title: How to fix HockeyApp namespace error in Xamarin?
body: <p>I built an old hockey App project using Xamarin.
  But I got some errors.</p>
  <blockquote>
  <p>CS0234    The type or namespace name 'CrashManagerListener' does not
  exist in the namespace 'HockeyApp' (are you missing an assembly
  reference?)</p>
  <p>CS0234    The type or namespace name 'TraceWriter' does not
  exist in the namespace 'HockeyApp' (are you missing an assembly
  reference?)</p>
  </blockquote>
  <p>I installed HockeySDK.Xamarin using Nugat package manager of VS2015.
  Thank you.</p>