I want to use this namespace because I want access to the ArcGISTiledMapServiceLayer class. I have included Esri.ArcGISRuntime and Esri.ArcGISRuntime.Xamarin.Form (version 100.9) from nuget in my project.
The error message I get is
CS0234: The type or namespace name 'Layers' does not exist in the namespace 'Esri.ArcGISRuntime' (are you missing an assembly rederence?)
Is there another nuget package I also need to include?

The error

My nuget
I am trying to work off this example Create an offline app—ArcGIS Runtime SDK for .NET | ArcGIS for Developers