title: Convert.FromBase64String does not work in code but works in online tool
body: <p>I am writing a C# application to decode this string:</p>
  
  <blockquote>
    <p>"--W3sic3RhcnRfdGltZSI6IjAiLCJwcm9kdWN0X2lkIjoiODQwMDMzMDQiLCJ1cmwiOiIifSx7InN0YXJ0X3RpbWUiOiI3OSIsInByb2R1Y3RfaWQiOiI4NDAzNjk2MSIsInVybCI6IiJ9LHsic3RhcnRfdGltZSI6IjgyIiwicHJvZHVjdF9pZCI6Ijg0MDAzMDIwIiwidXJsIjoiIn0seyJzdGFydF90aW1lIjoiMTA5IiwicHJvZHVjdF9pZCI6IiIsInVybCI6Imh0dHBzOi8vYmxvZy5sYXJlaW5lZHVzaG9wcGluZy5jYS8yMDE3LzAxL3RyYW5zZm9ybWVyLXNlcy12aWV1eC1nYW50cy1kZS1jdWlyLWVuLTUtbWludXRlcy8ifV0="</p>
  </blockquote>
  
  <p>It works when I copy/paste it into this online tool: <a href="https://www.base64decode.org" rel="noreferrer">https://www.base64decode.org</a></p>
  
  <p>But it throws an exception when I use <code>Convert.FromBase64String(str)</code>:</p>
  
  <blockquote>
    <p>System.FormatException: The input is not a valid Base-64 string as it
    contains a non-base 64 character, more than two padding characters, or
    an illegal character among the padding characters.</p>
  </blockquote>
  
  <p>Why?</p>