Basic example how to use Google's Geocode API on Xamarin Forms (and C# in general I guess).

Geocode.cs

using System.Collections.Generic;
using Newtonsoft.Json;

namespace YourApp.Models
{
    /// <Summary>
    /// Basic Google's geocode information model.
    /// </Summary>
    public class Geocode
    {
        [JsonProperty("formatted_address")]
        public string FormattedAddress { get; set; }

        [JsonProperty("address_components")]
        public AddressComponent[] AddressComponents { get; set; }
    }

    public class AddressComponent
    {
        [JsonProperty("long_name")]
        public string LongName { get; set; }
        [JsonProperty("short_name")]
        public string ShortName { get; set; }
        [JsonProperty("types")]
        public List<string> Types { get; set; }
    }
}

IGoogleService.cs

using System;
using System.Threading.Tasks;
using Newtonsoft.Json.Linq;
using Refit;

namespace YourApp.Services
{
    public interface IGoogleService
    {
        [Get("/geocode/json")]
        Task<JToken> GetGeocodeInformation(string latlng, string key);
    }
}

YourViewModel.cs

// Don't forget to initialize IGoogleService Inject the service or initialize it
// More information: https://github.com/reactiveui/refit

async Task GetGeocode (Position? selectedLocation) {
    if (selectedLocation != null) {
        try 
        {
            var googleApi = RestService.For<IGoogleService>("https://maps.googleapis.com/maps/api");
            var token = await googleService.GetGeocodeInformation 
            ($"{selectedLocation.Value.Latitude}, {selectedLocation.Value.Longitude}",
                    AppConstants.GoogleApiKey);
            var results = token["results"].ToObject<List<Geocode>> ();
            GetAddress (results);
        } 
        catch (Exception e) 
        {
            Console.WriteLine (e);
            //Analytics.TrackEvent("Error", new Dictionary<string, string>
            //{
            //    {"Exception", e.Message},
            //    {"From", "YourPage"}
            //});
        }
    }
    
    void GetAddress(List<Geocode> geocodes)
        {
            foreach (var geocode in geocodes)
            {
                foreach (var addressComponent in geocode.AddressComponents)
                {
                    if (addressComponent.Types.Contains("locality") || addressComponent.Types.Contains("administrative_area_level_1"))
                    {
                        State = addressComponent.LongName.Replace("Department", "").Trim().TrimEnd().TrimStart();
                    }
                    else if (addressComponent.Types.Contains("country"))
                    {
                        Country = addressComponent.LongName;
                    }
                }
            }
        }
    }
}