title: How to generate random numbers using only specific digits, e.g [1234] [4213] [3124]
body: <p>In VB.NET I am trying to figure out how exactly to generate numbers of a fixed length using specific digits.</p>
  
  <p>I have seen these questions but they do not cover what I am looking for:<br>
  <a href="https://stackoverflow.com/questions/363681/generating-random-integers-in-a-specific-range">How do I generate random integers within a specific range in Java?</a><br>
    <a href="https://stackoverflow.com/questions/3975290/produce-a-random-number-in-a-range-using-c-sharp">Produce a random number in a range using C#</a><br>
  <a href="https://stackoverflow.com/questions/2673385/how-to-generate-random-number-with-the-specific-length-in-python">How to generate random number with the specific length in python</a><br>
  <a href="https://stackoverflow.com/questions/32144346/generating-an-array-of-random-strings">Generating an array of random strings</a><br>
  <a href="https://stackoverflow.com/questions/3253157/generation-9-digits-random-number-including-leading-zero">Generation 9 digits random number including leading zero</a>  </p>
  
  <p>I am trying to generate 4 digit numbers using <em>only</em> 1, 2, 3, and 4.<br>
  It would be like this:</p>
  
  <pre><code>1234  
  2134  
  3124  
  2143  
  2431  
  2413  
  </code></pre>
  
  <p>etc...<br>
  Can someone explain to me how this can be achieved?</p>