New WPF 3.5 SP1 feature: Data Formatting (with Binding.StringFormat)

vinsibal — Fri, 16 May 2008 17:31:00 GMT

Background

Formatting data can be a pretty cumbersome task in WPF. To illustrate with a very simple example, let’s say I want to display the dollar value of some item in a TextBlock:

<sys:Double>168.361</sys:Double>

</ComboBoxItem>

<sys:Double>456.9832</sys:Double>

</ComboBoxItem>

</ComboBox>

<TextBlock.Text>

</TextBlock.Text>

</TextBlock>

</StackPanel>

To add in a $ symbol and/or any other formatting, I would need to write my own ValueConverter and do the formatting there.

<local:MoneyConverter x:Key="moneyConverter" />

<TextBlock.Text>

</TextBlock.Text>

</TextBlock>

public class MoneyConverter : IValueConverter

{

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)

{

return string.Format("Item cost: {0:C}", value);

}

// ConvertBack left out

}

It would be nice if I could just include the formatting as a definition with my binding. It would be more readable and self-documenting, as well as decrease the number of ValueConverter classes that I would need to write (which may not be very reusable in the rest of your application). Well, as it turns out this feature has been added in WPF 3.5 SP1.

What is it?

Strings can now be formatted directly in bindings, multibindings and many controls by String.Format(IFormatProvider, String, Object[]). Note that string formatting is only applied in the direction from source to target. Anytime the source is updated, the converter/formatting will be reapplied.

Examples

Single binding standard:

<TextBlock.Text>

</TextBlock.Text>

</TextBlock>

Single binding convenience:

<TextBlock.Text>

</TextBlock.Text>

</TextBlock>

Single binding escaping markup:

<TextBlock.Text>

</TextBlock.Text>

</TextBlock>

Formatting in DisplayMemberBinding:

MultiBinding:

<TextBlock.Text>

</MultiBinding>

</TextBlock.Text>

</TextBlock>

MultiBinding with a converter (note that the converter is called before the string is formatted):

<TextBlock.Text>

</MultiBinding>

</TextBlock.Text>

</TextBlock>

Many controls have also added a new property to set format on its content. For example, ContentControl has added ContentStringFormat, HeaderedContentControl has added HeaderStringFormat, and ItemsControl has added ItemStringFormat. These are only a few examples.

<sys:DateTime>2004/3/4 13:6:55</sys:DateTime>

</Label>

<sys:DateTime>2004/3/4 13:6:55</sys:DateTime>

</Button>

<sys:Double>3.14159</sys:Double>

<sys:Double>2.71828</sys:Double>

</ListBox>

There are a lot more examples that can be shown for controls. I may do an additional post on that as it can seem a little complicated at first when dealing with controls that have multiple ways of setting format. Anyway, I hope that you may find this new feature useful. It will definitely be handy for the DataGrid.

Vincent Sibal's Blog : StringFormat

New WPF 3.5 SP1 feature: Data Formatting (with Binding.StringFormat)