How do you read and write INI or configuration-like files manually (without third-party libraries)?

Question

Anubhav Kumar · Answer

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 Dictionaryandlt;string, Dictionaryandlt;string, stringandgt;andgt; 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 Dictionaryandlt;string, Dictionaryandlt;string, stringandgt;andgt; 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("[") andand trimmed.EndsWith("]"))
            {
                section = trimmed[1..^1].Trim();
                if (!Data.ContainsKey(section))
                    Data[section] = new Dictionaryandlt;string, stringandgt;(StringComparer.OrdinalIgnoreCase);
            }
            else if (section != null andand 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) andand 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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How do you read and write INI or configuration-like files manually (without third-party libraries)?

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1 Answers

INI Format Example

1. Reading INI Files Manually

2. Writing INI Files Manually

Notes and Best Practices

Liked By

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)