Back buttons

[M-Yankov]

It will be useful for latest versions of android, they not have navigation menu.

[M-Yankov]

Actually it seems not difficult and it's build in:

V7.Toolbar toolbar = FindViewById<V7.Toolbar>(Resource.Id.toolbar);
SetSupportActionBar(toolbar);
// The setting
SupportActionBar.SetDisplayHomeAsUpEnabled(true);

And need to set parent activity:
[Activity(Label = "@string/app_name", Theme = "@style/AppTheme.NoActionBar", ParentActivity = typeof(MainActivity))]

https://developer.android.com/training/appbar/up-action