What's new in XAML of .NET 4.0

Easy Object References with {x:Reference}

Built-in Types

Generics in XAML with x:TypeArguments

Support for Arbitrary Dictionary Keys

Use of Non-Default Constructors with x:Arguments

Use of Static Factory Methods with x:FactoryMethod

With .NET 4.0 Microsoft will bring up a improved version of XAML. This arcitle shows you the language enhancements they made.

If you want to create an object reference today you need to do a databinding and declare the source with an ElementName. In XAML 2009 you can use the new {x:Reference} markup extension

 
<!-- XAML 2006 -->
<Label Target="{Binding ElementName=firstName}">FirstName</Label>
<TextBox x:Name="firstName" />
 
<!-- XAML 2009 -->
<Label Target="{x:Reference firstName}">FirstName</Label>
<TextBox x:Name="firstName" />
 
 

If you want to add objects of simple types like string or double to a resource dictionary today you need to map the needed clr-namespaces to an XML namespaces. In XAML 2009 we a lot of simple types that are included in the XAML language.

 
<!-- XAML 2006 -->
<sys:String xmlns:sys="clr-namespace:System;assembly=mscorlib >Test</sys:String>
 
<!-- XAML 2009 -->
<x:String>Test</x:String>
 
 

The following types are included into the XAML language:

• <x:Object/>
• <x:Boolean/>
• <x:Char/>
• <x:String/>
• <x:Decimal/>
• <x:Single/>
• <x:Double/>
• <x:Int16/>
• <x:Int32/>
• <x:Int64/>
• <x:TimeSpan/>
• <x:Uri/>
• <x:Byte/>
• <x:Array/>
• <x:List/>
• <x:Dictionary/>

If you want to use an ObservableCollection<Employee> in XAML you need to create a type that derives from ObservableCollection because you cannot declare it in XAML. With XAML 2009 you can use the x:TypeArguments attribute to define the type of a generic type.

 
<!-- XAML 2006 -->
class EmployeeCollection : ObservableCollection<Employee>
{
}
 
<l:EmployeeCollection>
    <l:Employee FirstName="John" Name="Doe" />
    <l:Employee FirstName="Tim" Name="Smith" />
</lEmployeeCollection>
 
<!-- XAML 2009 -->
<ObservableCollection x:TypeArguments="Employee">
    <l:Employee FirstName="John" Name="Doe" />
    <l:Employee FirstName="Tim" Name="Smith" />
</ObservableCollection />
 
 

In XAML 2006 all explicit x:Key value were threated as strings. In XAML 2009 you can define any type of key you like by writing the key in ElementSyntax.

 
<!-- XAML 2006 -->
<StreamGeometry x:Key="CheckGeometry">M 0 0 L 12 8 l 9 12 z</StreamGeometry>
 
<!-- XAML 2009 -->
<StreamGeometry>M 0 0 L 12 8 l 9 12 z
    <x:Key><x:Double>10.0</x:Double></x:Key>
</StreamGeometry>
 
 

In XAML 2006 objects must have a public default constructor to use them. In XAML 2009 you can pass constructor arguments by using the x:Arguments syntax.

 
<!-- XAML 2006 -->
<DateTime>00:00:00.0000100</DateTime>
 
<!-- XAML 2009 -->
<DateTime>
    <x:Arguments>
        <x:Int64>100</x:Int64>
    </x:Arguments>
</DateTime>
 
 

When you have a type that has no public constructor but a static factory method you had to create that type in code in XAML 2006. With XAML 2009 you can use the x:FactoryMethodx:Arguments attribute to pass the argument values.

 
<!-- XAML 2006 -->
Guid id = Guid.NewGuid();
 
<!-- XAML 2009 -->
<Guid x:FactoryMethod="Guid.NewGuid" />
 
 

 Comments on this article

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Chatur	Commented on 7.July 2010 Blog likhnese kuch nahi hota he.. validation karna bhi ana chahiye... :)
Rajni Padhiyar	Commented on 12.July 2010 I like these new features, Thanks Rajni Padhiyar rajnicby.si@gmail.com
shreyas	Commented on 28.July 2010 Nice man.......
	Commented on 29.July 2010
Veni	Commented on 3.August 2010 Nice Ram.
bindu	Commented on 5.August 2010 hi very interesting features...but pls provide explanation with working examples apart from syntax..it will be more easy to understand for newbees like me...
Vimal	Commented on 13.August 2010 Hi That is very nice features
Vimal	Commented on 13.August 2010 Hi That is very nice features
this is nice...	Commented on 14.August 2010 explain with example
Mamta	Commented on 18.August 2010 This page is not detailed.