JsonFile.cs

using Newtonsoft.Json;
using System;
using System.IO;
using System.Threading.Tasks;

namespace JsonSettings
{
    public static class JsonFile
    {
        public static void Save<T>(string fileName, T @object, Action<JsonSerializerSettings> updateSettings = null, EventHandler<Newtonsoft.Json.Serialization.ErrorEventArgs> error = null)
        {
            string folder = Path.GetDirectoryName(fileName);
            if (!Directory.Exists(folder)) Directory.CreateDirectory(folder);

            using (StreamWriter writer = File.CreateText(fileName))
            {
                JsonSerializerSettings settings = new JsonSerializerSettings()
                {
                    Error = error,
                    Formatting = Formatting.Indented,
                    ContractResolver = new DataProtectionResolver()
                };

                updateSettings?.Invoke(settings);

                string json = JsonConvert.SerializeObject(@object, settings);
                writer.Write(json);
            }
        }

        public async static Task SaveAsync<T>(string fileName, T @object, Action<JsonSerializerSettings> updateSettings = null, EventHandler<Newtonsoft.Json.Serialization.ErrorEventArgs> error = null)
        {
            string folder = Path.GetDirectoryName(fileName);
            if (!Directory.Exists(folder)) Directory.CreateDirectory(folder);

            using (StreamWriter writer = File.CreateText(fileName))
            {
                JsonSerializerSettings settings = new JsonSerializerSettings()
                {
                    Error = error,
                    Formatting = Formatting.Indented,
                    ContractResolver = new DataProtectionResolver()
                };

                updateSettings?.Invoke(settings);

                string json = JsonConvert.SerializeObject(@object, settings);
                await writer.WriteAsync(json);
            }
        }

        public static T LoadOrCreate<T>(string fileName) where T : new()
        {
            if (!File.Exists(fileName)) return new T();

            return Load<T>(fileName);
        }

        public static T Load<T>(string fileName, Func<T> ifNotExists = null, EventHandler<Newtonsoft.Json.Serialization.ErrorEventArgs> error = null)
        {
            if (!File.Exists(fileName) && ifNotExists != null) return ifNotExists.Invoke();

            using (StreamReader reader = File.OpenText(fileName))
            {
                JsonSerializerSettings settings = new JsonSerializerSettings()
                {
                    Error = error,
                    ContractResolver = new DataProtectionResolver()
                };

                string json = reader.ReadToEnd();
                if (!string.IsNullOrEmpty(json) && !json.Equals("null"))
                {
                    return JsonConvert.DeserializeObject<T>(json, settings);
                }
            }
            return default(T);
        }

        public async static Task<T> LoadOrCreateAsync<T>(string fileName) where T : new()
        {
            if (!File.Exists(fileName)) return new T();

            return await LoadAsync<T>(fileName);
        }

        public async static Task<T> LoadAsync<T>(string fileName, Func<T> ifNotExists = null, EventHandler<Newtonsoft.Json.Serialization.ErrorEventArgs> error = null)
        {
            if (!File.Exists(fileName) && ifNotExists != null) return ifNotExists.Invoke();

            using (StreamReader reader = File.OpenText(fileName))
            {
                JsonSerializerSettings settings = new JsonSerializerSettings()
                {
                    Error = error,
                    ContractResolver = new DataProtectionResolver()
                };

                string json = await reader.ReadToEndAsync();
                if (!json.Equals(string.Empty))
                {
                    return JsonConvert.DeserializeObject<T>(json, settings);
                }
            }
            return default(T);
        }
    }
}