title: .NET negative lookbehind regex not working as expected
body: <p>I want to isolate the initials "Wrs" in the string </p>
  
  <pre><code>"agendapunt 5.4 (GAIA) asdf &lt;BR&gt;    Wrs    &lt;BR&gt;         medegedeeld"
  </code></pre>
  
  <p>This is the regular expression I'm using:</p>
  
  <pre><code>(?&lt;!&lt;BR&gt;)(\s{2,}[a-z]+\s{2,})(?=&lt;BR&gt;)
  </code></pre>
  
  <p>The initials "Wrs" must be followed by atleast two spaces and after that an html break <code>&lt;BR&gt;</code>. 
  Also the initials "Wrs" must be preceded by atleast two spaces and must NOT be preceded by an HTML <code>&lt;BR&gt;</code> tag.</p>
  
  <p>Unfortunately, in the above example, there's still a positive match for the initials, even with the preceding <code>&lt;BR&gt;</code> tag. 
  I don't understand why, cause the postive lookahead does seem to work as I would expect.
  I.E. when I'm removing the second <code>&lt;BR&gt;</code> tag, or part of it, from the input string, then there's no match to be found.</p>
  
  <p>Also, I tried using a positive lookbehind instead of a negative one just to see what it would do and it also works exactly as I would expect. 
  It seems like positive and negative lookarounds don't work by the same rules in the case.</p>
  
  <p>Any idea what I'm doing wrong?</p>