Articolo
11/18/2011

Rect Structure

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Describes the width, height, and point origin of a rectangle.

Namespace: System.Windows
Assembly: System.Windows (in System.Windows.dll)

Syntax

'Declaration
Public Structure Rect _
    Implements IFormattable

public struct Rect : IFormattable

<Rect ...>x,y,width,height</Rect>

<object property="x,y,width,height"/>

XAML Values

x
The x-coordinate location of the left side of the rectangle.
y
The y-coordinate location of the top side of the rectangle.
width
A value that represents the Width of the rectangle.
height
A value that represents the Height of the rectangle.

You can use a space rather than a comma as the delimiter between values. Mixed delimiter usages are also permitted.
You must specify all four values. 0,0 is not an implicit default for x,y, and no other conventions exist that can parse less than four values in the string.
X andY can be negative. width, and height can be negative and will invert the direction that width, and height are applied in rendering. See Remarks.

The Rect type exposes the following members.

Constructors

	Name	Description
	Rect(Point, Point)	Initializes a Rect structure that is exactly large enough to contain the two specified points.
	Rect(Point, Size)	Initializes a Rect structure based on an origin and size.
	Rect(Double, Double, Double, Double)	Initializes a Rect structure that has the specified x-coordinate, y-coordinate, width, and height.

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Properties

	Name	Description
	Bottom	Gets the y-axis value of the bottom of the rectangle.
	Empty	Gets a special value that represents a rectangle with no position or area.
	Height	Gets or sets the height of the rectangle.
	IsEmpty	Gets a value that indicates whether the rectangle is the Empty rectangle.
	Left	Gets the x-axis value of the left side of the rectangle.
	Right	Gets the x-axis value of the right side of the rectangle.
	Top	Gets the y-axis position of the top of the rectangle.
	Width	Gets or sets the width of the rectangle.
	X	Gets or sets the x-axis value of the left side of the rectangle.
	Y	Gets or sets the y-axis value of the top side of the rectangle.

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Methods

	Name	Description
	Contains	Indicates whether the rectangle described by the Rect contains the specified point.
	Equals(Object)	Indicates whether the specified object is equal to the current Rect. (Overrides ValueType.Equals(Object).)
	Equals(Rect)	Indicates whether the specified Rect is equal to the current Rect.
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetHashCode	Creates a hash code for the Rect. (Overrides ValueType.GetHashCode().)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	Intersect	Finds the intersection of the rectangle represented by the current Rect and the rectangle represented by the specified Rect, and stores the result as the current Rect.
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	ToString()	Returns a string representation of the Rect structure. (Overrides ValueType.ToString().)
	ToString(IFormatProvider)	Returns a string representation of the rectangle by using the specified format provider.
	Union(Point)	Expands the rectangle represented by the current Rect exactly enough to contain the specified point.
	Union(Rect)	Expands the rectangle represented by the current Rect exactly enough to contain the specified rectangle.

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Operators

	Name	Description
	Equality	Compares two Rect structures for equality.
	Inequality	Compares two Rect structures for inequality.

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Explicit Interface Implementations

	Name	Description
	IFormattable.ToString	Infrastructure. For a description of this member, see ToString.

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Remarks

Size is a similar structure that uses the same metaphor of specifying a height and width. However, a Rect specifies an origin point, whereas a Size does not. In general, Rect is used for APIs that relate to graphical presentation, and Size is used for APIs that relate to UI presentation and layout.

Do not confuse Rect and Rectangle. Rect is a common data structure that is used to specify rectangular regions as a single value for certain properties. But Rect has no meaning of its own or any direct UI connotation. The meaning of a Rect is entirely dependent on how it is handled as a value for a particular property. In contrast, a Rectangle is a Shape and therefore a UIElement. A Rectangle can be specified as a XAML element and instantiates a rectangular shape that is displayed in the UI and can process input events.

The programmatic upper limit for values is not PositiveInfinity, it is a lower number (approximately 1,000,000) that is enforced by the Silverlight native code.

Although the type of the property values of a Rect is Double, you generally should use integer values. For more information, see Layout Rounding.

Properties of Rect do not support an attribute syntax in XAML for Silverlight. In XAML you should always specify Rect-type properties through one of the following usages:

The XAML attribute usage, which infers properties that use the Rect type and uses a type converter to process the attribute string into the specific values for the Rect.
A property element usage, containing a Rect object element. For that object element, set the Rect properties using initialization text, as shown in the XAML Object Element Usage.

If you specify a Rect for use as a resource, use the object element usage and set the Rect properties using initialization text.

Note:
width and height can be negative if they are specified in XAML as part of the attribute string, with the result that the direction that the width or height applies to is inverted. For instance, a height of -20 will produce a Rect where the X,Y point is now the bottom left corner. However, the Rect constructor in the managed API does not permit negative values for width and height. You should adjust the coordinate reference of x,y, width and height such that the Rect can be specified using non-negative width and height values.

width and height can be negative if they are specified in XAML as part of the attribute string, with the result that the direction that the width or height applies to is inverted. For instance, a height of -20 will produce a Rect where the X,Y point is now the bottom left corner. However, the Rect constructor in the managed API does not permit negative values for width and height. You should adjust the coordinate reference of x,y, width and height such that the Rect can be specified using non-negative width and height values.

The following notes on Rect values apply for a Rect that is created in XAML as well as a Rect that is constructed in code.

X and Y can be negative, with the result that the Rect definition is off the screen, unless there is additional translation.
X and Y can be 0. A value of 0 is also valid for width or height. If a Rect with a value of 0 for either width or height is applied to a RectangleGeometry, the resulting RectangleGeometry does not render.
X, Y, width and height can be non-integer values in terms of permitted values.

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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