title: Get string between delimiters from file in C#
body: <p>Maybe the question is familiar but I need an explanation in this case.</p>
  
  <p>Let's assume that I have a file called <code>test.txt</code>. It has the following content:</p>
  
  <pre><code>An example of this line. The line has more than 20 characters.
  [sql]SELECT * FROM LINE WHERE aLine = '123'[/sql]
  blah blah blah blah...
  </code></pre>
  
  <p><strong>OR what's about</strong></p>
  
  <pre><code>An example of this line. The line has more than 20 characters.
  [sql]SELECT * FROM 
         LINE 
       WHERE aLine = '123'[/sql]
  blah blah blah blah...
  
  [sql] SELECT * FROM ME[/sql]
  
   etc..er
  [sql]
     SELECT * FROM ALL
   [/sql]
  </code></pre>
  
  <p>I want to get a string between <code>[sql]</code> and <code>[/sql]</code> delimiters.</p>
  
  <p>How to do that ? With Regular expression ?</p>
  
  <p>Thanks for patience ...</p>