title: How to insert space before the last 3 characters in a string C#?
body: <p>I am using windows forms and I am building application where the users enter their UK PostCode.</p>
  
  <p>The UK PostCode contains space before the last 3 characters, examples like:</p>
  
  <p><code>L22 9QY</code> , <code>L5 3SG</code> , <code>WA10 4RT</code> so there is always space just before the last 3 characters. What I am trying to do is: when a user enters their PostCode like this <code>L53SG</code> I want to insert space before the last 3 characters to make it like this <code>L5 3SG</code>.</p>
  
  <p>Say we have:</p>
  
  <pre><code>string PostCode = "L53SG"; 
  </code></pre>
  
  <p>how do I insert space before the last 3 characters in PostCode string?</p>
  
  <p>Anyone knows how to do that. Thank you</p>