ActivityIndicator

ActivityIndicator is the native indeterminate spinner. Bind IsAnimating to the operation state:

var loading = new ActivityIndicator
{
    IsLarge = true,
    Color = Colors.SecondaryLabel,
    IsAnimating = Bind(vm => vm.IsLoading)
};

IsLarge selects the larger native style and Color overrides the system color. The style is applied when the native view is created, so choose the size as part of constructing the control.

The spinner communicates activity, not what is happening. For operations lasting more than a moment, place a short label nearby. Use ProgressBar instead when there is meaningful determinate progress, and use Button.IsLoading when the activity belongs to one button action.

See ProgressBar and the button loading guide for those cases.