I was working on some SubSonic entities today and I wanted to access some of the properties of the generated classes, not knowing which database objects will exist.

Basically I wanted to write a utility method that would pull out all of the ActiveRecord<T> types in a given assembly.

This was my first attempt:

public static Type[] GetActiveRecordTypes(Assembly assembly)
{
	List<Type> types = new List<Type>();
	foreach (Type type in assembly.GetTypes())
	{
		if(type.IsSubClassOf( typeof(ActiveRecord<__WHAT_GOES_HERE_?__>) )
			types.Add(type);
	}
	return types.ToArray();
}

The part in bold is where I got stuck. Sticking in type there doesn't work. It won't compile.  I wouldn't let that stop me, so I created a temporary solution like this:

if(type.BaseType.Name.Contains("ActiveRecord")) { ... }

This works, but it's a hack and it's brittle. I asked a few friends and Gary DeReese came to my rescue with the following code:

  Type baseType = type.BaseType;
  if(baseType.IsGenericType && 
	baseType.GetGenericType() == typeof(ActiveRecord<>) &&
	baseType.GetGenericParameter()[0] == type) { ... }

It's good to have smart friends you can reach out to in times like this where you just aren't thinking about the problem the way the framework wants you to. Thanks Gary!

I installed Visual Studio Team Edition for Database Professionals the other day and I was about to create my first DB Pro project.

Check out the New Project dialog box.  This is with VSTS Developer, and DB Pro installed:

and…

Seeing as how I never used the standard database project in Visual Studio before, I couldn’t tell which one I was supposed to choose. 

It turns out that you need to pick the one in the 2^nd screenshot, the Microsoft SQL Server project. 

Wasn’t very intuitive which project to choose.

After talking to developers for a few days about basic HTML and ASP.NET topics, I find that I always focus on the Label control.

More specifically, I’m talking about the <label> tag in HTML.  What does this tag do?  Why should we care, when we can just write the text before an input control on the page?

For starters, the label has semantic meaning.  The <label> tag gives meaning to a textbox or a dropdown.  If you were blind and browsing using a screen reader, you’d appreciate the little semantic tidbits that give you an easier browser experience.

Another benefit is that we can select and style the label easily, making the transition to table-less forms so much easier.

A third and possibly more useful benefit is that the mouse stays as a pointer, and clicking on the text sets the focus to the corresponding control.

The usage in standard HTML is like this:

<label for='user_name'>User Name:</label>
<input type='text' id='user_name' />

This results in the following example:

User Name:

(notice how the mouse cursor stays as a pointer, instead of the standard text cursor)

If you were a reasonable person, you’d think that the <asp:label> control would render as an HTML <label>, but you’d be wrong.  ASP.NET renders a standard <asp:label> as a <span>.  ASP.NET 2.0 fixed this, however you have to specify the AssociatedControlID property to change the rendering behavior.

This leads me to another point that I’d like to make with the Label control.  Often times we just want a static label, like in the example above.  If we use the <asp:label> then we’ll have a server-side component as well and a viewstate hit.

We certainly don’t need viewstate in this scenario,  Often times we just neglect these things until they are a problem. 

I can hear you say it now… “but Ben, you can disable Viewstate by specifying EnableViewState=’false’ “…  I know you can.  But it’s too easy to just leave it as is.  There’s also an easy alternative.

You can accomplish the same rendering without the viewstate issue by just typing this:

<label for='<%= txtUsername.ClientID %>'>User Name:</label>

This will render the same way, but also ensure that we get the generated ID of the control that we are associating with.  This will not have any server-side component or any correlation to ViewState, and it is actually less characters to type.

Hope you find this information useful!

Last night I gave a talk to the largets crowd I have ever spoken in front of.  There were over 100 people in the room and they were a great audience.  I received lots of devoted attention and people were eager to participate.  I was quite nervous in the beginning, but once I got into the material I think it came across very well.

I spoke about why to use CSS and what we can do to overcome some of the pitfalls.  I also explained why we don’t want to be using tables for layout. 

I moved from there to some javascript techniques and a little bit of ajax.  From what I got from that portion, it could have probably warranted more time, but there was just so much to cover.

The files that I used during the demo are available for download here:

File Attachment: AdvancedCSSAndJavascript.zip (1140 KB)

 

I received a number of questions about the tools I was using during the demo.  The text editor I was using was e.  You can download it at www.e-texteditor.com.  The application launcher that I use is launchy.  It is available at www.launchy.net.  Finally the Keyboard shortcut window, called Key Jedi is available here.

If you attended the presentation, I would love to hear your feedback in the comments.  Thanks for coming!

Update:  The links that I wanted to show (but couldn't) during the presentation are:

• CSS Templates @ Intensivstation
• CSS Zen Garden
• Exploding-boy CSS Tabs
  

So I went out and installed Safari 3 for Windows yesterday.

I just had to see what all the fuss was about.  How do you piss off a number of Windows users simultaneously?  Release a product that has a different font rendering technology than their native OS.

Seriously, people are going nuts about this font thing.  Joel Spolsky and Jeff Atwood have covered the details nicely, but I find it quite interesting that something so trivial can make such an impact.  You generally don’t even think about it, but I’ve always noticed that Safari on Mac looked somehow different than Firefox on Windows.  I’m not talking about the browser itself, I’m talking about the pages that get rendered.

I can see everyones argument, but I really happen to like the Apple mentality, and as Atwood says, this debate will be gone once higher dpi screens become available.

There is just something beautiful about the way that plain text looks with Safari, particularly at large sizes.  At tiny sizes, however, I get a headache reading it.

Firefox is still my browser-o-choice, but Safari does give me a nice experience.  I hope more Mac software ends up on Windows.  Choice is good.

 

For those of you near Houston, I will be speaking about advanced CSS and javascript techniques on June 14^th.

The Houston .NET User Group is located in Westchase.  For more info, see their website at http://hdnug.org.

My presentation will cover some of the foundations of CSS-based web development and what it means to develop with web standards in mind.  We’ll also take a look at how to apply JavaScript in a safe and effective way to ensure that we still function when JavaScript is disabled, but also to allow the rest of the world to enjoy a richer web browsing experience.  If there’s time towards the end, we’ll also see how this applies to ajax.

Hope to see you there!

Back by popular demand… (and WAY too late, I might add…)

In this article, part 9 of the series, we’re going to wrap up our initial feature list and focus on building a user-interface for our video store, named Videocracy.

Here is our feature list:

• Add new Customer / Account
• Add other members to an account
• Restrict Certain members from renting certain content
• Query for a customer by customer # (swipe card, etc), phone number, or last name
• Add new rental item (move game, console, vcr, etc)
• Rent an item to a customer
• Check Items Back in
• Get movies checked out for a customer
• Query for an item, see who has it

Let’s implement Check Items Back In.

What is the use case here?  Typically a customer drops off a movie, either in the slot from the outside of the store, or directly to an employee.  Either case starts with the movie, or the Item.

So the employee is going to scan the item.  At this time, they are going to need to see the details of who and when the item was checked out (the Rental object), and then have a confirmation button to finalize the check-in (which will update the Rental object).

In order to facilitate scanning the item, we need to be able to query the database for a particular UPC.

In implementing this next test I noticed a large problem with my domain.  Our Item class defines a name property with a mapped column in the database.  The problem with this is that not all items have names of their own.  They might have display names that are a combination of other properties.  For example, a video copy of the movie The Matrix shouldn’t have a name of ‘The Matrix’ (it really belongs to the Movie class).  Typically the text on the outside of a video rental is the movie name followed by maybe the year, and the format that the movie is in.  These are deferred properties, so there is no more need for a database column in the item class.  I still provide a read-only Name property, and inherited classes have to provide this information.  Would you have made a large change like this so eagerly in your project?  If you did, how would you know if you broke some existing functionality?  As I always say, it’s a good thing I have the tests to back me up…

Here’s our next test:

There is a lot going on in this test, so let’s break it up and take a look at each part.

Here we setup our environment.  We have to have a lot of entities that already exist in order to test our new funtionality.  We need an item, a customer, and employee, and an account.  We create all of those and save them.  (Remember all of this happens within a transaction that is rolled back, so this doesn’t stay in the database).

Here we setup the rental and perform the rental transaction.  This is how the UI will structure the business process.  Once everything is saved, it’s time to verify that we can retrieve the data solely based on the item’s upc code.

The Rental Finder class will encapsultate common queries so that we can reuse them across the application.  Here’s the code for that method:

There is a lot going on here in this test, but what you need to get from this is that we are setting up the stage for our scenario.  As our tests get more involved we are verifying that business cases are being met.  If we make drastic changes later on, we will know if we have broken existing business functionality.

The next thing to check is to make sure that we can check the item back in.  I add a .Return() method on the rental, which doesn’t exist yet, so I need some additional tests.

I also need to be able to calculate late fees in a central place to make that easy to change later.  I add a few tests for this as well.

It turns out that the Return() method is easy to implement.  All we need to do is set the return date and calculate the late fee and save it.

which leads to the following code in the Rental class…

Now we need to finish the original test and verify that we can save the rental.

This test passes and we’ve implemented our feature!

I think I’m at a point where I have demonstrated how we can work on core business features for an application test-first, using NHibernate along the way for persistence.  A lot more work has to be done to complete our domain model, but that will be left as an excercise for the reader.

Instead, I would like to focus my efforts on getting a basic UI in place using ASP.NET.  I said in part 1 that I wanted to demonstrate how to work with the NHibernate Session in a web environment, so that’s where I will pick up next time.

Until then, you can download and view the current project here:

File Attachment: Videocracy_09.zip (3442 KB)

http://www.microsoft.com/surface/

This is so cool I just had to blog about it.  Take a minute to watch the videos, they are quite impressive.

Basically it's a 30 inch surface that is monitored by tiny wireless cameras.  Hand gestures can rotate and resize images and videos and things.  I don't think we're at a point where we can give up the keyboard or the mouse, but think of some of the other uses it would be good for.

In the videos they show a simple paint program that kids would enjoy.  They also show it at a restaurant where the menu is all digital and you flip through it using your fingers.  When you're ready to order, you just drag the item to the center.  The same would go for paying the bill.  Set your credit card on the table, split the checks up, calculate the tip, and charge the card all without waiting for a server to do it for you.

I think we're going to see some really cool uses for this thing outside of normal computing.

For the past several years people have been hearing about Service Oriented Architecture through various mediums across the internet.  Most of what you would read would be academic material that was difficult to think about in concrete terms.

Still today there are numerous articles and books on the subject that talk so much in theory that there isn’t enough good direction on where to go.  For Joe Developer at Company XYZ, how can he take advantage of these seemingly great ideas on his next .NET (or whatever) project?

Unfortunately, this lack of good direction has led to a misconception about what SOA is and how it should be implemented.

At its heart, SOA is the next evolution of development.  Just as we had objects to encapsulate our behavior and compose applications of objects, we now can encapsulate core functionality as services so that they are reusable across the enterprise, or even to our customers. 

We can also take these services and compose them to create more complex services, and this can be taken to the extreme where you model every process that the business performs as a service.  The idea is that new applications can be built without the need to deal with implementation, it can be done completely by composing services.  Want to change the way the business functions?  Rewire the business process services in a way that better suits the business.

Unfortunately, when you talk this high level, you often gloss over the technical guidance and people take the advice and run in any direction.  It’s like a scavenger hunt where the treasure map is handed out and it contains details about the glorious treasure, but not the direction on how to get there.

This also leads to the misconception that SOA == Web Services, which is not the case.  More on this in a minute.

So back at Company XYZ, Joe Developer is implementing his next project with an SOA.  His management has also read about SOA and knows that it’s the right thing to do.  In fact, they may even be pushing him in this direction.  He creates his business logic, he creates his UI.  Next comes the service layer.  Joe thinks to himself, what better way to implement services than to be the first consumer!  It will be perfect!  Then any new application can access the functionality and everything will be great.  I’ll have an SOA Seal of Approval on my app because I used web services and my management will be happy.  And my application will be unnecessarily SLOW.  And complicated.  For no reason.

The reality is that Web Services are meant for interoperability.  They are meant to be accessed across a variety of mediums and ports.  They are great for platform interoperability and cross-political communication between applications.  They are not suitable for inter-company, .NET to .NET interaction.  The overhead of WSDL, SOAP, XML, etc is wasted in this scenario.  Consuming a web service is not efficient.  To combat this overhead, it is advised to make your remote calls as coarse-grained as possible.  Chatty remote calls will kill an applications performance.  So now we are designing our (!) application around the limitation of a heavyweight service layer.

This is something that I see all too often.

UI
SERVICE AGENTS
WEB SERVICE LAYER
BUSINESS LOGIC LAYER
DATA ACCESS LAYER
 
A better solution would be to design your application the way that good software engineering principles have taught you.  Separate responsibilities.  Create a domain model that represents your problem domain.  Speak in terms of your domain.  Leverage object oriented programming.

Then, when management decides that the functionality that you have created would be suitable to expose outside the company, or to their Java project that is currently underway, you can introduce a service layer.  The service layer consumes your existing business logic layer.  The idea is to introduce a more coarse-grained interface suitable for remote calls.  You create Data Transfer Objects that aggregate your domain objects and are more stable for a service contract.

This is a much better approach, because we take into account the fact that we can expose the functionality of services, but we should not shoot ourselves in the foot to do so.

Now getting back to the misconception of SOA == Web Services.  Why is this so common to see?  First, the term Web Services is probably partially to blame.  A service can be native .NET code, it can be a remoting interface, it can be SOAP over HTTP.  A more effective service oriented architecture (especially one within an application) is achieved by choosing the best medium for the circumstances.

I think it’s time for an example.  Say we are writing an application that calculates massive financial data for our enterprise.  One component of this will calculate the exchange rate for many currencies.  Ignoring the specifics of the implementation, how should we reuse this component so that the entire enterprise can access it?  We want to take advantage of a plain .NET to .NET inter-process call because it’s the fastest.  We’d also like to expose this to other .NET applications within our corporation.  Finally we want to use this service in our Java system as well.  How can we accomplish all of these without just resorting to the lowest common denominator?

One of the great things that I learned while studying Enterprise SOA in Paris was what the IBM guys call a Service Component Architecture, or SCA.  This architecture is enables services to be composable.   The WebSphere Integration Developer emphasizes modeling all of your business processes as composable services.  Most of these will be Java to Java calls, but some may not.  What they do is have you design your interface using a GUI, which spits out the WSDL interfaced and the Java interface.  The best flavor of interface is chosen depending on the circumstances.

So we can solve the above problem by having one single interface, with both a .NET and WSDL versions.  The configuration can determine which is used to achieve the best results.

Hopefully I’m not leaving out some core SOA concepts (I’m sure I am).  What about you?  Do you see too many mis-uses of SOA like I do?  What other techniques can help bring the industry back to reality?

(I also must apologize for such a long-winded post.  My bus is stuck on an HOV lane (one single lane with walls) in rush hour traffic.  I’ve been here for over an hour already.)

I have gone on record and said before that TFS Source Control is a great step up from VSS, however I’d never want to be constrained to the IDE for my SCC tasks.  Granted, IDE integration is a nice feature, but it shouldn’t be your sole interface.

This is part of the reason that I love Subversion.  It has builtin command line support for the freaks out there (like me) who like to type.  TortoiseSVN gives us explorer integration, which is solid gold.  Then there’s AnkhSVN for the IDE integration.  See a pattern here?

So I just stumbled on a new TFS Source Control explorer plugin tool with a funny name.  It’s called Dubbelbock TFS and it was written by a friend of mine, Ben Day.

This is the kind of tool that will help bring the power of TFS source control out of the IDE and enable a much more usable and powerful experience.

So go out and buy a copy, it’s only $25 (I think).  And tell Ben I sent you.