Category: Technical Page 9 of 15

Tech Ed Talk: REST Patterns and .NET

On August 7, 2008

I’ll be giving a talk at Tech Ed this year on REST and how it can be implemented in .NET, much inspired by the thoughts of Jim Webber on good RESTful web services, and Garr Reynolds on the “Zen” presentation style. Here’s some more info:

REST Patterns and .NET

Sydney Convention Centre, Darling Harbour
5 September 2008
10:15am – 11:30am
(ARC306)

REST has sparked furious debate, and reactions from fan-boy adoration to hate. As the arguments quiet and the dust settles, it is becoming clear that the RESTful style is a viable choice for the Enterprise. Framework support is growing rapidly. WCF now provides basic REST support. Meanwhile, the budding MVC framework opens the door to building services which leverage hypermedia. This talk will leave you with an understanding of the RESTful architectural style and provide you with recommendations on designing and building both simple and hypermedia driven web services in .NET.

Hope to see you there!

F-Secure Optus Internet Suite – To be avoided!

By James

On July 6, 2008

In Personal, Technical

Optus, my ISP, is kind enough to give subscribers a free copy of F-Secure’s security suite which offers anti-virus, anti-spam and firewall. I read some half decent reviews of the product so I thought I’d install it and give it a go. Unfortunately, it was fraught with problems. First of all, after installing I got a blue screen on reboots. After uninstalling AVG (my previous anti-virus) in safe mode, my computer could boot. Next, I tried to do a full system scan, but the F-Secure automatic update kicked in at the same time and it crashed the scanner. So, I rebooted, and tried a full system scan. I tried twice, but each time, it hung on a random .class (compiled Java) from GlassFish. Not great. So I went to the F-Secure website to submit a bug report. I filled in the form, and couldn’t submit it because one of the drop down lists which was mandatory was disabled in Opera. I then thought I’d try the site in IE7, but IE7 just hung, presumably thanks to F-Secure’s firewall.

Overall, I would strongly suggest that you do not bother to try the F-Secure product suite, even if it is offered to you for free.

The Long Tail by Chris Anderson

By James

On June 9, 2008

In Book Reviews, Soft Skills and Mind Hacks, Technical

Just finished reading “The Long Tail – How Endless Choice is Creating Unlimited Demand” by Chris Anderson. In summary, the long tail is about selling small volumes of a vast variety of items instead of large volumes of a small number of “hits”. This possible when the cost of distribution to geographically distant customers is low and the cost of storage for stock is not a concern (eg, intellectual property in electronic format, JIT manufacture). Popular companies capitalising on the long tail include eBay, Amazon, Google Adwords and Lulu.

The book has a lot of interesting stories and statistics but tends to repeat itself often. The long tail idea is probably not new to most readers these days, and I think if you’re familiar with Amazon, there’s little that comes as a surprise. However, I did find an interesting section in the book about the tyranny of choice. Anderson suggests that choice is good, customers want choice, and choice is only a problem if you don’t know what to choose to suit your taste. Hence, an important part of a long tail business is helping people find what they want (ie, filter out noise) in all the vast array of choices. He suggests using user reviews, rankings, sorting etc as means to help people find the “best” choice for them. I also hadn’t come across Lulu before – looks worth checking out, a site for mini self-publishing.

Bounded Actions Using Lambda – IDisposable is old and ugly!

By James

On May 26, 2008

In C#, Technical

In .NET 2, it was all the rage to make hand-crafted, clever IDisposables that let you do a bounded action with clean up. Eg,

void SomeMethod()
{
        using (new SetCursorToWaitEggTimer())
        {
            VerySlowOperation();
        }
}

void VerySlowOperation()
{
    ... etc ...
}

This was kind of cute – you could make sure that, even if an exception was thrown, your clean up (eg, changing cursor back to normal) would occur. Implementing the IDisposable was a bit ugly but consuming it wasn’t bad.

Now, with the sexy C# 3 syntax, you can do something similar much more elegantly. Eg,

void SomeMethod()
{
       DoWithWaitEggTimer(VerySlowOperation);
}

void DoWithWaitEggTimer(Action action)
{
    try
    {
        Mouse.OverrideCursor = Cursors.Wait;
        action();
    }
    finally
    {
        Mouse.OverrideCursor = null;
    }
}

If you’re feeling like more adventures, you can also start passing these delegates around and injecting them. For example:

class SomeClass
{
    public Action RunSlowCode 
    {
    	get { return runSlowCode ?? new Action(a => a.Invoke()); }
    	set { runSlowCode = value; }
    }
    Action runSlowCode;

    void DoSomethingSlow()
    {
         RunSlowCode(PullDataFromExternalSystem);
    }
}

This approach allows you to inject the delegate for what happens when slow code is run. So you could inject DoWithWaitEggTimer() or something new like DoWithWaitMessageDisplayedToUser(). Similarly, it could be used for unit testing or injecting between layers in your application.

C# Default Access Modifier for Class Members – and drop that private habit!

By James

On May 26, 2008

In C#, Technical

The default access modifier for the members of a C# class (eg, fields, methods, and properties) is ‘private’. As such, I recommend never using the redundant ‘private’ keyword for class members. Leaving off the private nicely separates your privates from your public/inheritable interface in syntax highlighting. It also saves people having to read redundant code – you wouldn’t want your code to be full of un-needed casts, or redundant ‘this.’ references, would you?

WPF Control Inheritance With Generics

By James

On May 26, 2008

In C#, Technical, WPF

Working in WPF is quite exciting – there’s a lot of new possibilities, especially with easy control composition, much improved binding and Expression Blend to make sexy interfaces. One of the things you’re likely to want to do though, when writing anything more than a toy application, is to have a base class for your UserControls or Windows, to share common functionality. It is also quite likely you will want to use generics in conjunction with control inheritance. With both the code behind, and the XAML, it’s not immediately obvious how to do generic inheritance. It is a bit fiddly to get going, and sometimes the errors are not helpful. Here’s a simple example that outlines how to bring it together.

The base control

namespace WpfGenericsDemo
{
    public class BaseUserControl<T> : UserControl where T : IPresenter
    {
        public BaseUserControl()
        {
            ... various configurations ...
        }

         ... Awesome functionality to share ...
    }
}

The child control code-behind

namespace WpfGenericsDemo
{
    public partial class ChildUserControl : BaseUserControl<ChildPresenter>
    {
        public ChildUserControl()
        {
            InitializeComponent();
        }

         ... More code ...
    }
}

The child control XAML

<WpfGenericsDemo:BaseUserControl x:Class="WpfGenericsDemo.ChildUserControl"
    x:TypeArguments="WpfGenericsDemo:ChildPresenter"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:WpfGenericsDemo="clr-namespace:WpfGenericsDemo">
    
    ... The rest of your awesome XAML ...

</WpfGenericsDemo:BaseUserControl>

Notes

Your top level node is the parent class of the control you want to create (eg, BaseUserControl). You specify the control class you want to create with ‘x:class’ (eg, ChildUserControl)
‘x:TypeArguments’ is the way you specify the generic type (eg, ChildPresenter)
You need to namespace your classes – eg, with ‘xmlns:WpfGenericsDemo’ which uses a clr-namespace style reference
Only your top level node can be genericised in XAML

Treo 650 phone radio turns off by itself – a solution!

By James

On April 20, 2008

In Technical

Recently, I’ve been disappointed to find my Treo 650 turning off the phone radio by itself. If I was lucky, I heard the melodic sound that means “radio now off”, and then I manually turned the radio back on. If I was unlucky, I didn’t hear it, and missed phone calls and messages.

It seems that the cause is that the Treo 650 SIM case gets looser with wear, and any break in connection between the SIM and the phone causes the phone radio to be deactivated. The solution is pretty easy, and described at the end of a FAQ I came across. In summary, take out the SIM tray from the phone, remove the SIM. Put several layers of paper (cut small to fit) in the SIM tray, and then clip the SIM back on top. When you put the SIM tray back into your phone, it should work reliably again, with no more random turn-offs!

Loan Calulator: Monthly repayment and interest breakdown

By James

On April 14, 2008

In Finance, Personal, Ruby / Rails, Technical

Wondering if your loan repayment calculations have been performed correctly this month, taking into account interest rate rises and extra repayments? You might be interested in giving my monthly loan calculator a go.

As my home loan provider doesn’t show balances online, and only sends statements every 6 months, I like to ring up every month or two to make sure things are on track. I used to calculate interest, new balances etc in a spreadsheet / calculator but spent an afternoon writing a little Rails app to calculate it for me. Hopefully my little monthly loan calculator is of some use to you too.

NUnit Test Runners Were Not All Made Equal

By James

On April 8, 2008

In C#, Technical, Testing

NUnit tests can be run using a variety of different runners. Some common ones are:

The NUnit GUI and Test Driven create a new instance of the test class for each test run. This leads to more isolation but potentially slower performance.

Resharper and NUnit MSBuild Task re-use the same instance of the test class when running each test in the class. This can lead to unintended interaction between tests. Using these runners, it is vital to to assign initial values to instance variables in SetUp, rather than when they are defined or in the constructor.

If you use a mix of different test runners, you can end up with tests that pass on some machines and fail on others (eg, Test Driven locally works fine, but you use NUnit MSBuild Task on your build box and get intermittent failures).

NUnit SetUp Attribute and Subclassed Test Cases

By James

On April 8, 2008

In C#, Technical, Testing

If you have a ChildTestCase class that inherits from a ParentTestCase class, and both of these have a SetUp method, marked with the [SetUp] attribute, would you expect both to be called? If so, you would be sadly disappointed. Only the SetUp method of the ChildTestCase will be called, and the SetUp in the ParentTestCase will be ignored.

According to the NUnit documentation on the Set Up attribute, this is intended behaviour:

If you wish to add more SetUp functionality in a derived class you need to mark the method with the appropriate attribute and then call the base class method.

An alternative approach to get all your SetUps called is to have a base TestCase class define a protected virtual SetUp() (with the SetUp attribute), which all child classes override (and call base on their first line).