C# 4 and .NET 4

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A type converter derives from the base class TypeConverter in the System.
ComponentModel namespace. The type of the class that needs conversion defi nes the
type converter with the TypeConverter attribute. WPF uses many type converters to
convert XML attributes to a specifi c type. ColorConverter , FontFamilyConverter ,
PathFigureCollectionConverter , ThicknessConverter , GeometryConverter are
just a few of a large number of type converters.
Properties as elements
It ’ s always also possible to use the element syntax to supply the value for properties. The Background
property of the Button class can be set with the child element Button.Background . This way more
complex brushes can be applied to this property, for example, a LinearGradientBrush , as shown in
the example.
When setting the content in the sample, neither the Content attribute nor a Button.Content element is
used to write the content; instead, the content is written directly as a child value to the Button element.
That ’ s possible because with a base class of the Button class ( ContentControl ), the ContentProperty
attribute is applied, which marks the Content property as a ContentProperty : [ContentProperty
( “ Content “ )] . With such a marked property, the value of the property can be written as child element.
< Button >
Click Me!
< Button.Background >
< LinearGradientBrush StartPoint="0.5,0.0" EndPoint="0.5, 1.0" >
< GradientStop Offset="0" Color="Yellow" / >
< GradientStop Offset="0.3" Color="Orange" / >
< GradientStop Offset="0.7" Color="Red" / >
< GradientStop Offset="1" Color="DarkRed" / >
< /LinearGradientBrush >
< /Button.Background >
< /Button >
code snippet XAMLSyntax/MainWindow.xaml
essential .neT Types
In XAML 2006, core .NET types need to be referenced from an XML namespace like all other .NET
classes, for example, the String with the sys alias, as shown here:
< sys:String xmlns:sys="clr-namespace:System;assembly=mscorlib > Simple String < /sys:String >
XAML 2009 defi nes types such as String , Boolean , Object , Decimal , Double , Int32 and others with the
x alias.
< x:String > Simple String < /x:String >
Collections
In the ListBox that contains Person elements, you ’ ve already seen a collection within XAML. In the
ListBox , the items have been directly defi ned as child elements. Also, the LinearGradientBrush contained
a collection of GradientStop elements. This is possible because the base class ItemsControl has the
attribute ContentProperty set to the Items property of the class, and the GradientBrush base class sets
the attribute ContentProperty to GradientStops .
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