using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Runtime.Serialization.Formatters;

using System.IO;

using System.Data;

using System.ComponentModel.DataAnnotations;

using System.Globalization;

using System.Reflection;

​

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/58931339/change-property-name-in-json-string

​

    public static partial class JsonExtensions

    {

        // Taken verbatim from this answer https://stackoverflow.com/a/47269811/3744182

        // To https://stackoverflow.com/questions/47267542/rename-jproperty-in-json-net

        // By Brian Rogers https://stackoverflow.com/users/10263/brian-rogers

        public static void Rename(this JToken token, string newName)

        {

            if (token == null)

                throw new ArgumentNullException("token", "Cannot rename a null token");

​

            JProperty property;

​

            if (token.Type == JTokenType.Property)

            {

                if (token.Parent == null)

                    throw new InvalidOperationException("Cannot rename a property with no parent");

​

                property = (JProperty)token;

            }

            else

            {

                if (token.Parent == null || token.Parent.Type != JTokenType.Property)

                    throw new InvalidOperationException("This token's parent is not a JProperty; cannot rename");

​

                property = (JProperty)token.Parent;

            }

​

            // Note: to avoid triggering a clone of the existing property's value,

            // we need to save a reference to it and then null out property.Value

            // before adding the value to the new JProperty.  

            // Thanks to @dbc for the suggestion.

​

            var existingValue = property.Value;

            property.Value = null;

            var newProperty = new JProperty(newName, existingValue);

            property.Replace(newProperty);

        }

    }

​

    class TestClass

    {

        public static void Test()

        {

            var jsonString = GetJson();

            var root = JToken.Parse(jsonString);

            foreach (var item in root.SelectTokens("..profiles[*].name").ToList())

                item.Rename("profileName"); // Using the extension method here

​

            var newJsonString = root.ToString();

            Console.WriteLine("Output JSON:");

            Console.WriteLine(newJsonString);

        }   

        static string GetJson()

        {

            var json = @"[

    {

        ""name"": ""name 1"",

        ""profiles"":[{

            ""name"": ""profile 1.1""

            },{

            ""name"": ""profile 1.2""

        }]

    },{

        ""name"": ""name 2"",

        ""profiles"":[{

            ""name"": ""profile 2.1""

            }]

    }

]

";

            return json;

        }

    }

​

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: {0} ({1})", System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription , GetNetCoreVersion());

            Console.WriteLine("Json.NET version: " + typeof(JsonSerializer).Assembly.FullName);

            Console.WriteLine();

​

            try

            {

                TestClass.Test();

            }

            catch (Exception ex)

            {

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

                Console.WriteLine(ex);

                throw;

            }

        }

        public static string GetNetCoreVersion()

        {

            //https://techblog.dorogin.com/how-to-detect-net-core-version-in-runtime-ecd65ad695be

            //

            var assembly = typeof(System.Runtime.GCSettings).GetTypeInfo().Assembly;

            var assemblyPath = assembly.CodeBase.Split(new[] { '/', '\\' }, StringSplitOptions.RemoveEmptyEntries);

            int netCoreAppIndex = Array.IndexOf(assemblyPath, "Microsoft.NETCore.App");

            if (netCoreAppIndex > 0 && netCoreAppIndex < assemblyPath.Length - 2)

                return assemblyPath[netCoreAppIndex + 1];

            return null;

        }

    }

​

#if false

So is your question, *How can I rename the properties `..profiles[*].name` to `..profiles[*].profileName`using some sort of streaming transformation, without loading the entire JSON into memory?*  Because you can do it easily with [tag:json.net] if you load the entire thing into memory, see https://dotnetfiddle.net/W46243

​

#endif

​