Xamarin android Camera2 usage

I want to use camera2 on my android project into Xamarin studio (Mac).
I set reference from Camera to Android.Hardware.Camera2, but all method from camera are in error.
I can't use Camera2.Open(), or Camera2.Parameters.
What i am doing wrong?

Camera 2 works on Android L or later
Xamarin.Android 4.17 or later is needed

Sample code is here
https://github.com/xamarin/monodroid-samples/tree/master/android5.0/Camera2Basic/Camera2Basic

For version lower than Android L use  Android.Hardware.Camera

https://developer.xamarin.com/api/type/Android.Hardware.Camera/
Sample code is here 
https://github.com/xamarin/monodroid-samples/blob/master/ApiDemo/Graphics/CameraPreview.cs
https://forums.xamarin.com/discussion/8705/camera-sample