Elements and Attributes in XAML - Assigning XAML Attributes
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Regardless of their underlying types, all XAML attributes can be assigned in one of two ways. They can be assigned inline, as part of the element declaration, or they can be explicitly declared as nested elements within the element being described. As a general rule, complex attributes must be declared explicitly, while simple attributes can be defined inline, as shown in Example 3-9. Simple attributes are those whose data types are primitives, such as String , Integer , and Double . Enumerations are also declared inline, using a String representation of the name of the enumerated value. All inline attribute declarations must be enclosed in double quotes, regardless of the underlying data type of the property being described. You don’t have to enclose attributes of type String in two sets of quotes. String is sort of the exception to the rule, because it is, after all, already a String .
Example 3-9. Inline declaration of a simple attribute
<Button
Content="Click Me" />
Complex attributes are defined as a CLR class or are of type struct . They are declared explicitly, as shown in Example 3-10. In this example, GeometryDrawing has two complex attributes: Pen and Geometry . Neither attribute can be specified using abbreviated syntax, so it is necessary to explicitly declare them. The exception to this rule is the specification of child elements, which are declared by using standard XML mechanisms without the name of the attribute. This is illustrated in Example 3-10, in which two instances of EllipseGeometry are implicitly declared as children of GeometryGroup . It is not necessary to specify child elements as a complex attribute by name. Elements nested between the opening and closing tags of an element are assumed to be the children of that element and are automatically added to the appropriate container property according to the CLR class, usually the Children or InternalChildren property of the parent element.
Example 3-10. Explicit declaration of a complex attribute
<GeometryDrawing
Brush="Blue" >
<GeometryDrawing.Pen>
<Pen
Thickness="1"
Brush="Black" />
</GeometryDrawing.Pen>
<GeometryDrawing.Geometry>
<GeometryGroup>
<EllipseGeometr y
RadiusX="0.2"
RadiusY="0.45"
Center="0.5,0.5" />
<EllipseGeometry
RadiusX="0.45"
RadiusY="0.2"
Center="0.5,0.5" />
</GeometryGroup>
</GeometryDrawing.Geometry>
</GeometryDrawing>
Please check back next week for the conclusion of this article.
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 This article is excerpted from chapter 3 of The Basics of XAML, written by Lori A. MacVittie (O'Reilly, 2006; ISBN: 0596526733). Check it out today at your favorite bookstore. Buy this book now.
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