title: How to format a string with thousands separation and decimal comma?
body: <p>I have some strings:</p>
  
  <pre><code>string amount = "123456";
  string amount2 = "123456.78";
  </code></pre>
  
  <p>I want the output to be:</p>
  
  <pre><code>amount: 123.456,00
  amount2: 123.456,78
  </code></pre>
  
  <p>I already looked <a href="https://stackoverflow.com/questions/105770/net-string-format-to-add-commas-in-thousands-place-for-a-number">here</a>, but this does not work for my example.</p>