Time for a change

I've been considering this for several months and now got an opportunity to make a change. This post describes my next career move and why I decided to do this.

The history

The past four years I've been working for a software company that builds a product suite around Human Resources and Salary. The suite contains anything from salary calculation and HR registration to Employee and Manager Self Service systems. I was hired to help bring innovation and new technology to the existing team and work on the next version of the product.

As you might know we started with Silverlight 2 beta shortly after I joined the company. We worked on this product and upgraded it all the way to Silverlight 4 in two years time, until we decided that we needed to move away from Silverlight. For the past months our team has been working on delivering an ASP.NET solution.

My role has been to lead the team from a technical standpoint and architect the framework underlying the application. I've been happy to do this, however I still decided to change.

The Why

There are several reasons, some of which I'm not comfortable to discuss online, however the most important ones I can discuss.

The first reason, to me, is inherent to the assignment I had. If you complete the assignment, in this case developing a framework and getting a team up to speed on using it, you can't help but ask "What's next?". Unfortunately the answer was, "Finish the rest of the product." To me, this didn't (and still doesn't) sound very appealing. If you've been working on highly technical generic code and all of a sudden you're expected to do repetitive development, somethings got to give.

The second reason is more personal. I find it important to keep improving myself and I didn't see myself being challenged enough to improve on the skills I think are important to improve on as a senior developer, mainly soft skills. At some point you can get to comfortable in a certain situation.

The What

 So the final question is, what am I going to do? I've though about this and figured that in order to improve on soft skills a more customer facing role would suit my ambitions better. As I still wanted to be doing technical work as well a consultant role was the obvious choice. However I didn't want to be working with just another 'hour-factory' where you're just expected to bill as many hours to a customer as possible and I didn't feel much for being just another SharePoint 'specialist'.

I've been looking around and thinking about different routes to get what I'd like until an opportunity came along that I really liked. As of October 15th, I am working as a Senior Consultant in Enterprise Search. I've been working with enterprise search technology between 2004 and 2008 and I enjoyed it very much and always did want to go back to it and now I got the chance!

So what does a consultant in Enterprise Search do? I'll be working for customers that want to use Autonomy technology within their organization. Assignments can range from a simple advice all the way to a complete one off implementation for the customer. I'll be working multiple projects at a time and I'll be working with different programming languages and platforms a long the way.

So what about Developers 42?

What does all this mean for Developers 42? I will try to continue writing posts as time passes. However it does mean a change in direction for the topics I'll discuss. As I'll be using multiple programming languages, chances are I'll be writing more about my experiences with those.

Further more, as I explore more of the world of Enterprise Search and it's surroundings, I might be able to give some insight into what goes on in this field of expertise I'll be a part of once more.

I do hope you'll still be following this blog and to learn and teach together with you.


Follow me on twitter as well.

To Tweet or not to Tweet. That’s the question.

In this post I’d like to give an explanation of why I decided to start using Twitter and how it has worked out so far.

“Why on earth do you think you need to write a post explaining why you started using Twitter?”, you might ask.

I don’t like social networks

Well, people who now me, may have learned that I’m not a great fan of social media. I tried using several and most of them still don’t seem to add value for me.

Especially a network like Facebook appears like a serious waste of my, and others, time. I do have a Facebook profile, but I mostly use it to promote my blog posts.

The main reason I don’t like social networks is because I think most of us don’t have such an interesting live that you need to post updates about it every five minutes. Does anyone really care that I get up in the morning, go to work, when I drink coffee and when I go back home? Another question is, do I want others to know when I go to work and when I get home? To me it’s all a lot of noise and I don’t feel like spending time creating that noise for others to listen to.

Why Twitter might be different

So why go and use Twitter then? It seems like a lot of noise. Two things occurred to me. First of all, not a lot of people in my personal network actually use Twitter, so I don’t feel obligated to actually follow tweets by people that are close to me. The other thing is, and that applies to all Twitter users, Twitter is unique in the sense that it’s not automatically two way traffic. I can follow someone, but that doesn’t mean that someone will follow me.

This means that I can follow people who I think might have something interesting to say without me worrying about being intrusive and it also allows me to not follow a follower who I think is unlikely to tell me something interesting.

Besides the advantages of the platform I saw, I was looking for a platform to get some more interesting information about what others are doing in the field of software engineering.

I was also looking for a platform to promote this blog a bit better and a platform that allows me to post short updates appeared to me as a good way to do that and a challenge in the process. As some of you may know, I’m not blogging at a preset frequency. This does mean you may not hear anything from me for months. The reason for that can vary from being to busy to write something worth reading up to just not having a topic worth writing an entire post about (then again, maybe writing a post about why I joined Twitter might not qualify as a topic worth writing a post about ). With Twitter I can just write a one liner, share a link or a thought and it’s done.

Experience so far

So what has been my experience up to now? Well, I don’t have any real followers, so I don’t know about noise to others. I did tweet about ten times now of which two were retweets. I did find several Twitter accounts to follow that provided me with interesting Tweets. I got to some information I wouldn’t have got if I wasn’t on Twitter. I also stopped following some accounts as they provided me with to much noise. All in all that makes it meet my expectations.

This is another thing that struck me on Twitter. It seems more natural that people stop following other people. I had a follower and she stopped following me after about a day. I don’t know why and to be honest it doesn’t really matter. I see it more as a long running conversation. Once it stops being interesting for one of the parties involved, they leave the conversation. It makes sense to me.

Conclusion

So I have joined Twitter and up to now it has been a reasonable experience. I will continue to use Twitter for the upcoming months. If you think I might tweet something interesting, or if you want a tweeted update whenever I post something here, please join me on Twitter: @jvandeveen.

Feel free to share your experience with Twitter or other social media in the comments section below.

A TED video I think you should watch

In this post I would like to share a video from TED, that I think anyone even remotely interested in computers should watch.

Every now and then I like to watch videos that teach me something and/or inspire me when it comes to innovation. I used to limit myself to Channel 9, which is a great source for anything even remotely (and sometimes not) related to Microsoft. It has been inspiring and educational. Remember this post I wrote back in 2009?

Last year I was pointed to TED. As TED says on their website, they are a ‘nonprofit organization devoted to Ideas Worth Spreading’. Find out more about TED here. You should note that most videos on TED are presentations or talks. Sometimes there are interviews and sometimes there is a video with some kind of performing art.

The video I’d like to share with you is this one. It is a talk by John Graham-Cumming and it’s about the first ever design for a computer by Charles Babbage. I don’t want to give you to much information on the details, but you should definitely watch it. It’s only twelve minutes long, which is a common thing about these talks, they usually are not very long, which makes it easier to find the time to watch some of them.

One thing I took away from this is that although it is ok to doodle around with a whole bunch of different ideas, we should every now and then execute one of them.

If you have other great places where you find inspiring and/or educational videos, feel free to share them with us in the comment section.

Innovation can't be planned

The profession of software developer is a relative young one. As such we learn new things about it that other professions already have figured out. This post is about one of those things that managers who need to manage developers rarely seem to get: innovation.

Software development is devided in two different types of work, the standard projects for which you can simply apply well known en documented methods that lead to a predictable result, and the innovative projects where features and requirements can change based on the technical possibilities and impossibilities.

For example, implementing a corporate intranet in a CMS is well understood and tends to be predictable. On the other end, building a new product where the UI has to be available on a wide range of platforms and devices is not only new, but also has numerous variables that make it different every step along the way. Sure, there are methods to execute a project like that in a structured way.

Most agile methods appear to be suited to do highly innovative projects. However, they do have a single flaw, which I've recently experienced. Although they do allow for great flexibility in the big picture, once it comes down to the detailed work, they don't allow that same flexibility because at some point there still has to be some predictability so it can be sold to managers and executives alike.

In practice, when using an agile method, developers are still required to commit to delivering a certain amount of work within a certain amount of time. The only thing that has changed is the amount of work they are asked to make an estimate for. It's like instead of asking to design and build a spacecraft you're now asking for only the propulsion system. Sure, it's less work, but it's still highly unpredictable, especially when you find out the maximum speed in the specification is not nearly enough to get the craft to the destination within a reasonable amount of time and the fuel consumption needs to be cut in half.

Obviously the example above is exaggerated, but the point is that with innovation things can only become apparent once you're working on it. You encounter problems you could not have thought of and you have to solve them in order to deliver a product that's up to standard.

So how do you go about building an innovative software product? The first thing is to make sure you have the right people leading the team and trust them. Also make sure there is a clear set of boundaries that the team needs to operate within. Then support them and facilitate their work as much as possible.

This doesn't mean you can not put a timeconstraint on a project. However if you do, you should be prepared to compensate for that in functionality (some would argue that you can also assign more resources to a project, but why I think that has great limitations is a topic for another post).
So please, stop trying to plan your innovative development as you will only be disappointed.

Writing code != developing software

There has been some fuzz online about whether or not should everybody learn how to write code. In this post I’d like to add my point of view and take into account what the profession of developer involves (or should involve).

If you have not followed this discussion, you might want to read up on some other posts firsts:

Please Don't Learn To Code - Jeff Atwood

Please Learn To Think About Abstractions - Scott Hanselman

In a nutshell the fuzz is caused by public figures announcing they are going to learn how to write code.

The car mechanic

There has been several comparisons with other professionals already. However I think they are not really suited for what is happening here. I like to explain why learning how to write code doesn’t mean anything by projecting this to the profession of the car mechanic.

Let’s say I announce I’m going to learn how to work on an old car engine. If you analyze the skills I need to work on a car engine it almost becomes laughable:

• I need to be able to open the bonnet of the car
• I need a basic understanding of tools in the toolbox (a spanner, a screwdriver, etc.)
• I need to be able to start the car and drive it in order to test my work

Anyone can see that it I work on a car engine with only the above skills, I’m very likely to ruin the engine. At the very least we can conclude that being able to work on an old car engine doesn’t make me a car mechanic.

Let’s project this example back to the software developers profession. If you want to write code you need the following skills:

• I need to be able to install and run an IDE
• I need to be able to type code in the syntax for the language I’m using
• I need to be able to use the IDE to compile and/or run my code

If you are going to use only the above skills to write a program, changes are you are not going to achieve the results you want. In any case the above skills are not nearly enough to become a software developer.

The software developers profession

Jeff Atwood makes an excellent point in his post when he states that being a software developer is not about writing code, but about solving problems. I completely agree with Jeff on this point. If you read the post he refers to when making this point (here), you’ll see he paints a very bleak picture about developers being extremely disconnected from the users they are building software for. I personally do not have that experience, but then I’ve always worked in relatively small teams (six developers being the max).

In my career I’ve coached several developers and I’ve always been an advocate of what to me is the single most important skill any developer should have is the analytical skill. I’ve even given short trainings in analysis. When another developer asks for my help solving some problem, I always try to be very verbose on how I get to my analysis.

And as Jeff Atwood also states in his post, writing less code is better. In order to do that, being analytical about what you’re trying to achieve is crucial.

Obviously you can have all the analytical ability in the world, but if you don’t have a proper understanding about what you’re dealing with, it being the inner workings of an operating system, or the politics around some customers feature request, you can not make a proper analysis. This means you do need knowledge.

This brings me to a problem that is fairly unique to the software developers profession. Code is not knowledge, however it is transferred and documented online in vast quantities. This has created a whole breed of so called developers who simply go online and copy code for what they think solves a particular problem they’re having, without actually understanding what the code does, nor why they are having a certain problem. The term Lamer comes to mind.

The danger with that is that someone who does that might think that they solved a problem, however they might very well have not. And because of the lack of understanding they are unable to verify if the code solves the problem, nor are they able to troubleshoot the code if needed.

The software developer needs to analyze the users problems, then come up with a solution that fits the users needs. Again it’s not about the code. It’s about the solution. It requires a deep understanding of computers and the users needs and it requires analytical skills and a creative mind to come up with a fitting solution.

This is just my two cents. Please leave any comments, questions or rants below. I’d love to hear how others perceive this.

A new blogging opportunity

A little over a week ago I was contacted for a new blogging opportunity and I decided to give it a try.

When having a blog it’s nice to be noticed by people every once in a while. So when I was contacted by the Technorati Editorial Team (TET, really?) last week with an invitation to write for them I decided to at least investigate. It clearly was a mass-mailed invitation, so I was not as keen as I was when joining SilverlightShow.Net.

So what got me on board then? Well, let’s think about why I stopped writing for SilverlightShow, because let’s be honest, SilverlightShow did pay me for my articles and Technorati is not. Well, obviously there is the decision on stopping with Silverlight as our go-to UI technology, but it was not a deal breaker. In the end I was just to busy to crank out lengthy posts with lots of code and it became increasingly hard to find good topics to write about.

What makes writing for Technorati different is that they are looking for news and opinion posts in IT and they are looking for relatively short posts. Another thing that they allow, which I like, is reposting a post I wrote for Technorati here.

I finished my first post for Technorati last Friday and they published it a few hours later. By Saturday morning the link was Tweeted sixteen times, which means it generated more Tweets on its own than I did with all the posts I’ve done so far. I also got a very informative comment on the post, so to me this was a successful experiment. I do plan on writing more posts for Technorati and I also plan on reposting right here, for your convenience.

Enjoy.

Parsing CSS for analysis

This time we’ll look into parsing CSS so we can use the result for analysis.

The story

As we are starting a new project using ASP.NET MVC3 one of the things I was thinking about was how to better manage our CSS and JavaScript. The first thing that I figured would be great was if you could to some static analysis on all of your CSS files to see if certain situations arise.

The issue with multiple people working on the same HTML based UI is that it can be hard to find out what CSS class to use. Because of that you might end up with classes doing the same thing, classes being defined more then once with different definitions, etc..

All this leads up to a less then ideal situation. Removing the cause of the problem, not knowing what CSS class to use, proves difficult. Helping counter the symptoms of the problem is proving a lot easier, so that’s the path I chose for, right now.

A two part solution

In order to do static analysis on something that is only available to me in plain text, I first need to parse the plain text into something that is easier to analyze. Then I can use the result to do the actual analysis on and communicate the result.

Analyzing how to parse CSS

To write a parser for any language requires a deep understanding of its syntax. Fortunately for me CSS is not a very complex language. W3Schools.com proves to be very helpful in providing us with an explanation on the CSS syntax. It comes down to this:

• A CSS document consists of CSS rules
• A CSS rule consists of a Selector and a set of Declarations
• Each declaration consists of a property and a value
• Comments can exist at the top level of the CSS document (outside of the CSS rules) or in between declarations

In order to do static analysis on this I came up with some interface definitions that allow me to query the structure of a CSS document:

   1: public enum SelectorType

   2: {

   3:     Tag,

   4:     Id,

   5:     Class

   6: }

   7:  

   8: public interface ICSSDocument

   9: {

  10:     string FilePath { get; set; }

  11:     IEnumerable<IRule> Rules { get; }

  12:     void AddRule(IRule rule);

  13: }

  14:  

  15: public interface IRule

  16: {

  17:     ISelector Selector { get; set; }

  18:     IEnumerable<IDeclaration> Declarations { get; }

  19:     void AddDeclaration(IDeclaration declaration);

  20: }

  21:  

  22: public interface ISelector

  23: {

  24:     string Name { get; set; }

  25:     SelectorType SelectorType { get; set; }

  26: }

  27:  

  28: public interface IDeclaration

  29: {

  30:     string Name { get; set; }

  31:     string Value { get; set; }

  32: }

Note that this might not be final as I might come up with requirements implementing the static analysis.

For parsing text like this there are always several approaches. In this case I decided that using plain and simple text parsing would be the most flexible, as I might want to add features to the parser in the future. Here is what I came up with for the main parse loop:

   1: public void Parse()

   2: {

   3:     string data = File.ReadAllText(FilePath);

   4:  

   5:     _position = 0;

   6:     _isInComment = false;

   7:     while (_position < data.Length)

   8:     {

   9:         if (IsEndOfFile(data))

  10:         {

  11:             break;

  12:         }

  13:         HandleBeginOfComment(data);

  14:         HandleEndOfComment(data);

  15:         if (!_isInComment)

  16:         {

  17:             HandleRule(data);

  18:         }

  19:         else

  20:         {

  21:             _position++;

  22:         }

  23:     }

  24: }

As you can see I have a (private) field to keep track of the position within the CSS document and another field to keep track of comments.

You might find the IsEndOfFile method weird as I have a condition within the while loop that should do the same thing. However I need to check ahead one position in case I’m still checking for comments (or are in a comment for that matter). The definition of the method is quite simple:

   1: private bool IsEndOfFile(string data)

   2: {

   3:     return _position == data.Length - 1;

   4: }

The HandleBeginOfComment method checks for the start of a comment:

   1: private void HandleBeginOfComment(string data)

   2: {

   3:     if (data[_position] == '/' && data[_position + 1] == '*')

   4:     {

   5:         _position += 2;

   6:         _isInComment = true;

   7:     }

   8: }

Basically it checks for the string /* and if it finds that string at the current position it moves the cursor by two characters and sets the _isInComment flag. HandleEndOfComment does the same thing for */ and sets the _isInComment flag to false again. Any comments are currently ignored, but it is easy to extend the main parse loop to allow for parsing comments as well.

The HandleRule method takes care of all the parsing magic, which makes sense as the Rule is the main component of a CSS document.

   1: private void HandleRule(string data)

   2: {

   3:     while (_position < data.Length && !StartOfRule(data[_position]))

   4:     {

   5:         HandleBeginOfComment(data);

   6:         if (_isInComment)

   7:         {

   8:             return;

   9:         }

  10:         _position++;

  11:     }

  12:     string selectorData = GetSelector(data);

  13:     string declarationsData = GetDeclarations(data);

  14:  

  15:     IRule rule = _kernel.Get<IRule>();

  16:     

  17:     ISelector selector = _kernel.Get<ISelector>();

  18:     selector.Name = selectorData;

  19:     selector.SelectorType = GetSelectorTypeFromName(selectorData);

  20:     rule.Selector = selector;

  21:  

  22:     HandleDeclarations(rule, declarationsData);

  23:  

  24:     AddRule(rule);

  25: }

The first loop deals with running into a comment later on in the document. If we do run into a comment we simply return to the main loop, which will then deal with finding the end of the comment. In the same loop it checks for the start of a Rule.

If we are still in the method after this loop, we have reached the start of a Rule. As we’ve noted earlier a Rule consists of a Selector and a set of Declarations. The methods GetSelector and GetDeclarations take care of parsing those portions of the CSS document. Once we have that data we can use it to create a rule. We use a Ninject Kernel to create instances of both the IRule and ISelector implementations.

Note that right now we handle the Selector like it’s a single entity. A future improvement might be to split up the Selector into parts and assign types to them individually.

The HandleDeclarations method takes the declarations text, parses it into IDeclaration implementations and adds them to the given IRule:

   1: private void HandleDeclarations(IRule rule, string declarationsData)

   2: {

   3:     string[] declarations = declarationsData.Split(new char[] { ';' }, StringSplitOptions.RemoveEmptyEntries);

   4:     foreach (string declaration in declarations)

   5:     {

   6:         if (string.IsNullOrWhiteSpace(declaration))

   7:         {

   8:             continue;

   9:         }

  10:         int splitterIndex = declaration.IndexOf(":");

  11:         string declarationName = declaration.Substring(0, splitterIndex).Trim();

  12:         string declarationValue = declaration.Substring(splitterIndex + 1).Trim();

  13:  

  14:         IDeclaration declarationInstance = _kernel.Get<IDeclaration>();

  15:         declarationInstance.Name = declarationName;

  16:         declarationInstance.Value = declarationValue;

  17:         rule.AddDeclaration(declarationInstance);

  18:     }

  19: }

Note that I use String.Trim to make sure we don’t end up with white space in our declaration data, which could get in the way of our analysis (and is of no value any way in CSS).

So far so good. We can now parse CSS into an object model, which allows us to analyze the CSS in a structured way. I plan on writing a next post that shows the analysis based on this model.

No complete source included: Unfortunately, as this project is owned by my employer, I can not include full source code, however the parts I included should provide you with a good insight into parsing CSS.

Moving from Silverlight to MVC3

In this post I’d like to explain why we felt the need to abandon our Silverlight development in favor of MVC3.

As some of you may very well know, I’ve been pushing Silverlight within our company from as early as Silverlight 2 Beta 1, back in 2008. Still, this last summer I felt I had to raise the question: Is this still the right technology for our company?

Technology choices are about requirements

When we first chose Silverlight as our UI technology, we came up with a set of requirements. Our application should have a (near) zero footprint on client systems. It should be accessible through the web. Deployment on clients should be effortless or none existent. It should look great without a whole lot of effort. Silverlight checks all these boxes (it still does).

We write summer of 2010. The iPad has been around for several months now and it has been a great success. Smartphones are widely adopted to the point that we predict our customers will get interested in support for platforms like these when using our software.

Another thing we see is people working on more different platforms than before. Was it ok to ask for a certain browser in 2009, in 2010 our customers began to ask for a browser independent UI, not only on Windows, but also on a lot of other platforms.

To see what exactly would be the response of our customers we decided to build a native iPhone application with a limited set of functionality. We started the project early 2011 and published the first Dutch HRM app for any smartphone platform in may. It was a hit, not only because of responses by our clients, but also because of responses by our competitors.

Requirements shift, the world changes

This lead us to conclude that we needed to do something to support a new requirement. Our application, at least in part, should be available on mobile devices and tablets. And we should make sure we could drop the browser requirement we had active, even with our Silverlight 4 UI*.

That is why, during one of our meetings about what to build next, I felt the need to ask “Shouldn’t we move away from Silverlight and adopt ASP.NET MVC3 with HTML5?” It sure was painful, after investing over two and a half years in Silverlight to even suggest dropping it. However I felt then, and I still do, that a change had to be made. After some more debate on the consequences and some research, we are now putting in the effort to build the first parts of an MVC3 UI with the first steps into HTML 5 and CSS 3.

Luckily not all our efforts with Silverlight where in vain. We did deliver a good working product and we are committed to using, expanding and improving the middleware we developed for it. (Do you see the power of a Service Oriented Architecture?).

So is Silverlight really dead now?

Some of you may remember this post. In that post I state that Silverlight is actually the better technology for writing Line Of Business Applications. Even after researching ASP.NET MVC3 and HTML 5 further, I do still believe that, however because of the changes in how people use computers it simply fails to check one box for our customers.

Silverlight is no where near dead. It will still be used in many ways, including new platforms like Windows 8 and, for example Microsoft CRM 2011. Microsoft is integrating Silverlight in more and more of their own platforms. Also with the introduction of Silverlight 5 there will be many cool new features coming to the browser. Therefor I doubt Microsoft will drop Silverlight any time soon.

Consequences for Developers 42

Unfortunately our move away from Silverlight does have some consequences for this blog. First of all, my long running series of posts “Adventures while building a Silverlight Enterprise application has ended with part 41 (which is slightly painful for an obvious reason).

It also means I will no longer be writing posts for SilverlightShow.net. I’d like to use this opportunity to thank Svetla for supporting me for the past years.

And finally, it will also mean a lot less content on Silverlight, but hopefully a lot more content on MVC3, HTML 5, CSS 3, jQuery, etc..

It’s the end of another interesting period in my professional live and the start of a new one. I hope you have enjoyed my articles on Silverlight and I hope to see you around.

 

 

* The IE dependency was not actually caused by Silverlight, but by the integration with the Microsoft Report Viewer we used.

Trivialities about nullable types

Sometimes things in the world of software are not that hard. They are just poorly documented or documentation is hard to find. This surely applies for some use cases of nullable types. This post shows the use of nullable types in generic methods and how it’s easier than you might think.

An introduction to nullable types in C#

In order to understand the use of nullable types, it is imperative that you understand the difference between a value type and a reference type. For a complete description of these things have a look at chapter 4 of the C# 4.0 Language Specification (included with Visual Studio 2010). In short it comes down to this: value types directly contain their value, while reference types contain a reference to their value. Value types are always either a struct type or an enumeration type. Struct types include things like numeric types.

As value types always directly contain their value, they can not be null. However, in some cases, you might want to have a structure where you can identify if a value type is actually not defined. In lots of cases simply defining 0 as the undefined value for an int, for example. will not suffice. 0 might actually be a meaningful value for an int.

To provide a way of declaring a variable of a value type that can be null, C# introduces the question mark as a suffix to a value type:

int nonNullableInt = null;
int? nullableInt = null;

Line 1 doesn’t work, because null can not be assigned to a value type. Line 2 does work, because of the question mark behind the variable type.

Under the hood of nullable types

So what happens here? In fact the question mark in this context is syntactic sugar for Nullable<T>. So what happens is that nullableInt in the previous example is actually of type Nullable<int>. Because of this the variable now has a property Value, which contains the actual value if one is a available, and it gets HasValue of type bool, which indicates if a value is actually available.

Note that Nullable<T> is defined as a struct and is therefor a value type itself. Also note that T is limited to contain structs. Therefor it is not possible to apply Nullable<T> (or the question mark suffix for that matter) to a reference type.

Nullable types in generic methods

Now let’s get to the point. Let’s say you want to do some generic handling of input. So write a generic method with a signature like the following:

static string GetStringRepresentation<T>(T value)

You can simply call this with both non-nullable and nullable types. Because the compiler infers the type variable T I don’t even have to tell it what type value is explicitly. Let’s say we have the next program.

static void Main(string[] args)
{
	int nonNullableInt = 0;
	int? nullableInt = null;

	Console.WriteLine(GetStringRepresentation(nonNullableInt));
	Console.WriteLine(GetStringRepresentation(nullableInt));

	Console.WriteLine("IsNullable(int): {0}", IsNullable(typeof(int)));
	Console.WriteLine("IsNullable(int?): {0}", IsNullable(typeof(int?)));

	Console.ReadLine();
}

The output of line 7 is actually an empty string. This is because the call to value is actually boxed because the call to ToString() is actually a call to object.ToString(). Because nullableInt is in effect null, it will return an empty string.

Obviously there are many reasons why that might not be correct for a nullable int, so let’s find a way to handle nullable types better in our generic method. The first thing to do is to detect if the passed in value is actually a nullable type. To do this we can use the type system:

static bool IsNullable(Type valueType)
{
	return valueType.IsGenericType && valueType.GetGenericTypeDefinition().Equals(typeof(Nullable<>));
}

What this method does is use the type passed in and checks if it’s a generic type. If it isn’t, it can’t be nullable. It needs that check because otherwise our second check on GetGenericTypeDefinition would throw an exception as it would not have a generic type definition to return. Our second check compares the returned generic type definition with the Nullable<> type. Another task we need to accomplish is to get a default value for a nullable type, or, more specifically, get a default value for it’s generic argument:

static object GetDefaultValue(Type nullableType)
{
	Type valueType = nullableType.GetGenericArguments()[0];
	return Activator.CreateInstance(valueType);
}

This method takes a type and gets the first generic argument. This code assumes that you’ve already made sure this type is actually a nullable type. Normally you could use the default keyword to get a default value from a generic argument by writing default(T). As in this case we don’t have an actual type declaration, but a Type instance, we need a different approach to get a default value. If you’d check out the C# 4.0 reference you’d find out that the default keyword simply calls a default constructor on the type passed in and returns the result. To mimic that behavior, I simply call Activator.CreateInstance with the underlying type to get a default value. Now if we rewrite our GetStringRepresentation method to use the new methods above, we would end up with something like this:

static string GetStringRepresentation<T>(T value)
{
	if (IsNullable(typeof(T)) && value == null)
	{
		return GetDefaultValue(typeof(T)).ToString();
	}
	return value.ToString();
}

Now, if we call this method with a int? it would return 0 instead of an empty string. For your convenience, I’ve uploaded a sample project here. I hope you’ve found this an interesting tour around nullable types. If you have any questions or comments, please use the comments form below. Thank you for reading.