using System;

using Newtonsoft.Json.Linq;

​

public class Program

{

    public static void Main()

    {

        static JObject Projector(JObject originalJObject, string commaSeparatedListOfFields)

        {

            var finalJObject = new JObject();

            // For example: if propertiesArray looks like ["field1.field2.field3","field4", "field5.0"]

            var propertiesArray = commaSeparatedListOfFields.Split(',');

            // I am using for loop vs foreach because for loop is cheaper than for each https://stackoverflow.com/a/365658/10266116

            for (var i = 0; i < propertiesArray.Length; i++)

            {

                // Get the current element from the array

                var currentProperty = propertiesArray[i];

                // Assuming the current property is in the following format "field1.field2.field3"

                // we need to find the value of the leaf field i.e, 'field3'

                // fieldsArrary will look like ["field1", "field2", "field3"]

                var fieldsArray = currentProperty.Trim().Split('.');

                var arrayLength = fieldsArray.Length;

                if (arrayLength > 1)

                {

                    // if the property involves nested objects

                    var tempSourceJObject = new JObject();

                    var tempFinalJObject = new JObject();

                    for (var j = 0; j < arrayLength; j++)

                    {

                        // first Iteration currentField = field1

                        // second Iteration currentField = field2

                        // third Iteration currentField = field3

                        var currentField = fieldsArray[j];

                        if (j == 0)

                        {

                            // if the field is present use it from finalJObject first time or assign empty JObject.

                            finalJObject[currentField] = finalJObject[currentField] != null ? (JObject)finalJObject[currentField] : new JObject();

                            // Assign the value to the tempFinalJObject

                            tempFinalJObject = (JObject)finalJObject[currentField];

                            // Read the corresponding object from sourceJObject

                            tempSourceJObject = (JObject)originalJObject[currentField];

                        }

                        else if (j == arrayLength - 1)

                        {

                            // For the leaf field i.e, last field assign value from tempSourceJObject to tempFinalJObject

                            if (tempFinalJObject != null)

                                tempFinalJObject[currentField] = tempSourceJObject?[currentField];

                        }

                        else

                        {

                            // if the field is present use it from tempFinalJObject first time or assign empty JObject.

                            if (tempFinalJObject != null && tempSourceJObject != null)

                            {

                                tempFinalJObject[currentField] = tempFinalJObject[currentField] != null ? (JObject)tempFinalJObject[currentField] : new JObject();

                                // Assign the value to the tempFinalJObject again

                                tempFinalJObject = (JObject)tempFinalJObject[currentField];

                                tempSourceJObject = (JObject)tempSourceJObject[currentField];

                            }

                            else

                            {

                                break;

                            }

                        }

                    }

                }

                else

                {

                    // if the property has only one field then just assign the property from originalJObject

                    finalJObject[fieldsArray[0]] = originalJObject[fieldsArray[0]];

                }

            }

​

            return finalJObject;

        }

​

        dynamic jsonObject = new JObject();

        jsonObject.Date = DateTime.Now;

        jsonObject.Album = "Me Against the world";

        jsonObject.Year = 1995;

        jsonObject.Artist = "2Pac";

        jsonObject.Person = new JObject();

        jsonObject.Person.Details = new JObject();

        jsonObject.Person.Present = true;

        jsonObject.Person.Details.FirstName = "Baaji";

        jsonObject.Person.Details.LastName = "Shaik";

        //Console.Write(jsonObject);

        var hello = Projector(jsonObject, "Year, Person.Details.FirstName, Person.Details.LastName");

        Console.WriteLine(hello);

    }

}