selectedP,'Normal', 'White','Black', 'Blue', 'Steel Blue','Green','Light Green','Yellow','Orange' ,'Red',command=self.G) TL.opt1.config(fg="black",bg="grey90",activebackground="grey90",activeforeground="black", anchor="center",relief="raised",direction='right',font=('Arial', 10)) TL.opt1.grid(column=1,row=4,sticky='EW',padx=20,ipadx=20) TL.selectedP.set('Normal') TL.sclS = Tkinter.Scale(TL.separator, from_=10, to=2000, orient='horizontal', resolution=10, command=self.H) TL.sclS.grid(column=1,row=5,ipadx=27, sticky='w') TL.sclS.set(600) TL.entryVariableS = Tkinter.StringVar() TL.entryS = Tkinter.Entry(TL.separator,textvariable=TL.entryVariableS, fg="grey15",bg="grey90",relief="sunken",insertbackground="black",borderwidth=5,font=('Arial', 10)) TL.entryS.grid(column=1,row=6,ipadx=20, pady=10,sticky='EW') TL.entryS.bind("<Return>", self.I) TL.entryVariableS.set(600) # TL.resizable(False,False) TL.title('Options') geomPatt = re.compile(r"(\d+)?x?(\d+)?([+-])(\d+)([+-])(\d+)") s = self.wm_geometry() m = geomPatt.search(s) X = m.group(4) Y = m.group(6) TL.sclY.set(Y) TL.sclX.set(X) if self.selectedM.get() == 'Exit': self.destroy() def F (self): G = round(psutil.cpu_percent(), 1) G1 = str(G) + '%' self.labelVariable.set(G1) if G < 5: self.imageLabel.configure(image=self.image0) if G >= 5: self.imageLabel.configure(image=self.image5) if G >= 10: self.imageLabel.configure(image=self.image10) if G >= 15: self.imageLabel.configure(image=self.image15) if G >= 20: self.imageLabel.configure(image=self.image20) if G >= 25: self.imageLabel.configure(image=self.image25) if G >= 30: self.imageLabel.configure(image=self.image30) if G >= 35: self.imageLabel.configure(image=self.image35) if G >= 40: self.imageLabel.configure(image=self.image40) if G >= 45: self.imageLabel.configure(image=self.image45) if G >= 50: self.imageLabel.configure(image=self.image50) if G >= 55: self.imageLabel.configure(image=self.image55) if G >= 60: self.imageLabel.configure(image=self.image60) if G >= 65: self.imageLabel.configure(image=self.image65) if G >= 70: self.imageLabel.configure(image=self.image70) if G >= 75: self.imageLabel.configure(image=self.image75) if G >= 80: self.imageLabel.configure(image=self.image80) if G >= 85: self.imageLabel.configure(image=self.image85) if G >= 90: self.imageLabel.configure(image=self.image90) if 100> G >= 95: self.imageLabel.configure(image=self.image95) if G == 100: self.imageLabel.configure(image=self.image100) S2 = TL.entryVariableS.get() self.after(int(S2), self.F)

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  • Json object merge with unqiue id

    - by Hitu
    I have multiple json Objects json1 = [ {'category_id':1,'name':'test1' }, {'category_id':1,'name':'test2' }, {'category_id':1,'name':'test3' }, {'category_id':2,'name':'test2' }, {'category_id':3,'name':'test1' } ]; json2 = [{'category_id':1,'type':'test1'}]; json3 = [ {'category_id':1,'color':'black'}, {'category_id':2,'color':'black'}, {'category_id':3,'color':'white'} ]; I am expecting output like this final = [ {'category_id':1,'name':'test1','type':'test`','color':'black' }, {'category_id':1,'name':'test2','type':'test`','color':'black' }, {'category_id':1,'name':'test3','type':'test`','color':'black' }, {'category_id':2,'name':'test2','color':'black' }, {'category_id':3,'name':'test1','color':'white' } ]; As i have long json object. Looping is good idea or not ? Does there is any inbuilt function for doing the same.

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  • Oracle Application Express (APEX) - Slides & Webcast replay

    - by Alex Blyth
    G'day everyone Thanks to those who attended yesterdays webcast on Oracle Application Express (APEX). A big thanks to Andrew Clarke for presenting on of Oracle's best kept secrets. You can download the slides here and the replay here.4. Oracle Application Express (APEX)View more presentations from Oracle Australia. Next time, Yasin Mohammed will talk to us about all things "Flashback". Details about this session will be posted in the next day or so. Regards Alex

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  • Installing Sphinx on Ubuntu - install location

    - by Alex
    I have to install Sphinx on my Ubuntu 11.10 for it to work on a ruby app. I managed to install it through synaptics, however when I run my sphinx (rake ts:rebuild) I get an error message saying: Sphinx cannot be found on your system. You may need to configure the following settings in your config/sphinx.yml file: * bin_path * searchd_binary_name * indexer_binary_name I guess I just need to edit the sphinx.yml file with the right info but hey, i can't seem to find out where sphinx is. Any help? Thx Alex

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  • No Android SDK, neither Java found

    - by Alex
    I have Java installed correctly, I did it by the manual http://www.wikihow.com/Install-Oracle-Java-on-Ubuntu-Linux I also installed Android SDK. However when I try to create a new Project IntelliJ Idea 12 and specify Project SDk choosing New - /home/alex/android-sdk-linux , it says me No Java SDK of appropriate version found. In addition to the Android SDK, you need to define a JSDK 1.5, 1.6 or 1.7 What did I miss?

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