using Newtonsoft.Json.Linq;

using System;

public class Program

{

    public static JObject testObj = JObject.Parse(@"{

    'FaultDomainCount': 1,

    'SupportAutomaticPlacement': true,

    'host': 'test/host',

    'hostGroup': 'test/HostGroup'

    }");

    public static void Main()

    {

        var first = (string)testObj?.SelectToken("$.SupportAutomaticPlacement");

        var sec = (string)testObj.SelectToken("$.host");

        Console.WriteLine(first);

        Console.WriteLine(helperMethod(testObj));

    }

    public static string helperMethod(JObject testObj)

    {

        if(!string.IsNullOrWhiteSpace((string)testObj.SelectToken("$.host")))

        {

            return (string)testObj.SelectToken("$.host");

        }

        else if(!string.IsNullOrWhiteSpace((string)testObj.SelectToken("$.hostGroup")))

        {

            return (string)testObj.SelectToken("$.hostGroup");

        }

        else

        {

            return "null";

        }

    }

}