OnPlatform error Xamarin Forms Xaml

Hello,

I have this code

<StackLayout x:Name="TabsArea" HorizontalOptions="FillAndExpand" BackgroundColor="#A26FED" Padding="7,0,15,0">
    <StackLayout.HeightRequest>
        <OnPlatform x:TypeArguments="x:Double">
        <On Platform="Android" Value="30" />
        <On Platform="iOS" Value="27" />
        </OnPlatform>
    </StackLayout.HeightRequest>
    <StackLayout Orientation="Horizontal" x:Name="DayTabs" />
</StackLayout>

When i try to run the app i get this error

Error: Position 29:18. Type OnPlatform not found in xmlns http://xamarin.com/schemas/2014/forms

I am using Xamarin Forms 2.X

Any ideas?

Thx.