using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

​

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

using Newtonsoft.Json.Converters;

using Newtonsoft.Json.Serialization;    

​

using NUnit.Framework; // Throws NUnit.Framework.AssertionException

​

//https://stackoverflow.com/questions/77856068/c-sharp-how-can-i-check-if-a-field-exists-before-trying-to-query-it-in-a-json

    class TestClass

    {

        public static void Test()

        {

            Test0();

            Console.WriteLine();

            Test1();

            Test2();

        }

        public static void Test0()

        {

            foreach (var jsonString in GetJson())

            {

                var result = JsonConvert.DeserializeObject<JToken>(jsonString);

                var total = (string)result.SelectTokens("results.main[*].item.total").SingleOrDefault() ?? string.Empty;

                if (!string.IsNullOrEmpty(total))

                {

                    // Process the total somehow.

                }

                Console.WriteLine(total);

            }

        }

        public static void Test1()

        {

            foreach (var jsonString in GetJson())

            {

                var result = JToken.Parse(jsonString);

​

                var total = (string)result.SelectToken("results.main[0].item.total") ?? string.Empty;

                if (!string.IsNullOrEmpty(total))

                {

                    Console.WriteLine(total);

                }

                else

                {

                    Console.WriteLine("no total");

                }

            }

        }   

​

        public static void Test2()

        {

            foreach (var jsonString in GetJson())

            {

                var result = JToken.Parse(jsonString);

​

                var items = result.SelectTokens("results.main[?(@.item.total)].item");

                foreach (var item in items)

                {

                    var name = (string)item["name"];

                    var total = (decimal)item["total"];

                    Console.WriteLine("name = {0}, total = {1}", name, total);

                }

            }

        }   

        static IEnumerable<string> GetJson()

        {

            return new []

            {

                @"{

    ""results"": {

        ""copyright"": ""Copyright (c)"",

        ""main"": [{

            ""item"": {

                ""name"": ""fruit"",

                ""date"": ""1900-01-01"",

                ""total"": 123456

            }

        }]

    }

}

",

                @"{

    ""results"": {

        ""copyright"": ""Copyright (c)"",

        ""main"": [{

            ""item"": {

                ""name"": ""flubber"",

                ""date"": ""1900-01-01"",

            }

        }]

    }

}",

            };

        }

    }

​

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: " + Environment.Version);

            Console.WriteLine("{0} version: {1}", typeof(JsonSerializer).Namespace, typeof(JsonSerializer).Assembly.FullName);

            Console.WriteLine();

​

            try

            {

                TestClass.Test();

            }

            catch (Exception ex)

            {

                Console.WriteLine("Failed with unhandled exception: ");

                Console.WriteLine(ex);

                throw;

            }

        }

    }

​