Finding the last unclosed XML tag in a string

Question

I'm trying to create a function in C# that will try to automatically generate a closing XML tag when the user types </. Let's say I have following string:

<books>
  <book>
  <author>Tolkien</author>
  <title>Fellowship of the Ring</title>
  </book>
  <book>

When the user types </, this should be directly appended with the string book>.

I am kind of lost on how to find the last unclosed tag (in this case <book> programmatically. Is a regex the best way to do this? Using an XML parser seems to be out of the question since the XML at this point is not valid.

Possible duplicate of [RegEx match open tags except XHTML self-contained tags](https://stackoverflow.com/questions/1732348/regex-match-open-tags-except-xhtml-self-contained-tags) — EJoshuaS - Stand with Ukraine, Sep 25 '17 at 15:27
H̸̡̪̯ͨ͊̽̅̾̎Ȩ̬̩̾͛ͪ̈́̀́͘ ̶̧̨̱̹̭̯ͧ̾ͬC̷̙̲̝͖ͭ̏ͥͮ͟Oͮ͏̮̪̝͍M̲̖͊̒ͪͩͬ̚̚͜Ȇ̴̟̟͙̞ͩ͌͝S̨̥̫͎̭ͯ̿̔̀ͅ — EJoshuaS - Stand with Ukraine, Sep 25 '17 at 15:27

Giel · Accepted Answer · 2017-09-24T12:25:38.217

3

Consider using a stack, for every opening tag you push the tag, then whenever you come across '< /' you pop the tag from the stack

<books>
  <book>
  <author>Tolkien</author>
  <title>Fellowship of the Ring</title>
  </book>
  <book>

push books, push book, push author, pop author, push title, pop title, pop book, etc.

at the end of this, whatever is on the stack has not been properly closed

edited Sep 24 '17 at 12:25

answered Sep 24 '17 at 12:20

Giel

397
1
9

Of course, if you allow editing or deletion of text that has already been typed (and who doesn't?) then it gets rather more complicated. – Michael Kay Sep 24 '17 at 15:35

Finding the last unclosed XML tag in a string

1 Answers1