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  • SEO Services - Basics, Techniques and Value

    There are numerous SEO methods, which will actually out-do expectations. These methods are used for providing hits leading back to your site, yet reserving a reasonable ranking position. The simple explanation is that there is not a single SEO method guaranteeing instant success.

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  • SEO Training - Easy Ways to Be a SE Optimizer?

    SEO is one of the most famous methods for web promotion and for this promotion cause, three usual SEO training methods are castigated in order to get desired trainers. Some of these courses are free but those do not give proper accurate training. It is better to spend some money for thorough training. SEO training guides a Search Engine Optimizer how to achieve benefits from Search engines.

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  • How do I add a listener that will work on individual Fieldset in Extjs? Clicking the "Add" button sh

    - by Nair
    Testing Window /*! * Ext JS Library 3.0.0 * Copyright(c) 2006-2009 Ext JS, LLC * [email protected] * http://www.extjs.com/license */ Ext.onReady(function(){ Ext.override( Ext.data.Store, { findExact: function( fld, val ) { var hit = null; this.each( function(rec) { if( rec.get(fld) == val ) { hit = rec; return false; }; } ); return hit; } }); var listAdded = 0; var addListBtn = { text: 'Add', handler: function() { Ext.getCmp('tab_list').add(getList()); Ext.getCmp('tab_list').doLayout(); } } var testData = new Ext.data.SimpleStore({ fields: ['no', 'name', 'address','phone','businessPhone'], data: [['68', 'Target','123 Valley Road','(345) 908-9087','(345) 908-9087'], ['69', 'Walmart','456 Main Road','(345) 908-9999','(345) 908-9990']] }); var getList = function() { listAdded++; var items = new Ext.form.FieldSet( { id:listAdded, title: listAdded, collapsible: true, layout: 'form', autoHeight: true, defaults: {width: 300}, defaultType: 'textfield', bodyStyle: 'padding:5px', labelWidth: 225, items: [ { xtype: 'combo', fieldLabel: 'Customer No', name: 'changescustomerNo', hiddenName: 'changescustomerNo', store: new Ext.data.SimpleStore({ fields: ['id','value'], data: [['68','Test1'],['69','Test2']] }), displayField: 'value', valueField: 'id', selectOnFocus: true, mode: 'local', editable: false, triggerAction: 'all', value: ' ', listeners:{select:{ fn:function(combo, value) { var m = testData.findExact( 'no', this.value ); if(m) { //alert(this.id); Ext.getCmp('currentName').setValue(m.get('name')); Ext.getCmp('currentAddress').setValue(m.get('address')); Ext.getCmp('currentTelephoneNumber').setValue(m.get('phone')); Ext.getCmp('currentBusTelephoneNumber').setValue(m.get('businessPhone')); } }//function }//select }//listeners },{ id: 'currentName', fieldLabel: 'Current Name', name: 'currentName', value: '' },{ id: 'currentAddress', width: 298, xtype: 'textarea', fieldLabel: 'Current Address', name: 'currentAddress', value: '' },{ id:'currentTelephoneNumber', fieldLabel: 'Current Telephone Number', name: 'currentTelephoneNumber', value: '' },{ id: 'currentBusTelephoneNumber', fieldLabel: 'Current Business Telephone Number', name: 'currentBusTelephoneNumber', value: '' } ] } ); return items; } var pnlMain = new Ext.Panel({ id: 'theForm', title: 'Sample List', bodyStyle:'padding:5px', autoWidth: true, frame: true, items: [{ xtype: 'tabpanel', id: 'tabpanel', activeTab: 0, height: 540, width: '100%', resizeTabs: true, tabWidth: 125, minTabWidth: 125, layoutOnTabChange: true, deferredRender: false, // Create all form elements on load defaults: { bodyStyle: 'padding:10px', autoScroll: true, layout: 'form', defaultType: 'textfield', labelWidth: 160 }, items:[{ id: 'tab_list', title: 'List', items: getList(), buttons: [ addListBtn ] }] }] }); pnlMain.render('main'); });

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  • Generic method to create deep copy of all elements in a collection

    - by bwarner
    I have various ObservableCollections of different object types. I'd like to write a single method that will take a collection of any of these object types and return a new collection where each element is a deep copy of elements in the given collection. Here is an example for a specifc class private static ObservableCollection<PropertyValueRow> DeepCopy(ObservableCollection<PropertyValueRow> list) { ObservableCollection<PropertyValueRow> newList = new ObservableCollection<PropertyValueRow>(); foreach (PropertyValueRow rec in list) { newList.Add((PropertyValueRow)rec.Clone()); } return newList; } How can I make this method generic for any class which implements ICloneable?

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  • Scheme Formatting Help

    - by Logan
    I've been working on a project for school that takes functions from a class file and turns them into object/classes. The assignment is all about object oriented programming in scheme. My problem however is that my code doesn't format right. The output it gives me whenever I give it a file to pass in wraps the methods of the class in a list, making it so that the class never really gets declared. I can't for the life of me figure out how to get the parenthesis wrapping the method list to remove. I would really appreciate any help. Below is the code and the class file. ;;;; PART1 --- A super-easy set of classes. Just models points and lines. Tests all of the ;; basics of class behavior without touching on anything particularly complex. (class pointInstance (parent:) (constructor_args:) (ivars: (myx 1) (myy 2)) (methods: (getx () myx) (gety () myy) (setx (x) (set! myx x)) (show () (begin (display "[") (display myx) (display ",") (display myy) (display "]"))) )) (require (lib "trace.ss")) ;; Continue reading until you hit the end of the file, all the while ;; building a list with the contents (define load-file (lambda (port) (let ((rec (read port))) (if (eof-object? rec) '() (cons rec (load-file port)))))) ;; Open a port based on a file name using open-input-file (define (load fname) (let ((fport (open-input-file fname))) (load-file fport))) ;(define lis (load "C:\\Users\\Logan\\Desktop\\simpletest.txt")) ;(define lis (load "C:\\Users\\Logan\\Desktop\\complextest.txt")) (define lis (load "C:\\Users\\Logan\\Desktop\\pointinstance.txt")) ;(display (cdaddr (cdddar lis))) (define makeMethodList (lambda (listToMake retList) ;(display listToMake) (cond [(null? listToMake) retList ;(display "The list passed in to parse was null") ] [else (makeMethodList (cdr listToMake) (append retList (list (getMethodLine listToMake)))) ] ) )) ;(trace makeMethodList) ;this works provided you just pass in the function line (define getMethodLine (lambda (functionList) `((eq? (car msg) ,(caar functionList)) ,(caddar functionList)))) (define load-classes (lambda paramList (cond [(null? paramList) (display "Your parameters are null, man.")] [(null? (car paramList))(display "Done creating class definitions.")] [(not (null? (car paramList))) (begin (let* ((className (cadaar paramList)) (classInstanceVars (cdaddr (cddaar paramList))) (classMethodList (cdr (cadddr (cddaar paramList)))) (desiredMethodList (makeMethodList classMethodList '())) ) ;(display "Classname: ") ;(display className) ;(newline)(newline) ;(display "Class Instance Vars: ") ;(display classInstanceVars) ;(newline)(newline) ;(display "Class Method List: ") ;(display classMethodList) ;(newline) ;(display "Desired Method List: ") ;(display desiredMethodList)) ;(newline)(newline) ;---------------------------------------------------- ;do not delete the below code!` `(define ,className (let ,classInstanceVars (lambda msg ;return the function list here (cond ,(makeMethodList classMethodList '()))) )) ;--------------------------------------------------- ))] ) )) (load-classes lis) ;(load-classes lis) ;(load-classes-helper lis) ;(load-classes "simpletest.txt") ;(load-classes "complextest.txt") ;method list ;(display (cdr (cadddr (cddaar <class>))))

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  • Sorting a list in OCaml

    - by darkie15
    Hi All, Here is the code on sorting any given list: let rec sort lst = match lst with [] -> [] | head :: tail -> insert head (sort tail) and insert elt lst = match lst with [] -> [elt] | head :: tail -> if elt <= head then elt :: lst else head :: insert elt tail;; [Source: Code However, I am getting an Unbound error: Unbound value tail # let rec sort lst = match lst with [] -> [] | head :: tail -> insert head (sort tail) and insert elt lst = match lst with [] -> [elt] | head :: tail -> if elt <= head then elt :: lst else head :: insert elt tail;; Characters 28-29: | head :: tail -> if elt <= head then elt :: lst else head :: insert elt tail;; ^ Error: Syntax error Can anyone please help me understand the issue here?? I did not find head or tail to be predefined anywhere nor in the code

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  • SMS: AT COMMANDS

    - by I__
    i am trying to set up an SMS gateway on my computer here's some code i found: AT OK AT+CMGF=1 OK AT+CMGL="ALL" +CMGL: 1,"REC READ","+85291234567",,"06/11/11,00:30:29+32" Hello, welcome to our SMS tutorial. +CMGL: 2,"REC READ","+85291234567",,"06/11/11,00:32:20+32" A simple demo of SMS text messaging. OK can this be done in windows? what steps do i have to take in order to set this up? what is the compiler? how do i get started?

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  • Is this an F# quotations bug?

    - by ControlFlow
    [<ReflectedDefinition>] let rec x = (fun() -> x + "abc") () The sample code with the recursive value above produces the following F# compiler error: error FS0432: [<ReflectedDefinition>] terms cannot contain uses of the prefix splice operator '%' I can't see any slicing operator usage in the code above, looks like a bug... :) Looks like this is the problem with the quotation via ReflectedDefinitionAttribute only, normal quotation works well: let quotation = <@ let rec x = (fun() -> x + "abc") () in x @> produces expected result with the hidden Lazy.create and Lazy.force usages: val quotation : Quotations.Expr<string> = LetRecursive ([(x, Lambda (unitVar, Application (Lambda (unitVar0, Call (None, String op_Addition[String,String,String](String, String), [Call (None, String Force[String](Lazy`1[System.String]), [x]), Value ("abc")])), Value (<null>)))), (x, Call (None, Lazy`1[String] Create[String](FSharpFunc`2[Unit,String]), [x])), (x, Call (None, String Force[String](Lazy`1[String]), [x]))], x) So the question is: is this an F# compiler bug or not?

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  • Python: convert buffer type of SQLITE column into string

    - by Volatil3
    I am new to Python 2.6. I have been trying to fetch date datetime value which is in yyyy-mm-dd hh:m:ss format back in my Python program. On checking the column type in Python I get the error: 'buffer' object has no attribute 'decode'. I want to use the strptime() function to split the date data and use it but I can't find how to convert a buffer to string. The following is a sample of my code (also available here): conn = sqlite3.connect("mrp.db.db", detect_types=sqlite3.PARSE_DECLTYPES) cursor = conn.cursor() qryT = """ SELECT dateDefinitionTest FROM t WHERE IDproject = 4 AND IDstatus = 5 ORDER BY priority, setDate DESC """ rec = (4,4) cursor.execute(qryT,rec) resultsetTasks = cursor.fetchall() cursor.close() # closing the resultset for item in resultsetTasks: taskDetails = {} _f = item[10].decode("utf-8") The exception I get is: 'buffer' object has no attribute 'decode'

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  • MVC architectural question - Where should payment processing go?

    - by Keltex
    This question is related to my ASP.NET MVC 2 development, but it could apply to any MVC environment and a question of where the logic should go. So let's say I have a controller that takes an online payment such as a shopping cart application. And I have the method that accepts the customers' credit card information: public class CartController : Controller CartRepository cartRepository = new CartRepository() [HttpPost] public ActionResult Payment(PaymentViewModel rec) { if(!ModelState.IsValid) { return View(rec); } // process payment here return RedirectToAction("Receipt"); } At the comment process payment here should the payment processing be handled: In the controller? By the repository? Someplace else?

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  • Why doesn't infinite recursion hit a stack overflow exception in F#?

    - by Amazingant
    I know this is somewhat the reverse of the issue people are having when they ask about a stack overflow issue, but if I create a function and call it as follows, I never receive any errors, and the application simply grinds up a core of my CPU until I force-quit it: let rec recursionTest x = recursionTest x recursionTest 1 Of course I can change this out so it actually does something like this: let rec recursionTest (x: uint64) = recursionTest (x + 1UL) recursionTest 0UL This way I can occasionally put a breakpoint in my code and see the value of x is going up rather quickly, but it still doesn't complain. Does F# not mind infinite recursion?

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  • How to convert list into a string?

    - by PARIJAT
    I have extracted some data from the file and want to write it in the file 2 but the program says 'sequence item 1: expected string, list found', I want to know how I can convert buffer[] i.e. string into sequence, so that it could be saved in file 2. file = open('/ddfs/user/data/k/ktrip_01/hmm.txt','r') file2 = open('/ddfs/user/data/k/ktrip_01/hmm_write.txt','w') buffer = [] rec = file.readlines() for line in rec : field = line.split() print '>',field[0] term = field[0] buffer.append(term) print field[1], field[2], field[6], field[12] term1 = field [1] buffer.append(term1) term2 = field[2] buffer.append[term2] term3 = field[6] buffer.append[term3] term4 = field[12] buffer.append[term4] file2.write(buffer) file.close() file2.close()

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  • Bind event to shape on canvas

    - by Ben Shelock
    How can I bind an event to a shape drawn on a canvas? I presumed this would work but I get an error. <html> <head> <script type="application/javascript"> function draw() { var canvas = document.getElementById("canvas"); var ctx = canvas.getContext("2d"); ctx.fillStyle = "rgb(200,0,0)"; var rec = ctx.fillRect (0, 0, 55, 50); rec.onclick = function(){ alert('something'); } } </script> </head> <body onLoad="draw()"> <canvas id="canvas" width="300" height="300"></canvas> </body> </html>

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  • Can't record or play with a simple recorder?

    - by user1280535
    I have 2 classes, a record and a player. In my main scene, I create an instance of them and play and record. But, as I see, it only records and somehow does not play (the file is not there!) Here is the code for both : -(void)record { NSArray *dirPaths; NSString *docsDir; NSString *sound= @"sound0.caf" ; dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) ; docsDir = [dirPaths objectAtIndex:0]; NSString *soundFilePath = [docsDir stringByAppendingPathComponent:sound]; NSURL *soundFileURL = [NSURL fileURLWithPath:soundFilePath]; NSDictionary *settings = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithFloat: 44100.0], AVSampleRateKey, [NSNumber numberWithInt: kAudioFormatAppleLossless], AVFormatIDKey, [NSNumber numberWithInt: 1], AVNumberOfChannelsKey, [NSNumber numberWithInt: AVAudioQualityMax], AVEncoderAudioQualityKey, nil]; NSError *error; myRecorder = [[AVAudioRecorder alloc] initWithURL:soundFileURL settings:settings error:&error]; if (myRecorder) { NSLog(@"rec"); [myRecorder prepareToRecord]; myRecorder.meteringEnabled = YES; [myRecorder record]; } else NSLog( @"error" ); } I can see the log of rec. -(void)play { NSArray *dirPaths; NSString *docsDir; dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); docsDir = [dirPaths objectAtIndex:0]; NSString *soundFilePath1 = @"sound0.caf" ; NSURL *soundFileURL = [NSURL fileURLWithPath:soundFilePath1]; BOOL isMyFileThere = [[NSFileManager defaultManager] fileExistsAtPath:soundFilePath1]; if(isMyFileThere) { NSLog(@"PLAY"); avPlayer1 = [[AVAudioPlayer alloc] initWithContentsOfURL:soundFileURL error:NULL]; avPlayer1.volume = 8.0; avPlayer1.delegate = self; [avPlayer1 play]; } } I DONT SEE THE LOG OF PLAY ! I call them both with: recInst=[recorder alloc]; //to rec [recInst record]; plyInst=[player alloc]; //play [plyInst play]; and to stop the recorder: - (void)stopRecorder { NSLog(@"stopRecordings"); [myRecorder stop]; //[myRecorder release]; } What's wrong here? Thanks.

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  • How can I implement a tail-recursive list append?

    - by martingw
    A simple append function like this (in F#): let rec app s t = match s with | [] -> t | (x::ss) -> x :: (app ss t) will crash when s becomes big, since the function is not tail recursive. I noticed that F#'s standard append function does not crash with big lists, so it must be implemented differently. So I wondered: How does a tail recursive definition of append look like? I came up with something like this: let rec comb s t = match s with | [] -> t | (x::ss) -> comb ss (x::t) let app2 s t = comb (List.rev s) t which works, but looks rather odd. Is there a more elegant definition?

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  • Next Identity Key LINQ + SQL Server

    - by user569347
    To represent our course tree structure in our Linq Dataclasses we have 2 columns that could potentially be the same as the PK. My problem is that if I want to Insert a new record and populate 2 other columns with the PK that was generated there is no way I can get the next identity and stop conflict with other administrators who might be doing the same insert at the same time. Case: A Leaf node has right_id and left_id = itself (prereq_id) **dbo.pre_req:** prereq_id left_id right_id op_id course_id is_head is_coreq is_enforced parent_course_id and I basically want to do this: pre_req rec = new pre_req { left_id = prereq_id, right_id = prereq_id, op_id = 3, course_id = query.course_id, is_head = true, is_coreq = false, parent_course_id = curCourse.course_id }; db.courses.InsertOnSubmit(rec); try { db.SubmitChanges(); } Any way to solve my dilemma? Thanks!

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  • can list be converted into string

    - by PARIJAT
    Actually i have extracted some data from the file and want to write it in the file 2 but the program says 'sequence item 1: expected string, list found', I want to know how i can convert buffer[] ie string into sequence, so that it could be saved in file 2...I am new to the python please help* file = open('/ddfs/user/data/k/ktrip_01/hmm.txt','r') file2 = open('/ddfs/user/data/k/ktrip_01/hmm_write.txt','w') buffer = [] rec = file.readlines() for line in rec : field = line.split() print '>',field[0] term = field[0] buffer.append(term) print field[1], field[2], field[6], field[12] term1 = field [1] buffer.append(term1) term2 = field[2] buffer.append[term2] term3 = field[6] buffer.append[term3] term4 = field[12] buffer.append[term4] file2.write(buffer) file.close() file2.close()

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  • problem in extracting the data from text file

    - by parijat24
    hello , i am new to python , and I want to extract the data from this format FBpp0143497 5 151 5 157 PF00339.22 Arrestin_N Domain 1 135 149 83.4 1.1e-23 1 CL0135 FBpp0143497 183 323 183 324 PF02752.15 Arrestin_C Domain 1 137 138 58.5 6e-16 1 CL0135 FBpp0131987 60 280 51 280 PF00089.19 Trypsin Domain 14 219 219 127.7 3.7e-37 1 CL0124 to this format FBpp0143497 5 151 Arrestin_N 1.1e-23 FBpp0143497 183 323 Arrestin_C 6e-16 I have written code in hope that it works but it does not work , please help! file = open('/ddfs/user/data/k/ktrip_01/hmm.txt','r') rec = file.read() for line in rec : field = line.split("\t") print field print field[:] print '>',field[0] print field[1], field[2], field[6], field[12] the hmmtext file is FBpp0143497 5 151 5 157 PF00339.22 Arrestin_N Domain 1 135 149 83.4 1.1e-23 1 CL0135 FBpp0143497 183 323 183 324 PF02752.15 Arrestin_C Domain 1 137 138 58.5 6e-16 1 CL0135 FBpp0131987 60 280 51 280 PF00089.19 Trypsin Domain 14 219 219 127.7 3.7e-37 1 CL0124

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  • Setting up and using Bing Translate API Service for Machine Translation

    - by Rick Strahl
    Last week I spent quite a bit of time trying to set up the Bing Translate API service. I can honestly say this was one of the most screwed up developer experiences I've had in a long while - specifically related to the byzantine sign up process that Microsoft has in place. Not only is it nearly impossible to find decent documentation on the required signup process, some of the links in the docs are just plain wrong, and some of the account pages you need to access the actual account information once signed up are not linked anywhere from the administration UI. To make things even harder is the fact that the APIs changed a while back, with a completely new authentication scheme that's described and not directly linked documentation topic also made for a very frustrating search experience. It's a bummer that this is the case too, because the actual API itself is easy to use and works very well - fast and reasonably accurate (as accurate as you can expect machine translation to be). But the sign up process is a pain in the ass doubtlessly leaving many people giving up in frustration. In this post I'll try to hit all the points needed to set up to use the Bing Translate API in one place since such a document seems to be missing from Microsoft. Hopefully the API folks at Microsoft will get their shit together and actually provide this sort of info on their site… Signing Up The first step required is to create a Windows Azure MarketPlace account. Go to: https://datamarket.azure.com/ Sign in with your Windows Live Id If you don't have an account you will be taken to a registration page which you have to fill out. Follow the links and complete the registration. Once you're signed in you can start adding services. Click on the Data Link on the main page Select Microsoft Translator from the list This adds the Microsoft Bing Translator to your services. Pricing The page shows the pricing matrix and the free service which provides 2 megabytes for translations a month for free. Prices go up steeply from there. Pricing is determined by actual bytes of the result translations used. Max translations are 1000 characters so at minimum this means you get around 2000 translations a month for free. However most translations are probable much less so you can expect larger number of translations to go through. For testing or low volume translations this should be just fine. Once signed up there are no further instructions and you're left in limbo on the MS site. Register your Application Once you've created the Data association with Translator the next step is registering your application. To do this you need to access your developer account. Go to https://datamarket.azure.com/developer/applications/register Provide a ClientId, which is effectively the unique string identifier for your application (not your customer id!) Provide your name The client secret was auto-created and this becomes your 'password' For the redirect url provide any https url: https://microsoft.com works Give this application a description of your choice so you can identify it in the list of apps Now, once you've registered your application, keep track of the ClientId and ClientSecret - those are the two keys you need to authenticate before you can call the Translate API. Oddly the applications page is hidden from the Azure Portal UI. I couldn't find a direct link from anywhere on the site back to this page where I can examine my developer application keys. To find them you can go to: https://datamarket.azure.com/developer/applications You can come back here to look at your registered applications and pick up the ClientID and ClientSecret. Fun eh? But we're now ready to actually call the API and do some translating. Using the Bing Translate API The good news is that after this signup hell, using the API is pretty straightforward. To use the translation API you'll need to actually use two services: You need to call an authentication API service first, before you can call the actual translator API. These two APIs live on different domains, and the authentication API returns JSON data while the translator service returns XML. So much for consistency. Authentication The first step is authentication. The service uses oAuth authentication with a  bearer token that has to be passed to the translator API. The authentication call retrieves the oAuth token that you can then use with the translate API call. The bearer token has a short 10 minute life time, so while you can cache it for successive calls, the token can't be cached for long periods. This means for Web backend requests you typically will have to authenticate each time unless you build a more elaborate caching scheme that takes the timeout into account (perhaps using the ASP.NET Cache object). For low volume operations you can probably get away with simply calling the auth API for every translation you do. To call the Authentication API use code like this:/// /// Retrieves an oAuth authentication token to be used on the translate /// API request. The result string needs to be passed as a bearer token /// to the translate API. /// /// You can find client ID and Secret (or register a new one) at: /// https://datamarket.azure.com/developer/applications/ /// /// The client ID of your application /// The client secret or password /// public string GetBingAuthToken(string clientId = null, string clientSecret = null) { string authBaseUrl = https://datamarket.accesscontrol.windows.net/v2/OAuth2-13; if (string.IsNullOrEmpty(clientId) || string.IsNullOrEmpty(clientSecret)) { ErrorMessage = Resources.Resources.Client_Id_and_Client_Secret_must_be_provided; return null; } var postData = string.Format("grant_type=client_credentials&client_id={0}" + "&client_secret={1}" + "&scope=http://api.microsofttranslator.com", HttpUtility.UrlEncode(clientId), HttpUtility.UrlEncode(clientSecret)); // POST Auth data to the oauth API string res, token; try { var web = new WebClient(); web.Encoding = Encoding.UTF8; res = web.UploadString(authBaseUrl, postData); } catch (Exception ex) { ErrorMessage = ex.GetBaseException().Message; return null; } var ser = new JavaScriptSerializer(); var auth = ser.Deserialize<BingAuth>(res); if (auth == null) return null; token = auth.access_token; return token; } private class BingAuth { public string token_type { get; set; } public string access_token { get; set; } } This code basically takes the client id and secret and posts it at the oAuth endpoint which returns a JSON string. Here I use the JavaScript serializer to deserialize the JSON into a custom object I created just for deserialization. You can also use JSON.NET and dynamic deserialization if you are already using JSON.NET in your app in which case you don't need the extra type. In my library that houses this component I don't, so I just rely on the built in serializer. The auth method returns a long base64 encoded string which can be used as a bearer token in the translate API call. Translation Once you have the authentication token you can use it to pass to the translate API. The auth token is passed as an Authorization header and the value is prefixed with a 'Bearer ' prefix for the string. Here's what the simple Translate API call looks like:/// /// Uses the Bing API service to perform translation /// Bing can translate up to 1000 characters. /// /// Requires that you provide a CLientId and ClientSecret /// or set the configuration values for these two. /// /// More info on setup: /// http://www.west-wind.com/weblog/ /// /// Text to translate /// Two letter culture name /// Two letter culture name /// Pass an access token retrieved with GetBingAuthToken. /// If not passed the default keys from .config file are used if any /// public string TranslateBing(string text, string fromCulture, string toCulture, string accessToken = null) { string serviceUrl = "http://api.microsofttranslator.com/V2/Http.svc/Translate"; if (accessToken == null) { accessToken = GetBingAuthToken(); if (accessToken == null) return null; } string res; try { var web = new WebClient(); web.Headers.Add("Authorization", "Bearer " + accessToken); string ct = "text/plain"; string postData = string.Format("?text={0}&from={1}&to={2}&contentType={3}", HttpUtility.UrlEncode(text), fromCulture, toCulture, HttpUtility.UrlEncode(ct)); web.Encoding = Encoding.UTF8; res = web.DownloadString(serviceUrl + postData); } catch (Exception e) { ErrorMessage = e.GetBaseException().Message; return null; } // result is a single XML Element fragment var doc = new XmlDocument(); doc.LoadXml(res); return doc.DocumentElement.InnerText; } The first of this code deals with ensuring the auth token exists. You can either pass the token into the method manually or let the method automatically retrieve the auth code on its own. In my case I'm using this inside of a Web application and in that situation I simply need to re-authenticate every time as there's no convenient way to manage the lifetime of the auth cookie. The auth token is added as an Authorization HTTP header prefixed with 'Bearer ' and attached to the request. The text to translate, the from and to language codes and a result format are passed on the query string of this HTTP GET request against the Translate API. The translate API returns an XML string which contains a single element with the translated string. Using the Wrapper Methods It should be pretty obvious how to use these two methods but here are a couple of test methods that demonstrate the two usage scenarios:[TestMethod] public void TranslateBingWithAuthTest() { var translate = new TranslationServices(); string clientId = DbResourceConfiguration.Current.BingClientId; string clientSecret = DbResourceConfiguration.Current.BingClientSecret; string auth = translate.GetBingAuthToken(clientId, clientSecret); Assert.IsNotNull(auth); string text = translate.TranslateBing("Hello World we're back home!", "en", "de",auth); Assert.IsNotNull(text, translate.ErrorMessage); Console.WriteLine(text); } [TestMethod] public void TranslateBingIntegratedTest() { var translate = new TranslationServices(); string text = translate.TranslateBing("Hello World we're back home!","en","de"); Assert.IsNotNull(text, translate.ErrorMessage); Console.WriteLine(text); } Other API Methods The Translate API has a number of methods available and this one is the simplest one but probably also the most common one that translates a single string. You can find additional methods for this API here: http://msdn.microsoft.com/en-us/library/ff512419.aspx Soap and AJAX APIs are also available and documented on MSDN: http://msdn.microsoft.com/en-us/library/dd576287.aspx These links will be your starting points for calling other methods in this API. Dual Interface I've talked about my database driven localization provider here in the past, and it's for this tool that I added the Bing localization support. Basically I have a localization administration form that allows me to translate individual strings right out of the UI, using both Google and Bing APIs: As you can see in this example, the results from Google and Bing can vary quite a bit - in this case Google is stumped while Bing actually generated a valid translation. At other times it's the other way around - it's pretty useful to see multiple translations at the same time. Here I can choose from one of the values and driectly embed them into the translated text field. Lost in Translation There you have it. As I mentioned using the API once you have all the bureaucratic crap out of the way calling the APIs is fairly straight forward and reasonably fast, even if you have to call the Auth API for every call. Hopefully this post will help out a few of you trying to navigate the Microsoft bureaucracy, at least until next time Microsoft upends everything and introduces new ways to sign up again. Until then - happy translating… Related Posts Translation method Source on Github Translating with Google Translate without Google API Keys Creating a data-driven ASP.NET Resource Provider© Rick Strahl, West Wind Technologies, 2005-2013Posted in Localization  ASP.NET  .NET   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • Inside the Concurrent Collections: ConcurrentDictionary

    - by Simon Cooper
    Using locks to implement a thread-safe collection is rather like using a sledgehammer - unsubtle, easy to understand, and tends to make any other tool redundant. Unlike the previous two collections I looked at, ConcurrentStack and ConcurrentQueue, ConcurrentDictionary uses locks quite heavily. However, it is careful to wield locks only where necessary to ensure that concurrency is maximised. This will, by necessity, be a higher-level look than my other posts in this series, as there is quite a lot of code and logic in ConcurrentDictionary. Therefore, I do recommend that you have ConcurrentDictionary open in a decompiler to have a look at all the details that I skip over. The problem with locks There's several things to bear in mind when using locks, as encapsulated by the lock keyword in C# and the System.Threading.Monitor class in .NET (if you're unsure as to what lock does in C#, I briefly covered it in my first post in the series): Locks block threads The most obvious problem is that threads waiting on a lock can't do any work at all. No preparatory work, no 'optimistic' work like in ConcurrentQueue and ConcurrentStack, nothing. It sits there, waiting to be unblocked. This is bad if you're trying to maximise concurrency. Locks are slow Whereas most of the methods on the Interlocked class can be compiled down to a single CPU instruction, ensuring atomicity at the hardware level, taking out a lock requires some heavy lifting by the CLR and the operating system. There's quite a bit of work required to take out a lock, block other threads, and wake them up again. If locks are used heavily, this impacts performance. Deadlocks When using locks there's always the possibility of a deadlock - two threads, each holding a lock, each trying to aquire the other's lock. Fortunately, this can be avoided with careful programming and structured lock-taking, as we'll see. So, it's important to minimise where locks are used to maximise the concurrency and performance of the collection. Implementation As you might expect, ConcurrentDictionary is similar in basic implementation to the non-concurrent Dictionary, which I studied in a previous post. I'll be using some concepts introduced there, so I recommend you have a quick read of it. So, if you were implementing a thread-safe dictionary, what would you do? The naive implementation is to simply have a single lock around all methods accessing the dictionary. This would work, but doesn't allow much concurrency. Fortunately, the bucketing used by Dictionary allows a simple but effective improvement to this - one lock per bucket. This allows different threads modifying different buckets to do so in parallel. Any thread making changes to the contents of a bucket takes the lock for that bucket, ensuring those changes are thread-safe. The method that maps each bucket to a lock is the GetBucketAndLockNo method: private void GetBucketAndLockNo( int hashcode, out int bucketNo, out int lockNo, int bucketCount) { // the bucket number is the hashcode (without the initial sign bit) // modulo the number of buckets bucketNo = (hashcode & 0x7fffffff) % bucketCount; // and the lock number is the bucket number modulo the number of locks lockNo = bucketNo % m_locks.Length; } However, this does require some changes to how the buckets are implemented. The 'implicit' linked list within a single backing array used by the non-concurrent Dictionary adds a dependency between separate buckets, as every bucket uses the same backing array. Instead, ConcurrentDictionary uses a strict linked list on each bucket: This ensures that each bucket is entirely separate from all other buckets; adding or removing an item from a bucket is independent to any changes to other buckets. Modifying the dictionary All the operations on the dictionary follow the same basic pattern: void AlterBucket(TKey key, ...) { int bucketNo, lockNo; 1: GetBucketAndLockNo( key.GetHashCode(), out bucketNo, out lockNo, m_buckets.Length); 2: lock (m_locks[lockNo]) { 3: Node headNode = m_buckets[bucketNo]; 4: Mutate the node linked list as appropriate } } For example, when adding another entry to the dictionary, you would iterate through the linked list to check whether the key exists already, and add the new entry as the head node. When removing items, you would find the entry to remove (if it exists), and remove the node from the linked list. Adding, updating, and removing items all follow this pattern. Performance issues There is a problem we have to address at this point. If the number of buckets in the dictionary is fixed in the constructor, then the performance will degrade from O(1) to O(n) when a large number of items are added to the dictionary. As more and more items get added to the linked lists in each bucket, the lookup operations will spend most of their time traversing a linear linked list. To fix this, the buckets array has to be resized once the number of items in each bucket has gone over a certain limit. (In ConcurrentDictionary this limit is when the size of the largest bucket is greater than the number of buckets for each lock. This check is done at the end of the TryAddInternal method.) Resizing the bucket array and re-hashing everything affects every bucket in the collection. Therefore, this operation needs to take out every lock in the collection. Taking out mutiple locks at once inevitably summons the spectre of the deadlock; two threads each hold a lock, and each trying to acquire the other lock. How can we eliminate this? Simple - ensure that threads never try to 'swap' locks in this fashion. When taking out multiple locks, always take them out in the same order, and always take out all the locks you need before starting to release them. In ConcurrentDictionary, this is controlled by the AcquireLocks, AcquireAllLocks and ReleaseLocks methods. Locks are always taken out and released in the order they are in the m_locks array, and locks are all released right at the end of the method in a finally block. At this point, it's worth pointing out that the locks array is never re-assigned, even when the buckets array is increased in size. The number of locks is fixed in the constructor by the concurrencyLevel parameter. This simplifies programming the locks; you don't have to check if the locks array has changed or been re-assigned before taking out a lock object. And you can be sure that when a thread takes out a lock, another thread isn't going to re-assign the lock array. This would create a new series of lock objects, thus allowing another thread to ignore the existing locks (and any threads controlling them), breaking thread-safety. Consequences of growing the array Just because we're using locks doesn't mean that race conditions aren't a problem. We can see this by looking at the GrowTable method. The operation of this method can be boiled down to: private void GrowTable(Node[] buckets) { try { 1: Acquire first lock in the locks array // this causes any other thread trying to take out // all the locks to block because the first lock in the array // is always the one taken out first // check if another thread has already resized the buckets array // while we were waiting to acquire the first lock 2: if (buckets != m_buckets) return; 3: Calculate the new size of the backing array 4: Node[] array = new array[size]; 5: Acquire all the remaining locks 6: Re-hash the contents of the existing buckets into array 7: m_buckets = array; } finally { 8: Release all locks } } As you can see, there's already a check for a race condition at step 2, for the case when the GrowTable method is called twice in quick succession on two separate threads. One will successfully resize the buckets array (blocking the second in the meantime), when the second thread is unblocked it'll see that the array has already been resized & exit without doing anything. There is another case we need to consider; looking back at the AlterBucket method above, consider the following situation: Thread 1 calls AlterBucket; step 1 is executed to get the bucket and lock numbers. Thread 2 calls GrowTable and executes steps 1-5; thread 1 is blocked when it tries to take out the lock in step 2. Thread 2 re-hashes everything, re-assigns the buckets array, and releases all the locks (steps 6-8). Thread 1 is unblocked and continues executing, but the calculated bucket and lock numbers are no longer valid. Between calculating the correct bucket and lock number and taking out the lock, another thread has changed where everything is. Not exactly thread-safe. Well, a similar problem was solved in ConcurrentStack and ConcurrentQueue by storing a local copy of the state, doing the necessary calculations, then checking if that state is still valid. We can use a similar idea here: void AlterBucket(TKey key, ...) { while (true) { Node[] buckets = m_buckets; int bucketNo, lockNo; GetBucketAndLockNo( key.GetHashCode(), out bucketNo, out lockNo, buckets.Length); lock (m_locks[lockNo]) { // if the state has changed, go back to the start if (buckets != m_buckets) continue; Node headNode = m_buckets[bucketNo]; Mutate the node linked list as appropriate } break; } } TryGetValue and GetEnumerator And so, finally, we get onto TryGetValue and GetEnumerator. I've left these to the end because, well, they don't actually use any locks. How can this be? Whenever you change a bucket, you need to take out the corresponding lock, yes? Indeed you do. However, it is important to note that TryGetValue and GetEnumerator don't actually change anything. Just as immutable objects are, by definition, thread-safe, read-only operations don't need to take out a lock because they don't change anything. All lockless methods can happily iterate through the buckets and linked lists without worrying about locking anything. However, this does put restrictions on how the other methods operate. Because there could be another thread in the middle of reading the dictionary at any time (even if a lock is taken out), the dictionary has to be in a valid state at all times. Every change to state has to be made visible to other threads in a single atomic operation (all relevant variables are marked volatile to help with this). This restriction ensures that whatever the reading threads are doing, they never read the dictionary in an invalid state (eg items that should be in the collection temporarily removed from the linked list, or reading a node that has had it's key & value removed before the node itself has been removed from the linked list). Fortunately, all the operations needed to change the dictionary can be done in that way. Bucket resizes are made visible when the new array is assigned back to the m_buckets variable. Any additions or modifications to a node are done by creating a new node, then splicing it into the existing list using a single variable assignment. Node removals are simply done by re-assigning the node's m_next pointer. Because the dictionary can be changed by another thread during execution of the lockless methods, the GetEnumerator method is liable to return dirty reads - changes made to the dictionary after GetEnumerator was called, but before the enumeration got to that point in the dictionary. It's worth listing at this point which methods are lockless, and which take out all the locks in the dictionary to ensure they get a consistent view of the dictionary: Lockless: TryGetValue GetEnumerator The indexer getter ContainsKey Takes out every lock (lockfull?): Count IsEmpty Keys Values CopyTo ToArray Concurrent principles That covers the overall implementation of ConcurrentDictionary. I haven't even begun to scratch the surface of this sophisticated collection. That I leave to you. However, we've looked at enough to be able to extract some useful principles for concurrent programming: Partitioning When using locks, the work is partitioned into independant chunks, each with its own lock. Each partition can then be modified concurrently to other partitions. Ordered lock-taking When a method does need to control the entire collection, locks are taken and released in a fixed order to prevent deadlocks. Lockless reads Read operations that don't care about dirty reads don't take out any lock; the rest of the collection is implemented so that any reading thread always has a consistent view of the collection. That leads us to the final collection in this little series - ConcurrentBag. Lacking a non-concurrent analogy, it is quite different to any other collection in the class libraries. Prepare your thinking hats!

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  • Loosely coupled .NET Cache Provider using Dependency Injection

    - by Rhames
    I have recently been reading the excellent book “Dependency Injection in .NET”, written by Mark Seemann. I do not generally buy software development related books, as I never seem to have the time to read them, but I have found the time to read Mark’s book, and it was time well spent I think. Reading the ideas around Dependency Injection made me realise that the Cache Provider code I wrote about earlier (see http://geekswithblogs.net/Rhames/archive/2011/01/10/using-the-asp.net-cache-to-cache-data-in-a-model.aspx) could be refactored to use Dependency Injection, which should produce cleaner code. The goals are to: Separate the cache provider implementation (using the ASP.NET data cache) from the consumers (loose coupling). This will also mean that the dependency on System.Web for the cache provider does not ripple down into the layers where it is being consumed (such as the domain layer). Provide a decorator pattern to allow a consumer of the cache provider to be implemented separately from the base consumer (i.e. if we have a base repository, we can decorate this with a caching version). Although I used the term repository, in reality the cache consumer could be just about anything. Use constructor injection to provide the Dependency Injection, with a suitable DI container (I use Castle Windsor). The sample code for this post is available on github, https://github.com/RobinHames/CacheProvider.git ICacheProvider In the sample code, the key interface is ICacheProvider, which is in the domain layer. 1: using System; 2: using System.Collections.Generic; 3:   4: namespace CacheDiSample.Domain 5: { 6: public interface ICacheProvider<T> 7: { 8: T Fetch(string key, Func<T> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry); 9: IEnumerable<T> Fetch(string key, Func<IEnumerable<T>> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry); 10: } 11: }   This interface contains two methods to retrieve data from the cache, either as a single instance or as an IEnumerable. the second paramerter is of type Func<T>. This is the method used to retrieve data if nothing is found in the cache. The ASP.NET implementation of the ICacheProvider interface needs to live in a project that has a reference to system.web, typically this will be the root UI project, or it could be a separate project. The key thing is that the domain or data access layers do not need system.web references adding to them. In my sample MVC application, the CacheProvider is implemented in the UI project, in a folder called “CacheProviders”: 1: using System; 2: using System.Collections.Generic; 3: using System.Linq; 4: using System.Web; 5: using System.Web.Caching; 6: using CacheDiSample.Domain; 7:   8: namespace CacheDiSample.CacheProvider 9: { 10: public class CacheProvider<T> : ICacheProvider<T> 11: { 12: public T Fetch(string key, Func<T> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry) 13: { 14: return FetchAndCache<T>(key, retrieveData, absoluteExpiry, relativeExpiry); 15: } 16:   17: public IEnumerable<T> Fetch(string key, Func<IEnumerable<T>> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry) 18: { 19: return FetchAndCache<IEnumerable<T>>(key, retrieveData, absoluteExpiry, relativeExpiry); 20: } 21:   22: #region Helper Methods 23:   24: private U FetchAndCache<U>(string key, Func<U> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry) 25: { 26: U value; 27: if (!TryGetValue<U>(key, out value)) 28: { 29: value = retrieveData(); 30: if (!absoluteExpiry.HasValue) 31: absoluteExpiry = Cache.NoAbsoluteExpiration; 32:   33: if (!relativeExpiry.HasValue) 34: relativeExpiry = Cache.NoSlidingExpiration; 35:   36: HttpContext.Current.Cache.Insert(key, value, null, absoluteExpiry.Value, relativeExpiry.Value); 37: } 38: return value; 39: } 40:   41: private bool TryGetValue<U>(string key, out U value) 42: { 43: object cachedValue = HttpContext.Current.Cache.Get(key); 44: if (cachedValue == null) 45: { 46: value = default(U); 47: return false; 48: } 49: else 50: { 51: try 52: { 53: value = (U)cachedValue; 54: return true; 55: } 56: catch 57: { 58: value = default(U); 59: return false; 60: } 61: } 62: } 63:   64: #endregion 65:   66: } 67: }   The FetchAndCache helper method checks if the specified cache key exists, if it does not, the Func<U> retrieveData method is called, and the results are added to the cache. Using Castle Windsor to register the cache provider In the MVC UI project (my application root), Castle Windsor is used to register the CacheProvider implementation, using a Windsor Installer: 1: using Castle.MicroKernel.Registration; 2: using Castle.MicroKernel.SubSystems.Configuration; 3: using Castle.Windsor; 4:   5: using CacheDiSample.Domain; 6: using CacheDiSample.CacheProvider; 7:   8: namespace CacheDiSample.WindsorInstallers 9: { 10: public class CacheInstaller : IWindsorInstaller 11: { 12: public void Install(IWindsorContainer container, IConfigurationStore store) 13: { 14: container.Register( 15: Component.For(typeof(ICacheProvider<>)) 16: .ImplementedBy(typeof(CacheProvider<>)) 17: .LifestyleTransient()); 18: } 19: } 20: }   Note that the cache provider is registered as a open generic type. Consuming a Repository I have an existing couple of repository interfaces defined in my domain layer: IRepository.cs 1: using System; 2: using System.Collections.Generic; 3:   4: using CacheDiSample.Domain.Model; 5:   6: namespace CacheDiSample.Domain.Repositories 7: { 8: public interface IRepository<T> 9: where T : EntityBase 10: { 11: T GetById(int id); 12: IList<T> GetAll(); 13: } 14: }   IBlogRepository.cs 1: using System; 2: using CacheDiSample.Domain.Model; 3:   4: namespace CacheDiSample.Domain.Repositories 5: { 6: public interface IBlogRepository : IRepository<Blog> 7: { 8: Blog GetByName(string name); 9: } 10: }   These two repositories are implemented in the DataAccess layer, using Entity Framework to retrieve data (this is not important though). One important point is that in the BaseRepository implementation of IRepository, the methods are virtual. This will allow the decorator to override them. The BlogRepository is registered in a RepositoriesInstaller, again in the MVC UI project. 1: using Castle.MicroKernel.Registration; 2: using Castle.MicroKernel.SubSystems.Configuration; 3: using Castle.Windsor; 4:   5: using CacheDiSample.Domain.CacheDecorators; 6: using CacheDiSample.Domain.Repositories; 7: using CacheDiSample.DataAccess; 8:   9: namespace CacheDiSample.WindsorInstallers 10: { 11: public class RepositoriesInstaller : IWindsorInstaller 12: { 13: public void Install(IWindsorContainer container, IConfigurationStore store) 14: { 15: container.Register(Component.For<IBlogRepository>() 16: .ImplementedBy<BlogRepository>() 17: .LifestyleTransient() 18: .DependsOn(new 19: { 20: nameOrConnectionString = "BloggingContext" 21: })); 22: } 23: } 24: }   Now I can inject a dependency on the IBlogRepository into a consumer, such as a controller in my sample code: 1: using System; 2: using System.Collections.Generic; 3: using System.Linq; 4: using System.Web; 5: using System.Web.Mvc; 6:   7: using CacheDiSample.Domain.Repositories; 8: using CacheDiSample.Domain.Model; 9:   10: namespace CacheDiSample.Controllers 11: { 12: public class HomeController : Controller 13: { 14: private readonly IBlogRepository blogRepository; 15:   16: public HomeController(IBlogRepository blogRepository) 17: { 18: if (blogRepository == null) 19: throw new ArgumentNullException("blogRepository"); 20:   21: this.blogRepository = blogRepository; 22: } 23:   24: public ActionResult Index() 25: { 26: ViewBag.Message = "Welcome to ASP.NET MVC!"; 27:   28: var blogs = blogRepository.GetAll(); 29:   30: return View(new Models.HomeModel { Blogs = blogs }); 31: } 32:   33: public ActionResult About() 34: { 35: return View(); 36: } 37: } 38: }   Consuming the Cache Provider via a Decorator I used a Decorator pattern to consume the cache provider, this means my repositories follow the open/closed principle, as they do not require any modifications to implement the caching. It also means that my controllers do not have any knowledge of the caching taking place, as the DI container will simply inject the decorator instead of the root implementation of the repository. The first step is to implement a BlogRepository decorator, with the caching logic in it. Note that this can reside in the domain layer, as it does not require any knowledge of the data access methods. BlogRepositoryWithCaching.cs 1: using System; 2: using System.Collections.Generic; 3: using System.Linq; 4: using System.Text; 5:   6: using CacheDiSample.Domain.Model; 7: using CacheDiSample.Domain; 8: using CacheDiSample.Domain.Repositories; 9:   10: namespace CacheDiSample.Domain.CacheDecorators 11: { 12: public class BlogRepositoryWithCaching : IBlogRepository 13: { 14: // The generic cache provider, injected by DI 15: private ICacheProvider<Blog> cacheProvider; 16: // The decorated blog repository, injected by DI 17: private IBlogRepository parentBlogRepository; 18:   19: public BlogRepositoryWithCaching(IBlogRepository parentBlogRepository, ICacheProvider<Blog> cacheProvider) 20: { 21: if (parentBlogRepository == null) 22: throw new ArgumentNullException("parentBlogRepository"); 23:   24: this.parentBlogRepository = parentBlogRepository; 25:   26: if (cacheProvider == null) 27: throw new ArgumentNullException("cacheProvider"); 28:   29: this.cacheProvider = cacheProvider; 30: } 31:   32: public Blog GetByName(string name) 33: { 34: string key = string.Format("CacheDiSample.DataAccess.GetByName.{0}", name); 35: // hard code 5 minute expiry! 36: TimeSpan relativeCacheExpiry = new TimeSpan(0, 5, 0); 37: return cacheProvider.Fetch(key, () => 38: { 39: return parentBlogRepository.GetByName(name); 40: }, 41: null, relativeCacheExpiry); 42: } 43:   44: public Blog GetById(int id) 45: { 46: string key = string.Format("CacheDiSample.DataAccess.GetById.{0}", id); 47:   48: // hard code 5 minute expiry! 49: TimeSpan relativeCacheExpiry = new TimeSpan(0, 5, 0); 50: return cacheProvider.Fetch(key, () => 51: { 52: return parentBlogRepository.GetById(id); 53: }, 54: null, relativeCacheExpiry); 55: } 56:   57: public IList<Blog> GetAll() 58: { 59: string key = string.Format("CacheDiSample.DataAccess.GetAll"); 60:   61: // hard code 5 minute expiry! 62: TimeSpan relativeCacheExpiry = new TimeSpan(0, 5, 0); 63: return cacheProvider.Fetch(key, () => 64: { 65: return parentBlogRepository.GetAll(); 66: }, 67: null, relativeCacheExpiry) 68: .ToList(); 69: } 70: } 71: }   The key things in this caching repository are: I inject into the repository the ICacheProvider<Blog> implementation, via the constructor. This will make the cache provider functionality available to the repository. I inject the parent IBlogRepository implementation (which has the actual data access code), via the constructor. This will allow the methods implemented in the parent to be called if nothing is found in the cache. I override each of the methods implemented in the repository, including those implemented in the generic BaseRepository. Each override of these methods follows the same pattern. It makes a call to the CacheProvider.Fetch method, and passes in the parentBlogRepository implementation of the method as the retrieval method, to be used if nothing is present in the cache. Configuring the Caching Repository in the DI Container The final piece of the jigsaw is to tell Castle Windsor to use the BlogRepositoryWithCaching implementation of IBlogRepository, but to inject the actual Data Access implementation into this decorator. This is easily achieved by modifying the RepositoriesInstaller to use Windsor’s implicit decorator wiring: 1: using Castle.MicroKernel.Registration; 2: using Castle.MicroKernel.SubSystems.Configuration; 3: using Castle.Windsor; 4:   5: using CacheDiSample.Domain.CacheDecorators; 6: using CacheDiSample.Domain.Repositories; 7: using CacheDiSample.DataAccess; 8:   9: namespace CacheDiSample.WindsorInstallers 10: { 11: public class RepositoriesInstaller : IWindsorInstaller 12: { 13: public void Install(IWindsorContainer container, IConfigurationStore store) 14: { 15:   16: // Use Castle Windsor implicit wiring for the block repository decorator 17: // Register the outermost decorator first 18: container.Register(Component.For<IBlogRepository>() 19: .ImplementedBy<BlogRepositoryWithCaching>() 20: .LifestyleTransient()); 21: // Next register the IBlogRepository inmplementation to inject into the outer decorator 22: container.Register(Component.For<IBlogRepository>() 23: .ImplementedBy<BlogRepository>() 24: .LifestyleTransient() 25: .DependsOn(new 26: { 27: nameOrConnectionString = "BloggingContext" 28: })); 29: } 30: } 31: }   This is all that is needed. Now if the consumer of the repository makes a call to the repositories method, it will be routed via the caching mechanism. You can test this by stepping through the code, and seeing that the DataAccess.BlogRepository code is only called if there is no data in the cache, or this has expired. The next step is to add the SQL Cache Dependency support into this pattern, this will be a future post.

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  • LiteSpeed enable Access-Control-Allow-Origin (no response header on CORS request)

    - by Joe Coder Guy
    Seriously, I can't find a single page discussing this for litespeed. Using this format in the htaccess "Header set Access-Control-Allow-Origin http://aSite.com" (and https) sends the setting in the http response header, but I still get the "XMLHttpRequest cannot load https://aSite.com/aFile.php. Origin aSite.com is not allowed by Access-Control-Allow-Origin" error when trying to access https from http origin. Also, I receive no response header for https, only that message shows up in Chrome. Is the server still blocking it even though I've sent the proper headers? I read elsewhere that it helps to add these terms Access-Control-Allow-Headers X-Requested-With Access-Control-Allow-Methods OPTIONS, GET, POST Access-Control-Allow-Headers Content-Type, Depth, User-Agent, X-File-Size, X-Requested-With, If-Modified-Since, X-File-Name, Cache-Control but I don't see these in my headers. Using these, my PHP files aren't even reached (because they register no errors or anything), so it looks like it comes from the server only, but what do I know. Thanks in advance! Update Since no response header, Prashant seems to suggest it's a server issue in his error since it worked on another server. http://stackoverflow.com/questions/11953132/no-response-obtained-while-implementing-cors Anyone know how to flip this switch? Headers work now Bad litespeed format. Should look like this. Still being denied though. Header set Access-Control-Allow-Headers X-Requested-With Header set Access-Control-Allow-Methods OPTIONS Header set Access-Control-Allow-Methods GET Header set Access-Control-Allow-Methods POST Header set Access-Control-Allow-Headers Content-Type Header set Access-Control-Allow-Headers Depth Header set Access-Control-Allow-Headers User-Agent Header set Access-Control-Allow-Headers X-File-Size Header set Access-Control-Allow-Headers X-Requested-With Header set Access-Control-Allow-Headers If-Modified-Since Header set Access-Control-Allow-Headers X-File-Name Header set Access-Control-Allow-Headers Cache-Control

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  • Invariant code contracts – using class-wide contracts

    - by DigiMortal
    It is possible to define invariant code contracts for classes. Invariant contracts should always hold true whatever member of class is called. In this posting I will show you how to use invariant code contracts so you understand how they work and how they should be tested. This is my randomizer class I am using to demonstrate code contracts. I added one method for invariant code contracts. Currently there is one contract that makes sure that random number generator is not null. public class Randomizer {     private IRandomGenerator _generator;       private Randomizer() { }       public Randomizer(IRandomGenerator generator)     {         _generator = generator;     }       public int GetRandomFromRangeContracted(int min, int max)     {         Contract.Requires<ArgumentOutOfRangeException>(             min < max,             "Min must be less than max"         );           Contract.Ensures(             Contract.Result<int>() >= min &&             Contract.Result<int>() <= max,             "Return value is out of range"         );           return _generator.Next(min, max);     }       [ContractInvariantMethod]     private void ObjectInvariant()     {         Contract.Invariant(_generator != null);     } } Invariant code contracts are define in methods that have ContractInvariantMethod attribute. Some notes: It is good idea to define invariant methods as private. Don’t call invariant methods from your code because code contracts system does not allow it. Invariant methods are defined only as place where you can keep invariant contracts. Invariant methods are called only when call to some class member is made! The last note means that having invariant method and creating Randomizer object with null as argument does not automatically generate exception. We have to call at least one method from Randomizer class. Here is the test for generator. You can find more about contracted code testing from my posting Code Contracts: Unit testing contracted code. There is also explained why the exception handling in test is like it is. [TestMethod] [ExpectedException(typeof(Exception))] public void Should_fail_if_generator_is_null() {     try     {         var randomizer = new Randomizer(null);         randomizer.GetRandomFromRangeContracted(1, 4);     }     catch (Exception ex)     {         throw new Exception(ex.Message, ex);     } } Try out this code – with unit tests or with test application to see that invariant contracts are checked as soon as you call some member of Randomizer class.

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  • ASP.NET Web API - Screencast series Part 3: Delete and Update

    - by Jon Galloway
    We're continuing a six part series on ASP.NET Web API that accompanies the getting started screencast series. This is an introductory screencast series that walks through from File / New Project to some more advanced scenarios like Custom Validation and Authorization. The screencast videos are all short (3-5 minutes) and the sample code for the series is both available for download and browsable online. I did the screencasts, but the samples were written by the ASP.NET Web API team. In Part 1 we looked at what ASP.NET Web API is, why you'd care, did the File / New Project thing, and did some basic HTTP testing using browser F12 developer tools. In Part 2 we started to build up a sample that returns data from a repository in JSON format via GET methods. In Part 3, we'll start to modify data on the server using DELETE and POST methods. So far we've been looking at GET requests, and the difference between standard browsing in a web browser and navigating an HTTP API isn't quite as clear. Delete is where the difference becomes more obvious. With a "traditional" web page, to delete something'd probably have a form that POSTs a request back to a controller that needs to know that it's really supposed to be deleting something even though POST was really designed to create things, so it does the work and then returns some HTML back to the client that says whether or not the delete succeeded. There's a good amount of plumbing involved in communicating between client and server. That gets a lot easier when we just work with the standard HTTP DELETE verb. Here's how the server side code works: public Comment DeleteComment(int id) { Comment comment; if (!repository.TryGet(id, out comment)) throw new HttpResponseException(HttpStatusCode.NotFound); repository.Delete(id); return comment; } If you look back at the GET /api/comments code in Part 2, you'll see that they start the exact same because the use cases are kind of similar - we're looking up an item by id and either displaying it or deleting it. So the only difference is that this method deletes the comment once it finds it. We don't need to do anything special to handle cases where the id isn't found, as the same HTTP 404 handling works fine here, too. Pretty much all "traditional" browsing uses just two HTTP verbs: GET and POST, so you might not be all that used to DELETE requests and think they're hard. Not so! Here's the jQuery method that calls the /api/comments with the DELETE verb: $(function() { $("a.delete").live('click', function () { var id = $(this).data('comment-id'); $.ajax({ url: "/api/comments/" + id, type: 'DELETE', cache: false, statusCode: { 200: function(data) { viewModel.comments.remove( function(comment) { return comment.ID == data.ID; } ); } } }); return false; }); }); So in order to use the DELETE verb instead of GET, we're just using $.ajax() and setting the type to DELETE. Not hard. But what's that statusCode business? Well, an HTTP status code of 200 is an OK response. Unless our Web API method sets another status (such as by throwing the Not Found exception we saw earlier), the default response status code is HTTP 200 - OK. That makes the jQuery code pretty simple - it calls the Delete action, and if it gets back an HTTP 200, the server-side delete was successful so the comment can be deleted. Adding a new comment uses the POST verb. It starts out looking like an MVC controller action, using model binding to get the new comment from JSON data into a c# model object to add to repository, but there are some interesting differences. public HttpResponseMessage<Comment> PostComment(Comment comment) { comment = repository.Add(comment); var response = new HttpResponseMessage<Comment>(comment, HttpStatusCode.Created); response.Headers.Location = new Uri(Request.RequestUri, "/api/comments/" + comment.ID.ToString()); return response; } First off, the POST method is returning an HttpResponseMessage<Comment>. In the GET methods earlier, we were just returning a JSON payload with an HTTP 200 OK, so we could just return the  model object and Web API would wrap it up in an HttpResponseMessage with that HTTP 200 for us (much as ASP.NET MVC controller actions can return strings, and they'll be automatically wrapped in a ContentResult). When we're creating a new comment, though, we want to follow standard REST practices and return the URL that points to the newly created comment in the Location header, and we can do that by explicitly creating that HttpResposeMessage and then setting the header information. And here's a key point - by using HTTP standard status codes and headers, our response payload doesn't need to explain any context - the client can see from the status code that the POST succeeded, the location header tells it where to get it, and all it needs in the JSON payload is the actual content. Note: This is a simplified sample. Among other things, you'll need to consider security and authorization in your Web API's, and especially in methods that allow creating or deleting data. We'll look at authorization in Part 6. As for security, you'll want to consider things like mass assignment if binding directly to model objects, etc. In Part 4, we'll extend on our simple querying methods form Part 2, adding in support for paging and querying.

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  • Analysing and measuring the performance of a .NET application (survey results)

    - by Laila
    Back in December last year, I asked myself: could it be that .NET developers think that you need three days and a PhD to do performance profiling on their code? What if developers are shunning profilers because they perceive them as too complex to use? If so, then what method do they use to measure and analyse the performance of their .NET applications? Do they even care about performance? So, a few weeks ago, I decided to get a 1-minute survey up and running in the hopes that some good, hard data would clear the matter up once and for all. I posted the survey on Simple Talk and got help from a few people to promote it. The survey consisted of 3 simple questions: Amazingly, 533 developers took the time to respond - which means I had enough data to get representative results! So before I go any further, I would like to thank all of you who contributed, because I now have some pretty good answers to the troubling questions I was asking myself. To thank you properly, I thought I would share some of the results with you. First of all, application performance is indeed important to most of you. In fact, performance is an intrinsic part of the development cycle for a good 40% of you, which is much higher than I had anticipated, I have to admit. (I know, "Have a little faith Laila!") When asked what tool you use to measure and analyse application performance, I found that nearly half of the respondents use logging statements, a third use performance counters, and 70% of respondents use a profiler of some sort (a 3rd party performance profilers, the CLR profiler or the Visual Studio profiler). The importance attributed to logging statements did surprise me a little. I am still not sure why somebody would go to the trouble of manually instrumenting code in order to measure its performance, instead of just using a profiler. I personally find the process of annotating code, calculating times from log files, and relating it all back to your source terrifyingly laborious. Not to mention that you then need to remember to turn it all off later! Even when you have logging in place throughout all your code anyway, you still have a fair amount of potentially error-prone calculation to sift through the results; in addition, you'll only get method-level rather than line-level timings, and you won't get timings from any framework or library methods you don't have source for. To top it all, we all know that bottlenecks are rarely where you would expect them to be, so you could be wasting time looking for a performance problem in the wrong place. On the other hand, profilers do all the work for you: they automatically collect the CPU and wall-clock timings, and present the results from method timing all the way down to individual lines of code. Maybe I'm missing a trick. I would love to know about the types of scenarios where you actively prefer to use logging statements. Finally, while a third of the respondents didn't have a strong opinion about code performance profilers, those who had an opinion thought that they were mainly complex to use and time consuming. Three respondents in particular summarised this perfectly: "sometimes, they are rather complex to use, adding an additional time-sink to the process of trying to resolve the existing problem". "they are simple to use, but the results are hard to understand" "Complex to find the more advanced things, easy to find some low hanging fruit". These results confirmed my suspicions: Profilers are seen to be designed for more advanced users who can use them effectively and make sense of the results. I found yet more interesting information when I started comparing samples of "developers for whom performance is an important part of the dev cycle", with those "to whom performance is only looked at in times of crisis", and "developers to whom performance is not important, as long as the app works". See the three graphs below. Sample of developers to whom performance is an important part of the dev cycle: Sample of developers to whom performance is important only in times of crisis: Sample of developers to whom performance is not important, as long as the app works: As you can see, there is a strong correlation between the usage of a profiler and the importance attributed to performance: indeed, the more important performance is to a development team, the more likely they are to use a profiler. In addition, developers to whom performance is an important part of the dev cycle have a higher tendency to use a much wider range of methods for performance measurement and analysis. And, unsurprisingly, the less important performance is, the less varied the methods of measurement are. So all in all, to come back to my random questions: .NET developers do care about performance. Those who care the most use a wider range of performance measurement methods than those who care less. But overall, logging statements, performance counters and third party performance profilers are the performance measurement methods of choice for most developers. Finally, although most of you find code profilers complex to use, those of you who care the most about performance tend to use profilers more than those of you to whom performance is not so important.

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