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GetPreviousElement Method

Summary

Returns the item in the Data Set that immediately precedes the specified item.

Syntax
C#
VB
Java
C++
public DicomElement GetPreviousElement( 
   DicomElement element, 
   bool tree, 
   bool includeVolatile 
) 
Public Function GetPreviousElement( _ 
   ByVal element As DicomElement, _ 
   ByVal tree As Boolean, _ 
   ByVal includeVolatile As Boolean _ 
) As DicomElement 
public DicomElement getPreviousElement(DicomElement element, boolean tree, boolean includeVolatile) 
public: 
DicomElement^ GetPreviousElement(  
   DicomElement^ element, 
   bool tree, 
   bool includeVolatile 
)  

Parameters

element
An item in the Data Set. The item in the Data Set that immediately precedes this item will be returned.

tree
true to evaluate the Data Set as a tree; false to evaluate the Data Set as a list.

includeVolatile
true to retrieve the previous element, volatile or non-volatile; false to retrieve the previous non-volatile element.

Return Value

The item in the Data Set that immediately precedes the item specified by element, or a null reference (Nothing in VB) if there is no item preceding element (element is the first item in the Data Set).

Remarks

If the Data Set is evaluated as a tree structure, this method returns the previous item on the same level as element with the same parent as element. Please note that the numbering of the items in the following illustration is arbitrary and does not imply order. getpvtr.gif

If the passed object points to: The method returns an object pointing to:
Item 1 Item 2
Item 3 Item 4
Item 5 null
Item 6 Item 7

If the Data Set is evaluated as a list, the previous item in the list is returned. Please note that the numbering of the items in the following illustration does indicate the order of the items when the Data Set is evaluated as a list.

getpvlst.gif
If the passed object points to: The method returns an object pointing to:
Item 1 null
Item 15 Item 14
Item 5 Item 4
Item 9 Item 8
Item 22 Item 21
Item 25 Item 24

The following methods will also help you navigate the Data Set as either a tree or a list:

GetFirstElement

GetLastElement

GetNextElement

If you evaluate the Data Set as a tree, you can also use the following methods to navigate the tree:

GetRootElement

GetParentElement

GetChildElement

A volatile element is an element that can be changed or destroyed in the process of inserting or setting an image. A non-volatile element is an element that must be changed manually. It is not changed or destroyed by inserting or setting an image.

For example, a grayscale image has elements DicomTag.SmallestImagePixelValue, DicomTag.LargestImagePixelValue, etc. If the image is changed to a color image, these elements disappear and the following elements appear: DicomTagType.RedPaletteColorLookupTableDescriptor, etc. These are volatile elements since they are changed or destroyed when an image is changed or set.

To retrieve a previous element that must be changed manually, i.e., is not volatile, set includeVolatile to false. To retrieve the first element, either volatile or non-volatile, set includeVolatile to true.

Example

For an example, refer to Load.

Requirements

Target Platforms

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