TransformToDescendant Method

Visual.TransformToDescendant Method (Visual)

 

Returns a transform that can be used to transform coordinates from the Visual to the specified visual object descendant.

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

Public Function TransformToDescendant (
	descendant As Visual
) As GeneralTransform

Parameters

descendant
Type: System.Windows.Media.Visual

The Visual to which the coordinates are transformed.

Return Value

Type: System.Windows.Media.GeneralTransform

A value of type GeneralTransform.

Exception Condition
ArgumentNullException

descendant is null.

ArgumentException

The visual is not an ancestor of the descendant visual.

InvalidOperationException

The visual objects are not related.

The following markup example shows a TextBlock that is contained within a StackPanel object.

<StackPanel Name="myStackPanel" Margin="8">
  <TextBlock Name="myTextBlock" Margin="4" Text="Hello, world" />
</StackPanel>

The following code example shows how to use the TransformToDescendant method to retrieve the offset of the StackPanel relative to its child TextBlock. The offset values are contained within the returned GeneralTransform value.

' Return the general transform for the specified visual object.
Dim generalTransform1 As GeneralTransform = myStackPanel.TransformToDescendant(myTextBlock)

' Retrieve the point value relative to the child.
Dim currentPoint As Point = generalTransform1.Transform(New Point(0, 0))

The offset takes into account the Margin values for all objects. In this case, X is -4, and Y is -4. The offset values are negative values because the parent object is negatively offset relative to its child object.

.NET Framework
Available since 3.0
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