A day in the life of...

I’ve been looking at Prism some more recently. I’m a bit annoyed with myself really because someone has been telling me to look at it for years but I wanted to concentrate on C#. Now that I am looking at it I see things in there which I really like. Recently I am looking at invariants, pre-conditions, and post-conditions. First let me show you the invariant support. An invariant is like a class constraint, it specifies a condition which must be true but when must it be true? type   BankAccount = public class   public     property Balance : Decimal read write;   public invariants     Balance >= 0;   end; The invariant is enforced each time a public method exits. Actually it is enforced after the post-conditions of a public method exits but we don’t have any post conditions yet. class method ConsoleApp.Main; begin   var account : BankAccount := new BankAccount();   //The next line throws an assertion error   account.Balance := -1; end; Property getters and setters are considered

In my previous post I showed an interface ILockable. The actual interface is public interface ILockable {   Guid GetLockID();   Type GetLockObjectType(); } Any lockable resource implements this interface. In its constructor it creates an instance of a class which descends from LockObject, a Document class for example would create an instance of DocumentLockObject which descends from LockObject. The "Document" class would store away the ID of the DocumentLockObject in a private attribute. Now when my LockingService is asked to lock multiple (un-related) instances which implement ILockable I want to do this 1: Create a new EcoSpace 2: Load objects efficiently 3: Get locks 4: Update the DB 5: Dispose of the EcoSpace If I experience an OptimisticLockingException then loop and try again. The item I would like to discuss is #2, "Load objects efficiently". In my model a LockObject has a *--1 association to Session identifying which session has locked it, I want to en

This might seem like a bit of an odd requirement. I am currently implementing an offline pessimistic locking service in an ECO app. This will mean that I can use a LockingService to place read/write locks on objects. As usual I have gone for an interface approach (ILockable) rather than making all my lockable classes descend from a base Lockable class. Remember, it's what I DO , not what I AM . The idea is that I have a Lockable object which holds a list of Sessions. These Sessions indicate who has a read lock, and who has a write lock on the object. Each ILockable business entity will create its own private instance of Lockable when it is created. The thing is, this application will at times need to lock thousands of objects in as little time as possible. As there is no common ancester for these ILockable classes I can't just use EnsureRelatedObjects to traverse an association name and load all LockObject instances in a single select. I decided that what I needed was to

Drop a DefaultORMappingBuilder component next to your persistence mapper. Point PersistenceMapperxxxxx1.NewMappingProvider and RuntimeMappingProvider to point to this new component. On your PersistenceMapper component expand SqlDatabaseConfig and click the [...] next to KeyMappers, ensure that you have an item named "GuidMapper" with the MapperTypeName set to "Eco.Persistence.GuidKeyMapper". If not then add it. On your DefaultORMapperBuilder set IdKeySignature to System.Guid (case sensitive). Set its IdMapperName to GuidMapper. Now regenerate your DB.

I’ve played a little more with Prism. I find it a little difficult to mentally code on two levels. Level one being the code I am writing for the aspect, and level two being the code I am writing which will executed by the target. Having said that, as soon as I ran my app and saw the output everything was worthwhile. Here is my Person class type   [aspect: EcoAspects.BusinessClass(’DomainClasses.Package1’)]   Person = public class   private     FFirstName: String;     FLastName: String;   protected   public     property FirstName : String read FFirstName write FFirstName;     property LastName : String read FLastName write FLastName;   end; here is the code which uses that class class method ConsoleApp.Main; var   P: Person; begin   P := new Person();   for A in typeOf(Package1).GetCustomAttributes(true) do     Console.WriteLine(a.ToString());      P.FirstName := ’Peter’;   P.LastName := ’Morris’;   ShowGetValueByIndexResult(P as ILoopBack2, 0);   ShowGetValueByIndexResult(P as ILoop

Sometimes you have a list of objects (say List<PurchaseOrder>) and you want to get all associated objects (say OrderLines) for all the orders in the list. There are 2 ways of doing this in ECO You call a PersistenceService method which takes the list of orders and a string identifying the association name. I don't like this approach because the name of the association may change during modelling and this wont be picked up as an error until runtime. You use the overloaded method which takes an IAssociationEnd. I don't like this either because you have to find the IAssociationEnd instance from the meta-model at runtime, and to do this you'd probably use a name anyway. So, what's the alternative? public static void EnsureRelatedObjects<T>(this IPersistenceService instance, IEnumerable<T> objects, Expression<Func<T, object>> member) where T : IEcoObject {     MemberExpression memberExpression = (MemberExpression)member.Body;     instance.Ensure

I am playing with Prism’s new Aspect Oriented Programming feature. As a learning exercise I am implementing some of the features ECO requires on a class. If all goes well I will end up with aspects I can apply to plain classes and have them run in ECO. One of those features is the ILoopBack2 interface. In order to tackle this interface a small piece at a time I have created my own ILoopBack2 interface, so far with only one method. ILoopBack2 = public interface   function GetValueByIndex(I: Integer): System.Object; end; This method allows the ECO to evaluate OCL (Object Constraint Language) expressions such as "self.FirstName" and have them route via the class’s property, just in case there is any logic in the getter. By implementing an interface which uses an index to identify the property to read it is possible to avoid reflection. So, getting on with it, here is my class definition type   [aspect: EcoAspects.BusinessClass(’DomainClasses.Package1’)]   Person = public cla

This is fun :-) I’ve created an aspect like so type   BusinessClassAttribute = public class(System.Attribute, ITypeInterfaceDecorator)   private     FPackageName: String;     property PackageName: String read FPackageName;   protected   public     constructor (PackageName: String);     method HandleInterface(Services: RemObjects.Oxygene.Cirrus.IServices; aType: RemObjects.Oxygene.Cirrus.ITypeDefinition);   end; I can now decorator my class like so type   [aspect: BusinessClass(’DomainClasses.Package1’)]   Person = class   end; I can ensure this class  exists in the aspect implementation method. constructor BusinessClassAttribute(PackageName: String); begin   FPackageName := PackageName; end; method BusinessClassAttribute.HandleInterface(Services: RemObjects.Oxygene.Cirrus.IServices; aType: RemObjects.Oxygene.Cirrus.ITypeDefinition); var   PackageType: ITypeReference; begin   PackageType := Services.FindType(PackageName);   if (PackageType = nil) then     Services.EmitError(’Package cl

Here’s what I did. 01: I created a support project which just has a logger class in it. namespace EcoSupport.pas; interface uses   System.Collections.Generic,   System.Linq,   System.Text; type   Logger = public class   private   protected   public     class procedure Log(Message : String);   end; implementation class procedure Logger.Log(Message : String); begin   System.Diagnostics.Debug.WriteLine(’Log: ’ + Message); end; end. 02: I created an Aspect which decorates methods, giving me the opportunity to intercept all method calls on the class it decorates. namespace EcoAspects; interface uses   System.Collections.Generic,   System.Linq,   System.Text,   RemObjects.Oxygene.Cirrus,   EcoSupport; type   [AttributeUsage(AttributeTargets.Class)]   LogAspect = public class(System.Attribute, RemObjects.Oxygene.Cirrus.IMethodImplementationDecorator)   private   protected   public     method HandleImplementation(Services: IServices; aMethod: IMethodDefinition);   end; implementation method

http://blogs.remobjects.com/blogs/ck/2009/02/06/p251 Read the comments I posted to see why I like it!

My employer's support contract has finally come to an end which means I have to look for another job, haven't had to do that in a while! Drop me an email if you have any positions vacant, in the meantime it's time to do a little "networking".

The outcome of this fairly long exchange on codeplex has made me very happy!

It seems they are unable to spell the word "money", because every time they send me their drivel of a newsletter they always want money. Usually it is for their "Van of truth" (which amuses me immensely) but this time it is to help them to become "the most technically advanced political party in the UK". So, what are they going to do to earn this esteemed title? Set up our own BNP call centre Set up the party campaign central office Purchase 18 computers/screens/software Activate our brand new central database platform Recruit more staff to cope Train all staff in new systems Set up central mailing and telephone points for party Open our new logistical distribution warehouse Riiight. Call centre – Surely other parties have these? Central office – I am pretty sure other parties have these! 18 computers / screens / software – Screens? Are they going to watch TV on them? MONITORS! At least we are talking I.T. now though. Central database

I'm trying to view this page in Firefox. When it loads the browser tells me I need Silverlight, so I download and install it and then restart my browser only to be told I need to install Silverlight. That's not impressive at all!

My app has a wizard approach, the current control appears within a panel with Align set to fill the hosting panel. My first wizard step control merely had an image on it which resizes with its parent control. When I resize the form the host panel resizes, which resizes the wizard control, which resizes the image; and boy does it flicker! I just had to spend some time upgrading my old Delphi DIB controls to D2009 just to get an image that doesn't flicker, crazy! By the way, I tried the same thing in VS2008 and there was no flicker at all, and I thought Delphi was supposed to be the tool that produced fast UI apps.

There was a potential deadlock in the last piece of code. When you obtain any kind of lock you will mostly use a try..finally block to ensure the lock is released when you have finished with it. The using() command expands to a try..finally block so the original code might look okay, however if you mentally expand the code you will see the problem. using (FileLockingService.FileReadLock(product1.ID)) {     //Some code here } This becomes var disposable = FileLockingService.FileReadLock(product1.ID); try {     //Some code here } finally {     disposable.Dispose(); } So why is this a problem? In a single threaded application it isn't, but this is a website so there are multiple threads running at the same time. Now take into account the fact that a web request has a timeout, what if the thread is aborted after the lock is obtained? Ordinarily this isn't a problem because the acquisition is followed immediately by a "try", but if we expand this code further it is ev

Apparently my boss used to be annoyed with something on his old website. When he wanted to upload an updated binary he often couldn't because his product was so popular that someone was always downloading it at the same time. He'd have to continuously hit Delete in his FTP client until eventually he'd slip in and manage to delete it before updating the new version. This obviously isn't an ideal solution because: He constantly had to sit there for around an hour trying to delete it. Once deleted from the disk any user attempting to download would get a 404 – Not Found error. During upload any user attempting to download would get an Access Denied error of some kind. For this website I have decided first of all to only update the files via a HTTP form post. So firstly any long running upload will not deny access to the currently available file, this eliminates problem 3. Additionally, using a form post means I can overwrite the existing file, so this eliminates problem 2.

If I had to write a large business app which accessed a DB, or a website, I would use .NET without hesitation. When it comes to small apps (less than 10MB) that will be downloaded by home users what should I use? I have such a project coming up soon, my boss has bought D2009 and wants me to use that because he is paranoid about people reverse engineering the binaries. I'm a little hesitant but I must admit that I think in this case Delphi 2009 probably is the best tool for the job, and I like to use the best tool for the job rather than the tool I like to use best for my job. Hopefully things will go smoothly, it will be nice writing apps in two different languages.

An odd title for a coding blog I know, but I love martial arts too, especially competitive ones. I'm just putting together a CD for my car. The tunes on the CD music really make my adrenaline pump, so I am putting together a compilation of tunes which make me want to win a fight...with style! Nirvana – Smells like teen spirit. Fat boy slim – Right here right now. William Orbit – Adagio for strings (Ferry Corsten Remix with first 2 mins cut off). The Prodigy – Breathe. The Prodidy – Firestarter. Chemical Brothers – Block rockin' beat. Chemical Brothers – Setting Sun.

I can't believe it, I really can't! I'm writing a shopping cart for a website. One of the features required is to give the user an X amount discount off their next order when they buy a specific product. So let's say the user has a £20 discount on their next order, how does PayPal let me apply that? Simple answer, it doesn't! You can't send a cart line with a negative price "Discount for 20 GBP", nor can you send a cart line with a positive price but a negative quantity (that was desperation). The way to do this apparently is to send a cart total. YES! By sending the entire order aggregated into a single order line. NOOOOOOO!!!!!! So PayPal wants my user to order £100 of goods, click Check-out, and then be presented with "Total for your order £100 (£20 discount)", that's it? In my opinion, that's not very good. In fact, considering PayPal is probably the largest Internet payment organisation in the world I consider this to be

Someone pointed this link out to me today: http://www.screensketcher.com/examples.html It's another application along the lines of Balsamiq. This app does seem very "sharp", it has very snappy response times etc, which is nice and everything BUT I still don't like these kinds of apps! I do prefer the name though, it suggests "I sketch screens" rather than "I am a bottle of vinegar ".

I've just spotted a "Publish to Blog" option in Word 2007. So I thought I'd give it a spin and see what happens. If it works then Blogging is going to be a much more pleasurable experience. My spelling is atrocious. I find complex formatting on BlogSpot is terrible. I will no longer have to edit HTML just to get my code to look right. Talking of code, I had better try that out too...     public class PreSaveConstraint     {         public readonly IObject Instance;         public readonly string Name;         public readonly Func<bool> CheckIsValid;           public PreSaveConstraint(IObject instance, string name, Func<bool> checkIsValid)         {             if (instance == null)                 throw new ArgumentNullException("Instance");             if (string.IsNullOrEmpty(name))                 throw new ArgumentNullException("Name");             if (checkIsValid == null)                 throw new ArgumentNullException("Che

Finally there is proof that God exists. The proof has come in the guise of a product named Balsamiq . Balsamiq allows you to create mock GUI when specifying an application. Rather than having graphics that look like real forms etc it uses a pencil drawing lookalike approach. Here is my reasoning. It does nothing you can't do for free in the IDE you undoubtedly already have. The result looks far worse than a mock up you can create in your IDE. Once you have the mock up you can't do anything useful with it except export it as an image or print it. You can't, for example, actually use that for a real form later in the project's life cycle. The result looks crap. Not poor, crap! It looks like a 7 year old has drawn it with a wax crayon....a blunt one. Balsamiq brought in revenue of over 100,000 US Dollars in its first 5 months. Now the way I see it is this. Lots of people are sending money to a guy to buy software that does something they can already do much better f

I am currently developing part of a website where I pass cart information to PayPal to accept payment. PayPal will call back a "secret URL" on my website to allow me to confirm the cart details haven't been tampered with. I hate installing software I don't need. This is especially the case with software like IIS which just feels so intrusive, which is why I use the ASP.NET Development Server when creating websites. The problem with this server is that it only accepts connections from the local machine. My computer is behind a hardware firewall and my web server wont accept remote connections, so how can I test my PayPal IPN call back? Simple. Obviously I have to open a port on my firewall and direct it to my machine. So I opened port 80. Then I used this tool to list on port 80 and redirect all traffic to port 10101 (the port my ASP.NET development server was listening on). The result is that a remote computer can now make a HTTP request to my computer, and I

I am just creating some classes that allow the user of an app to specify date/time validity. As I am modeling them it reminded me of some recurring event classes I once wrote to schedule payments between bank accounts. One day my customer phoned me up. "Has your invoice been paid this month?" he asked. "Yes" I said. "Ah good, your code works then!"

Jeff seems to have put it very well in his blog. Much better than I did myself back in December 2006 when I blogged about my "Onion" idea. My mistakes were 01: I was missing a domain services layer. 02: I tried to explain it using a specific example (wizard app with a "process stack" aka "task stack"), and later decided I didn't like the example :-) 03: When I drew my diagrams I showed them as a typical stacked diagram, because my graphics skills are crap :-) Here's my badly put idea of onion layered applications: http://mrpmorris.blogspot.com/2006/12/net-onion-part-1.html Here's Jeffrey's http://jeffreypalermo.com/blog/the-onion-architecture-part-1/ Well done Jeff, very nicely put!

[TestMethod] public void Meh() { var mockFileSystem = MockRepository.GenerateMock<IFileSystemService>(); mockFileSystem.Stub(fs => fs.CreateFileStream(null, FileMode.Append, FileAccess.Write, FileShare.None)) .IgnoreArguments() .Return(new MemoryStream()); var result1 = mockFileSystem.CreateFileStream(null, FileMode.Append, FileAccess.Write, FileShare.None); var result2 = mockFileSystem.CreateFileStream(null, FileMode.Append, FileAccess.Write, FileShare.None); Assert.AreNotSame(result1, result2); } This test case shows a problem I was having. The return value of the stubbed CreateFileStream method isn't calculated each time it is called, it is calculated once at the point you defined the stub method and then returned for every subsequent call. The problem with this is that my real test needed to call CreateFileStream twice and get two different streams, the test was failing because the method being tested disposes of the stream it uses; this was resulti

When I run my unit tests in my project I am seeing a result "Not executed" for every one. I have restarted my computer so I doubt this is some kind of hung process issue. Google has revealed nothing that is not related to load balancing, and I am not load balancing! Solved In order to determine the error you have to do this Open the Visual Studio command prompt Change to the directory where the binary output of your test project is. Type mstest /testcontainer:The.Name.Of.Your.Test.Assembly.dll At the bottom of the output you will see the following text Run has the following issue(s): In my case it was the following: Failed to queue test run 'Peter Morris@PETERMORRIS-PC 2009-02-09 10:00:37': Test Run deployment issue: The location of the file or directory 'C:\SomePath\SomeProject.Tests\bin\Debug\Rhino.Mocks.dll' is not trusted. Now if VS had told me this in the IDE I could have fixed it in minutes! All you have to do is open Windows Explorer and

I'm working on an app which uses a 3rd party library for producing SWF and FLV files. For some reason the trial worked perfectly but when I switched my app to the full version there was no audio output. We'd been looking at this problem for a while, emailing support etc, but just couldn't see what was wrong. It wasn't until I went back to my proof of concept app and ran it that we realised the full version did produce audio, it was just my main app that wouldn't work properly. Then I spotted the error... var compressor = new TVE4(); compressor.LoadSettings(SettingsPath); compressor.SetOutputFile(outputFileName); compressor.EncodeSequenceAudio(Composition.EffectiveProductionAudioFileName); compressor.Key1 = 12345; compressor.Key2 = 54321; (loop to encode frames) Do you see the error? It was only as I switched between the proof of concept code and my app code in the IDE that I noticed the two following lines moving up and down... compressor.Key1 = 12345;

I'm writing an app which basically performs the following steps in a wizard-like interface: Select an audio file of someone speaking + loads a text script in. Process the audio file and the script, can take about 5 seconds for a minute of audio. Select a character to use in the animation. Select some additional graphics and scene settings. Use the data generated in step #2. Sitting there for 5 seconds wasn't really a problem, not to process a 1 minute audio file. A longer audio file would take a little longer, but 10-15 seconds is okay, isn't it? Well, what if I could make it take no time at all? Obviously I can't, but I can make it look like it takes no time at all. The fact is that I don't need the processed data until Step 5. The user will probably spend at least 30 seconds twiddling settings in each Step 3 and 4. How much processing power does a bit of GUI interaction take? Hardly any at all! So I made Step 2 run in a separate thread. As soon as the user

My observations on data transfer objects They should not be a one to one representation of your domain classes. Sometimes you want a subset of the information of a single instance, sometimes your DTO will collect data from various instances (starting with an aggregate root ). You might create different types of DTO from the same domain classes based on what the user needs to do. Sometimes the user only wants OrderNumber + DateRaised + TotalValue (to show as a list of orders), sometimes they want the entire order details (including lines) for editing. The domain classes should have no knowledge of your DTO classes. So you shouldn't have any methods such as pubic PersonDto CreateDto(); public UpdateFromDto(personDto); DTO's are not part of the business domain, so you should never do this! The DTO you send out might not be the same type as you get back. For example you don't want the user to edit the order number or the date raised. If there are only a couple of properties

I am lazy.  I don't mean that I don't work, I mean that I like to get my work done with as little effort as possible.  Writing tests before my code used to look like too much extra work, but I've realised just how much time they actually save me. When you make a small change to something it's very easy to think to yourself "That's such a small change, I can't see how it can possibly fail", what I have also realised is this really means "Despite this being a small change, it will fail and I can't possibly see how". I recently observed a change to some code that introduced a simple if statement, and all existing tests passed.  The problem is that the existing tests only checked the expected behaviour worked (which it still did), but by introducing the "if" statement (and an additional parameter on the method) the developer had changed the expected behaviour under certain circumstances .  Thinking it was so simple it couldn't p

To me this book has been a huge disappointment. Someone told me "Pete, there's a name for what you do!" and pointed me to this book. Now personally I prefer technical books, as I read the Ubiquitous Language part at the start I thought to myself "Not technical, but fair enough some people will get value from being taught how to ask questions" and I stuck with it. The first thing I must say that I cannot stand and which happens a lot in this book is over emphasis. When you want to emphasise something it needs to stand out. This book not only emphasises whole paragraphs but does it far too often too. Being an Internet user for some time now when I read upper case letters the imagined vocalisation actually SHOUTS at me, when I read bold my brain vocalises it as a loud and punctuated word, so when I read a whole paragraph in bold I, READ, EACH, WORD, LIKE, THIS ; it makes it difficult to read. Another thing I don't like when reading something is reading i