as the Channel 9 website says: using real-life code examples Sander will demonstrate how to model, generate and build smart use cases and introduce the positive impact smart use cases have on your layered software architecture.
Anyway, here’s the video for my DevDays 2011 session:
One of the major items on my wish list – that is on the professional half of it – is to write a book that displays my ideas on software architecture, patterns and frameworks. Yes I know, there are many books on software architecture, and there are many books that explain patterns, and yes there also are a lot of books that show you how to work with framework A, B or C.
So you would say, why on earth would you want to write a book on these subjects? Well there’s three major reasons. First, there’s not a lot of books out there that combine all these subjects into one single coherent story that will actually help you to write your applications better. Second, maybe I’m a bit arrogant on this, but I feel like I have something to all the stuff that’s out there. And last but not least, I finally need to get this stuff out of my head! Maybe ambitious, but let´s see!
To be honest, you might like or not like all of the ideas in this book, or even may totally disagree with some of them. Actually, you probably will. But on the whole, I hope this book will be able to inspire you and illuminate you in how to build software. It´s often a matter of taste. So consider this book as a menu. Just order from it what you like. You don´t need to copy the C# and .NET code examples from the book, but rather I hope that use can use them to shape your own ideas on software architecture, frameworks and patterns. Take from it what you like, and forget about the few things you don’t like.
What’s the first step towards writing this book? I’ve been teaching about software architecture, patterns and frameworks for .NET for quite a number of years, and the material from these courses will be a good start, similar to the way I shaped my book on UML – from iterating over the material I had for my UML courses.
Along with the course material comes the work I’ve done in projects, and as a result the work we (the core team) do on our ever-evolving and improving ADF.NET framework.
So here’s the overview of the material in the software architecture and patterns course:
In the next chapters I will slowly go through the individual layers. First, let’s investigate the presentation layer:
Next the process layer gets a rub:
The layer it all revolves about:
All the way down to the bottom, in the cellar of your application, lies the data / services layer:
From April 12-14 the next edition of Microsoft’s MIX Conference will take place in Las Vegas. I’ve sent in two proposals for the Open Call. Today heard that both proposals made it through the first cut, which means they’re open for public voting (you don’t have to be registered). It would be great if you would cast your vote for my proposals on how smart use case can drive web development, and on how frameworks can kill your projects.
Use cases have been around for many years describing the requirements of software development projects. By developers, use cases are often seen as too abstract and too complex to develop code from. That is, until now.
During this interactive talk speaker Sander Hoogendoorn will demonstrate how to model, generate and build smart use cases. This great technique allows projects to model use cases at a much more pragmatic, and low-granular level, that can be implemented straightforward and directly into our applications, such as ASP.NET or Silverlight web application. The speaker will introduce both the positive impact smart use cases have on your layered software architecture, as well as the design patterns required to implement smart use cases. This talk comes with many real-life code examples.
When it comes to .Net development, more and more frameworks enter the market. Both from Microsoft and from open source. think of ASP.NET MVC, Castle, WF, Entity Framework, Unity, Linq2SQL, ADO.NET Data Services, WCF, nHibernate, Spring.NET, CSLA, NUnit, Enterprise Library or ADF.
Once a project chooses to apply one or more frameworks, trouble begins. What if you require features that aren’t implemented in the framework? What if you decide that another framework would have been better and want to switch halfway your project? What if the author of your favorite open source framework suddenly stops developing? What if the framework contains bugs or omissions? And what if a new version of the framework is released that is implemented totally different? These and many more everyday problems will cause your project to come to a halt, or at least make you perform serious refactoring.
During this highly interactive talk Sander Hoogendoorn, chief architect of Capgemini?s agile Accelerated Delivery Platform, and member of Microsoft?s Partner Advisory Council .NET, demonstrates pragmatic architectures and patterns that will help your projects to stay away from framework issues, and how to keep code independent of framework choices. Sander will present models of layered architectures, and apply bridge patterns, managers-providers, dependency injection, descriptors, and layer super-types.
Of course, the speaker will illustrate these insightful patterns with lots of demo?s and (bad) code examples using blocks from Microsoft?s Enterprise Library, NHibernate, Log4Net, and the Entity Framework. Delegates benefit by learning how to improve the structure and quality of their software architecture and code, and how to avoid the pitfalls of applying frameworks to .Net software development.
Handling events in ASP.NET is not always as straightforward as it seems. One particular pattern that often occurs is that there’s several items in a row in a GridView control that trigger commands. Now the GridView supports several standard commands such as Select and Delete, but what if you want to issue your own command?
As an example, here’s my situation. I have a GridView that displays relationships between contacts, such as in the picture below.
Here, the left part triggers another use case to update the relationship, but the second part needs to start a use case to view the other contact in the relationship. How did I implement this?
First of all, you will need to add a DataCommand to the control (in my case a LinkButton. Here I specified it with “OtherContact”.
1: CommandName="OtherContact"
When you now click on the LinkButton you will be able to capture this command from the event arguments of the RowCommand event, which fires upon clicking the button. So first you will need to add a handler to the event.
1: this.grdRelationship.RowCommand += new GridViewCommandEventHandler(grdRelationship_RowCommand);
The RowCommand event comes with event arguments, which is an instance of the GridViewCommandEventArgs class. As you might expect this class has a property CommandName you will be able to verify.
Now for the somewhat harder part. My GridView is bound to a collection of Relationship objects, and I need to find out which of the rows is actually clicked to be able to pass the right Relationship to the next use case. Hence, I need to get hold of the index of the row that was clicked. Unfortunately, this index is not a valid property of the GridViewCommandEventArgs, nor on any of its properties properties.
However, there is an additional property available that might help, and that is the CommandArgument property. Just like the CommandName this property can be set on the LinkButton in the GridView. The trick here is to set it (for example) to the index of the row it is in. I’ve used the following expression to achieve this.
1: CommandArgument='<%# DataBinder.Eval(Container, "RowIndex")%>'
Of course there’s alternatives such as putting in the Id for the actual Relationship object, but RowIndex seems fine to me – this way the object’s identification at least doesn’t show up in HTML.
The last step here is to put it all together in handling the RowCommand event. The remaining code isn’t hard to understand.
1: void grdRelationship_RowCommand(object sender, GridViewCommandEventArgs e)
2: {
3: if (e.CommandName == "OtherContact")
4: {
5: Relationship r = Relationships[Convert.ToInt32(e.CommandArgument)];
6:
7: MyTask.ShowOtherContact(r);
8: }
I simply validate the CommandName and use the CommandArgument to identify the relationship that was clicked as pass that relationship to the underlying use case (in the MyTask property of the page).
[Session ARC205 at Microsoft TechEd Europe 2010 in Berlin]
Use cases have been around for many years describing the requirements of software development projects. From a developer’s point of view, use cases are often seen as too abstract and too complex to develop code from. Until now, that is.
![IMAGE_004[5]](http://sanderhoogendoorn.com/blog/wp-content/IMAGE_0045.jpg "IMAGE_004[5]")
During this interactive talk, speaker Sander Hoogendoorn will demonstrate how to model, generate and build smart use cases.
![image[8]_thumb[2]](http://sanderhoogendoorn.com/blog/wp-content/image8_thumb21.png "image[8]_thumb[2]")
This great technique allows you to model use cases at a much more pragmatic, low-granular level, enabling them to be implemented simply and directly into applications such as ASP.NET or Silverlight. Using many real-life code examples, the speaker will introduce both the positive impact that smart use cases have on your layered software architecture, as well as the design patterns required to implement them.
[Session ARC203 at Microsoft TechEd Europe 2010 in Berlin]
When it comes to Microsoft .NET-connected development, more and more frameworks are entering the market, both from Microsoft and from open source. Think of ASP.NET MVC, Castle, Windows Workflow Foundation (WF), Entity Framework, Unity, Linq2SQL, ADO.NET Data Services, Windows Communication Foundation (WCF), nHibernate, Spring.NET, CSLA, NUnit, Enterprise Library, MEF or ADF.
Once you apply one or more frameworks to a project, the trouble begins. What if you require features that aren’t implemented in the framework? What if you decide that another framework would have been better and want to switch halfway through your project? What if the author of your favorite open source framework suddenly stops developing? What if the framework contains bugs or omissions? And what if a new version of the framework is released that is implemented differently?
![image[8]](http://sanderhoogendoorn.com/blog/wp-content/image83.png "image[8]")
These and many more everyday problems can bring your project a halt, or at least require serious refactoring. During this highly interactive talk, Sander Hoogendoorn, chief architect of Capgemini’s agile Accelerated Delivery Platform and member of Microsoft’s Partner Advisory Council .NET, demonstrates pragmatic architectures and patterns that will help your projects avoid framework issues and to keep code independent of framework choices. Sander presents models of layered architectures, and looks at applying bridge patterns, managers-providers, dependency injection, descriptors and layer super-types, accompanied by lots of demos and (bad) code examples using blocks from Microsoft’s Enterprise Library, NHibernate, Log4Net, and the Entity Framework.
Join this interactive discussion to share your experience of improving the structure and quality of your software architecture and code, and to discuss how to avoid common pitfalls of applying frameworks to .NET software development.
Sometimes there’s these really little things that hardly seem worth the effect blogging about. But when you start googling for the apparent solution, there’s a million-and-one blogs, forum questions that at the least are contradicting.
In this particular case I wanted to set different images in different rows in a Repeater or GridView depending on some property of the domain object I’m binding to. This seems to be pretty straigtforward. And it is. However it’s all these little details that still take up some much time googling, trying them out, debugging that makes it nasty enough.
So a live example. I have a class called ValidationResult. This class has a number of properties, such as Name, Description, but also a Severity. The type of Severity is the following enum.
public enum ValidationResultSeverity
{
Success = 0,
Informational = 1,
Warning = 2,
Error = 3
}
Nothing fancy here.
Now I’ve created small iconic images that match the names of the elments in the enum. So there’s an image informational.gif, warning.gif, etc. You get the picture. The images resides in a sub-directory called Images in my web project.
Next I’ve defined a user control with a Repeater control on it. In code this Repeater is databound to a List<ValidationResult>, using the following code.
List<ValidationResult> views = FormatMessages(validationResults);
repException.DataSource = views;
repException.DataBind();
This straightforward code causes the individual items (rows) in the Repeater to bind to the properties of one of the ValidationResult items in the list.
The Repeater is defined as follows. Most noteworthy is the construct I’ve used to bind the images of course. After googling and puzzling a bit I came up with the following simple solution.
<asp:Repeater ID="repException" runat="server">
<ItemTemplate>
<tr>
<td valign="middle">
<asp:Image ID="imbIcon" runat="server" Width="11" ImageUrl='<%# "~/images/" + DataBinder.Eval(Container.DataItem, "Severity") + ".gif" %>'></asp:Image>
</td>
<td valign="middle">
<asp:Label runat="server"><%#DataBinder.Eval(Container.DataItem, "Message") %></asp:Label>
</td>
</tr>
</ItemTemplate>
</asp:Repeater>
Nothing too difficult use of DataBinder.Eval() constructions. I’m not very fond of Eval(), simply because of it’s use of strings, which make binding very type unsafe, but it this case I stuck to it.
But note the most interesting code fragmet in here.
ImageUrl='<%# "~/images/" + DataBinder.Eval(Container.DataItem, "Severity") + ".gif" %>'
This very little fragment took me about 20 minutes to get it right. Why? Well, first you will try to use the literals "~/images/" and ".gif" outside of the Eval() expression, just because it seems more logical. Doesn’t work – at least not how I like it. Compiling renders invalid tag errors. Next you find all kinds of blogs that put these literals inside of the expression. Still no result. You will have to be really careful here. And only then I thought of putting the whole expression between single quotes instead of double quotes, which you would do normally. And then it works, as you can see below.
Last week, the Microsoft TechEd North America 2010 took place in the great city of New Orleans. I was lucky to be invited to do a talk on how frameworks can kill your projects.
When it comes to Microsoft .NET-connected development, more and more frameworks enter the market. Both from Microsoft and from open source. Think of ASP.NET MVC, Castle, Windows Workflow Foundation (WF), Entity Framework, Unity, Linq2SQL, ADO.NET Data Services, Windows Communication Foundation (WCF), nHibernate, Spring.NET, CSLA, NUnit, Enterprise Library or ADF.
Once a project chooses to apply one or more frameworks, trouble begins. What if you require features that aren’t implemented in the framework? What if you decide that another framework would have been better and want to switch halfway through your project? What if the author of your favorite open source framework suddenly stops developing? What if the framework contains bugs or omissions? And, what if a new version of the framework is released that is implemented differently? These and many more everyday problems will cause your project to come to a halt, or at least make you perform serious refactoring.
During this highly interactive talk, Sander Hoogendoorn, chief architect of Capgemini’s agile Accelerated Delivery Platform, and member of Microsoft’s Partner Advisory Council .NET, demonstrates pragmatic architectures and patterns that will help your projects to stay away from framework issues, and how to keep code independent of framework choices. Sander presents models of layered architectures, and applying bridge patterns, managers-providers, dependency injection, descriptors, and layer super-types.
Of course, Sander illustrates these insightful patterns with lots of demos and (bad) code examples using blocks from Microsoft’s Enterprise Library, NHibernate, Log4Net, and the Entity Framework. Learn how to improve the structure and quality of your software architecture and code, and how to avoid the pitfalls of applying frameworks to .NET software development.
Capgemini BAS, Faustlaan, Apeldoorn.
With Capgemini BAS joining Capgemini in 2009, some new initiatiaves in model driven development opened up, more particularly, hoping I’ve interpreted it correctly, based on naterual language. I discussed this initiative in June with Freek Bosch, manager of the unit where this natueral langauge based approach originated.
During the same inspriing conversation I illustrated the pragmaitc model driven development approach in our Accelerated Delivery Platform (ADP). Immediately Freek invited me to present our approach during one of his unit’s meetings. Unfortunately my agenda left little room until now. So I will drive to Apeldoorn in the morning, and discuss our approach during a one-and-a-half hour lunch meeting.
Think I will talk about the following subjects tomorrow:
Published in my Interesting Things column in SDN Magazine, November 2009.
Looking back on twenty years of software development, I must have spent most of that time trying to improve the quality and productivity of software development.
Ever since I started to write small applications in Turbo Pascal in 1988 I got infected with the writing-better-software-faster virus. Right after I finished the second of fourteen of these applications, I wrote my first framework. It took some effort, but writing the following twelve applications took me less time than building the first two.
There are good reasons for increasing productivity and quality. First of all, we have to increase productivity by a hundred-fold to meet up with current demands, says Gartner. Furthermore, technology is becoming increasingly complex. Ten years ago I was working in both Microsoft and Java projects. Anno 2009, I’ve let go of the idea that I even have an overview of either one of them. It is hard enough working with a small subset of frameworks. A Silverlight designer is not likely knowledgeable in NHibernate. Being a Spring guru does not guarantee foxy JavaFX user interfaces.
Despite this darkening perspective, there’s techniques and technologies that might keep you from drowning, by simply raising the level of abstraction. Good frameworks help. Smart use cases certainly do. And even UML assists. And then there’s model driven development a.k.a. model driven architecture a.k.a. model driven engineering a.k.a. domain specific languages. Different names for generating code and other deliverables from a model. What model? To be honest, any model will do the trick. Business process models, use case diagrams, user interface models, domain models, and last but not least data models.
Eight years ago I was helping a customer set up the domain model for a help desk application. After that I started to build the software in ASP.NET. Having modeled all domain objects, their properties and their services, I was typing them out in C#. So, as any decent developer would do I wrote a code generator. That helped.
I suspect most code generation efforts have a similar empirical start. That’s probably why there are so many approaches to generating code. Some really high-brow, squeezing everything-and-the-kitchen-sink into a model, and then trying to generate the whole application. From front to back. Or, at the very low and of the spectrum, inspecting the database, generating create-read-update-delete screens in a flat two-tier architecture.
Recently I was invited in a panel on model driven development, together with some academic and commercial experts. For starters, each of the panel members introduced their position briefly to the audience. This noteworthy event learned me two things. One: never allow four enthusiastic innovators talk freely on their innovations. The word brief isn’t in their vocabulary. Two: coming from a business background, I didn’t have a clue to what model driven development does in the academic world. A whole new spectrum of approaches met my eye.
So where’s the value in this? Following the good old Scrum adagio I’d say: it depends. Model driven development can be highly rewarding for projects. But I’ve also witnessed projects that made a terrible mess of it.
In my opinion, being successful at model driven development requires some preconditions to be met:
Embed approach. Successful model driven development projects share a single principle: it’s all in a day’s work. Model driven development is never a goal. It’s just a means to an end. Making better software faster. No guru’s, no heroes.
Allow changes. Projects go through changes. That’s a fact of life. Model driven development should never be blocking changes, but rather should stimulate creativity, by allowing projects to show quickly what effect new or changing requirements have.
Stabilize architecture. Knowing how to model, and where to generate what code is key. Set up a stable (layered) software architecture, pick frameworks that match it, and only then elaborate on code generation.
Be pragmatic. My general advice in life also holds for model driven development. Be pragmatic. Never overdo it. Don’t try to squeeze the whole world in your model. It’s not necessarily a bad thing to still have to write some code manually.
Having said all that, and having seen projects that very successfully apply model driven development, why is there still so much skepticism? After all, the paradigm really helps to deliver high quality at high productivity.
After witnessing both highly successful and extremely failing model driven development projects recently, I have given this some consideration. The vast majority of projects are in the middle of the wide spectrum of approaches. They run smoothly, being fairly practical. But it’s the failing projects at either end of the spectrum that draw the attention. Highly complex, slow moving, rigor projects on the one end, and oversimplified, bug-absorbing, underestimated projects on the other end. It’s no fun at either end.
My team and I have always adopted a highly pragmatic approach to model driven development, modeling smart use cases, applying domain driven design, run the model through our code generators (Tobago MDA) and we’re set to go. We do make better software faster.
Can life be this simple? It certainly can. We have applied this approach to all kinds of projects, and generated code in a variety of languages and frameworks, from Visual Basic to C#, from PHP and Java to Cobol. At the upcoming SDC, I’m going the check out a combination of Silverlight, .NET RIA Services, ADF and probably Fluent NHibernate. Should be fun!
To leave you with some words of wisdom (ahum). If there’s one thing I’ve learned from being successful at model driven development, it’s this: modeling and generating code should be everyday practice in your project. There’s no such thing as a “model driven development project”. There’s only software development projects. You don’t have to be a Jedi knight to steer a code generator. It’s all in a day’s work.