Saw this in my email today wizpert – billed as “is a fast growing community of experts, where users seek advice and coaching on a range of programming languages, including Python, HTML, PHP, JavaScript and more.


Powershell equivalent of xargs

I wanted to be able to build extmap.xml for all the files that were in my packages\ directory. I had a Powershell script called ToExtMap which automated most of my tasks, and a little experimentation with Powershell gave me this one liner:

PS C:\Users\Chui\Projects\SAM-GET\packages>
Get-ChildItem -Filter *.dll -Recurse -name |
%{ ToExtMap $_ | Out-File ($_ -replace "dll", "extmap.xml") -encoding ASCII}

A bit of explanation might be in order:

  1. Get-ChildItem -Recurse finds all the files I require.
  2. The %{} is the shortcut for the foreach operator.
  3. Powershell is object oriented. $_ -replace ... executes a string substitution

Over at Forbes

It started with making one presentation slide for each idea. Each slide would have a heading and several bullet points defining the scope of the feature and metrics describing what success would look like and how it would impact the business. That’s all people got to make their case. And given the speed of the whole process, there was little time for precision.

Business Forms in Silverlight Part 2

(this is a continuation of Part 1)

From the previous post:

Basic DataForm experience

Basic DataForm experience

The first problem is the OrderDate is unintialized and renders as 0/00/0000.

The first thought is to change the OrderDate from DateTime to Nullable<DateTime>. This will require either the database schema be changed, or a second viewmodel created. Changing the database schema just to support a user-interface tweak is obviously out of the question. However, writing a viewmodel and copying all the properties over breaks a rule of “DRY” (Don’t Repeat Yourself).

Luckily, XAML binding supports the notion of binding converters. This lets us transforms inputs from one type to another.

public class NullValueConverter : IValueConverter

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        if (value is DateTime && targetType == typeof(Nullable<DateTime>))
            if ((DateTime)value == DateTime.MinValue)
                return null;
        return value;

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        return value;

Applying the converter to the date picker, we get reasonably good results. For example, after entering a date and then clearing it, we get a validation error showing (see picture below). Furthermore, hitting cancel restores the control back to default value.


This done, we are ready to tackle our next problem.


Here’s a sample of how converters are applied.

    <local:NullValueConverter x:Key="NullValueConverter" />
  <sdk:DataField Label="Order Date">
    <sdk:DatePicker SelectedDate="{Binding OrderDate, Converter={StaticResource NullValueConverter}}" />

Fool-Proof Business Forms in Silverlight Part I

Silverlight DataForms makes it quick and easy to get started with database applications. However, it has some downsides. The default isn’t particularly customizable, and to do anything more takes a great deal more effort.

Take the following example:

        internal sealed class OrderMetadata

            // Metadata classes are not meant to be instantiated.
            private OrderMetadata()

            [Display(Name = "Order date", GroupName = "Order", Order = 1)]
            public DateTime OrderDate { get; set; }

            [Range(0, 100.0, ErrorMessage = "Please enter more than $0.00")]
            [Display(Name = "Total Amount", GroupName = "Order", Order = 2)]
            public decimal Amount { get; set; }

            [Display(Name = "Purchase Order No", GroupName = "Order", Order = 3)]
            public string PurchaseOrder { get; set; }

            [Display(Name = "Customer Name", GroupName = "Customer", Order = 1)]
            public Customer Customer { get; set; }

            [Display(Name = "Is Delivered", GroupName = "Customer", Order = 2)]
            public byte[] IsDelivered { get; set; }

            public int CustomerId { get; set; }

            public int OrderId { get; set; }
            public float Weight { get; set; }

            [UIHint("Image", "SL", "ScannedFilename")]
            public Byte[] ScannedImage { get; set; }

            public String ScannedFilename { get; set; }

This generates a data form that gets us pretty close. See the picture below.


However, there are several issues:

  1. The Order date is very ugly. It should have default to a null value
  2. The Customer field should have been bound to a combo box or something more custom
  3. The Total Amount validation message could not be customized. It reports “Input is not in the correct format”. Ideally, the message should be customizable and localizable.
  4. CustomerId and OrderId should be hidden
  5. Scanned file name and Scanned image should be combined into a single image control, showing the image, the file name, and provide a method to replace the image.

Over the next few posts, I’ll discuss how to overcome these problems using a custom view model and avoid unnecessary code duplication.

Dell Service Drop off Brisbane

The Dell service center in Brisbane has moved to 8 Castlemaine St, Cooparoo (effective 6 Jan 2014). It is in the big courier’s shed, and there’s a small narrow storefront. If you need to drop off your computer for repairs, it is no longer at Mowbray Tce.

Hopefully this post finds you before you get lost.