title: Select from a range but exclude certain numbers
body: <p>Is it possible to pick a random number from a given range (1-90), but exclude certain numbers. The excluded numbers are dynamically created but lets say they are 3, 8, and 80. </p>
  
  <p>I have managed to create random number generator but couldn't identify any functions that let me fulfill my requirements.</p>
  
  <pre><code>Random r = new Random();
  this.num = r.Next(1, 90);
  </code></pre>
  
  <p>The numbers which are to be excluded are previously generated numbers. So, if the random number is one, this would then get added to the excluded numbers list. </p>