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  • Senior programming 'guru' who can't program - should I find a different career?

    - by confess
    Background: According to my resume I'm supposed to be pretty good at programming. I've worked on a ton of big projects at big companies over many years. When I go for an interview and someone looks at my resume they immediately assume I really know what I'm talking about. I generally communicate well, present myself well, know the 'jargon' and know a lot about technology at a high level, which makes matters worse because after talking to me for a while an interviewer really believes that what my resume says is probably true. The Problem: The problem arises when someone asks me to code something. I choke. As a programmer I have almost no capacity to come up with creative solutions of my own. I can't think through solutions to a programming problem the way good programmers are usually able to. I read questions on StackOverflow and the answer is obvious to me after I read other people's answers but if I am the first person to look at a question with no hints from anyone else I usually don't know where to start. At work it's the same thing. I'm fine if I'm correcting other people's code. I can identify the source of a bug quicker than anyone I work with. But if you ask me to sit down and code up a new application from scratch I will spend ten times longer than programmers who are much more junior than me. Question: Now that I am looking for work this is raising its ugly head in interview situations and making me feel desperately that I'm in the wrong career. I don't know if this problem is incompetence, laziness or some combination of these. Does anyone have any ideas about what I might be dealing with - are there books or exercises that could help me with this basic problem?

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  • What guarantees are there on the run-time complexity (Big-O) of LINQ methods?

    - by tzaman
    I've recently started using LINQ quite a bit, and I haven't really seen any mention of run-time complexity for any of the LINQ methods. Obviously, there are many factors at play here, so let's restrict the discussion to the plain IEnumerable LINQ-to-Objects provider. Further, let's assume that any Func passed in as a selector / mutator / etc. is a cheap O(1) operation. It seems obvious that all the single-pass operations (Select, Where, Count, Take/Skip, Any/All, etc.) will be O(n), since they only need to walk the sequence once; although even this is subject to laziness. Things are murkier for the more complex operations; the set-like operators (Union, Distinct, Except, etc.) work using GetHashCode by default (afaik), so it seems reasonable to assume they're using a hash-table internally, making these operations O(n) as well, in general. What about the versions that use an IEqualityComparer? OrderBy would need a sort, so most likely we're looking at O(n log n). What if it's already sorted? How about if I say OrderBy().ThenBy() and provide the same key to both? I could see GroupBy (and Join) using either sorting, or hashing. Which is it? Contains would be O(n) on a List, but O(1) on a HashSet - does LINQ check the underlying container to see if it can speed things up? And the real question - so far, I've been taking it on faith that the operations are performant. However, can I bank on that? STL containers, for example, clearly specify the complexity of every operation. Are there any similar guarantees on LINQ performance in the .NET library specification?

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  • Top 4 Lame Tech Blogging Posts

    - by jkauffman
    From a consumption point of view, tech blogging is a great resource for one-off articles on niche subjects. If you spend any time reading tech blogs, you may find yourself running into several common, useless types of posts tech bloggers slip into. Some of these lame posts may just be natural due to common nerd psychology, and some others are probably due to lame, lemming-like laziness. I’m sure I’ll do my fair share of fitting the mold, but I quickly get bored when I happen upon posts that hit these patterns without any real purpose or personal touches. 1. The Content Regurgitation Posts This is a common pattern fueled by the starving pan-handlers in the web traffic economy. These are posts that are terse opinions or addendums to an existing post. I commonly see these involve huge block quotes from the linked article which almost always produces over 50% of the post itself. I’ve accidentally gone to these posts when I’m knowingly only interested in the source material. Web links can degrade as well, so if the source link is broken, then, well, I’m pretty steamed. I see this occur with simple opinions on technologies, Stack Overflow solutions, or various tech news like posts from Microsoft. It’s not uncommon to go to the linked article and see the author announce that he “added a blog post” as a response or summary of the topic. This is just rude, but those who do it are probably aware of this. It’s a matter of winning that sweet, juicy web traffic. I doubt this leeching is fooling anybody these days. I would like to rally human dignity and urge people to avoid these types of posts, and just leave a comment on the source material. 2. The “Sorry I Haven’t Posted In A While” Posts This one is far too common. You’ll most likely see this quote somewhere in the body of the offending post: I have been really busy. If the poster is especially guilt-ridden, you’ll see a few volleys of excuses. Here are some common reasons I’ve seen, which I’ll list from least to most painfully awkward. Out of town Vague allusions to personal health problems (these typically includes phrases like “sick”, “treatment'”, and “all better now!”) “Personal issues” (which I usually read as "divorce”) Graphic or specific personal health problems (maximum awkwardness potential is achieved if you see links to charity fund websites) I can’t help but to try over-analyzing why this occurs. Personally, I see this an an amalgamation of three plain factors: Life happens Us nerds are duty-driven, and driven to guilt at personal inefficiencies Tech blogs can become personal journals I don’t think we can do much about the first two, but on the third I think we could certainly contain our urges. I’m a pretty boring guy and, whether or I like it or not, I have an unspoken duty to protect the world from hearing about my unremarkable existence. Nobody cares what kind of sandwich I’m eating. Similarly, if I disappear for a while, it’s unlikely that anybody who happens upon my blog would care why. Rest assured, if I stop posting for a while due to a vasectomy, you will be the first to know. 3. The “At A Conference”, or “Conference Review” Posts I don’t know if I’m like everyone else on this one, but I have never been successfully interested in these posts. It even sounds like a good idea: if I can’t make it to a particular conference (like the KCDC this year), wouldn’t I be interested in a concentrated summary of events? Apparently, no! Within this realm, I’ve never read a post by a blogger that held my interest. What really baffles is is that, for whatever reason, I am genuinely engaged and interested when talking to someone in person regarding the same topic. I have noticed the same phenomenon when hearing about others’ vacations. If someone sends me an email about their vacation, I gloss over it and forget about it quickly. In contrast, if I’m speaking to that individual in person about their vacation, I’m actually interested. I’m unsure why the written medium eradicates the intrigue. I was raised by a roaming pack of friendly wild video games, so that may be a factor. 4. The “Top X Number of Y’s That Z” Posts I’ve seen this one crop up a lot more in the past few of years. Here are some fabricated examples: 5 Easy Ways to Improve Your Code Top 7 Good Habits Programmers Learn From Experience The 8 Things to Consider When Giving Estimates Top 4 Lame Tech Blogging Posts These are attention-grabbing headlines, and I’d assume they rack up hits. In fact, I enjoy a good number of these. But, I’ve been drawn to articles like this just to find an endless list of identically formatted posts on the blog’s archive sidebar. Often times these posts have overlapping topics, too. These types of posts give the impression that the author has given thought to prioritize and organize the points as a result of a comprehensive consideration of a particular topic. Did the author really weigh all the possibilities when identifying the “Top 4 Lame Tech Blogging Patterns”? Unfortunately, probably not. What a tool. To reiterate, I still enjoy the format, but I feel it is abused. Nowadays, I’m pretty skeptical when approaching posts in this format. If these trends continue, my brain will filter these blog posts out just as effectively as it ignores the encroaching “do xxx with this one trick” advertisements. Conclusion To active blog readers, I hope my guide has served you precious time in being able to identify lame blog posts at a glance. Save time and energy by skipping over the chaff of the internet! And if you author a blog, perhaps my insight will help you to avoid the occasional urge to produce these needless filler posts.

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  • Test-Drive ASP.NET MVC Review

    - by Ben Griswold
    A few years back I started dallying with test-driven development, but I never fully committed to the practice. This wasn’t because I didn’t believe in the value of TDD; it was more a matter of not completely understanding how to incorporate “test first” into my everyday development. Back in my web forms days, I could point fingers at the framework for my ignorance and laziness. After all, web forms weren’t exactly designed for testability so who could blame me for not embracing TDD in those conditions, right? But when I switched to ASP.NET MVC and quickly found myself fresh out of excuses and it became instantly clear that it was time to get my head around red-green-refactor once and for all or I would regretfully miss out on one of the biggest selling points the new framework had to offer. I have previously written about how I learned ASP.NET MVC. It was primarily hands on learning but I did read a couple of ASP.NET MVC books along the way. The books I read dedicated a chapter or two to TDD and they certainly addressed the benefits of TDD and how MVC was designed with testability in mind, but TDD was merely an afterthought compared to, well, teaching one how to code the model, view and controller. This approach made some sense, and I learned a bunch about MVC from those books, but when it came to TDD the books were just a teaser and an opportunity missed.  But then I got lucky – Jonathan McCracken contacted me and asked if I’d review his book, Test-Drive ASP.NET MVC, and it was just what I needed to get over the TDD hump. As the title suggests, Test-Drive ASP.NET MVC takes a different approach to learning MVC as it focuses on testing right from the very start. McCracken wastes no time and swiftly familiarizes us with the framework by building out a trivial Quote-O-Matic application and then dedicates the better part of his book to testing first – first by explaining TDD and then coding a full-featured Getting Organized application inspired by David Allen’s popular book, Getting Things Done. If you are a learn-by-example kind of coder (like me), you will instantly appreciate and enjoy McCracken’s style – its fast-moving, pragmatic and focused on only the most relevant information required to get you going with ASP.NET MVC and TDD. The book continues with the test-first theme but McCracken moves away from the sample application and incorporates other practical skills like persisting models with NHibernate, leveraging Inversion of Control with the IControllerFactory and building a RESTful web service. What I most appreciated about this section was McCracken’s use of and praise for open source libraries like Rhino Mocks, SQLite and StructureMap (to name just a few) and productivity tools like ReSharper, Web Platform Installer and ASP.NET SQL Server Setup Wizard.  McCracken’s emphasis on real world, pragmatic development was clearly demonstrated in every tool choice, straight-forward code block and developer tip. Whether one is already familiar with the tools/tips or not, McCracken’s thought process is easily understood and appreciated. The final section of the book walks the reader through security and deployment – everything from error handling and logging with ELMAH, to ASP.NET Health Monitoring, to using MSBuild with automated builds, to the deployment  of ASP.NET MVC to various web environments. These chapters, like those prior, offer enough information and explanation to simply help you get the job done.  Do I believe Test-Drive ASP.NET MVC will turn you into an expert MVC developer overnight?  Well, no.  I don’t think any book can make that claim.  If that were possible, I think book list prices would skyrocket!  That said, Test-Drive ASP.NET MVC provides a solid foundation and a unique (and dare I say necessary) approach to learning ASP.NET MVC.  Along the way McCracken shares loads of very practical software development tips and references numerous tools and libraries. The bottom line is it’s a great ASP.NET MVC primer – if you’re new to ASP.NET MVC it’s just what you need to get started.  Do I believe Test-Drive ASP.NET MVC will give you everything you need to start employing TDD in your everyday development?  Well, I used to think that learning TDD required a lot of practice and, if you’re lucky enough, the guidance of a mentor or coach.  I used to think that one couldn’t learn TDD from a book alone. Well, I’m still no pro, but I’m testing first now and Jonathan McCracken and his book, Test-Drive ASP.NET MVC, played a big part in making this happen.  If you are an MVC developer and a TDD newb, Test-Drive ASP.NET MVC is just the book for you.

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  • What Counts For A DBA: Foresight

    - by drsql
    Of all the valuable attributes of a DBA covered so far in this series, ranging from passion to humility to practicality, perhaps one of the most important attributes may turn out to be the most seemingly-nebulous: foresight. According to Free Dictionary foresight is the "perception of the significance and nature of events before they have occurred". Foresight does not come naturally to most people, as the parent of any teenager will attest. No matter how clearly you see their problems coming they won't listen, and have to fail before eventually (hopefully) learning for themselves. Having graduated from the school of hard knocks, the DBA, the naive teenager no longer, acquires the ability to foretell how events will unfold in response to certain actions or attitudes with the unerring accuracy of a doom-laden prophet. Like Simba in the Lion King, after a few blows to the head, we foretell that a sore head that will be the inevitable consequence of a swing of Rafiki's stick, and we take evasive action. However, foresight is about more than simply learning when to duck. It's about taking the time to understand and prevent the habits that caused the stick to swing in the first place. And based on this definition, I often think there is a lot less foresight on display in my industry than there ought to be. Most DBAs reading this blog will spot a line such as the following in a piece of "working" code, understand immediately why it is less than optimimum, and take evasive action. …WHERE CAST (columnName as int) = 1 However, the programmers who regularly write this sort of code clearly lack that foresight, and this and numerous other examples of similarly-malodorous code prevail throughout our industry (and provide premium-grade fertilizer for the healthy growth of many a consultant's bank account). Sometimes, perhaps harried by impatient managers and painfully tight deadlines, everyone makes mistakes. Yes, I too occasionally write code that "works", but basically stinks. When the problems manifest, it is sometimes accompanied by a sense of grim recognition that somewhere in me existed the foresight to know that that approach would lead to this problem. However, in the headlong rush, warning signs got overlooked, lessons learned previously, which could supply the foresight to the current project, were lost and not applied.   Of course, the problem often is a simple lack of skills, training and knowledge in the relevant technology and/or business space; programmers and DBAs forced to do their best in the face of inadequate training, or to apply their skills in areas where they lack experience. However, often the problem goes deeper than this; I detect in some DBAs and programmers a certain laziness of attitude.   They veer from one project to the next, going with "whatever works", unwilling or unable to take the time to understand where their actions are leading them. Of course, the whole "Agile" mindset is often interpreted to favor flexibility and rapid production over aiming to get things right the first time. The faster you try to travel in the dark, frequently changing direction, the more important it is to have someone who has the foresight to know at least roughly where you are heading. This is doubly true for the data tier which, no matter how you try to deny it, simply cannot be "redone" every month as you learn aspects of the world you are trying to model that, with a little bit of foresight, you would have seen coming.   Sometimes, when as a DBA you can glance briefly at 200 lines of working SQL code and know instinctively why it will cause problems, foresight can feel like magic, but it isn't; it's more like muscle memory. It is acquired as the consequence of good experience, useful communication with those around you, and a willingness to learn continually, through continued education as well as from failure. Foresight can be deployed only by finding time to understand how the lessons learned from other DBAs, and other projects, can help steer the current project in the right direction.   C.S. Lewis once said "The future is something which everyone reaches at the rate of sixty minutes an hour, whatever he does, whoever he is." It cannot be avoided; the quality of what you build now is going to affect you, and others, at some point in the future. Take the time to acquire foresight; it is a love letter to your future self, to say you cared.

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  • My Red Gate Experience

    - by Colin Rothwell
    I’m Colin, and I’ve been an intern working with Mike in publishing on Simple-Talk and SQLServerCentral for the past ten weeks. I’ve mostly been working “behind the scenes”, making improvements to the spam filtering, along with various other small tweaks. When I arrived at Red Gate, one of the first things Mike asked me was what I wanted to get out of the internship. It wasn’t a question I’d given a great deal of thought to, but my immediate response was the same as almost anybody: to support my growing family. Well, ok, not quite that, but money was certainly a motivator, along with simply making sure that I didn’t get bored over the summer. Three months is a long time to fill, and many of my friends end up getting bored, or worse, knitting obsessively. With the arrogance which seems fairly common among Cambridge people, I wasn’t expecting to really learn much here! In my mind, the part of the year where I am at Uni is the part where I learn things, whilst Red Gate would be an opportunity to apply what I’d learnt. Thankfully, the opposite is true: I’ve learnt a lot during my time here, and there has been a definite positive impact on the way I write code. The first thing I’ve really learnt is that test-driven development is, in general, a sensible way of working. Before coming, I didn’t really get it: how could you test something you hadn’t yet written? It didn’t make sense! My problem was seeing a test as having to test all the behaviour of a given function. Writing tests which test the bare minimum possible and building them up is a really good way of crystallising the direction the code needs to grow in, and ensures you never attempt to write too much code at time. One really good experience of this was early on in my internship when Mike and I were working on the query used to list active authors: I’d written something which I thought would do the trick, but by starting again using TDD we grew something which revealed that there were several subtle mistakes in the query I’d written. I’ve also been awakened to the value of pair programming. Whilst I could sort of see the point before coming, I also thought that it was impossible that two people would ever get more done at the same computer than if they were working separately. I still think that this is true for projects with pieces that developers can easily work on independently, and with developers who both know the codebase, but I’ve found that pair programming can be really good for learning a code base, and for building up small projects to the point where you can start working on separate components, as well as solving particularly difficult problems. Later on in my internship, for my down tools week project, I was working on adding Python support to Glimpse. Another intern and I we pair programmed the entire project, using ping pong pair programming as much as possible. One bonus that this brought which I wasn’t expecting was that I found myself less prone to distraction: with someone else peering over my shoulder, I didn’t have the ever-present temptation to open gmail, or facebook, or yammer, or twitter, or hacker news, or reddit, and so on, and so forth. I’m quite proud of this project: I think it’s some of the best code I’ve written. I’ve also been really won over to the value of descriptive variables names. In my pre-Red Gate life, as a lone-ranger style cowboy programmer, I’d developed a tendency towards laziness in variable names, sometimes abbreviating or, worse, using acronyms. I’ve swiftly realised that this is a bad idea when working with a team: saving a few key strokes is inevitably not worth it when it comes to reading code again in the future. Longer names also mean you can do away with a majority of comments. I appreciate that if you’ve come up with an O(n*log n) algorithm for something which seemed O(n^2), you probably want to explain how it works, but explaining what a variable name means is a big no no: it’s so very easy to change the behaviour of the code, whilst forgetting about the comments. Whilst at Red Gate, I took the opportunity to attend a code retreat, which really helped me to solidify all the things I’d learnt. To be completely free of any existing code base really lets you focus on best practises and think about how you write code. If you get a chance to go on a similar event, I’d highly recommend it! Cycling to Red Gate, I’ve also become much better at fitting inner tubes: if you’re struggling to get the tube out, or re-fit the tire, letting a bit of air out usually helps. I’ve also become quite a bit better at foosball and will miss having a foosball table! I’d like to finish off by saying thank you to everyone at Red Gate for having me. I’ve really enjoyed working with, and learning from, the team that brings you this web site. If you meet any of them, buy them a drink!

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  • What's the right way to do mutable data structures (e.g., skip lists, splay trees) in F#?

    - by dan
    What's a good way to implement mutable data structures in F#? The reason I’m asking is because I want to go back and implement the data structures I learned about in the algorithms class I took this semester (skip lists, splay trees, fusion trees, y-fast tries, van Emde Boas trees, etc.), which was a pure theory course with no coding whatsoever, and I figure I might as well try to learn F# while I’m doing it. I know that I “should” use finger trees to get splay tree functionality in a functional language, and that I should do something with laziness to get skip-list functionality, etc. , but I want to get the basics nailed down before I try playing with purely functional implementations. There are lots of examples of how to do functional data structures in F#, but there isn’t much on how to do mutable data structures, so I started by fixing up the doubly linked list here into something that allows inserts and deletes anywhere. My plan is to turn this into a skip list, and then use a similar structure (discriminated union of a record) for the tree structures I want to implement. Before I start on something more substantial, is there a better way to do mutable structures like this in F#? Should I just use records and not bother with the discriminated union? Should I use a class instead? Is this question "not even wrong"? Should I be doing the mutable structures in C#, and not dip into F# until I want to compare them to their purely functional counterparts? And, if a DU of records is what I want, could I have written the code below better or more idiomatically? It seems like there's a lot of redundancy here, but I'm not sure how to get rid of it. module DoublyLinkedList = type 'a ll = | None | Node of 'a ll_node and 'a ll_node = { mutable Prev: 'a ll; Element : 'a ; mutable Next: 'a ll; } let insert x l = match l with | None -> Node({ Prev=None; Element=x; Next=None }) | Node(node) -> match node.Prev with | None -> let new_node = { Prev=None; Element=x; Next=Node(node)} node.Prev <- Node(new_node) Node(new_node) | Node(prev_node) -> let new_node = { Prev=node.Prev; Element=x; Next=Node(node)} node.Prev <- Node(new_node) prev_node.Next <- Node(new_node) Node(prev_node) let rec nth n l = match n, l with | _,None -> None | _,Node(node) when n > 0 -> nth (n-1) node.Next | _,Node(node) when n < 0 -> nth (n+1) node.Prev | _,Node(node) -> Node(node) //hopefully only when n = 0 :-) let rec printLinkedList head = match head with | None -> () | Node(x) -> let prev = match x.Prev with | None -> "-" | Node(y) -> y.Element.ToString() let cur = x.Element.ToString() let next = match x.Next with | None -> "-" | Node(y) -> y.Element.ToString() printfn "%s, <- %s -> %s" prev cur next printLinkedList x.Next

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  • Fluent Nhibernate - how do i specify table schemas when auto generating tables in SQL CE 4

    - by daffers
    I am using SQL CE as a database for running local and CI integration tests (normally our site runs on normal SQL server). We are using Fluent Nhibernate for our mapping and having it create our schema from our Mapclasses. There are only two classes with a one to many relationship between them. In our real database we use a non dbo schema. The code would not work with this real database at first until i added schema names to the Table() methods. However doing this broke the unit tests with the error... System.Data.SqlServerCe.SqlCeException : There was an error parsing the query. [ Token line number = 1,Token line offset = 26,Token in error = User ] These are the classes and associatad MapClasses (simplified of course) public class AffiliateApplicationRecord { public virtual int Id { get; private set; } public virtual string CompanyName { get; set; } public virtual UserRecord KeyContact { get; private set; } public AffiliateApplicationRecord() { DateReceived = DateTime.Now; } public virtual void AddKeyContact(UserRecord keyContactUser) { keyContactUser.Affilates.Add(this); KeyContact = keyContactUser; } } public class AffiliateApplicationRecordMap : ClassMap<AffiliateApplicationRecord> { public AffiliateApplicationRecordMap() { Schema("myschema"); Table("Partner"); Id(x => x.Id).GeneratedBy.Identity(); Map(x => x.CompanyName, "Name"); References(x => x.KeyContact) .Cascade.All() .LazyLoad(Laziness.False) .Column("UserID"); } } public class UserRecord { public UserRecord() { Affilates = new List<AffiliateApplicationRecord>(); } public virtual int Id { get; private set; } public virtual string Forename { get; set; } public virtual IList<AffiliateApplicationRecord> Affilates { get; set; } } public class UserRecordMap : ClassMap<UserRecord> { public UserRecordMap() { Schema("myschema"); Table("[User]");//Square brackets required as user is a reserved word Id(x => x.Id).GeneratedBy.Identity(); Map(x => x.Forename); HasMany(x => x.Affilates); } } And here is the fluent configuraton i am using .... public static ISessionFactory CreateSessionFactory() { return Fluently.Configure() .Database( MsSqlCeConfiguration.Standard .Dialect<MsSqlCe40Dialect>() .ConnectionString(ConnectionString) .DefaultSchema("myschema")) .Mappings(m => m.FluentMappings.AddFromAssembly(typeof(AffiliateApplicationRecord).Assembly)) .ExposeConfiguration(config => new SchemaExport(config).Create(false, true)) .ExposeConfiguration(x => x.SetProperty("connection.release_mode", "on_close")) //This is included to deal with a SQLCE issue http://stackoverflow.com/questions/2361730/assertionfailure-null-identifier-fluentnh-sqlserverce .BuildSessionFactory(); } The documentation on this aspect of fluent is pretty weak so any help would be appreciated

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  • Connecting Linux to WatchGuard Firebox SSL (OpenVPN client)

    Recently, I got a new project assignment that requires to connect permanently to the customer's network through VPN. They are using a so-called SSL VPN. As I am using OpenVPN since more than 5 years within my company's network I was quite curious about their solution and how it would actually be different from OpenVPN. Well, short version: It is a disguised version of OpenVPN. Unfortunately, the company only offers a client for Windows and Mac OS which shouldn't bother any Linux user after all. OpenVPN is part of every recent distribution and can be activated in a couple of minutes - both client as well as server (if necessary). WatchGuard Firebox SSL - About dialog Borrowing some files from a Windows client installation Initially, I didn't know about the product, so therefore I went through the installation on Windows 8. No obstacles (and no restart despite installation of TAP device drivers!) here and the secured VPN channel was up and running in less than 2 minutes or so. Much appreciated from both parties - customer and me. Of course, this whole client package and my long year approved and stable installation ignited my interest to have a closer look at the WatchGuard client. Compared to the original OpenVPN client (okay, I have to admit this is years ago) this commercial product is smarter in terms of file locations during installation. You'll be able to access the configuration and key files below your roaming application data folder. To get there, simply enter '%AppData%\WatchGuard\Mobile VPN' in your Windows/File Explorer and confirm with Enter/Return. This will display the following files: Application folder below user profile with configuration and certificate files From there we are going to borrow four files, namely: ca.crt client.crt client.ovpn client.pem and transfer them to the Linux system. You might also be able to isolate those four files from a Mac OS client. Frankly, I'm just too lazy to run the WatchGuard client installation on a Mac mini only to find the folder location, and I'm going to describe why a little bit further down this article. I know that you can do that! Feedback in the comment section is appreciated. Configuration of OpenVPN (console) Depending on your distribution the following steps might be a little different but in general you should be able to get the important information from it. I'm going to describe the steps in Ubuntu 13.04 (Raring Ringtail). As usual, there are two possibilities to achieve your goal: console and UI. Let's what it is necessary to be done. First of all, you should ensure that you have OpenVPN installed on your system. Open your favourite terminal application and run the following statement: $ sudo apt-get install openvpn network-manager-openvpn network-manager-openvpn-gnome Just to be on the safe side. The four above mentioned files from your Windows machine could be copied anywhere but either you place them below your own user directory or you put them (as root) below the default directory: /etc/openvpn At this stage you would be able to do a test run already. Just in case, run the following command and check the output (it's the similar information you would get from the 'View Logs...' context menu entry in Windows: $ sudo openvpn --config client.ovpn Pay attention to the correct path to your configuration and certificate files. OpenVPN will ask you to enter your Auth Username and Auth Password in order to establish the VPN connection, same as the Windows client. Remote server and user authentication to establish the VPN Please complete the test run and see whether all went well. You can disconnect pressing Ctrl+C. Simplifying your life - authentication file In my case, I actually set up the OpenVPN client on my gateway/router. This establishes a VPN channel between my network and my client's network and allows me to switch machines easily without having the necessity to install the WatchGuard client on each and every machine. That's also very handy for my various virtualised Windows machines. Anyway, as the client configuration, key and certificate files are located on a headless system somewhere under the roof, it is mandatory to have an automatic connection to the remote site. For that you should first change the file extension '.ovpn' to '.conf' which is the default extension on Linux systems for OpenVPN, and then open the client configuration file in order to extend an existing line. $ sudo mv client.ovpn client.conf $ sudo nano client.conf You should have a similar content to this one here: dev tunclientproto tcp-clientca ca.crtcert client.crtkey client.pemtls-remote "/O=WatchGuard_Technologies/OU=Fireware/CN=Fireware_SSLVPN_Server"remote-cert-eku "TLS Web Server Authentication"remote 1.2.3.4 443persist-keypersist-tunverb 3mute 20keepalive 10 60cipher AES-256-CBCauth SHA1float 1reneg-sec 3660nobindmute-replay-warningsauth-user-pass auth.txt Note: I changed the IP address of the remote directive above (which should be obvious, right?). Anyway, the required change is marked in red and we have to create a new authentication file 'auth.txt'. You can give the directive 'auth-user-pass' any file name you'd like to. Due to my existing OpenVPN infrastructure my setup differs completely from the above written content but for sake of simplicity I just keep it 'as-is'. Okay, let's create this file 'auth.txt' $ sudo nano auth.txt and just put two lines of information in it - username on the first, and password on the second line, like so: myvpnusernameverysecretpassword Store the file, change permissions, and call openvpn with your configuration file again: $ sudo chmod 0600 auth.txt $ sudo openvpn --config client.conf This should now work without being prompted to enter username and password. In case that you placed your files below the system-wide location /etc/openvpn you can operate your VPNs also via service command like so: $ sudo service openvpn start client $ sudo service openvpn stop client Using Network Manager For newer Linux users or the ones with 'console-phobia' I'm going to describe now how to use Network Manager to setup the OpenVPN client. For this move your mouse to the systray area and click on Network Connections => VPN Connections => Configure VPNs... which opens your Network Connections dialog. Alternatively, use the HUD and enter 'Network Connections'. Network connections overview in Ubuntu Click on 'Add' button. On the next dialog select 'Import a saved VPN configuration...' from the dropdown list and click on 'Create...' Choose connection type to import VPN configuration Now you navigate to your folder where you put the client files from the Windows system and you open the 'client.ovpn' file. Next, on the tab 'VPN' proceed with the following steps (directives from the configuration file are referred): General Check the IP address of Gateway ('remote' - we used 1.2.3.4 in this setup) Authentication Change Type to 'Password with Certificates (TLS)' ('auth-pass-user') Enter User name to access your client keys (Auth Name: myvpnusername) Enter Password (Auth Password: verysecretpassword) and choose your password handling Browse for your User Certificate ('cert' - should be pre-selected with client.crt) Browse for your CA Certificate ('ca' - should be filled as ca.crt) Specify your Private Key ('key' - here: client.pem) Then click on the 'Advanced...' button and check the following values: Use custom gateway port: 443 (second value of 'remote' directive) Check the selected value of Cipher ('cipher') Check HMAC Authentication ('auth') Enter the Subject Match: /O=WatchGuard_Technologies/OU=Fireware/CN=Fireware_SSLVPN_Server ('tls-remote') Finally, you have to confirm and close all dialogs. You should be able to establish your OpenVPN-WatchGuard connection via Network Manager. For that, click on the 'VPN Connections => client' entry on your Network Manager in the systray. It is advised that you keep an eye on the syslog to see whether there are any problematic issues that would require some additional attention. Advanced topic: routing As stated above, I'm running the 'WatchGuard client for Linux' on my head-less server, and since then I'm actually establishing a secure communication channel between two networks. In order to enable your network clients to get access to machines on the remote side there are two possibilities to enable that: Proper routing on both sides of the connection which enables both-direction access, or Network masquerading on the 'client side' of the connection Following, I'm going to describe the second option a little bit more in detail. The Linux system that I'm using is already configured as a gateway to the internet. I won't explain the necessary steps to do that, and will only focus on the additional tweaks I had to do. You can find tons of very good instructions and tutorials on 'How to setup a Linux gateway/router' - just use Google. OK, back to the actual modifications. First, we need to have some information about the network topology and IP address range used on the 'other' side. We can get this very easily from /var/log/syslog after we established the OpenVPN channel, like so: $ sudo tail -n20 /var/log/syslog Or if your system is quite busy with logging, like so: $ sudo less /var/log/syslog | grep ovpn The output should contain PUSH received message similar to the following one: Jul 23 23:13:28 ios1 ovpn-client[789]: PUSH: Received control message: 'PUSH_REPLY,topology subnet,route 192.168.1.0 255.255.255.0,dhcp-option DOMAIN ,route-gateway 192.168.6.1,topology subnet,ping 10,ping-restart 60,ifconfig 192.168.6.2 255.255.255.0' The interesting part for us is the route command which I highlighted already in the sample PUSH_REPLY. Depending on your remote server there might be multiple networks defined (172.16.x.x and/or 10.x.x.x). Important: The IP address range on both sides of the connection has to be different, otherwise you will have to shuffle IPs or increase your the netmask. {loadposition content_adsense} After the VPN connection is established, we have to extend the rules for iptables in order to route and masquerade IP packets properly. I created a shell script to take care of those steps: #!/bin/sh -eIPTABLES=/sbin/iptablesDEV_LAN=eth0DEV_VPNS=tun+VPN=192.168.1.0/24 $IPTABLES -A FORWARD -i $DEV_LAN -o $DEV_VPNS -d $VPN -j ACCEPT$IPTABLES -A FORWARD -i $DEV_VPNS -o $DEV_LAN -s $VPN -j ACCEPT$IPTABLES -t nat -A POSTROUTING -o $DEV_VPNS -d $VPN -j MASQUERADE I'm using the wildcard interface 'tun+' because I have multiple client configurations for OpenVPN on my server. In your case, it might be sufficient to specify device 'tun0' only. Simplifying your life - automatic connect on boot Now, that the client connection works flawless, configuration of routing and iptables is okay, we might consider to add another 'laziness' factor into our setup. Due to kernel updates or other circumstances it might be necessary to reboot your system. Wouldn't it be nice that the VPN connections are established during the boot procedure? Yes, of course it would be. To achieve this, we have to configure OpenVPN to automatically start our VPNs via init script. Let's have a look at the responsible 'default' file and adjust the settings accordingly. $ sudo nano /etc/default/openvpn Which should have a similar content to this: # This is the configuration file for /etc/init.d/openvpn## Start only these VPNs automatically via init script.# Allowed values are "all", "none" or space separated list of# names of the VPNs. If empty, "all" is assumed.# The VPN name refers to the VPN configutation file name.# i.e. "home" would be /etc/openvpn/home.conf#AUTOSTART="all"#AUTOSTART="none"#AUTOSTART="home office"## ... more information which remains unmodified ... With the OpenVPN client configuration as described above you would either set AUTOSTART to "all" or to "client" to enable automatic start of your VPN(s) during boot. You should also take care that your iptables commands are executed after the link has been established, too. You can easily test this configuration without reboot, like so: $ sudo service openvpn restart Enjoy stable VPN connections between your Linux system(s) and a WatchGuard Firebox SSL remote server. Cheers, JoKi

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  • NHibernate Conventions

    - by Ricardo Peres
    Introduction It seems that nowadays everyone loves conventions! Not the ones that you go to, but the ones that you use, that is! It just happens that NHibernate also supports conventions, and we’ll see exactly how. Conventions in NHibernate are supported in two ways: Naming of tables and columns when not explicitly indicated in the mappings; Full domain mapping. Naming of Tables and Columns Since always NHibernate has supported the concept of a naming strategy. A naming strategy in NHibernate converts class and property names to table and column names and vice-versa, when a name is not explicitly supplied. In concrete, it must be a realization of the NHibernate.Cfg.INamingStrategy interface, of which NHibernate includes two implementations: DefaultNamingStrategy: the default implementation, where each column and table are mapped to identically named properties and classes, for example, “MyEntity” will translate to “MyEntity”; ImprovedNamingStrategy: underscores (_) are used to separate Pascal-cased fragments, for example, entity “MyEntity” will be mapped to a “my_entity” table. The naming strategy can be defined at configuration level (the Configuration instance) by calling the SetNamingStrategy method: 1: cfg.SetNamingStrategy(ImprovedNamingStrategy.Instance); Both the DefaultNamingStrategy and the ImprovedNamingStrategy classes offer singleton instances in the form of Instance static fields. DefaultNamingStrategy is the one NHibernate uses, if you don’t specify one. Domain Mapping In mapping by code, we have the choice of relying on conventions to do the mapping automatically. This means a class will inspect our classes and decide how they will relate to the database objects. The class that handles conventions is NHibernate.Mapping.ByCode.ConventionModelMapper, a specialization of the base by code mapper, NHibernate.Mapping.ByCode.ModelMapper. The ModelMapper relies on an internal SimpleModelInspector to help it decide what and how to map, but the mapper lets you override its decisions.  You apply code conventions like this: 1: //pick the types that you want to map 2: IEnumerable<Type> types = Assembly.GetExecutingAssembly().GetExportedTypes(); 3:  4: //conventions based mapper 5: ConventionModelMapper mapper = new ConventionModelMapper(); 6:  7: HbmMapping mapping = mapper.CompileMappingFor(types); 8:  9: //the one and only configuration instance 10: Configuration cfg = ...; 11: cfg.AddMapping(mapping); This is a very simple example, it lacks, at least, the id generation strategy, which you can add by adding an event handler like this: 1: mapper.BeforeMapClass += (IModelInspector modelInspector, Type type, IClassAttributesMapper classCustomizer) => 2: { 3: classCustomizer.Id(x => 4: { 5: //set the hilo generator 6: x.Generator(Generators.HighLow); 7: }); 8: }; The mapper will fire events like this whenever it needs to get information about what to do. And basically this is all it takes to automatically map your domain! It will correctly configure many-to-one and one-to-many relations, choosing bags or sets depending on your collections, will get the table and column names from the naming strategy we saw earlier and will apply the usual defaults to all properties, such as laziness and fetch mode. However, there is at least one thing missing: many-to-many relations. The conventional mapper doesn’t know how to find and configure them, which is a pity, but, alas, not difficult to overcome. To start, for my projects, I have this rule: each entity exposes a public property of type ISet<T> where T is, of course, the type of the other endpoint entity. Extensible as it is, NHibernate lets me implement this very easily: 1: mapper.IsOneToMany((MemberInfo member, Boolean isLikely) => 2: { 3: Type sourceType = member.DeclaringType; 4: Type destinationType = member.GetMemberFromDeclaringType().GetPropertyOrFieldType(); 5:  6: //check if the property is of a generic collection type 7: if ((destinationType.IsGenericCollection() == true) && (destinationType.GetGenericArguments().Length == 1)) 8: { 9: Type destinationEntityType = destinationType.GetGenericArguments().Single(); 10:  11: //check if the type of the generic collection property is an entity 12: if (mapper.ModelInspector.IsEntity(destinationEntityType) == true) 13: { 14: //check if there is an equivalent property on the target type that is also a generic collection and points to this entity 15: PropertyInfo collectionInDestinationType = destinationEntityType.GetProperties().Where(x => (x.PropertyType.IsGenericCollection() == true) && (x.PropertyType.GetGenericArguments().Length == 1) && (x.PropertyType.GetGenericArguments().Single() == sourceType)).SingleOrDefault(); 16:  17: if (collectionInDestinationType != null) 18: { 19: return (false); 20: } 21: } 22: } 23:  24: return (true); 25: }); 26:  27: mapper.IsManyToMany((MemberInfo member, Boolean isLikely) => 28: { 29: //a relation is many to many if it isn't one to many 30: Boolean isOneToMany = mapper.ModelInspector.IsOneToMany(member); 31: return (!isOneToMany); 32: }); 33:  34: mapper.BeforeMapManyToMany += (IModelInspector modelInspector, PropertyPath member, IManyToManyMapper collectionRelationManyToManyCustomizer) => 35: { 36: Type destinationEntityType = member.LocalMember.GetPropertyOrFieldType().GetGenericArguments().First(); 37: //set the mapping table column names from each source entity name plus the _Id sufix 38: collectionRelationManyToManyCustomizer.Column(destinationEntityType.Name + "_Id"); 39: }; 40:  41: mapper.BeforeMapSet += (IModelInspector modelInspector, PropertyPath member, ISetPropertiesMapper propertyCustomizer) => 42: { 43: if (modelInspector.IsManyToMany(member.LocalMember) == true) 44: { 45: propertyCustomizer.Key(x => x.Column(member.LocalMember.DeclaringType.Name + "_Id")); 46:  47: Type sourceType = member.LocalMember.DeclaringType; 48: Type destinationType = member.LocalMember.GetPropertyOrFieldType().GetGenericArguments().First(); 49: IEnumerable<String> names = new Type[] { sourceType, destinationType }.Select(x => x.Name).OrderBy(x => x); 50:  51: //set inverse on the relation of the alphabetically first entity name 52: propertyCustomizer.Inverse(sourceType.Name == names.First()); 53: //set mapping table name from the entity names in alphabetical order 54: propertyCustomizer.Table(String.Join("_", names)); 55: } 56: }; We have to understand how the conventions mapper thinks: For each collection of entities found, it will ask the mapper if it is a one-to-many; in our case, if the collection is a generic one that has an entity as its generic parameter, and the generic parameter type has a similar collection, then it is not a one-to-many; Next, the mapper will ask if the collection that it now knows is not a one-to-many is a many-to-many; Before a set is mapped, if it corresponds to a many-to-many, we set its mapping table. Now, this is tricky: because we have no way to maintain state, we sort the names of the two endpoint entities and we combine them with a “_”; for the first alphabetical entity, we set its relation to inverse – remember, on a many-to-many relation, only one endpoint must be marked as inverse; finally, we set the column name as the name of the entity with an “_Id” suffix; Before the many-to-many relation is processed, we set the column name as the name of the other endpoint entity with the “_Id” suffix, as we did for the set. And that’s it. With these rules, NHibernate will now happily find and configure many-to-many relations, as well as all the others. You can wrap this in a new conventions mapper class, so that it is more easily reusable: 1: public class ManyToManyConventionModelMapper : ConventionModelMapper 2: { 3: public ManyToManyConventionModelMapper() 4: { 5: base.IsOneToMany((MemberInfo member, Boolean isLikely) => 6: { 7: return (this.IsOneToMany(member, isLikely)); 8: }); 9:  10: base.IsManyToMany((MemberInfo member, Boolean isLikely) => 11: { 12: return (this.IsManyToMany(member, isLikely)); 13: }); 14:  15: base.BeforeMapManyToMany += this.BeforeMapManyToMany; 16: base.BeforeMapSet += this.BeforeMapSet; 17: } 18:  19: protected virtual Boolean IsManyToMany(MemberInfo member, Boolean isLikely) 20: { 21: //a relation is many to many if it isn't one to many 22: Boolean isOneToMany = this.ModelInspector.IsOneToMany(member); 23: return (!isOneToMany); 24: } 25:  26: protected virtual Boolean IsOneToMany(MemberInfo member, Boolean isLikely) 27: { 28: Type sourceType = member.DeclaringType; 29: Type destinationType = member.GetMemberFromDeclaringType().GetPropertyOrFieldType(); 30:  31: //check if the property is of a generic collection type 32: if ((destinationType.IsGenericCollection() == true) && (destinationType.GetGenericArguments().Length == 1)) 33: { 34: Type destinationEntityType = destinationType.GetGenericArguments().Single(); 35:  36: //check if the type of the generic collection property is an entity 37: if (this.ModelInspector.IsEntity(destinationEntityType) == true) 38: { 39: //check if there is an equivalent property on the target type that is also a generic collection and points to this entity 40: PropertyInfo collectionInDestinationType = destinationEntityType.GetProperties().Where(x => (x.PropertyType.IsGenericCollection() == true) && (x.PropertyType.GetGenericArguments().Length == 1) && (x.PropertyType.GetGenericArguments().Single() == sourceType)).SingleOrDefault(); 41:  42: if (collectionInDestinationType != null) 43: { 44: return (false); 45: } 46: } 47: } 48:  49: return (true); 50: } 51:  52: protected virtual new void BeforeMapManyToMany(IModelInspector modelInspector, PropertyPath member, IManyToManyMapper collectionRelationManyToManyCustomizer) 53: { 54: Type destinationEntityType = member.LocalMember.GetPropertyOrFieldType().GetGenericArguments().First(); 55: //set the mapping table column names from each source entity name plus the _Id sufix 56: collectionRelationManyToManyCustomizer.Column(destinationEntityType.Name + "_Id"); 57: } 58:  59: protected virtual new void BeforeMapSet(IModelInspector modelInspector, PropertyPath member, ISetPropertiesMapper propertyCustomizer) 60: { 61: if (modelInspector.IsManyToMany(member.LocalMember) == true) 62: { 63: propertyCustomizer.Key(x => x.Column(member.LocalMember.DeclaringType.Name + "_Id")); 64:  65: Type sourceType = member.LocalMember.DeclaringType; 66: Type destinationType = member.LocalMember.GetPropertyOrFieldType().GetGenericArguments().First(); 67: IEnumerable<String> names = new Type[] { sourceType, destinationType }.Select(x => x.Name).OrderBy(x => x); 68:  69: //set inverse on the relation of the alphabetically first entity name 70: propertyCustomizer.Inverse(sourceType.Name == names.First()); 71: //set mapping table name from the entity names in alphabetical order 72: propertyCustomizer.Table(String.Join("_", names)); 73: } 74: } 75: } Conclusion Of course, there is much more to mapping than this, I suggest you look at all the events and functions offered by the ModelMapper to see where you can hook for making it behave the way you want. If you need any help, just let me know!

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  • The Art of Productivity

    - by dwahlin
    Getting things done has always been a challenge regardless of gender, age, race, skill, or job position. No matter how hard some people try, they end up procrastinating tasks until the last minute. Some people simply focus better when they know they’re out of time and can’t procrastinate any longer. How many times have you put off working on a term paper in school until the very last minute? With only a few hours left your mental energy and focus seem to kick in to high gear especially as you realize that you either get the paper done now or risk failing. It’s amazing how a little pressure can turn into a motivator and allow our minds to focus on a given task. Some people seem to specialize in procrastinating just about everything they do while others tend to be the “doers” who get a lot done and ultimately rise up the ladder at work. What’s the difference between these types of people? Is it pure laziness or are other factors at play? I think that some people are certainly more motivated than others, but I also think a lot of it is based on the process that “doers” tend to follow - whether knowingly or unknowingly. While I’ve certainly fought battles with procrastination, I’ve always had a knack for being able to get a lot done in a relatively short amount of time. I think a lot of my “get it done” attitude goes back to the the strong work ethic my parents instilled in me at a young age. I remember my dad saying, “You need to learn to work hard!” when I was around 5 years old. I remember that moment specifically because I was on a tractor with him the first time I heard it while he was trying to move some large rocks into a pile. The tractor was big but so were the rocks and my dad had to balance the tractor perfectly so that it didn’t tip forward too far. It was challenging work and somewhat tedious but my dad finished the task and taught me a few important lessons along the way including persistence, the importance of having a skill, and getting the job done right without skimping along the way. In this post I’m going to list a few of the techniques and processes I follow that I hope may be beneficial to others. I blogged about the general concept back in 2009 but thought I’d share some updated information and lessons learned since then. Most of the ideas that follow came from learning and refining my daily work process over the years. However, since most of the ideas are common sense (at least in my opinion), I suspect they can be found in other productivity processes that are out there. Let’s start off with one of the most important yet simple tips: Start Each Day with a List. Start Each Day with a List What are you planning to get done today? Do you keep track of everything in your head or rely on your calendar? While most of us think that we’re pretty good at managing “to do” lists strictly in our head you might be surprised at how affective writing out lists can be. By writing out tasks you’re forced to focus on the most important tasks to accomplish that day, commit yourself to those tasks, and have an easy way to track what was supposed to get done and what actually got done. Start every morning by making a list of specific tasks that you want to accomplish throughout the day. I’ll even go so far as to fill in times when I’d like to work on tasks if I have a lot of meetings or other events tying up my calendar on a given day. I’m not a big fan of using paper since I type a lot faster than I write (plus I write like a 3rd grader according to my wife), so I use the Sticky Notes feature available in Windows. Here’s an example of yesterday’s sticky note: What do you add to your list? That’s the subject of the next tip. Focus on Small Tasks It’s no secret that focusing on small, manageable tasks is more effective than trying to focus on large and more vague tasks. When you make your list each morning only add tasks that you can accomplish within a given time period. For example, if I only have 30 minutes blocked out to work on an article I don’t list “Write Article”. If I do that I’ll end up wasting 30 minutes stressing about how I’m going to get the article done in 30 minutes and ultimately get nothing done. Instead, I’ll list something like “Write Introductory Paragraphs for Article”. The next day I may add, “Write first section of article” or something that’s small and manageable – something I’m confident that I can get done. You’ll find that once you’ve knocked out several smaller tasks it’s easy to continue completing others since you want to keep the momentum going. In addition to keeping my tasks focused and small, I also make a conscious effort to limit my list to 4 or 5 tasks initially. I’ve found that if I list more than 5 tasks I feel a bit overwhelmed which hurts my productivity. It’s easy to add additional tasks as you complete others and you get the added benefit of that confidence boost of knowing that you’re being productive and getting things done as you remove tasks and add others. Getting Started is the Hardest (Yet Easiest) Part I’ve always found that getting started is the hardest part and one of the biggest contributors to procrastination. Getting started working on tasks is a lot like getting a large rock pushed to the bottom of a hill. It’s difficult to get the rock rolling at first, but once you manage to get it rocking some it’s really easy to get it rolling on its way to the bottom. As an example, I’ve written 100s of articles for technical magazines over the years and have really struggled with the initial introductory paragraphs. Keep in mind that these are the paragraphs that don’t really add that much value (in my opinion anyway). They introduce the reader to the subject matter and nothing more. What a waste of time for me to sit there stressing about how to start the article. On more than one occasion I’ve spent more than an hour trying to come up with 2-3 paragraphs of text.  Talk about a productivity killer! Whether you’re struggling with a writing task, some code for a project, an email, or other tasks, jumping in without thinking too much is the best way to get started I’ve found. I’m not saying that you shouldn’t have an overall plan when jumping into a task, but on some occasions you’ll find that if you simply jump into the task and stop worrying about doing everything perfectly that things will flow more smoothly. For my introductory paragraph problem I give myself 5 minutes to write out some general concepts about what I know the article will cover and then spend another 10-15 minutes going back and refining that information. That way I actually have some ideas to work with rather than a blank sheet of paper. If I still find myself struggling I’ll write the rest of the article first and then circle back to the introductory paragraphs once I’m done. To sum this tip up: Jump into a task without thinking too hard about it. It’s better to to get the rock at the top of the hill rocking some than doing nothing at all. You can always go back and refine your work.   Learn a Productivity Technique and Stick to It There are a lot of different productivity programs and seminars out there being sold by companies. I’ve always laughed at how much money people spend on some of these motivational programs/seminars because I think that being productive isn’t that hard if you create a re-useable set of steps and processes to follow. That’s not to say that some of these programs/seminars aren’t worth the money of course because I know they’ve definitely benefited some people that have a hard time getting things done and staying focused. One of the best productivity techniques I’ve ever learned is called the “Pomodoro Technique” and it’s completely free. This technique is an extremely simple way to manage your time without having to remember a bunch of steps, color coding mechanisms, or other processes. The technique was originally developed by Francesco Cirillo in the 80s and can be implemented with a simple timer. In a nutshell here’s how the technique works: Pick a task to work on Set the timer to 25 minutes and work on the task Once the timer rings record your time Take a 5 minute break Repeat the process Here’s why the technique works well for me: It forces me to focus on a single task for 25 minutes. In the past I had no time goal in mind and just worked aimlessly on a task until I got interrupted or bored. 25 minutes is a small enough chunk of time for me to stay focused. Any distractions that may come up have to wait until after the timer goes off. If the distraction is really important then I stop the timer and record my time up to that point. When the timer is running I act as if I only have 25 minutes total for the task (like you’re down to the last 25 minutes before turning in your term paper….frantically working to get it done) which helps me stay focused and turns into a “beat the clock” type of game. It’s actually kind of fun if you treat it that way and really helps me focus on a the task at hand. I automatically know how much time I’m spending on a given task (more on this later) by using this technique. I know that I have 5 minutes after each pomodoro (the 25 minute sprint) to waste on anything I’d like including visiting a website, stepping away from the computer, etc. which also helps me stay focused when the 25 minute timer is counting down. I use this technique so much that I decided to build a program for Windows 8 called Pomodoro Focus (I plan to blog about how it was built in a later post). It’s a Windows Store application that allows people to track tasks, productive time spent on tasks, interruption time experienced while working on a given task, and the number of pomodoros completed. If a time estimate is given when the task is initially created, Pomodoro Focus will also show the task completion percentage. I like it because it allows me to track my tasks, time spent on tasks (very useful in the consulting world), and even how much time I wasted on tasks (pressing the pause button while working on a task starts the interruption timer). I recently added a new feature that charts productive and interruption time for tasks since I wanted to see how productive I was from week to week and month to month. A few screenshots from the Pomodoro Focus app are shown next, I had a lot of fun building it and use it myself to as I work on tasks.   There are certainly many other productivity techniques and processes out there (and a slew of books describing them), but the Pomodoro Technique has been the simplest and most effective technique I’ve ever come across for staying focused and getting things done.   Persistence is Key Getting things done is great but one of the biggest lessons I’ve learned in life is that persistence is key especially when you’re trying to get something done that at times seems insurmountable. Small tasks ultimately lead to larger tasks getting accomplished, however, it’s not all roses along the way as some of the smaller tasks may come with their own share of bumps and bruises that lead to discouragement about the end goal and whether or not it is worth achieving at all. I’ve been on several long-term projects over my career as a software developer (I have one personal project going right now that fits well here) and found that repeating, “Persistence is the key!” over and over to myself really helps. Not every project turns out to be successful, but if you don’t show persistence through the hard times you’ll never know if you succeeded or not. Likewise, if you don’t persistently stick to the process of creating a daily list, follow a productivity process, etc. then the odds of consistently staying productive aren’t good.   Track Your Time How much time do you actually spend working on various tasks? If you don’t currently track time spent answering emails, on phone calls, and working on various tasks then you might be surprised to find out that a task that you thought was going to take you 30 minutes ultimately ended up taking 2 hours. If you don’t track the time you spend working on tasks how can you expect to learn from your mistakes, optimize your time better, and become more productive? That’s another reason why I like the Pomodoro Technique – it makes it easy to stay focused on tasks while also tracking how much time I’m working on a given task.   Eliminate Distractions I blogged about this final tip several years ago but wanted to bring it up again. If you want to be productive (and ultimately successful at whatever you’re doing) then you can’t waste a lot of time playing games or on Twitter, Facebook, or other time sucking websites. If you see an article you’re interested in that has no relation at all to the tasks you’re trying to accomplish then bookmark it and read it when you have some spare time (such as during a pomodoro break). Fighting the temptation to check your friends’ status updates on Facebook? Resist the urge and realize how much those types of activities are hurting your productivity and taking away from your focus. I’ll admit that eliminating distractions is still tough for me personally and something I have to constantly battle. But, I’ve made a conscious decision to cut back on my visits and updates to Facebook, Twitter, Google+ and other sites. Sure, my Klout score has suffered as a result lately, but does anyone actually care about those types of scores aside from your online “friends” (few of whom you’ve actually met in person)? :-) Ultimately it comes down to self-discipline and how badly you want to be productive and successful in your career, life goals, hobbies, or whatever you’re working on. Rather than having your homepage take you to a time wasting news site, game site, social site, picture site, or others, how about adding something like the following as your homepage? Every time your browser opens you’ll see a personal message which helps keep you on the right track. You can download my ubber-sophisticated homepage here if interested. Summary Is there a single set of steps that if followed can ultimately lead to productivity? I don’t think so since one size has never fit all. Every person is different, works in their own unique way, and has their own set of motivators, distractions, and more. While I certainly don’t consider myself to be an expert on the subject of productivity, I do think that if you learn what steps work best for you and gradually refine them over time that you can come up with a personal productivity process that can serve you well. Productivity is definitely an “art” that anyone can learn with a little practice and persistence. You’ve seen some of the steps that I personally like to follow and I hope you find some of them useful in boosting your productivity. If you have others you use please leave a comment. I’m always looking for ways to improve.

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  • Little more help with writing a o buffer with libjpeg

    - by Richard Knop
    So I have managed to find another question discussing how to use the libjpeg to compress an image to jpeg. I have found this code which is supposed to work: Compressing IplImage to JPEG using libjpeg in OpenCV Here's the code (it compiles ok): /* This a custom destination manager for jpeglib that enables the use of memory to memory compression. See IJG documentation for details. */ typedef struct { struct jpeg_destination_mgr pub; /* base class */ JOCTET* buffer; /* buffer start address */ int bufsize; /* size of buffer */ size_t datasize; /* final size of compressed data */ int* outsize; /* user pointer to datasize */ int errcount; /* counts up write errors due to buffer overruns */ } memory_destination_mgr; typedef memory_destination_mgr* mem_dest_ptr; /* ------------------------------------------------------------- */ /* MEMORY DESTINATION INTERFACE METHODS */ /* ------------------------------------------------------------- */ /* This function is called by the library before any data gets written */ METHODDEF(void) init_destination (j_compress_ptr cinfo) { mem_dest_ptr dest = (mem_dest_ptr)cinfo->dest; dest->pub.next_output_byte = dest->buffer; /* set destination buffer */ dest->pub.free_in_buffer = dest->bufsize; /* input buffer size */ dest->datasize = 0; /* reset output size */ dest->errcount = 0; /* reset error count */ } /* This function is called by the library if the buffer fills up I just reset destination pointer and buffer size here. Note that this behavior, while preventing seg faults will lead to invalid output streams as data is over- written. */ METHODDEF(boolean) empty_output_buffer (j_compress_ptr cinfo) { mem_dest_ptr dest = (mem_dest_ptr)cinfo->dest; dest->pub.next_output_byte = dest->buffer; dest->pub.free_in_buffer = dest->bufsize; ++dest->errcount; /* need to increase error count */ return TRUE; } /* Usually the library wants to flush output here. I will calculate output buffer size here. Note that results become incorrect, once empty_output_buffer was called. This situation is notified by errcount. */ METHODDEF(void) term_destination (j_compress_ptr cinfo) { mem_dest_ptr dest = (mem_dest_ptr)cinfo->dest; dest->datasize = dest->bufsize - dest->pub.free_in_buffer; if (dest->outsize) *dest->outsize += (int)dest->datasize; } /* Override the default destination manager initialization provided by jpeglib. Since we want to use memory-to-memory compression, we need to use our own destination manager. */ GLOBAL(void) jpeg_memory_dest (j_compress_ptr cinfo, JOCTET* buffer, int bufsize, int* outsize) { mem_dest_ptr dest; /* first call for this instance - need to setup */ if (cinfo->dest == 0) { cinfo->dest = (struct jpeg_destination_mgr *) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT, sizeof (memory_destination_mgr)); } dest = (mem_dest_ptr) cinfo->dest; dest->bufsize = bufsize; dest->buffer = buffer; dest->outsize = outsize; /* set method callbacks */ dest->pub.init_destination = init_destination; dest->pub.empty_output_buffer = empty_output_buffer; dest->pub.term_destination = term_destination; } /* ------------------------------------------------------------- */ /* MEMORY SOURCE INTERFACE METHODS */ /* ------------------------------------------------------------- */ /* Called before data is read */ METHODDEF(void) init_source (j_decompress_ptr dinfo) { /* nothing to do here, really. I mean. I'm not lazy or something, but... we're actually through here. */ } /* Called if the decoder wants some bytes that we cannot provide... */ METHODDEF(boolean) fill_input_buffer (j_decompress_ptr dinfo) { /* we can't do anything about this. This might happen if the provided buffer is either invalid with regards to its content or just a to small bufsize has been given. */ /* fail. */ return FALSE; } /* From IJG docs: "it's not clear that being smart is worth much trouble" So I save myself some trouble by ignoring this bit. */ METHODDEF(void) skip_input_data (j_decompress_ptr dinfo, INT32 num_bytes) { /* There might be more data to skip than available in buffer. This clearly is an error, so screw this mess. */ if ((size_t)num_bytes > dinfo->src->bytes_in_buffer) { dinfo->src->next_input_byte = 0; /* no buffer byte */ dinfo->src->bytes_in_buffer = 0; /* no input left */ } else { dinfo->src->next_input_byte += num_bytes; dinfo->src->bytes_in_buffer -= num_bytes; } } /* Finished with decompression */ METHODDEF(void) term_source (j_decompress_ptr dinfo) { /* Again. Absolute laziness. Nothing to do here. Boring. */ } GLOBAL(void) jpeg_memory_src (j_decompress_ptr dinfo, unsigned char* buffer, size_t size) { struct jpeg_source_mgr* src; /* first call for this instance - need to setup */ if (dinfo->src == 0) { dinfo->src = (struct jpeg_source_mgr *) (*dinfo->mem->alloc_small) ((j_common_ptr) dinfo, JPOOL_PERMANENT, sizeof (struct jpeg_source_mgr)); } src = dinfo->src; src->next_input_byte = buffer; src->bytes_in_buffer = size; src->init_source = init_source; src->fill_input_buffer = fill_input_buffer; src->skip_input_data = skip_input_data; src->term_source = term_source; /* IJG recommend to use their function - as I don't know **** about how to do better, I follow this recommendation */ src->resync_to_restart = jpeg_resync_to_restart; } All I need to do is replace the jpeg_stdio_dest in my program with this code: int numBytes = 0; //size of jpeg after compression char * storage = new char[150000]; //storage buffer JOCTET *jpgbuff = (JOCTET*)storage; //JOCTET pointer to buffer jpeg_memory_dest(&cinfo,jpgbuff,150000,&numBytes); So I need some help to incorporate the above four lines into this function which now works but writes to a file instead of a memory: int write_jpeg_file( char *filename ) { struct jpeg_compress_struct cinfo; struct jpeg_error_mgr jerr; /* this is a pointer to one row of image data */ JSAMPROW row_pointer[1]; FILE *outfile = fopen( filename, "wb" ); if ( !outfile ) { printf("Error opening output jpeg file %s\n!", filename ); return -1; } cinfo.err = jpeg_std_error( &jerr ); jpeg_create_compress(&cinfo); jpeg_stdio_dest(&cinfo, outfile); /* Setting the parameters of the output file here */ cinfo.image_width = width; cinfo.image_height = height; cinfo.input_components = bytes_per_pixel; cinfo.in_color_space = color_space; /* default compression parameters, we shouldn't be worried about these */ jpeg_set_defaults( &cinfo ); /* Now do the compression .. */ jpeg_start_compress( &cinfo, TRUE ); /* like reading a file, this time write one row at a time */ while( cinfo.next_scanline < cinfo.image_height ) { row_pointer[0] = &raw_image[ cinfo.next_scanline * cinfo.image_width * cinfo.input_components]; jpeg_write_scanlines( &cinfo, row_pointer, 1 ); } /* similar to read file, clean up after we're done compressing */ jpeg_finish_compress( &cinfo ); jpeg_destroy_compress( &cinfo ); fclose( outfile ); /* success code is 1! */ return 1; } Anybody could help me out a bit with it? I've tried meddling with it but I am not sure how to do it. I I just replace this line: jpeg_stdio_dest(&cinfo, outfile); It's not going to work. There is more stuff that needs to be changed a bit in that function and I am being a little lost from all those pointers and memory management.

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  • Introduction to the ASP.NET Web API

    - by Stephen.Walther
    I am a huge fan of Ajax. If you want to create a great experience for the users of your website – regardless of whether you are building an ASP.NET MVC or an ASP.NET Web Forms site — then you need to use Ajax. Otherwise, you are just being cruel to your customers. We use Ajax extensively in several of the ASP.NET applications that my company, Superexpert.com, builds. We expose data from the server as JSON and use jQuery to retrieve and update that data from the browser. One challenge, when building an ASP.NET website, is deciding on which technology to use to expose JSON data from the server. For example, how do you expose a list of products from the server as JSON so you can retrieve the list of products with jQuery? You have a number of options (too many options) including ASMX Web services, WCF Web Services, ASHX Generic Handlers, WCF Data Services, and MVC controller actions. Fortunately, the world has just been simplified. With the release of ASP.NET 4 Beta, Microsoft has introduced a new technology for exposing JSON from the server named the ASP.NET Web API. You can use the ASP.NET Web API with both ASP.NET MVC and ASP.NET Web Forms applications. The goal of this blog post is to provide you with a brief overview of the features of the new ASP.NET Web API. You learn how to use the ASP.NET Web API to retrieve, insert, update, and delete database records with jQuery. We also discuss how you can perform form validation when using the Web API and use OData when using the Web API. Creating an ASP.NET Web API Controller The ASP.NET Web API exposes JSON data through a new type of controller called an API controller. You can add an API controller to an existing ASP.NET MVC 4 project through the standard Add Controller dialog box. Right-click your Controllers folder and select Add, Controller. In the dialog box, name your controller MovieController and select the Empty API controller template: A brand new API controller looks like this: using System; using System.Collections.Generic; using System.Linq; using System.Net.Http; using System.Web.Http; namespace MyWebAPIApp.Controllers { public class MovieController : ApiController { } } An API controller, unlike a standard MVC controller, derives from the base ApiController class instead of the base Controller class. Using jQuery to Retrieve, Insert, Update, and Delete Data Let’s create an Ajaxified Movie Database application. We’ll retrieve, insert, update, and delete movies using jQuery with the MovieController which we just created. Our Movie model class looks like this: namespace MyWebAPIApp.Models { public class Movie { public int Id { get; set; } public string Title { get; set; } public string Director { get; set; } } } Our application will consist of a single HTML page named Movies.html. We’ll place all of our jQuery code in the Movies.html page. Getting a Single Record with the ASP.NET Web API To support retrieving a single movie from the server, we need to add a Get method to our API controller: using System; using System.Collections.Generic; using System.Linq; using System.Net; using System.Net.Http; using System.Web.Http; using MyWebAPIApp.Models; namespace MyWebAPIApp.Controllers { public class MovieController : ApiController { public Movie GetMovie(int id) { // Return movie by id if (id == 1) { return new Movie { Id = 1, Title = "Star Wars", Director = "Lucas" }; } // Otherwise, movie was not found throw new HttpResponseException(HttpStatusCode.NotFound); } } } In the code above, the GetMovie() method accepts the Id of a movie. If the Id has the value 1 then the method returns the movie Star Wars. Otherwise, the method throws an exception and returns 404 Not Found HTTP status code. After building your project, you can invoke the MovieController.GetMovie() method by entering the following URL in your web browser address bar: http://localhost:[port]/api/movie/1 (You’ll need to enter the correct randomly generated port). In the URL api/movie/1, the first “api” segment indicates that this is a Web API route. The “movie” segment indicates that the MovieController should be invoked. You do not specify the name of the action. Instead, the HTTP method used to make the request – GET, POST, PUT, DELETE — is used to identify the action to invoke. The ASP.NET Web API uses different routing conventions than normal ASP.NET MVC controllers. When you make an HTTP GET request then any API controller method with a name that starts with “GET” is invoked. So, we could have called our API controller action GetPopcorn() instead of GetMovie() and it would still be invoked by the URL api/movie/1. The default route for the Web API is defined in the Global.asax file and it looks like this: routes.MapHttpRoute( name: "DefaultApi", routeTemplate: "api/{controller}/{id}", defaults: new { id = RouteParameter.Optional } ); We can invoke our GetMovie() controller action with the jQuery code in the following HTML page: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Get Movie</title> </head> <body> <div> Title: <span id="title"></span> </div> <div> Director: <span id="director"></span> </div> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> getMovie(1, function (movie) { $("#title").html(movie.Title); $("#director").html(movie.Director); }); function getMovie(id, callback) { $.ajax({ url: "/api/Movie", data: { id: id }, type: "GET", contentType: "application/json;charset=utf-8", statusCode: { 200: function (movie) { callback(movie); }, 404: function () { alert("Not Found!"); } } }); } </script> </body> </html> In the code above, the jQuery $.ajax() method is used to invoke the GetMovie() method. Notice that the Ajax call handles two HTTP response codes. When the GetMove() method successfully returns a movie, the method returns a 200 status code. In that case, the details of the movie are displayed in the HTML page. Otherwise, if the movie is not found, the GetMovie() method returns a 404 status code. In that case, the page simply displays an alert box indicating that the movie was not found (hopefully, you would implement something more graceful in an actual application). You can use your browser’s Developer Tools to see what is going on in the background when you open the HTML page (hit F12 in the most recent version of most browsers). For example, you can use the Network tab in Google Chrome to see the Ajax request which invokes the GetMovie() method: Getting a Set of Records with the ASP.NET Web API Let’s modify our Movie API controller so that it returns a collection of movies. The following Movie controller has a new ListMovies() method which returns a (hard-coded) collection of movies: using System; using System.Collections.Generic; using System.Linq; using System.Net; using System.Net.Http; using System.Web.Http; using MyWebAPIApp.Models; namespace MyWebAPIApp.Controllers { public class MovieController : ApiController { public IEnumerable<Movie> ListMovies() { return new List<Movie> { new Movie {Id=1, Title="Star Wars", Director="Lucas"}, new Movie {Id=1, Title="King Kong", Director="Jackson"}, new Movie {Id=1, Title="Memento", Director="Nolan"} }; } } } Because we named our action ListMovies(), the default Web API route will never match it. Therefore, we need to add the following custom route to our Global.asax file (at the top of the RegisterRoutes() method): routes.MapHttpRoute( name: "ActionApi", routeTemplate: "api/{controller}/{action}/{id}", defaults: new { id = RouteParameter.Optional } ); This route enables us to invoke the ListMovies() method with the URL /api/movie/listmovies. Now that we have exposed our collection of movies from the server, we can retrieve and display the list of movies using jQuery in our HTML page: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>List Movies</title> </head> <body> <div id="movies"></div> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> listMovies(function (movies) { var strMovies=""; $.each(movies, function (index, movie) { strMovies += "<div>" + movie.Title + "</div>"; }); $("#movies").html(strMovies); }); function listMovies(callback) { $.ajax({ url: "/api/Movie/ListMovies", data: {}, type: "GET", contentType: "application/json;charset=utf-8", }).then(function(movies){ callback(movies); }); } </script> </body> </html>     Inserting a Record with the ASP.NET Web API Now let’s modify our Movie API controller so it supports creating new records: public HttpResponseMessage<Movie> PostMovie(Movie movieToCreate) { // Add movieToCreate to the database and update primary key movieToCreate.Id = 23; // Build a response that contains the location of the new movie var response = new HttpResponseMessage<Movie>(movieToCreate, HttpStatusCode.Created); var relativePath = "/api/movie/" + movieToCreate.Id; response.Headers.Location = new Uri(Request.RequestUri, relativePath); return response; } The PostMovie() method in the code above accepts a movieToCreate parameter. We don’t actually store the new movie anywhere. In real life, you will want to call a service method to store the new movie in a database. When you create a new resource, such as a new movie, you should return the location of the new resource. In the code above, the URL where the new movie can be retrieved is assigned to the Location header returned in the PostMovie() response. Because the name of our method starts with “Post”, we don’t need to create a custom route. The PostMovie() method can be invoked with the URL /Movie/PostMovie – just as long as the method is invoked within the context of a HTTP POST request. The following HTML page invokes the PostMovie() method. <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Create Movie</title> </head> <body> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> var movieToCreate = { title: "The Hobbit", director: "Jackson" }; createMovie(movieToCreate, function (newMovie) { alert("New movie created with an Id of " + newMovie.Id); }); function createMovie(movieToCreate, callback) { $.ajax({ url: "/api/Movie", data: JSON.stringify( movieToCreate ), type: "POST", contentType: "application/json;charset=utf-8", statusCode: { 201: function (newMovie) { callback(newMovie); } } }); } </script> </body> </html> This page creates a new movie (the Hobbit) by calling the createMovie() method. The page simply displays the Id of the new movie: The HTTP Post operation is performed with the following call to the jQuery $.ajax() method: $.ajax({ url: "/api/Movie", data: JSON.stringify( movieToCreate ), type: "POST", contentType: "application/json;charset=utf-8", statusCode: { 201: function (newMovie) { callback(newMovie); } } }); Notice that the type of Ajax request is a POST request. This is required to match the PostMovie() method. Notice, furthermore, that the new movie is converted into JSON using JSON.stringify(). The JSON.stringify() method takes a JavaScript object and converts it into a JSON string. Finally, notice that success is represented with a 201 status code. The HttpStatusCode.Created value returned from the PostMovie() method returns a 201 status code. Updating a Record with the ASP.NET Web API Here’s how we can modify the Movie API controller to support updating an existing record. In this case, we need to create a PUT method to handle an HTTP PUT request: public void PutMovie(Movie movieToUpdate) { if (movieToUpdate.Id == 1) { // Update the movie in the database return; } // If you can't find the movie to update throw new HttpResponseException(HttpStatusCode.NotFound); } Unlike our PostMovie() method, the PutMovie() method does not return a result. The action either updates the database or, if the movie cannot be found, returns an HTTP Status code of 404. The following HTML page illustrates how you can invoke the PutMovie() method: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Put Movie</title> </head> <body> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> var movieToUpdate = { id: 1, title: "The Hobbit", director: "Jackson" }; updateMovie(movieToUpdate, function () { alert("Movie updated!"); }); function updateMovie(movieToUpdate, callback) { $.ajax({ url: "/api/Movie", data: JSON.stringify(movieToUpdate), type: "PUT", contentType: "application/json;charset=utf-8", statusCode: { 200: function () { callback(); }, 404: function () { alert("Movie not found!"); } } }); } </script> </body> </html> Deleting a Record with the ASP.NET Web API Here’s the code for deleting a movie: public HttpResponseMessage DeleteMovie(int id) { // Delete the movie from the database // Return status code return new HttpResponseMessage(HttpStatusCode.NoContent); } This method simply deletes the movie (well, not really, but pretend that it does) and returns a No Content status code (204). The following page illustrates how you can invoke the DeleteMovie() action: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Delete Movie</title> </head> <body> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> deleteMovie(1, function () { alert("Movie deleted!"); }); function deleteMovie(id, callback) { $.ajax({ url: "/api/Movie", data: JSON.stringify({id:id}), type: "DELETE", contentType: "application/json;charset=utf-8", statusCode: { 204: function () { callback(); } } }); } </script> </body> </html> Performing Validation How do you perform form validation when using the ASP.NET Web API? Because validation in ASP.NET MVC is driven by the Default Model Binder, and because the Web API uses the Default Model Binder, you get validation for free. Let’s modify our Movie class so it includes some of the standard validation attributes: using System.ComponentModel.DataAnnotations; namespace MyWebAPIApp.Models { public class Movie { public int Id { get; set; } [Required(ErrorMessage="Title is required!")] [StringLength(5, ErrorMessage="Title cannot be more than 5 characters!")] public string Title { get; set; } [Required(ErrorMessage="Director is required!")] public string Director { get; set; } } } In the code above, the Required validation attribute is used to make both the Title and Director properties required. The StringLength attribute is used to require the length of the movie title to be no more than 5 characters. Now let’s modify our PostMovie() action to validate a movie before adding the movie to the database: public HttpResponseMessage PostMovie(Movie movieToCreate) { // Validate movie if (!ModelState.IsValid) { var errors = new JsonArray(); foreach (var prop in ModelState.Values) { if (prop.Errors.Any()) { errors.Add(prop.Errors.First().ErrorMessage); } } return new HttpResponseMessage<JsonValue>(errors, HttpStatusCode.BadRequest); } // Add movieToCreate to the database and update primary key movieToCreate.Id = 23; // Build a response that contains the location of the new movie var response = new HttpResponseMessage<Movie>(movieToCreate, HttpStatusCode.Created); var relativePath = "/api/movie/" + movieToCreate.Id; response.Headers.Location = new Uri(Request.RequestUri, relativePath); return response; } If ModelState.IsValid has the value false then the errors in model state are copied to a new JSON array. Each property – such as the Title and Director property — can have multiple errors. In the code above, only the first error message is copied over. The JSON array is returned with a Bad Request status code (400 status code). The following HTML page illustrates how you can invoke our modified PostMovie() action and display any error messages: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Create Movie</title> </head> <body> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> var movieToCreate = { title: "The Hobbit", director: "" }; createMovie(movieToCreate, function (newMovie) { alert("New movie created with an Id of " + newMovie.Id); }, function (errors) { var strErrors = ""; $.each(errors, function(index, err) { strErrors += "*" + err + "\n"; }); alert(strErrors); } ); function createMovie(movieToCreate, success, fail) { $.ajax({ url: "/api/Movie", data: JSON.stringify(movieToCreate), type: "POST", contentType: "application/json;charset=utf-8", statusCode: { 201: function (newMovie) { success(newMovie); }, 400: function (xhr) { var errors = JSON.parse(xhr.responseText); fail(errors); } } }); } </script> </body> </html> The createMovie() function performs an Ajax request and handles either a 201 or a 400 status code from the response. If a 201 status code is returned then there were no validation errors and the new movie was created. If, on the other hand, a 400 status code is returned then there was a validation error. The validation errors are retrieved from the XmlHttpRequest responseText property. The error messages are displayed in an alert: (Please don’t use JavaScript alert dialogs to display validation errors, I just did it this way out of pure laziness) This validation code in our PostMovie() method is pretty generic. There is nothing specific about this code to the PostMovie() method. In the following video, Jon Galloway demonstrates how to create a global Validation filter which can be used with any API controller action: http://www.asp.net/web-api/overview/web-api-routing-and-actions/video-custom-validation His validation filter looks like this: using System.Json; using System.Linq; using System.Net; using System.Net.Http; using System.Web.Http.Controllers; using System.Web.Http.Filters; namespace MyWebAPIApp.Filters { public class ValidationActionFilter:ActionFilterAttribute { public override void OnActionExecuting(HttpActionContext actionContext) { var modelState = actionContext.ModelState; if (!modelState.IsValid) { dynamic errors = new JsonObject(); foreach (var key in modelState.Keys) { var state = modelState[key]; if (state.Errors.Any()) { errors[key] = state.Errors.First().ErrorMessage; } } actionContext.Response = new HttpResponseMessage<JsonValue>(errors, HttpStatusCode.BadRequest); } } } } And you can register the validation filter in the Application_Start() method in the Global.asax file like this: GlobalConfiguration.Configuration.Filters.Add(new ValidationActionFilter()); After you register the Validation filter, validation error messages are returned from any API controller action method automatically when validation fails. You don’t need to add any special logic to any of your API controller actions to take advantage of the filter. Querying using OData The OData protocol is an open protocol created by Microsoft which enables you to perform queries over the web. The official website for OData is located here: http://odata.org For example, here are some of the query options which you can use with OData: · $orderby – Enables you to retrieve results in a certain order. · $top – Enables you to retrieve a certain number of results. · $skip – Enables you to skip over a certain number of results (use with $top for paging). · $filter – Enables you to filter the results returned. The ASP.NET Web API supports a subset of the OData protocol. You can use all of the query options listed above when interacting with an API controller. The only requirement is that the API controller action returns its data as IQueryable. For example, the following Movie controller has an action named GetMovies() which returns an IQueryable of movies: public IQueryable<Movie> GetMovies() { return new List<Movie> { new Movie {Id=1, Title="Star Wars", Director="Lucas"}, new Movie {Id=2, Title="King Kong", Director="Jackson"}, new Movie {Id=3, Title="Willow", Director="Lucas"}, new Movie {Id=4, Title="Shrek", Director="Smith"}, new Movie {Id=5, Title="Memento", Director="Nolan"} }.AsQueryable(); } If you enter the following URL in your browser: /api/movie?$top=2&$orderby=Title Then you will limit the movies returned to the top 2 in order of the movie Title. You will get the following results: By using the $top option in combination with the $skip option, you can enable client-side paging. For example, you can use $top and $skip to page through thousands of products, 10 products at a time. The $filter query option is very powerful. You can use this option to filter the results from a query. Here are some examples: Return every movie directed by Lucas: /api/movie?$filter=Director eq ‘Lucas’ Return every movie which has a title which starts with ‘S’: /api/movie?$filter=startswith(Title,’S') Return every movie which has an Id greater than 2: /api/movie?$filter=Id gt 2 The complete documentation for the $filter option is located here: http://www.odata.org/developers/protocols/uri-conventions#FilterSystemQueryOption Summary The goal of this blog entry was to provide you with an overview of the new ASP.NET Web API introduced with the Beta release of ASP.NET 4. In this post, I discussed how you can retrieve, insert, update, and delete data by using jQuery with the Web API. I also discussed how you can use the standard validation attributes with the Web API. You learned how to return validation error messages to the client and display the error messages using jQuery. Finally, we briefly discussed how the ASP.NET Web API supports the OData protocol. For example, you learned how to filter records returned from an API controller action by using the $filter query option. I’m excited about the new Web API. This is a feature which I expect to use with almost every ASP.NET application which I build in the future.

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  • Introduction to the ASP.NET Web API

    - by Stephen.Walther
    I am a huge fan of Ajax. If you want to create a great experience for the users of your website – regardless of whether you are building an ASP.NET MVC or an ASP.NET Web Forms site — then you need to use Ajax. Otherwise, you are just being cruel to your customers. We use Ajax extensively in several of the ASP.NET applications that my company, Superexpert.com, builds. We expose data from the server as JSON and use jQuery to retrieve and update that data from the browser. One challenge, when building an ASP.NET website, is deciding on which technology to use to expose JSON data from the server. For example, how do you expose a list of products from the server as JSON so you can retrieve the list of products with jQuery? You have a number of options (too many options) including ASMX Web services, WCF Web Services, ASHX Generic Handlers, WCF Data Services, and MVC controller actions. Fortunately, the world has just been simplified. With the release of ASP.NET 4 Beta, Microsoft has introduced a new technology for exposing JSON from the server named the ASP.NET Web API. You can use the ASP.NET Web API with both ASP.NET MVC and ASP.NET Web Forms applications. The goal of this blog post is to provide you with a brief overview of the features of the new ASP.NET Web API. You learn how to use the ASP.NET Web API to retrieve, insert, update, and delete database records with jQuery. We also discuss how you can perform form validation when using the Web API and use OData when using the Web API. Creating an ASP.NET Web API Controller The ASP.NET Web API exposes JSON data through a new type of controller called an API controller. You can add an API controller to an existing ASP.NET MVC 4 project through the standard Add Controller dialog box. Right-click your Controllers folder and select Add, Controller. In the dialog box, name your controller MovieController and select the Empty API controller template: A brand new API controller looks like this: using System; using System.Collections.Generic; using System.Linq; using System.Net.Http; using System.Web.Http; namespace MyWebAPIApp.Controllers { public class MovieController : ApiController { } } An API controller, unlike a standard MVC controller, derives from the base ApiController class instead of the base Controller class. Using jQuery to Retrieve, Insert, Update, and Delete Data Let’s create an Ajaxified Movie Database application. We’ll retrieve, insert, update, and delete movies using jQuery with the MovieController which we just created. Our Movie model class looks like this: namespace MyWebAPIApp.Models { public class Movie { public int Id { get; set; } public string Title { get; set; } public string Director { get; set; } } } Our application will consist of a single HTML page named Movies.html. We’ll place all of our jQuery code in the Movies.html page. Getting a Single Record with the ASP.NET Web API To support retrieving a single movie from the server, we need to add a Get method to our API controller: using System; using System.Collections.Generic; using System.Linq; using System.Net; using System.Net.Http; using System.Web.Http; using MyWebAPIApp.Models; namespace MyWebAPIApp.Controllers { public class MovieController : ApiController { public Movie GetMovie(int id) { // Return movie by id if (id == 1) { return new Movie { Id = 1, Title = "Star Wars", Director = "Lucas" }; } // Otherwise, movie was not found throw new HttpResponseException(HttpStatusCode.NotFound); } } } In the code above, the GetMovie() method accepts the Id of a movie. If the Id has the value 1 then the method returns the movie Star Wars. Otherwise, the method throws an exception and returns 404 Not Found HTTP status code. After building your project, you can invoke the MovieController.GetMovie() method by entering the following URL in your web browser address bar: http://localhost:[port]/api/movie/1 (You’ll need to enter the correct randomly generated port). In the URL api/movie/1, the first “api” segment indicates that this is a Web API route. The “movie” segment indicates that the MovieController should be invoked. You do not specify the name of the action. Instead, the HTTP method used to make the request – GET, POST, PUT, DELETE — is used to identify the action to invoke. The ASP.NET Web API uses different routing conventions than normal ASP.NET MVC controllers. When you make an HTTP GET request then any API controller method with a name that starts with “GET” is invoked. So, we could have called our API controller action GetPopcorn() instead of GetMovie() and it would still be invoked by the URL api/movie/1. The default route for the Web API is defined in the Global.asax file and it looks like this: routes.MapHttpRoute( name: "DefaultApi", routeTemplate: "api/{controller}/{id}", defaults: new { id = RouteParameter.Optional } ); We can invoke our GetMovie() controller action with the jQuery code in the following HTML page: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Get Movie</title> </head> <body> <div> Title: <span id="title"></span> </div> <div> Director: <span id="director"></span> </div> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> getMovie(1, function (movie) { $("#title").html(movie.Title); $("#director").html(movie.Director); }); function getMovie(id, callback) { $.ajax({ url: "/api/Movie", data: { id: id }, type: "GET", contentType: "application/json;charset=utf-8", statusCode: { 200: function (movie) { callback(movie); }, 404: function () { alert("Not Found!"); } } }); } </script> </body> </html> In the code above, the jQuery $.ajax() method is used to invoke the GetMovie() method. Notice that the Ajax call handles two HTTP response codes. When the GetMove() method successfully returns a movie, the method returns a 200 status code. In that case, the details of the movie are displayed in the HTML page. Otherwise, if the movie is not found, the GetMovie() method returns a 404 status code. In that case, the page simply displays an alert box indicating that the movie was not found (hopefully, you would implement something more graceful in an actual application). You can use your browser’s Developer Tools to see what is going on in the background when you open the HTML page (hit F12 in the most recent version of most browsers). For example, you can use the Network tab in Google Chrome to see the Ajax request which invokes the GetMovie() method: Getting a Set of Records with the ASP.NET Web API Let’s modify our Movie API controller so that it returns a collection of movies. The following Movie controller has a new ListMovies() method which returns a (hard-coded) collection of movies: using System; using System.Collections.Generic; using System.Linq; using System.Net; using System.Net.Http; using System.Web.Http; using MyWebAPIApp.Models; namespace MyWebAPIApp.Controllers { public class MovieController : ApiController { public IEnumerable<Movie> ListMovies() { return new List<Movie> { new Movie {Id=1, Title="Star Wars", Director="Lucas"}, new Movie {Id=1, Title="King Kong", Director="Jackson"}, new Movie {Id=1, Title="Memento", Director="Nolan"} }; } } } Because we named our action ListMovies(), the default Web API route will never match it. Therefore, we need to add the following custom route to our Global.asax file (at the top of the RegisterRoutes() method): routes.MapHttpRoute( name: "ActionApi", routeTemplate: "api/{controller}/{action}/{id}", defaults: new { id = RouteParameter.Optional } ); This route enables us to invoke the ListMovies() method with the URL /api/movie/listmovies. Now that we have exposed our collection of movies from the server, we can retrieve and display the list of movies using jQuery in our HTML page: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>List Movies</title> </head> <body> <div id="movies"></div> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> listMovies(function (movies) { var strMovies=""; $.each(movies, function (index, movie) { strMovies += "<div>" + movie.Title + "</div>"; }); $("#movies").html(strMovies); }); function listMovies(callback) { $.ajax({ url: "/api/Movie/ListMovies", data: {}, type: "GET", contentType: "application/json;charset=utf-8", }).then(function(movies){ callback(movies); }); } </script> </body> </html>     Inserting a Record with the ASP.NET Web API Now let’s modify our Movie API controller so it supports creating new records: public HttpResponseMessage<Movie> PostMovie(Movie movieToCreate) { // Add movieToCreate to the database and update primary key movieToCreate.Id = 23; // Build a response that contains the location of the new movie var response = new HttpResponseMessage<Movie>(movieToCreate, HttpStatusCode.Created); var relativePath = "/api/movie/" + movieToCreate.Id; response.Headers.Location = new Uri(Request.RequestUri, relativePath); return response; } The PostMovie() method in the code above accepts a movieToCreate parameter. We don’t actually store the new movie anywhere. In real life, you will want to call a service method to store the new movie in a database. When you create a new resource, such as a new movie, you should return the location of the new resource. In the code above, the URL where the new movie can be retrieved is assigned to the Location header returned in the PostMovie() response. Because the name of our method starts with “Post”, we don’t need to create a custom route. The PostMovie() method can be invoked with the URL /Movie/PostMovie – just as long as the method is invoked within the context of a HTTP POST request. The following HTML page invokes the PostMovie() method. <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Create Movie</title> </head> <body> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> var movieToCreate = { title: "The Hobbit", director: "Jackson" }; createMovie(movieToCreate, function (newMovie) { alert("New movie created with an Id of " + newMovie.Id); }); function createMovie(movieToCreate, callback) { $.ajax({ url: "/api/Movie", data: JSON.stringify( movieToCreate ), type: "POST", contentType: "application/json;charset=utf-8", statusCode: { 201: function (newMovie) { callback(newMovie); } } }); } </script> </body> </html> This page creates a new movie (the Hobbit) by calling the createMovie() method. The page simply displays the Id of the new movie: The HTTP Post operation is performed with the following call to the jQuery $.ajax() method: $.ajax({ url: "/api/Movie", data: JSON.stringify( movieToCreate ), type: "POST", contentType: "application/json;charset=utf-8", statusCode: { 201: function (newMovie) { callback(newMovie); } } }); Notice that the type of Ajax request is a POST request. This is required to match the PostMovie() method. Notice, furthermore, that the new movie is converted into JSON using JSON.stringify(). The JSON.stringify() method takes a JavaScript object and converts it into a JSON string. Finally, notice that success is represented with a 201 status code. The HttpStatusCode.Created value returned from the PostMovie() method returns a 201 status code. Updating a Record with the ASP.NET Web API Here’s how we can modify the Movie API controller to support updating an existing record. In this case, we need to create a PUT method to handle an HTTP PUT request: public void PutMovie(Movie movieToUpdate) { if (movieToUpdate.Id == 1) { // Update the movie in the database return; } // If you can't find the movie to update throw new HttpResponseException(HttpStatusCode.NotFound); } Unlike our PostMovie() method, the PutMovie() method does not return a result. The action either updates the database or, if the movie cannot be found, returns an HTTP Status code of 404. The following HTML page illustrates how you can invoke the PutMovie() method: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Put Movie</title> </head> <body> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> var movieToUpdate = { id: 1, title: "The Hobbit", director: "Jackson" }; updateMovie(movieToUpdate, function () { alert("Movie updated!"); }); function updateMovie(movieToUpdate, callback) { $.ajax({ url: "/api/Movie", data: JSON.stringify(movieToUpdate), type: "PUT", contentType: "application/json;charset=utf-8", statusCode: { 200: function () { callback(); }, 404: function () { alert("Movie not found!"); } } }); } </script> </body> </html> Deleting a Record with the ASP.NET Web API Here’s the code for deleting a movie: public HttpResponseMessage DeleteMovie(int id) { // Delete the movie from the database // Return status code return new HttpResponseMessage(HttpStatusCode.NoContent); } This method simply deletes the movie (well, not really, but pretend that it does) and returns a No Content status code (204). The following page illustrates how you can invoke the DeleteMovie() action: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Delete Movie</title> </head> <body> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> deleteMovie(1, function () { alert("Movie deleted!"); }); function deleteMovie(id, callback) { $.ajax({ url: "/api/Movie", data: JSON.stringify({id:id}), type: "DELETE", contentType: "application/json;charset=utf-8", statusCode: { 204: function () { callback(); } } }); } </script> </body> </html> Performing Validation How do you perform form validation when using the ASP.NET Web API? Because validation in ASP.NET MVC is driven by the Default Model Binder, and because the Web API uses the Default Model Binder, you get validation for free. Let’s modify our Movie class so it includes some of the standard validation attributes: using System.ComponentModel.DataAnnotations; namespace MyWebAPIApp.Models { public class Movie { public int Id { get; set; } [Required(ErrorMessage="Title is required!")] [StringLength(5, ErrorMessage="Title cannot be more than 5 characters!")] public string Title { get; set; } [Required(ErrorMessage="Director is required!")] public string Director { get; set; } } } In the code above, the Required validation attribute is used to make both the Title and Director properties required. The StringLength attribute is used to require the length of the movie title to be no more than 5 characters. Now let’s modify our PostMovie() action to validate a movie before adding the movie to the database: public HttpResponseMessage PostMovie(Movie movieToCreate) { // Validate movie if (!ModelState.IsValid) { var errors = new JsonArray(); foreach (var prop in ModelState.Values) { if (prop.Errors.Any()) { errors.Add(prop.Errors.First().ErrorMessage); } } return new HttpResponseMessage<JsonValue>(errors, HttpStatusCode.BadRequest); } // Add movieToCreate to the database and update primary key movieToCreate.Id = 23; // Build a response that contains the location of the new movie var response = new HttpResponseMessage<Movie>(movieToCreate, HttpStatusCode.Created); var relativePath = "/api/movie/" + movieToCreate.Id; response.Headers.Location = new Uri(Request.RequestUri, relativePath); return response; } If ModelState.IsValid has the value false then the errors in model state are copied to a new JSON array. Each property – such as the Title and Director property — can have multiple errors. In the code above, only the first error message is copied over. The JSON array is returned with a Bad Request status code (400 status code). The following HTML page illustrates how you can invoke our modified PostMovie() action and display any error messages: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Create Movie</title> </head> <body> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> var movieToCreate = { title: "The Hobbit", director: "" }; createMovie(movieToCreate, function (newMovie) { alert("New movie created with an Id of " + newMovie.Id); }, function (errors) { var strErrors = ""; $.each(errors, function(index, err) { strErrors += "*" + err + "n"; }); alert(strErrors); } ); function createMovie(movieToCreate, success, fail) { $.ajax({ url: "/api/Movie", data: JSON.stringify(movieToCreate), type: "POST", contentType: "application/json;charset=utf-8", statusCode: { 201: function (newMovie) { success(newMovie); }, 400: function (xhr) { var errors = JSON.parse(xhr.responseText); fail(errors); } } }); } </script> </body> </html> The createMovie() function performs an Ajax request and handles either a 201 or a 400 status code from the response. If a 201 status code is returned then there were no validation errors and the new movie was created. If, on the other hand, a 400 status code is returned then there was a validation error. The validation errors are retrieved from the XmlHttpRequest responseText property. The error messages are displayed in an alert: (Please don’t use JavaScript alert dialogs to display validation errors, I just did it this way out of pure laziness) This validation code in our PostMovie() method is pretty generic. There is nothing specific about this code to the PostMovie() method. In the following video, Jon Galloway demonstrates how to create a global Validation filter which can be used with any API controller action: http://www.asp.net/web-api/overview/web-api-routing-and-actions/video-custom-validation His validation filter looks like this: using System.Json; using System.Linq; using System.Net; using System.Net.Http; using System.Web.Http.Controllers; using System.Web.Http.Filters; namespace MyWebAPIApp.Filters { public class ValidationActionFilter:ActionFilterAttribute { public override void OnActionExecuting(HttpActionContext actionContext) { var modelState = actionContext.ModelState; if (!modelState.IsValid) { dynamic errors = new JsonObject(); foreach (var key in modelState.Keys) { var state = modelState[key]; if (state.Errors.Any()) { errors[key] = state.Errors.First().ErrorMessage; } } actionContext.Response = new HttpResponseMessage<JsonValue>(errors, HttpStatusCode.BadRequest); } } } } And you can register the validation filter in the Application_Start() method in the Global.asax file like this: GlobalConfiguration.Configuration.Filters.Add(new ValidationActionFilter()); After you register the Validation filter, validation error messages are returned from any API controller action method automatically when validation fails. You don’t need to add any special logic to any of your API controller actions to take advantage of the filter. Querying using OData The OData protocol is an open protocol created by Microsoft which enables you to perform queries over the web. The official website for OData is located here: http://odata.org For example, here are some of the query options which you can use with OData: · $orderby – Enables you to retrieve results in a certain order. · $top – Enables you to retrieve a certain number of results. · $skip – Enables you to skip over a certain number of results (use with $top for paging). · $filter – Enables you to filter the results returned. The ASP.NET Web API supports a subset of the OData protocol. You can use all of the query options listed above when interacting with an API controller. The only requirement is that the API controller action returns its data as IQueryable. For example, the following Movie controller has an action named GetMovies() which returns an IQueryable of movies: public IQueryable<Movie> GetMovies() { return new List<Movie> { new Movie {Id=1, Title="Star Wars", Director="Lucas"}, new Movie {Id=2, Title="King Kong", Director="Jackson"}, new Movie {Id=3, Title="Willow", Director="Lucas"}, new Movie {Id=4, Title="Shrek", Director="Smith"}, new Movie {Id=5, Title="Memento", Director="Nolan"} }.AsQueryable(); } If you enter the following URL in your browser: /api/movie?$top=2&$orderby=Title Then you will limit the movies returned to the top 2 in order of the movie Title. You will get the following results: By using the $top option in combination with the $skip option, you can enable client-side paging. For example, you can use $top and $skip to page through thousands of products, 10 products at a time. The $filter query option is very powerful. You can use this option to filter the results from a query. Here are some examples: Return every movie directed by Lucas: /api/movie?$filter=Director eq ‘Lucas’ Return every movie which has a title which starts with ‘S’: /api/movie?$filter=startswith(Title,’S') Return every movie which has an Id greater than 2: /api/movie?$filter=Id gt 2 The complete documentation for the $filter option is located here: http://www.odata.org/developers/protocols/uri-conventions#FilterSystemQueryOption Summary The goal of this blog entry was to provide you with an overview of the new ASP.NET Web API introduced with the Beta release of ASP.NET 4. In this post, I discussed how you can retrieve, insert, update, and delete data by using jQuery with the Web API. I also discussed how you can use the standard validation attributes with the Web API. You learned how to return validation error messages to the client and display the error messages using jQuery. Finally, we briefly discussed how the ASP.NET Web API supports the OData protocol. For example, you learned how to filter records returned from an API controller action by using the $filter query option. I’m excited about the new Web API. This is a feature which I expect to use with almost every ASP.NET application which I build in the future.

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