title: Only one "0" before "." in textBox_TextChanged
body: <p>How can I left only one "0" before "."? I'm making <code>TextBox</code> which accepts only digits and you can write only one "0" before ".", but you can write any numbers like 900 or 5000.</p>
  
  <p>Here is the pseudocode I use: </p>
  
  <pre><code>if (0 &gt; 1 before "." &amp;&amp; 0 is first digit) 
  {
      Remove all zeros before "." and left one; 
  }
  </code></pre>
  
  <p><img src="https://i.imgur.com/mkCkhEr.png?1" alt=""></p>