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x:Array Markup Extension

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Provides general support for arrays of objects in XAML through a markup extension. This corresponds to the x:ArrayExtension XAML type in [MS-XAML].

XAML Object Element Usage

<x:Array Type="typeName">
  arrayContents
</x:Array>

XAML Values

Value Description
typeName The name of the type that your x:Array will contain. typeName may be (and often is) prefixed for a XAML namespace that contains the XAML type definitions.
arrayContents The items content that is assigned to the intrinsic ArrayExtension.Items property. Typically, these items are specified as one or more object elements contained within the x:Array opening and closing tags. Objects specified here are expected to be assignable to the XAML type specified in typeName.

Remarks

Type is a required attribute for all x:Array object elements. A Type parameter value does not need to use an x:Type markup extension; the short name of the type is a XAML type, which can be specified as a string.

In .NET XAML Services implementation, the relationship between the input XAML type and the output CLR Type of the created array is influenced by service context for markup extensions. The output Type is the UnderlyingType of the input XAML type, after looking up the necessary XamlType based on XAML schema context and the IXamlTypeResolver service the context provides.

When processed, the array contents are assigned to the ArrayExtension.Items intrinsic property. In the ArrayExtension implementation, this is represented by ArrayExtension.Items.

In .NET XAML Services implementation, the handling for this markup extension is defined by the ArrayExtension class. ArrayExtension is not sealed, and could be used as the basis for a markup extension implementation for a custom array type.

x:Array is more intended for general language extensibility in XAML. But x:Array can also be useful for specifying XAML values of certain properties that take XAML-supported collections as their structured property content. For example, you could specify the contents of an IEnumerable property with an x:Array usage.

x:Array is a markup extension. Markup extensions are typically implemented when there is a requirement to escape attribute values to be other than literal values or handler names, and the requirement is more global than just putting type converters on certain types or properties. x:Array is partially an exception to that rule because instead of providing alternative attribute value handling, x:Array provides alternative handling of its inner text content. This behavior enables types that might not be supported by an existing content model to be grouped into an array and referenced later in code-behind by accessing the named array; you can call Array methods to get individual array items.

All markup extensions in XAML use the braces ({,}) in their attribute syntax, which is the convention by which a XAML processor recognizes that a markup extension must process the attribute value. For more information about markup extensions in general, see Type Converters and Markup Extensions for XAML.

In XAML 2009, x:Array is defined as a language primitive instead of a markup extension. For more information, see Built-in Types for Common XAML Language Primitives.

WPF Usage Notes

Typically, the object elements that populate an x:Array are not elements that exist in the WPF XAML namespace, and require a prefix mapping to a non-default XAML namespace.

For example, the following is a simple array of two strings, with the sys prefix (and also x) defined at the level of the array.

<x:Array Type="sys:String"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:sys="clr-namespace:System;assembly=mscorlib">
  <sys:String>Hello</sys:String>
  <sys:String>World</sys:String>
</x:Array>

For custom types that are used as array elements, the class must also support the requirements for being instantiated in XAML as object elements. For more information, see XAML and Custom Classes for WPF.

See also