title: OneDrive get access token request case-sensitivity
body: <p>I have a WinForms C# app using the OneDrive API. All was working up until last week when new token requests after authorizing the user started failing telling me that the 'code' parameter was invalid.</p>
  
  <p>After reviewing my code, I noticed that routine that was extracting the authorization code from the authorize call back was using <code>.ToLowerInvariant</code> which resulted in the authorization code starting with a lower-case 'm'. When I removed the <code>.ToLowerInvariant</code>, the code started with an upper-case 'M' and the token request worked correctly.</p>
  
  <p>Obviously I'm happy that my code is now working, but I'd like to try and understand why it suddenly started having problems.</p>
  
  <p>Many thanks</p>
  
  <p>James</p>