Custom INI File Class - light-weight and simple

IniFile.cs

// The following was tested using RolsynPad 20.0

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;

// Example usage
var ini = new IniFile();
ini.Load("config.ini");

ini.SetValue("MySection", "MyKey", "Somevalue12345");
var data1 = ini.GetValue("MySection", "MyKey");
Console.WriteLine("Data-1.1: " + data1);


ini.SetValue("MySection", "MyKey", "Data with spaces");
data1 = ini.GetValue("MySection", "MyKey");
Console.WriteLine("Data-1.2: " + data1);

var data2 = ini.GetValue("MySection", "MISSING_KEY");
Console.WriteLine("Invalid-Key: " + data2);

var data3 = ini.GetValue("NO_SECTION", "MISSING_KEY");
Console.WriteLine("Invalid-Section: " + data3);

// ----------

public class IniFile
{
  public const char Semi = ';';
  public const char Hash = '#';
  public const char BracketOpen = '[';
  public const char BracketClose = ']';
  public const char Equals = '=';

  private readonly Dictionary<string, Dictionary<string, string>> _iniData =
    new(StringComparer.OrdinalIgnoreCase);

  public PreferenceService()
  {
  }

  public string? GetValue(string section, string key, string? defaultValue = null)
  {
    if (_iniData.ContainsKey(section) && _iniData[section].ContainsKey(key))
      return _iniData[section][key];

    return defaultValue;
  }

  public void Load(string filePath)
  {
    _iniData.Clear();

    if (!File.Exists(filePath))
      return;

    string currentSection = string.Empty;
    foreach (string line in File.ReadAllLines(filePath))
    {
      string trimmedLine = line.Trim();

      // Skip empty lines and comments
      if (string.IsNullOrWhiteSpace(trimmedLine) || trimmedLine.StartsWith(Semi) || trimmedLine.StartsWith(Hash))
        continue;

      if (trimmedLine.StartsWith(BracketOpen) && trimmedLine.EndsWith(BracketClose))
      {
        ////currentSection = trimmedLine.Substring(1, trimmedLine.Length - 2);
        currentSection = trimmedLine[1..^1];
        if (!_iniData.ContainsKey(currentSection))
          _iniData[currentSection] = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
      }
      else if (trimmedLine.Contains(Equals))
      {
        int equalsIndex = trimmedLine.IndexOf(Equals);

        ////string key = trimmedLine.Substring(0, equalsIndex).Trim();
        ////string value = trimmedLine.Substring(equalsIndex + 1).Trim();
        string key = trimmedLine[..equalsIndex].Trim();
        string value = trimmedLine[(equalsIndex + 1)..].Trim();

        if (!string.IsNullOrEmpty(currentSection) && _iniData.ContainsKey(currentSection))
          _iniData[currentSection][key] = value;
      }
    }
  }

  public void Save(string filePath)
  {
    using StreamWriter writer = new(filePath);
    foreach (var sectionEntry in _iniData)
    {
      writer.WriteLine($"{BracketOpen}{sectionEntry.Key}{BracketClose}");
      foreach (var keyValuePair in sectionEntry.Value)
        writer.WriteLine($"{keyValuePair.Key}{Equals}{keyValuePair.Value}");

      // Add a blank line between sections for readability
      writer.WriteLine();
    }
  }

  public void SetValue(string section, string key, string value)
  {
    if (!_iniData.ContainsKey(section))
      _iniData[section] = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);

    _iniData[section][key] = value;
  }
}