SdtRangeStart start = grpContentControls.Where(c => Convert.ToString(c.SdtProperties.Tag) ==  "purchlastname").First();

var properties = new SdtProperties(start.SdtProperties);
properties.ID = 123456;
var currentItem = editor.InsertStructuredDocumentTag(properties);

<w:tblCellMar>
	<w:top w:w="2880" w:type="dxa"/>
	<w:bottom w:w="2880" w:type="dxa"/>
</w:tblCellMar>

<w:tblCellMar>
	<w:top w:w="2880" w:type="dxa"/>
	<w:left w:w="0" w:type="dxa"/>
	<w:right w:w="0" w:type="dxa"/>
	<w:bottom w:w="2880" w:type="dxa"/>
</w:tblCellMar>

foreach (var image in images)
{
      if (image.Image.ImageSource == null)
      {
               image.Paragraph.Inlines.Remove(image);
      }
}

private void EmptyIfSecondArgumentWorkaround(RadFlowDocument document)
{
	List<FieldCharacter> collection = document.EnumerateChildrenOfType<FieldCharacter>().Where(f => f.FieldCharacterType == FieldCharacterType.Start).ToList();

	for (int i = 0; i < collection.Count; i++)
	{
		FieldInfo item = collection[i].FieldInfo;
		string code = item.GetCode();
		FieldCharacter separator = item.Separator;
		FieldCharacter end = item.End;

		if (code.TrimStart().StartsWith("IF"))
		{
			FieldCharacter codeEnd;
			if (separator.Paragraph != null)
			{
				codeEnd = separator;
			}
			else
			{
				codeEnd = end;
			}
			string emptyString = " \"\" ";
			string mergeFormatCodeSuffix = "\\*";
			if (codeEnd.Paragraph.Inlines.Count > 1)
			{

				string editedMergeFormatCodeSuffix = string.Join("", new string[] { emptyString, mergeFormatCodeSuffix });
				int codeEndIndex = codeEnd.Paragraph.Inlines.IndexOf(codeEnd);
				Run run = codeEnd.Paragraph.Inlines[codeEndIndex - 1] as Run;
				if (run.Text.Contains(mergeFormatCodeSuffix))
				{
					run.Text=run.Text.Replace(mergeFormatCodeSuffix, editedMergeFormatCodeSuffix);
				}
				else
				{
					run.Text += emptyString;
				}
			}
		}
	}
}

Paragraph paragraph1 = editor.InsertParagraph();
Paragraph paragraph2 = editor.InsertParagraph();
editor.InsertSection();
Paragraph paragraph3 = editor.InsertParagraph();