.netizen

Mad Media Remote goes LIVE!

kurt_ev — Sat, 26 Feb 2011 11:33:00 +0300

A month ago I dedicded to go self-employed, and life has been hectic since, trying to take care of everything. I've started a new company, and now my first public app has been released for the Windows 7 Phone.

Mad Media Remote is a new product of my company Mad Savant, and its just been approved on the marketplace.

You can find it here:

http://social.zune.net/redirect?type=phoneApp&id=ec1c377e-9e21-e011-854c-00237de2db9e

To make a long story short, Geotrust took almost a month to verify my fledgeling company, hence the delays. Lucky I had the 'hero of the month' Ben at Microsoft Phone Support who helped a lot in speeding up the process. After a small initial graphics change in the logos, Mad Media Remote was easily certified. It makes use of all the neat features like its orientation aware, passed the test that it preserves battery life when the phone is obscured so it's allowed to keep running, and much much more. If you have a Windows Phone 7, theres a one month trial so you can just check it out for free!

More info can also be found here:

http://www.mad-savant.com/Product/Phone

Windows Phone 7 Appstore: Submission in progress

kurt_ev — Tue, 18 Jan 2011 21:52:00 +0300

Note to beginning submitters: "submission in progress" is the stage that precedes "testing in progress". If you stay on that for too long, return and check if youve clicked "submit now", otherwise you can wait for a very long time!

Weak references in C#

kurt_ev — Thu, 06 Jan 2011 13:53:00 +0300

To start the story off, let’s examine how a normal reference works:
[code:c#]public class Circle
{
public double Radius { get; set; }
}

Circle circle = new Circle();
Circle theSameCircle = circle;[/code]

In this example, we assign a reference pointing to an already existing circle to the variable “anotherCircle”.

When the variable “circle” goes out of scope, does this mean the Circle object is eligible for garbage collection?
The reference to the created Circle is removed, but the variable “anotherCircle” still holds a reference to it. The created Circle object is not eligible until the last reference to it has gone (or is out of scope), in this case the “anotherCircle” variable is preventing the object from being garbage collected. You could say that in this scenario, both “circle” and “anotherCircle” share responsibility over the Circle variable in terms of existance.

You may wonder, “Why is this important? When they’re both gone they get garbage collected anyway.” That is not really the point. The point is that, while not necessarily important in every case, the distinction is similar to the difference in composition and aggregation in UML: a strong reference is a ‘strong link’ and a weak reference a ‘weak link’, similar to how composition and aggregation differ from one another. Theyre not really the same thing, but maybe you see my point: a ‘strong link’ assumes some responsibility over the object (in this case, keeping it alive), a ‘weak link’ assumes that another else has the ‘keep alive’ responsibility over the object, which is similar to the concept of programming C++ where theres always one object responsible for the cleanup of the another object. Except there it's more active. In .NET memory gets cleaned up regardless, just when and how efficiently is something you can control with classes like WeakReference.

In the case of UML’s composition, a child part cannot exist without the parent part. With aggregation, both parts can exist independantly. Does it make sense then for the child part to prevent the parent from being garbage collected (if the programmer using your API retains a reference to the child part, the parent part is kept in memory)? Ofcourse not, in most scenarios if the programmer wants to work with the wheel of a car and doesn’t keep the car in memory himself, he just wants to work with the wheel, if he wanted to work with the car he’d have kept the car. Unless the wheel has a ‘Car’ or ‘Parent’ public property, the developer has no way of knowing your internal implementation references the car. Enter the WeakReference class.

A weak reference is a reference that does not keep the referenced object alive. This is especially handy for circular references (where objects keep themselves alive and need extra work by the garbage collector to detect they’re actually both dead instead, for example a an item in a list that also references the list it’s in).   In terms of cleanup it is many times faster, and it relinquishes the responsibility of keeping the object alive to another object, meaning that a weak reference does not prevent garbage collection. If the programmer lets the referenced object go out of scope and does not retain their own reference to it, the object will be garbage collected.
So how does this work?

If the object has been garbage collected, the WeakReference’s Target property returns null. Therefore, you need to check if the target is null before use.
Maybe the following class will make it easier for you:

[code:c#]public class WeakReference<T>: WeakReference
        where T: class
    {
        public WeakReference(T target): base(target)
        {

        }
        public new T Target
        {
            get
            {
                return (T)base.Target;
            }
            set
            {
                base.Target = value;
            }
        }

        public static implicit operator T(WeakReference<T> reference)
        {
            return reference.Target;
        }

    }[/code]

A nice thing about a WeakReference is that you’re absolutely sure you don’t have to call Dispose or do anything with the IDisposable interface. If it’s IDisposable, its someone else’s responsibility to dispose, not the WeakReference’s. Therefore, a weak reference adds to clarity when it comes to disposable types that are supposed to be cleaned up elsewhere (very useful in template methods for example)
On top of that, a WeakReference to an IDisposable is not disposable, so the class that holds member variables that are WeakReferences to IDisposable types do not need to be IDisposable themselves (I’m looking at users of Code Analysis or FXCop), which is a large bonus.

Let me show you another example:

[code:c#]List circleList = new List<Circle>();
circleList.Add(new Circle());[/code]

In this example, we have a list and we’ve added a new circle object to it. Do you expect the list to be responsible for retaining the circles? Yes, obviously you do, you do not want to hold a reference to every circle in the list you created like this:

[code:c#]Circle circle1 = new Circle();
circleList.Add(circle1);
Circle circle2 = new Circle();
circleList.Add(circle2);[/code]

That would be very tiresome. Lists, dictionaries, normal variable assignments: they’re all strong references. Strong references prevent garbage collection, and therefore take or share ownership of an object. But that’s not always what you want. A perfect example where you could use weak references would be an observer/observable system or events. You would not want to keep every and any object in memory just because they have attached an event, right? If they’d forget to remove the event handler, the object instance would remain in memory forever. In this case, you’d prefer to have it turned to ‘null’ automatically and check for null before calling anything on the object. Which is exactly what a WeakReference does.

Can't find MVC2 templates?

kurt_ev — Thu, 06 Jan 2011 11:14:00 +0300

Then you may have had the same issue i did: the MVC2 project templates did not show up in the "add new project" list, they only show up in the "create new project" list. Just create the project like that and then add the newly created project as an existing project to your solution. Happy MVC'ing.

ReactionGrid Groups soon to be released

kurt_ev — Sat, 18 Dec 2010 13:47:00 +0300

Over the past while I've been working with ReactionGrid to create group services for OpenSim. They should be released back into the OpenSim community in january, and by then the bugfixes to OpenSim will also be released back to them.

What does this mean?

Basicially this allows standalone, networked or hypergridded Open Simulator servers to use shared groups, and perform group based chat. Amongst others, these services remember who opted in or out of which group chat and keep group records. The system comes with an administrative website that takes care of common maintenance tasks. Group server owners will also have the option of overriding the default rights group roles get and specify extra roles. More details to follow later.

The technolgy behind this system is WCF, MVC2 and uses both .NET 3.5 (for OpenSim addins) and .NET 4.0 (for the services and website)

Windows Phone 7 devices available

kurt_ev — Thu, 21 Oct 2010 11:47:00 +0300

As of today, Windows Phone 7 will be available as a purchase in Europe. Theres phones available from Samsung, LG and HTC, for example from PDA Shop.

Can I use the marketplace if no such marketplace exists for my coutry yet

- Yes, but you have to set your billing address to an(y) address in the country that has the marketplace you want to buy from

Will I get stung if I buy it now instead of waiting?

- You can always wait. Does your computer run windows 3.11 too? That said theres a few updates that are still in the works like copy/paste. Unless you are a real avid fan of tethering, you should get the updates you want.

Will there be a tethering update?

- Microsoft has failed to respond to this question, sorry. If you think this is an essential feature, I'd wait to buy.

What price range can I expect the devices to be?

- Your wallet will get bitten for 500-600 euros.

Can I just put my own apps on there without the marketplace?

- No you cannot. Microsoft isnt being clear whether they have plans to allow you to install your own things on your own hardware (eg with a developer key) in the future. There is an emulator you can download for free though.

Update: as a dev you can install your own apps on your phone for 99$ a year.

Reviews:

In dutch: De Standaard

In English: Engadget

Juval Lowy visiting VISUG

kurt_ev — Tue, 05 Oct 2010 22:19:00 +0300

Juval Lowy- the head honcho of IDesign- is visiting Belgium on Oct 13, and coming to talk to the local user groups about what it means to be an architect.

If you can still get a seat, I would highly recommend attending- Juval is considered extraordinarily talented and is the author of very in-depth WCF books.

Head over to the VISUG website to sign up or enter in line and hope someone cancels! See you there!

Unity 3D 3 released and introducing Jibe

kurt_ev — Tue, 05 Oct 2010 21:51:00 +0300

Unity3D is a game engine that allows you to control it using C# code, Boo (similar to Python) or Javascript. Version three got released recently.

You might say "Isnt that XNA" but XNA isnt a game engine- its a development framework. And XNA only works on the XBOX360, Windows and Windows Phone 7. Unity works in your browser, on XBOX, iPhone and a number of others. Depending on your hardware, certain visuals will be enabled or disabled (obviously the iPhone is no match for a proper gaming PC). A game engine means that the rendering,c common game objects, animations, collisions and complex 3D related math is already present for you to use, and you can control camera's, or 3D aniimated figures for example.

Unity is an easy download and comes with an integrated UI- plus integration with Visual Studio. There's a learning curve, but as long as you dont make big bucks with it the're offering a free version you an use to develop your own 3D games. It's well worth checking out, and writing something similar will be almost impossible for most casual developers.

Built on Unity, people from ReactionGrid.com have created an extensible toolset: objects, middleware etc- everything you need to create a virtual interactive world (like social games that are appearing more and more). They're aiming at the business and academic users who needto meet or teach remotely. For example a school could present educational materials through real-time classes on a private virtual world, with live feedback of people attending the class. This is what ReactionGrid sells as "Jibe". There's a demo you can try on their website- you can try it right in your browser by pressing "Systemic" on the main page. Its not very expensive to play around with, and can also serve as a showcase for what unity can do in the browser (IE, Firefox).

MCTS: ADO.NET and MCPD Windows Developer 4 ready for consumption

kurt_ev — Wed, 30 Jun 2010 20:11:00 +0300

As stated in the previous post, Microsoft is finishing up the cert exams. If you head to the Prometric site, you'll see you can actually schedule all of them already.
Microsoft really did their best on getting them out the door quickly after the VS2010 was released.

Oh, and lucky me: I'm now an MCPD for .NET 4.

More info on the new exams is found here.

MCTS: Windows apps with .NET 4

kurt_ev — Sat, 26 Jun 2010 09:01:00 +0300

Apparently Microsoft is getting on track for the release of the .NET 4 certification, and you'll be able to schedule your .NET 4 exams around the expected date of June 2nd.

On thursday I received confirmation about the first 'pass'.

If you ever wanted to certify for WPF, the new 70-511 exam is your thing and should be released any time now. In .NET 2.0 and 3.5 you had to do the Application Development Foundation exam too get certified as MCTS, but this time around there's no such exam. You certify for MCTS with just one exam now.