Constant NullReference Exception using OpenXML on a DOCX file

Question

I'm trying to parse through a lengthy file and remove sections that I don't want. From research It appears that the OpenXml SDK was the easiest reference for manipulating and searching through the word doc. Unfortunately, it's not always consistent because I keep getting NullReferenceExceptions when trying to assign nodes like to a run object. Essentially, my program should go through the docx file and find the tags (ver 1) and then remove everything in between it and the closing tag (/ver 1). this only seems to work for some section as other sections I get the NullReferenceException and I feel it has to do with the messy formatting that MS Word uses but I don't know.

Here's the code for a particular section if anyone could help I'd Appreciate it.

IEnumerable<OpenXmlElement> elem = main.Document.Body.Descendants().ToList();
foreach (OpenXmlElement elems in elem)
{
   if (elems is Text && elems.InnerText == s_Ver1)// s_Ver1 = "(Ver 1)"
   {
      Run run = (Run)elems.Parent;
      Paragraph p = (Paragraph)run.Parent;
      p.RemoveAllChildren();
      p.Remove();

      foreach (OpenXmlElement endelems in elem)
      {
         if (endelems is Text && elems.InnerText == e_Ver1)//e_Ver1 = "(/Ver1)"
         {
            run = (Run)endelems.Parent;
            p = (Paragraph)run.Parent;
            p.Remove();
            break;
         }

         else
         {
            Run d_Run = (Run)endelems.Parent;
            Paragraph d_p = (Paragraph)d_Run.Parent;
            d_p.RemoveAllChildren();
            d_p.Remove();*/

            try
            {
               endelems.Remove();
            }

            catch(Exception err)
            {
               MessageBox.Show(err.ToString());
            }
          }
       }
    }
}

Edit

try catch with in the code ( around the endelems.remove() )

 System.InvalidOperationException: The Parent of this element is Null
 //it also says line 141 but I'm not sure how to get line numbering in vs2010

try catch error around entire thing

 System.NullReferenceException: Object reference not set to an instance of an object
 //line 114 which would be Paragraph p = (Paragraph)run.Parent; line

I would guess that somewhere the elems.Parent or endelems.Parent returns a null value. Is it possible that they eventually represent root nodes? EDIT: Why don't you run through the debugger and see where/why it's failing, or at least to provide us with more information. — Chris Sinclair
Can you surround the whole thing with a try-catch and post the error? — devilfish17
@devilfish17 I added the exceptions I'm receiving along with the line it's referring to if that helps. (Chris Sinclair) Not sure if those exceptions I added help you but if elems.Parent does end up representing a root node is there anyway I can add a check method so I can than drop down a node or just move to the paragraph node within the root? — user1704863

jn1kk jn1kk · Accepted Answer · 2013-04-24T14:04:35

I am not quite sure what you are trying to do here, but...

You get a static list of children from the body.

You iterate over possibly deleted children. And then call remove a child that were already removed with RemoveAllChildren().

Not to mention this faulty logic.

if (endelems is Text && elems.InnerText == e_Ver1)//e_Ver1 = "(/Ver1)"
{
    ...
else
{
    Run d_Run = (Run)endelems.Parent;
}

In the else clause, endelems will probably not have a parent that is a Run, since it probably wouldn't be a Text element.

--- EDIT --- pseudocode

IEnumerable<Text> elems = wd.MainDocumentPart.Document.Body.Descendants<Text>();
foreach (Text elem in elems) 
{

    if(elem.InnerText.Equals("Ver 1"))
    {
        IEnumerable<OpenXmlElement> afterelems = elem.ElementsAfter();
        foreach(OpenXmlElement openelem in afterelems)
        {
            if(openelem is Text && ((Text)openelem).InnerText.Equals("Ver 2"))
            {
                break;
            } else if(openelem is Text) {
                openelem.Remove();
            }
        }
        break;
    }

}

foreach (Run run in wd.MainDocumentPart.Document.Body.Descendants<Run>().Where(run => run.Descendants<Text>().Count() == 0 && run.Descendants<Break>().Count() == 0))
{
    run.Remove();
}

foreach (Paragraph par in wd.MainDocumentPart.Document.Body.Descendants<Paragraph>().Where(par => par.Descendants<Run>().Count() == 0 && par.Descendants<Table>().Count() == 0))
{
    par.Remove();
}

Constant NullReference Exception using OpenXML on a DOCX file

1 Answers