What's new in XAML of .NET 4.0

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

使用.NET 4.0，Microsoft将推出XAML的改进版本。这个arcitle向您展示了他们所做的语言增强。

Easy Object References with {x:Reference}

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" />

Built-in Types

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/>

Generics in XAML with `x:TypeArguments`

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 />

Support for Arbitrary Dictionary Keys

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>

Use of Non-Default Constructors with `x:Arguments`

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>

Use of Static Factory Methods with `x:FactoryMethod`

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" />