GetFirstElement Method

Summary

Returns the first item in the Data Set.

Syntax

Objective-C

C++/CLI

Java

public DicomElement GetFirstElement( 
   DicomElement element, 
   bool tree, 
   bool includeVolatile 
)

- (nullable LTDicomElement *)firstElement:(nullable LTDicomElement *)element tree:(BOOL)tree includeVolatile:(BOOL)includeVolatile;

public DicomElement getFirstElement(DicomElement element, boolean tree, boolean includeVolatile)

public: 
DicomElement^ GetFirstElement(  
   DicomElement^ element, 
   bool tree, 
   bool includeVolatile 
)

Parameters

element
An item in the Data Set.

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

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

Return Value

The first item in the Data Set, or a null reference (Nothing in VB) if the Data Set is empty.

Remarks

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

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

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

If the passed object points to:	The method returns an object pointing to:
null	Item 1
Item 12	Item 1
Item 14	Item 1
Item 22	Item 1
Item 25	Item 1

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

GetLastElement

GetPreviousElement

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: DicomTag.RedPaletteColorLookupTableDescriptor, etc. These are volatile elements since they are changed or destroyed when an image is changed or set.

To retrieve the first 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

using Leadtools; 
using Leadtools.Dicom; 
 
 
public void LoadEnumerateSample() 
{ 
   string dicomFileName = Path.Combine(LEAD_VARS.ImagesDir, "DICOM", "image3.dcm"); 
   //Make sure to initialize the DICOM engine, this needs to be done only once  
   //In the whole application 
   DicomEngine.Startup(); 
   using (DicomDataSet ds = new DicomDataSet()) 
   { 
      //Load DICOM File 
      ds.Load(dicomFileName, DicomDataSetLoadFlags.None); 
      //Insert patient name element, if it doesn't already exist 
      DicomElement element = ds.FindFirstElement(null, DicomTag.PatientName, false); 
      if (element == null) 
      { 
         element = ds.InsertElement(null, false, DicomTag.PatientName, DicomVRType.PN, false, 0); 
      } 
      //The dataset should include the patient name element or an error occurred 
      element = ds.FindLastElement(null, DicomTag.PatientName, false); 
      Debug.Assert(element != null); 
      //There can be only one patient element in the root level 
      element = ds.FindPreviousElement(null, false); 
      Debug.Assert(element == null); 
      element = ds.FindNextElement(null, false); 
      Debug.Assert(element == null); 
 
      element = ds.FindFirstElement(null, DicomTag.PatientName, false); 
      //Since the patient name element is in the root level, 
      //GetRootElement will return the same element. 
      DicomElement element1 = ds.GetRootElement(element); 
      Debug.Assert((element1.Tag == element.Tag), "GetRootElement should return same element"); 
 
      //Since the patient name element has no parent then GetParentElement will return null 
      element1 = ds.GetParentElement(element); 
      Debug.Assert(element1 == null, "GetParentElement should return null"); 
 
      //Since the patient name element has no children then GetChildElement will return null 
      element1 = ds.GetChildElement(element, false); 
      Debug.Assert(element1 == null, "GetChildElement should return null"); 
 
      element1 = ds.GetFirstElement(element, false, false); 
      Debug.Assert(element1 != null, "GetFirstElement Can't return null in this case"); 
 
      element1 = ds.GetLastElement(element, false, false); 
      Debug.Assert(element1 != null, "GetLastElement Can't return null in this case"); 
 
      element1 = ds.GetPreviousElement(element, false, true); 
      DicomElement element2 = ds.GetNextElement(element, false, true); 
 
      Debug.Assert(ds.GetElementLevel(element) == 0); 
 
      Debug.Assert(ds.ExistsElement(element)); 
      Debug.Assert(ds.IsVolatileElement(element) == false); 
 
      //Patient Name is not the only element in this level 
      Debug.Assert((element1 != null) && (element2 != null)); 
      //Delete the patient name element 
      ds.DeleteElement(element); 
   } 
   DicomEngine.Shutdown(); 
} 
 
static class LEAD_VARS 
{ 
   public const string ImagesDir = @"C:\LEADTOOLS23\Resources\Images"; 
}