Configuration.cs

using System;
using System.Linq;
using System.IO;
using System.Xml.Serialization;
using UnityEngine;

public abstract class Configuration<C> where C : class, new()
{
    private static C instance;
        
    public static C Load()
    {
        if (instance == null)
        {
            var configPath = GetConfigPath();
            XmlSerializer xmlSerializer = new XmlSerializer(typeof(C));
            try
            {
                if (File.Exists(configPath))
                {
                    using (StreamReader streamReader = new System.IO.StreamReader(configPath))
                    {
                        instance = xmlSerializer.Deserialize(streamReader) as C;
                    }
                }
            }
            catch (Exception e)
            {
                Debug.LogException(e);
            }
        }
        return instance ?? (instance = new C());
    }

    public static void Save()
    {
        if (instance == null) return;

        var configPath = GetConfigPath();

        var xmlSerializer = new XmlSerializer(typeof(C));
        var noNamespaces = new XmlSerializerNamespaces();
        noNamespaces.Add("", "");
        try
        {
            using (var streamWriter = new System.IO.StreamWriter(configPath))
            {
                xmlSerializer.Serialize(streamWriter, instance, noNamespaces);
            }
        }
        catch (Exception e)
        {
            Debug.LogException(e);
        }
    }

    private static string GetConfigPath() 
    {
        var configPathAttribute = typeof(C).GetCustomAttributes(typeof(ConfigurationPathAttribute), true)
            .FirstOrDefault() as ConfigurationPathAttribute;

        if (configPathAttribute != null)
        {
            return configPathAttribute.Value;
        }
        else
        {
            Debug.LogError("ConfigurationPath attribute missing in " + typeof(C).Name);
            return typeof(C).Name + ".xml";
        }
    }
}

[AttributeUsage(AttributeTargets.Class)]
public class ConfigurationPathAttribute : Attribute
{
    public ConfigurationPathAttribute(string value)
    {
        Value = value;
    }

    public string Value { get; private set; }
}