using System;

using System.Collections.Generic;

using System.Text.Json;

​

class Program

{

    static void Main()

    {

        var stringJson = "{ \"Key\": \"TextA\" }";

        var outcome = SerializeWithCamelCase(stringJson);

        Console.WriteLine(outcome);

    }

​

    private static string SerializeWithCamelCase(string jsonContent)

    {

        using var document = JsonDocument.Parse(jsonContent);

        var root = document.RootElement;

        var modifiedObject = ConvertPropertyNamesToCamelCase(root);

        var options = new JsonSerializerOptions

        {

            PropertyNamingPolicy = JsonNamingPolicy.CamelCase,

            WriteIndented = true

        };

​

        return JsonSerializer.Serialize(modifiedObject, options);

    }

​

    private static JsonElement ConvertPropertyNamesToCamelCase(JsonElement element)

    {

        switch (element.ValueKind)

        {

            case JsonValueKind.Object:

                var objBuilder = new Dictionary<string, JsonElement>();

                foreach (var property in element.EnumerateObject())

                {

                    var camelCaseName = ToCamelCase(property.Name);

                    var camelCaseValue = ConvertPropertyNamesToCamelCase(property.Value);

                    objBuilder[camelCaseName] = camelCaseValue;

                }

                return JsonDocument.Parse(JsonSerializer.Serialize(objBuilder)).RootElement;

​

            case JsonValueKind.Array:

                var arrayBuilder = new List<JsonElement>();

                foreach (var item in element.EnumerateArray())

                {

                    var camelCaseItem = ConvertPropertyNamesToCamelCase(item);

                    arrayBuilder.Add(camelCaseItem);

                }

                return JsonDocument.Parse(JsonSerializer.Serialize(arrayBuilder)).RootElement;

​

            default:

                return element.Clone();

        }

    }

​

    private static string ToCamelCase(string name)

    {

        if (string.IsNullOrEmpty(name))

            return name;

​

        if (name.Length == 1)

            return name.ToLowerInvariant();

​

        return char.ToLowerInvariant(name[0]) + name.Substring(1);

    }

}

​