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Home Forums How do you read and write INI or configuration-like files manually (without third-party libraries)? – MindStick
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1 Answers

Anubhav Sharma
Anubhav Sharma 27 May 2025
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To read and write INI or configuration-like files manually in C# (without using third-party libraries), you can create a simple parser using StreamReader, StreamWriter, and Dictionary<string, Dictionary<string, string>> to represent sections and key-value pairs.

INI Format Example

[Database]
Server=localhost
Port=1433
User=admin

[Logging]
Level=Debug
FilePath=logs/app.log

1. Reading INI Files Manually

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

public class IniFile
{
    public Dictionary<string, Dictionary<string, string>> Data { get; } = new();

    public void Load(string filePath)
    {
        string? section = null;

        foreach (var line in File.ReadLines(filePath))
        {
            var trimmed = line.Trim();

            if (string.IsNullOrWhiteSpace(trimmed) || trimmed.StartsWith(";") || trimmed.StartsWith("#"))
                continue;

            if (trimmed.StartsWith("[") && trimmed.EndsWith("]"))
            {
                section = trimmed[1..^1].Trim();
                if (!Data.ContainsKey(section))
                    Data[section] = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
            }
            else if (section != null && trimmed.Contains('='))
            {
                var parts = trimmed.Split('=', 2);
                var key = parts[0].Trim();
                var value = parts[1].Trim();
                Data[section][key] = value;
            }
        }
    }

    public string? Get(string section, string key)
    {
        if (Data.TryGetValue(section, out var kv) && kv.TryGetValue(key, out var value))
            return value;

        return null;
    }
}

Usage:

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

string? server = ini.Get("Database", "Server");
Console.WriteLine(server);  // Outputs: localhost

2. Writing INI Files Manually

public void Save(string filePath)
{
    using var writer = new StreamWriter(filePath);

    foreach (var section in Data)
    {
        writer.WriteLine($"[{section.Key}]");
        foreach (var kvp in section.Value)
        {
            writer.WriteLine($"{kvp.Key}={kvp.Value}");
        }
        writer.WriteLine(); // Blank line between sections
    }
}

Usage:

ini.Data["Database"]["Server"] = "127.0.0.1";
ini.Data["Database"]["User"] = "newadmin";
ini.Save("new_config.ini");

Notes and Best Practices

Feature Support
Comments (; or #) Skipped
Whitespace handling Trimmed
Case-insensitive keys Yes
Section support Yes
Multi-line values No (simple implementation)
Escaped characters No (extend if needed)

Let me know if you want extended support for features like multi-line values or type conversion (int, bool, etc.).

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