Snake Case Serilization with System.Text.Json

JsonSerializationExtensions.cs

using System;
using System.Linq;
using System.Text.Json;
using System.Text.Json.Serialization;

namespace Infrastructure
{
    public static class JsonSerializationExtensions
    {
        public static readonly JsonSerializerOptions SnakeCaseSerializerOptions = new()
        {
            WriteIndented = false,
            PropertyNamingPolicy = new SnakeCaseNamingPolicy(),
            PropertyNameCaseInsensitive = true,
            IgnoreNullValues = true,
            Converters = { new JsonStringEnumConverter(allowIntegerValues: false) }
        };

        /// <summary>
        /// Converts the object instance passed in to JSON using <see cref="System.Text.Json.JsonSerializer"/>
        /// </summary>
        /// <param name="objectToSerialize">The object instance to serialize</param>
        /// <param name="serializerOptions">A <see cref="JsonSerializerOptions"/> instance. Defaults to snake_case</param>
        /// <typeparam name="T"></typeparam>
        public static string ToJson<T>(this T objectToSerialize, JsonSerializerOptions? serializerOptions = null)
        {
            return JsonSerializer.Serialize(objectToSerialize, serializerOptions ?? SnakeCaseSerializerOptions);
        }

        /// <summary>
        /// Converts the string passed in to an instance of T using <see cref="System.Text.Json.JsonSerializer"/>
        /// </summary>
        /// <param name="json">The string to convert</param>
        /// <param name="serializerOptions">A <see cref="JsonSerializerOptions"/> instance. Defaults to snake_case</param>
        /// <typeparam name="T"></typeparam>
        public static T FromJson<T>(this string json, JsonSerializerOptions? serializerOptions = null)
        {
            return JsonSerializer.Deserialize<T>(json, serializerOptions ?? SnakeCaseSerializerOptions)!;
        }

        // Copied from https://github.com/michaelrosedev/snakecase_json/blob/dbc70b7e137e42716350685f684bd46d0458d056/Sample.Serialization/StringExtensions.cs#L12
        public static string ToSnakeCaseAsSpan(this string str)
        {
            const char Separator = '_';

            if (str == null)
            {
                return string.Empty;
            }

            var strSpan = str.AsSpan();

            var bufferSize = str.Length + str.Count(t => t >= 'A' && t <= 'Z' && t != str[0]);
            Span<char> buffer = new char[bufferSize];
            var bufferPosition = 0;
            var namePosition = 0;

            while (bufferPosition < buffer.Length)
            {
                if (namePosition > 0 && strSpan[namePosition] >= 'A' && strSpan[namePosition] <= 'Z')
                {
                    buffer[bufferPosition] = Separator;
                    buffer[bufferPosition + 1] = strSpan[namePosition];
                    bufferPosition += 2;
                    namePosition++;
                    continue;
                }
                buffer[bufferPosition] = strSpan[namePosition];
                bufferPosition++;
                namePosition++;
            }

            return new string(buffer).ToLower();
        }
    }

    public class SnakeCaseNamingPolicy : JsonNamingPolicy
    {
        public override string ConvertName(string name)
        {
            return name.ToSnakeCaseAsSpan();
        }
    }
}