There are four predefined markup extensions in XAML:
x:Type
supplies the Type object for the named type. This facility is used most frequently in styles and templates.
<object property="{x:Type prefix:typeNameValue}" .../>
x:Static
produces static values. The values come from value-type code entities that are not directly the type of a target property's value, but can be evaluated to that type.
<object property="{x:Static prefix:typeName.staticMemberName}" .../>
x:Null
specifies null as a value for a property and can be used either for attributes or property element values.
<object property="{x:Null}" .../>
x:Array
provides support for the creation of general arrays in XAML syntax, for cases where the collection support provided by WPF base elements and control models is deliberately not used.
<x:Array Type="typeName">
arrayContents
</x:Array>