Tuesday, November 25, 2008

Naming and conventions in XAML

I think the naming and code/markup conventions in XAML is a bit unclear. This post will raise some of the issues.

I posted a new thread in the Silverlight.net forums about why there is no PART_ convention in Silverlight when this convention exists in WPF. I described the problem like this:

"In WPF there is a convention for TemplateElements in controls that distinguishes controls that must exist in a template from other controls. This means that if I edit a control template I know that all elements named PART_* must be in the template and all other parts I can remove or do whatever I like to.

When I looked in Silverlight Toolkit and the shipped controls there are no such standard, why? How should the user know which controls that must be in the template? I think it is sad that the framework doesn't look the same in all parts (yes I know that the Silverlight Toolkit is not in the framework, but realize that it will be a template and a teacher for many control developers). Is there a reason?"

I did not get a clear answer for why they have made it this way but the replies made me realize that PART_ convention can probably not be entered in the future because this will break the released code. And on the other side, in WPF the PART_ convention can not be removed because that will break the WPF code. I think the problem is that the two so similar frameworks differ in conventions and readability. What about the problem?

Yes, I know about the TemplatePart attribute and I know that the functionality does not change because of the naming convention. I think that the problem is that the tools does not use this information today. Tools like Visual Studio and Blend will soon be consuming the attribute but there are a lot of other tools that won't. This brings us to my second opinion.

I think this is a usability and design issue. If you read Framework Design Guidelines (K. Cwalina, B. Abrams) they have an important point when they say that the .NET Framework should "look the same" wherever you are. Therefore I think its a bad thing that Silverlight and WPF differs. A developer should recognize himself/herself when adopting a new area within the framework, and the framework code should be clear and readable. This is not a big issue and maybe I'm whining a little bit too much about this, but I think it is important that we create conventions for markup (XAML) in the same way that we use camelCasing and PascalCasing in e.g. C#. I have seen some unclear naming within the framework (in XAML), are there any conventions for naming and so on and do people use them?

Another part that is related to this is how you should name your members in XAML. Your XAML-file are compiled into the same container as the code behind (in the case of a UserControl) and there they will be members of that class. This means that if you name e.g. a Button "MyButton" it will appear as a member of the class with a field name "MyButton". In C# and in standard naming conventions fields should be named with camelCasing which means that the right name for MyButton should be myButton. The same thing for naming resources. Right now the naming is unclear and it differs within Silverlight and WPF and also between XAML and e.g. C#.

I think it is sad that Silverlight/WPF differs and I think it is important to create conventions for writing XAML. This is not about the functionality of the code you write, it is about the usability and the experience for the next developer that will read and try to understand your code. What do you think?

Friday, November 21, 2008

The Misuse of var in .NET - it's bad programming!

This post will argue that many .NET developers misuse implicit typing (var) in their programming. I see this more often and I really think this is really, really bad programming. This is why:

About implicit variables
Fist of all, what does the documentation say about var?
var keyword[C#]:
"Variables that are declared at method scope can have an implicit type var. An implicitly typed local variable is strongly typed just as if you had declared the type yourself, but the compiler determines the type. The following two declarations of i are functionally equivalent:
var i = 10; // implicitly typed
int i = 10; //explicitly typed

Overuse of var can make source code less readable for others. It is recommended to use var only when it is necessary, that is, when the variable will be used to store an anonymous type or a collection of anonymous types." Many developers do not read the remarks text and I can also add that if you are looking at var [C#] instead of the var keyword [C#] this warning is less obvious. So when should you use it?

How to use var
var is a way of implicitly create a type, an temporary anonymous type. Note that this is not the same as variant in other languages. This means that the variable is still typesafe and can not change its type. For example the variable "i" in var i=10; can not be set to i="foo";. When declaring "i" we will implicitly say that i is an int. var is powerful for example when we use LINQ. It is a way of letting .NET help us create a temporary type for us (it is often temporary since it can only be used for local variables).
var somePerson = new { SomeProperty1 = 10, SomeProperty2 = "Foo" };

var persons1
= from p in Person
where p.Age == 30
select p.Name;

var persons2
= from p in Person
where p.Age == 30
new { p.Name, p.Age, p.EyeColor };

In persons1 the type will be a string (if p.Name is a string) and in persons2 it will be a temporary type containing name, age and eye color. This is a ok syntax and it is also a very powerful feature. Implicit typing can also be used in lambda expressions but sometimes I think it makes the code unreadable. What about my rage against var?

How not to use var!
A colleague of mine has a motto that says: "Any fool can write code that a computer can understand. Good programmers write code that humans can understand." In a time where usability and collaboration with people is key features you must write code that anyone can understand and that is self-explaining. Lately I have see more and more misuse of var and here are some examples of misuse:
var sample1 = 10; // Why not just type int? Maybe I really wanted a double?
var sample2 = GetPersonName(person); // What will be returned, an object, a string?
var sample3 = someReference.DoSomethingReallyFancy<ReallyStrangeObject>(); // Same as above!
var sample4 = new MyClass(); // Maybe ok?

The first sample is just stupid and makes the code hard to read. As the comment say, maybe you really wanted a double but forgot the ".0", this can be hard to see in debugging a calculation. In sample2 you really have no clue what type of object the method is returning. Sure you have intellisense but you should NEVER have to use intellisense to read code, maybe you are in an editor without intellisense. Sample3 is the same as sample2 but in a more complex format. I see this a lot and I hate it! Sample4 is not my favorite but it can be ok if you have a really long class name. In this samploe you can see the type in the declaration. I see a small risk here and that is if you refactor sample4 to a factory or some method, then sample4 will be the same as sample2. In this short context these use of var might not seem to ugly, but try a method that only uses var to declare its variables and get all instances from other methods and then do some fancy stuff with it. I promise you that the code will be hard to read bot for you and especially for another developer.

I think this use of var is really bad programming and I think that developers that use this type of coding are bad developers writing bad code, so please stop the misuse of var! Please!

Wednesday, November 19, 2008

Oredev 2008 - First day

The first day of Öredev 2008 is at its end and it's really been a great day. I just love the exchange of knowledge and all the people you meet at the conference. Today the highlight were: meeting people, Glenn Block talking about Composite WPF/Silverlight and the keynote speaker Ted Neward talking about "The New Big Thing".