<cv:BindableComboBox ItemsSource="{Binding Themes}" SelectedValue="{Binding SelectedTheme}">
      <cv:BindableComboBox.Title>
        <OnPlatform x:TypeArguments="x:String"
            iOS="{Binding ThemePickerTitle}"
            Android="{Binding ThemePickerTitle}"/>
      </cv:BindableComboBox.Title>
    </cv:BindableComboBox>