title: How to find a string which doesnot contain a specific using regular expression in c# .net
body: <p>I have a long string.</p>
  
  <pre><code>Example
  This is a dog.
  This is a cat.
  A cat and a cat is a pet animal.
  A tiger is a wild animal.
  </code></pre>
  
  <p>Now I want the string which does not contain 'cat' but contain a animal.
  How can I do this using regex.
  I know that I have to use(?!) but how that i dont know.
  So the output would be </p>
  
  <pre><code>A tiger is a wild animal.
  </code></pre>