XmlDocument.GetElementById() is returning null

Question

Here is my XML:

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE taxes[
<!ELEMENT tax (name,percent,description)>
<!ATTLIST tax id CDATA #REQUIRED>
<!ELEMENT name (#PCDATA)>
<!ELEMENT percent (#PCDATA)>
<!ELEMENT description (#PCDATA)>
]>
<taxes>
    <tax id="Tax-1">
        <name>Tax 1</name>
        <percent>6.75</percent>
        <description>Ohio sales tax</description>
    </tax>
</taxes>

And my C# code:

XmlDocument doc = new XmlDocument();
doc.Load("path-to-file");

XmlElement element = doc.GetElementById("Tax-1");

Whenever I try to do stuff with element, I get a NullReferenceException.

I did some research and I found that a valid DTD is required, but as far as I know everything is valid...

@kennyzx did you read the question? I already have a DTD and this is not HTML... — djmordigal, Jan 14 '15 at 03:27
Based on http://xmlwriter.net/xml_guide/attlist_declaration.shtml & http://msdn.microsoft.com/en-us/library/system.xml.xmldocument.getelementbyid%28v=vs.110%29.aspx it seems like you have to declare id as ID in the DocType and not as CDATA. — user92454, Jan 14 '15 at 03:30
Would you show us please your full error message. Is `element` null? — Quality Catalyst, Jan 14 '15 at 03:32

score 3 · Accepted Answer · answered Jan 14 '15 at 03:29

3

Your DTD is incorrect. For your XML proper DTD is:

<!DOCTYPE taxes[
<!ELEMENT taxes (tax*)>
<!ELEMENT tax (name,percent,description)>
<!ATTLIST tax id CDATA #REQUIRED>
<!ELEMENT name (#PCDATA)>
<!ELEMENT percent (#PCDATA)>
<!ELEMENT description (#PCDATA)>
]>

answered Jan 14 '15 at 03:29

Kirill Polishchuk

54,804
11
122
125

1

Fixed it! Thank you so much. I also changed the CDATA for "id" to ID and that seems to work fine as well. – djmordigal Jan 14 '15 at 03:45

score 0 · Answer 2 · answered Jan 14 '15 at 03:47

0

<!ATTLIST tax id ID #REQUIRED>

Your id attribute on your tax element could also be called something other than id, e.g., taxid:

<!ATTLIST tax taxid ID #REQUIRED>

answered Jan 14 '15 at 03:47

John Castleman

1,552
11
12

XmlDocument.GetElementById() is returning null

2 Answers2