title: What are appSettings keys valid characters?
body: <p>This is strange. I thought I would easily find this information googling, but I haven't had much success. All I want to know is what are the valid characters that can be used for the keys in the AppSettings section of a Web.config file. Eg:</p>
  
  <pre><code>&lt;add key="MySpeed" value="100" /&gt;
  &lt;add key="My.Speed" value="100" /&gt;
  &lt;add key="My Speed" value="100" /&gt;
  &lt;add key="Vélocité" value="100" /&gt;
  </code></pre>
  
  <p>Would all of the above keys be permitted?</p>