<Entry IsPassword="true" Placeholder="Password" TextColor="Green" BackgroundColor="#2c3e50" />

public override bool CanPerform(Selector action, NSObject withSender)
    {
        if(action.Name == "paste:" || action.Name == "copy:" || action.Name == "cut:")
            return false;

        return base.CanPerform(action, withSender);
    }

class Callback : Java.Lang.Object, ActionMode.ICallback
{

    public bool OnActionItemClicked(ActionMode mode, IMenuItem item)
    {
        return false;
    }

    public bool OnCreateActionMode(ActionMode mode, IMenu menu)
    {
        return false;
    }

    public void OnDestroyActionMode(ActionMode mode)
    {

    }

    public bool OnPrepareActionMode(ActionMode mode, IMenu menu)
    {
        return false;
    }
}

protected override void OnElementChanged(ElementChangedEventArgs<Entry> e)
    {
        base.OnElementChanged(e);

        if (Control != null)
        {
            Control.CustomSelectionActionModeCallback = new Callback();
        }
    }