title: Xamarin.Forms Android cannot access USB OTG folder
body: <p>I'm on an Android 5.0 device where a usb mass storage is mounted at "/storage/usbotg" via USB OTG cable. 
  Unfortunately from my app I only have read access to that folder. Please note that I set the write external storage permission as I'm able to write to device storage.</p>
  
  <p>I post the following code as reference:</p>
  
  <pre><code>string Root = "/storage/usbotg";                        
  string[] Dirs = Directory.GetDirectories(Root);
  
  string NewFolder = Path.Combine(Root, "NewFolder");          
  Directory.CreateDirectory(NewFolder);
  </code></pre>
  
  <p>This gives me an exception on the last line (but I'm able to list subdirectories in Dirs)</p>
  
  <p>Exception:
  System.UnauthorizedAccessException</p>
  
  <p>Exception Message:
  Access to the path "/storage/usbotg/NewFolder" is denied.</p>
  
  <p>If I use:</p>
  
  <pre><code>string Root =  "/storage/emulated/0"; 
  </code></pre>
  
  <p>everything is working fine and the "NewFolder" is created.</p>
  
  <p>What I'm missing? How can I write to that folder?</p>
  
  <p>I'm using Xamarin.Forms 2.5.0</p>
  
  <p>Thanks for your help</p>