Understanding word headers, footers and section break manipulation

To access a header or footer you can double click at the top or bottom of your word document page.

I'm going to go through some of the areas of the headers/footers. Under the options section there are 2 check boxes "Different First Page" and "Different Odd & Even Pages". So if you check these boxes word will allow the first page to have a different header & footer. The odd and even check box will allow every second page to have a different header/footer. So how does this look in the xml?

In the xml you can see 3 headerReferences and 3 footReferences and they are a child of the "w:sectPr"/section properties node.  A document must contain at least one section property at the bottom of the body and it can contain more depending on whether you add section breaks inside the document. There are 3 types of header/footer references that can be associated with one section property - "even", "default" and "first".

To access the header/footer parts in a document using open xml you can use the following code

byte[] document = File.ReadAllBytes("C:\Demo Doc.docx");
using (MemoryStream memoryStream = new MemoryStream())
{
  memoryStream.Write(document, 0, document.Length);
  using (WordprocessingDocument wordprocessingDocument =     WordprocessingDocument.Open(memoryStream, true))
  {
     foreach (HeaderPart headerPart in wordprocessingDocument.MainDocumentPart.HeaderParts)
     {
         // do something
     }

     foreach (FooterPart footerPart in wordprocessingDocument.MainDocumentPart.FooterParts)
     {
        // do something
     }
  }
}

Another way to have different headers/footers on a page is to insert a section break in your document. To do this go to Page Layout -> Breaks -> Next Page.

Go into the header/footer and then unselect the "Link to Previous" option. Then modify the header/footer.

Something important to note about section breaks if you are planning on modifying them programmatically is the placement of the section break in document.xml. As I mentioned earlier, the document.xml will always have a section break at the end of the body element. The elements that are applicable to this section are all the ones above it - until the previous section break (if there is one). But all the other section breaks refer to the elements below them - until the next section break.

For example. I've created a new word document and inserted 2 section breaks. On each page I have added text to indicate what page number it is. Look at the xml that got generated to understand further what I am trying to explain:

What is also very important to note here is that the last section property exists as a child of body however the other section properties are nested inside a paragraph object (w:p).