DotNetNerd's blog

Finally LINQ is supported in IronRuby now from v. 1.1 and I think it has been solved quite elegantly without any real syntactical gooeyness. Trying it out has been made very straight forward by looking at the 101 LINQ samples rewrite for IronRuby.

From day one LINQ has seemed a natural fit with IronRuby already having a similar approach with functions such as .each {|item| ...} which is accessible on anything that can be enumerated - very much like a big part of LINQ is extentions methods to the IEnumerable interface. No doubt there has been some challanges around how to map generics, extention methods etc between the languages, but syntactically it seems a natural fit.

products.where(lambda { |p| p.units_in_stock > 0 and p.unit_price > 3.00 }).each { |x| puts x.product_name }

Combining functional methods from LINQ with the existing Ruby methods just makes the "Integrated Query" syntax even better. So now we get a .each method with LINQ even though Microsoft originally didn't want to include it :)

 

This will probably be one of the shortest blogposts I'll ever write, and probably the one with the least amount of code - besides an occational rant. The reason is that like pictures sometimes say more than a 1000 words, so does elegant code.

module MyModule
class MyClass
def write_stuff text
puts text
end
end
end

m = MyModule::MyClass.new
actions = {:write_stuff => "Hello action packed world!"}
actions.each {|key, value| m.method(key).call(value) }

It might just be me who is weird - but I think this way of doing eg. a strategy pattern is pretty cool.

A couple of months ago I was starting to read about IronRuby, and while thinking about what my first little pet project should be I saw a tweet from a guy who was enjoying the combination with Silverlight. I gave the idea some thought and liked the idea of using a dynamic language to make a rich internet application. So after reading IronRuby UnleashedI started out doing a version 2 of my dotnetnerd.dk site – which is just a little toy selfpromotion site.

Getting started was pretty straight forward because with IronRuby there is a small webserver called Chiron, which can make a project template. All you have to do is open a cmd, and go to the library where IronRuby is installed and type script\sl.bat ruby <projectpath>

Armed with my starter template I began playing around and got my layout in place. I also tried using some 3rd party components by referencing some dll’s and all that basic stuff. Most of it went smoothly, but I did run into an assembly (Flickr.net) that threw an exception when used with Silverlight/IronRuby. Using it from a console project in IronRuby worked fine, so I quickly decided to just go directly against the flickr api using the .NET WebClient class. Running the site from chiron was as easy as calling script\chr.bat /d:<projectpath> /b:index.html

When I had the first couple of pages ready and had written a picturegallery showing the last 5 pictures I have uploaded to flickr I wanted to get the site deployed, so I would no longer depend on chiron. From my book and by looking at blogs it seemed to be smooth sailing, because chiron has a function that makes a .xap file which is all you need. To my surprise when I referenced the .xap file from the html file in my my project it looked like it loaded, but then just stopped at 100% without showing my actual site. I felt pretty stuck, because I had no exception or anything to go on, and my site ran fine when I was using chiron.

I then wrote an email to “Iron” Shay Friendman, who wrote the book that I was using as my inspiration. I thought it was worth a shot, and that I could not be the only one with that problem. Later that day he wrote back, and (as the nice guy he is) told me that he did not know the solution off the top of his head but he would look at it as soon as he had a couple of available hours. A few days later he had found a solution, and it turnes out a few things need to be done differently when running it outside of chiron. So this is basically what I want to share with this post :)

What you need to do is:

1) If your .rb files contain references like “app.xaml” it should be changed to app\app.xaml – in other words the references should be from the root of the solution and not from the app folder where the file is located.

2) Make the .xap file using the command script\chr /d:<projectpath> /z:<projectpath>\app.xap

3) In the index.html file where the .xap file is referenced find the like starting with <param name="initParams".
Change its value attribute to "start=app\app.rb,reportErrors=errorLocation".

And easy as 1-2-3, your site should work when running the index.html file.

Shortly put it really has been a fun project, and I really like the IronRuby and Silverlight combination, so it is definately not my last project where I will combine the two.

I have been working primarily with ASP.NET MVC for a little over a year now, and this has prompted me to do quite a bit more Ajaxy functionality. So while doing this I have been looking at quite a few Ajax/Javascript libraries.

As most other developers I have been swept away by JQuery, which by far is the most important component when I am doing Ajax and manipulating the html DOM - see cheatsheet. Besides making a lot of these things easier, it also provides a wide variety of plugins that enable all sorts of shiny fancy features without much work. One of the very usefull ones that I find myself using on all kinds of projects is tablesorter- that makes clientside table sorting almost free.

Working in the Microsoft domain I have of course also been working with Microsofts ASP.NET Ajax Librarywhich also brings quite a few cool things to the table. Most basically it enriches the javascript experience by providing namespaces, intellisence and a bunch of extentions to the basic javascript type system. On top of that there are a lot of extenders to work with accordions, watermarks, listsearch etc. were most projects will find something that is useful to provide a better UI experience. The latest addition, that I am already very fond of even though it is still just in the beta version is templates. This gives us a easy way to do databinding on the client - one-way/two-way livebindings, and ways to do this both declaratively and imperatively. In other words it provides a rich templating experience and no more clumbsy string manipulation!

Next thing that is important when working with Ajax is having some solid libraries to do JSon serialization. Here I will strongly recommend JSON2for the client because eval is evil. Also a small but important thing to know is that data must be serialized and provided as a string when using JQuery to call a WCF service. On the serverside, I recommend Json.NET or maybe Json for the compact framework if you need something that is easier and more extendable than the .NET build in DataContractSerializer.

Finally something that might also be worth looking at to get better performance is using a content delivery network to reference the different scripting librarys. Here I will recommend looking at either Microsoft Ajax Content Delivery Networkor Google AJAX Libraries. Both seem very reliable and will give what you need, so its mostly a matter of personal preference.

A little while ago I read about a nice little library called .less, which is a port from ruby less, that lets you write css, but with the added features of enabeling variables, operations, mixins and nesting. Today I decided to try it out, and I definately want to give it my recommendation.

Using variables makes stylesheets a lot more maintainable because it allows you to avoid having colorcodes scattered all around the stylesheet simply by writing:

@listbackground_color: #E3EFFF;

Nesting just makes it more maintainable and gives the stylesheet a better sence of structure like this:

table.MapsList
{
  background-color: @listbackground_color;       
  tr th
  {
    width: 300px;
    background-color: @listbackgroundheader_color;
  }
}

Finally mixins makes it possible to keep the stylesheets more DRY (don't repeat yourself) like so:

.rightBackground { background-repeat:no-repeat;background-position:right; }
th.headerSortUp { .rightBackground; background-image: url(desc.gif); }
th.headerSortDown { .rightBackground; background-image: url(asc.gif); }

An added bonus is that you can toggle caching and minimizing from your web.config.

 

Last time I looked at how IronPython is integrated with .NET which makes it possible to use all of the good stuff that we know and love from .NET. The obvious next thing to look at is doing the inverse and see how it is possible to run IronPython code from within a .NET app written in this case in C#.

The main scenario for this is to allow advanced users to write their own scripts that can extend the behavior of the application, or allow them to express complex logic. An example that comes to mind for me is a system I am working on at work, where we are doing payroll processing for any kind of company. Here a viable option could be to allow the rules for the processing to be expressed with scripts – since the tax laws have a tendency to change frequently it would be a valuable extensibility point.

The most basic way to run IronPython code from C# is to do like this:

var engine = new PythonEngine();
engine.ExecuteToConsole(@"print ""Sweet dude!""");

As you can see it is pretty simple to get code to run in the first place. It is not of much use however if it is not possible to pass in variables to the context in which the IronPython code is run. This is accomplished by passing in a module and a dictionary of variables like so:

engine.ExecuteToConsole(@"print ""Cool: "" + str(2+val)",
    engine.DefaultModule, new Dictionary<string, object>() { { "val", 6 } });

Again, this is pretty straight forward. Besides passing variables it would also be nice to be able to define global variables that can be used and accessed again after the script is run. This example shows how to do just that:

engine.DefaultModule.Globals["val"] = 6;
engine.ExecuteToConsole(@"val = ""Cool: "" + str(2+val+2)",    engine.DefaultModule, null);
string modifiedValue = (string)engine.DefaultModule.Globals["val"];

One thing to note here is that i set the global variable to a value of 6 which is an integer but I end up getting a string back. This is because IronPython is a dynamic language which allows the type to be changed which is done in the script because it is added with a string.

Now my guess is you might be thinking that there must be other ways to run scripts than to execute them to a console. Well of course there is. The PythonEngine has several overloads and alternate methods that can be used to run scripts. I wont go over them all but I’ll finish up with a sample that I think will probably be one of the ways I will end up using most often. In this case I simply evaluate a script that returns a value. This way a script could be used to define some logic and simply return the kind of result I need:

string myResult = engine.EvaluateAs<string>(@"str(2+2)");

Mainly there are two groups of methods to run IronPython code – you can either execute or evaluate the code, with the difference being that evaluating it returnes a value. There are also methods to execute code from a file, which might be convenient.

One of the great things about IronPython compared to other Python implementations is that is running on the .NET platform and was written in C#. This lets the developer use all the stuff he already knows from using .NET and he will have the possibility of writing components in C# that can extend or be used from IronPython. I regular Python writing extensions would be done I C which is enough to scare a big part of the developer community away. On top of that the IronPython syntax and type system is pretty close to C#, so if you are already programming in C# you will have a fairly easy time getting started with IronPython.

Doing integration of an existing language into a framework is always going to be a challenge. Some concepts in Python map fairly well to the existing .NET languages, while others require that you learn how to get about doing things from IronPython as they will require a little deeper understanding. A good deal of these challanges are covered in “The dark corners of IronPython”. The most basic thing you need to know though, is how to access classes and navigate namespaces from IronPython.

Namespaces are a concept that maps pretty well between C#/VB and IronPython, because Python has a similar concept which is called modules. In Python a module is a file which can contain any number of classes and which can be grouped into packages, which are actually just folders on the file system.

To gain access to using a class it is imported by writing an import statement - in roughly the same way as namespaces are used to group classes in C# and VB. This means that doing a import in IronPython that allows us to access a .NET class is very straight forward. (Iron)Python does have differences though. One difference is that a package contains a file named __init__.py, where you can write code that is run when the package is imported. Secondly and probably more importantly in Python the import allows you specify exactly which classes to import instead of the whole namespace/module.

from System.IO import Directory, File

This line of code will allow us to use the Directory and File class of the System.IO namespace. Writing a * instead of the filenames will mean that all classes in the namespace are imported. This is regarded as somewhat of a bad practice in the Python community though. This is basically what you need to know to start accessing .NET classes from IronPython like this:

from System.IO import File, Directory, FileInfo 
from System.Text.RegularExpressions import Regex

files = Directory.GetFiles("D:\MyFiles")
for i in range(0,files.Length):
    file = files[i]
    fileInfo = FileInfo(file)
    reg = Regex("^\d\d[\s-]+")
    res = reg.Replace(fileInfo.Name, "")
    print res

Actually I had not planned to go to JAOO this year, but first my good colleagues who run ANUG struck a good deal where Mads Torgersenand Oren Eini alias Ayende Rahienwould give a special talk in the evening for the usergroup. This was simply too good to pass up. After all, how often do you get the chance to see one of the Danes from the C# language team and Ayende – who is the guy behind tools like NHibernate and Rhino.Mocks.

On top of the “Geek night” as it was coined, I ended up going Wednesday for the .NET track as well. To my gain a colleague who already had a ticket could not go, so I was lucky enough to get the offer to go in his place.

It ended up being a very interesting night and day I think – with my only small complaint to Trifork, who did brilliantly, being that the .NET track was held in a building that was below par compared to “Musik huset” where the rest was held.

Key points for me was hearing Mads, Ayende twice and Udi Dahan. Madses talked about what it is like to work in the C# team, and the considerations they have to take. This was really interesting and its hard not to be a bit hit by national pride that there are actually two Danes on a team like that. 

Ayende mostly talked about his own projects with the talks focused around NH Prof and NHibernate. It is impressive to see him with a keyboard, even though I had hoped the focus of his talks would have been a bit wider. The one general issue he talked about was at the ANUG talk where he talked about concepts and features. On the upside in the day session we did get to see some of the stuff he has added to NHibernate where especially NHibernate Search looked quite interesting.

Udi Dahan gave my personal “talk of the day”, because I think he got the focus of the talk right, and managed to make it fun and interesting. The subject was pretty broad being “Scalability, Availability and Reliability”, but he made it pretty concrete without making it about a single product. The focus was on how a one way messaging architecture based around transactional queues could solve a lot of the typical issues that we run into as developers. Actually the fact that he has worked on NServiceBus did not come up until the talk was basically over and it was just named as a possible solution amongst a bunch of others.

NServiceBus will be the focus of the next ANUG meeting where my colleague Lasse Eskildsen will  be showing a bunch of good examples on how it can be used. So this was the perfect fuel to light up my interest for the subject. Besides what I have already written about there is one more topic that tickled my taste buds, which is Scala. It does not take much to get me going when it comes to programming languages, so maybe it is just me, but I think Ill have to take a look even though my focus right now is more on IronPython.

 

One of my favorite features from when I was playing around with F# was high order functions. A high order function is quite simply a function that takes a function as an argument and returnes a function. A basic sample just to get the point accross could be:

def Outer():
    innerText = "Hey dude! "
    def Inner(text):
        print innerText + text
    return Inner

myfunc = Outer()
myfunc("My function was called successfully")

This technique can be quite useful when composing functions, but also to wrap code and handle cross cutting concerns (e.g. like logging) through Aspect Oriented Programming. IronPython takes this concept a bit farther through what is called decorators. A decorator is to some extent similar to an attribute, and can be used to do AOP. Using decorators is as simple as defining a high order function and decorating the method that should be wrapped with @myHighOrderFunction like this:

def logging(function):
    def inner():
        print "Do pre call logging"
        function()
        print "Do post call logging"       
    return inner

@logging
def myfunc():
    print "Could do what interesting stuff you like"   
   
myfunc()

As you can see from the code it makes for a very straight foreward and elegant way og doing AOP.

UPDATE: I stumbled across this video with DevHawk where he actually shows a similar example during his talks here in DK.

Det har været lidt stille med blogindlæg på det seneste, idet jeg har været travlt beskæftiget med at flytte, så jeg kunne komme tættere på Århus. I den forbindelse har jeg haft en virkelig skuffende oplevelse med Equinox, hvor jeg ellers har været en god kunde i 1½ år. For 6 måneder siden ca meldte jeg mig på deres "kommer du betaler vi ordning". Det viser sig nu at der åbenbart stod i den kontrakt man får ved indmeldelse at man binder sig i 12 måneder. Et faktum jeg aldrig var blevet gjort klar over, og derfor var lykkeligt uvidende om.

I mellemtiden har de kørt en ny kampagne, hvor bindingen ikke længere er med. Da jeg var blevet underlagt en række stramninger der var i den forbindelse i forhold til deres fortolkning af hvad det vil sige at træne "en gang om ugen", tænkte jeg at så måtte det være en generel ændring om ikke andet. Det fastholder de imidlertid at det ikke er.

På trods at at jeg har prøvet at forklare dem at jeg er flyttet og aldrig var blevet informeret om at der var en binding insisterer de på at holde mig fast på kontrakten. Jeg har endda tilbudt om ikke de kan komme med et fornuftigt bud på et gebyr de kan tage for at ophæve medlemsskabet - det er de heller ikke interesserede i. I princippet kan jeg "bare" køre forbi Equinox hver 7'ende dag (+ de dage hvor der er 4 dage i en uge inden for slutningen af en måned) og checke ind i det næste halve år. Det virker selvsagt bare fuldstændigt tåbeligt, og jeg synes det er ret usmageligt at de i den grad fastholder en binding de har narret mig ind i. Jeg vil nu undersøge hvor vidt jeg kan komme udenom, da de efter min opfattelse klart er i konflikt med paragraf 3 i markedsføringsloven hvor der står:

"Der må heller ikke anvendes fremgangsmåder eller forretningmetoder, som kan være vildledende eller utilbørlige/urimelige over for forbrugere og andre erhvervsdrivende.Markedsføringen skal i det hele taget være korrekt, hæderlig og sandfærdig, og de erhvervsdrivende skal optræde loyalt og ærligt."

Imellemtiden vil jeg blot råde folk til at gå i en blød bue udenom Equinox.