Problems with SaveAsync task in DynamoDB for C#

I'm trying to save my administrator class object to DynamoDB using Context.SaveAsync method:

// Save admin to DynamoDB.
context.SaveAsync(admin,(result)=>{
  if (result.Exception == null)
  { 
    Console.WriteLine("admin saved");
  }
});

but it keeps bothering me with following error:

cannot convert `lambda expression' to non-delegate type `system.threading.cancellationtoken'

How do I handle this issue ?. I'm using Xamarin Studio for OS X