[Tips] How to read write Ini File in C#

How to Read and Write INI Files in C#

INI files are a simple and widely used format for storing configuration settings. They consist of sections, keys, and values, separated by brackets, equal signs, and newlines. For example, an INI file might look like this:

[General]
Name=John
Age=25
[Preferences]
Color=Blue
Font=Arial

In this article, we will show you how to read and write INI files in C# using the Windows API functions WritePrivateProfileString and GetPrivateProfileString. These functions are defined in the kernel32.dll library, which we can access using the Platform Invoke (P/Invoke) feature of .NET.

To use these functions, we need to declare them in our code using the DllImport attribute. We also need to specify the character set, the entry point, and the parameters of each function. For example:

 
	using System.Runtime.InteropServices;
	[DllImport("kernel32.dll", CharSet = CharSet.Unicode)]	
	static extern long WritePrivateProfileString(string section, string key, string value, string filePath);
	
	[DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
	static extern int GetPrivateProfileString(string section, string key, string defaultValue, StringBuilder retVal, int size, string filePath);
	

The WritePrivateProfileString function writes a value to a specified key in a specified section of an INI file. The parameters are:

•  section: The name of the section to write to.

•  key: The name of the key to write to.

•  value: The value to write.

•  filePath: The path of the INI file.

The GetPrivateProfileString function reads a value from a specified key in a specified section of an INI file. The parameters are:

•  section: The name of the section to read from.

•  key: The name of the key to read from.

•  defaultValue: The default value to return if the key is not found.

•  retVal: A StringBuilder object that receives the value.

•  size: The maximum number of characters to copy to the retVal object.

•  filePath: The path of the INI file.

To use these functions in our code, we can create a helper class that wraps them in more convenient methods. For example:

 
	using System.IO;
	using System.Text; 
	public class IniFile {
		private string filePath; 
	
		public IniFile(string filePath) {
			this.filePath = filePath;
			public void Write(string section, string key, string value) {
				WritePrivateProfileString(section, key, value, filePath);
			}
		}
		
		public string Read(string section, string key) {
			StringBuilder retVal = new StringBuilder(255);
			GetPrivateProfileString(section, key, "", retVal, 255, filePath);
			return retVal.ToString();
		} 
		
		public bool Exists() { 
			return File.Exists(filePath); 
		}
		
	}

With this class, we can easily read and write INI files in C#. For example:

 
	IniFile ini = new IniFile("settings.ini");

 
	// Write some values
	ini.Write("General", "Name", "John");
	ini.Write("General", "Age", "25");
	ini.Write("Preferences", "Color", "Blue");
	ini.Write("Preferences", "Font", "Arial");

 
	// Read some values
	string name = ini.Read("General", "Name"); 
	string age = ini.Read("General", "Age"); 
	string color = ini.Read("Preferences", "Color"); 
	string font = ini.Read("Preferences", "Font"); 

We can also check if the INI file exists using the Exists method. For example:

 
	if (ini.Exists()) { 
		Console.WriteLine("INI file found."); 
	} else { 
		Console.WriteLine("INI file not found.");
	}

This is how we can read and write INI files in C# using the Windows API functions. For more information and examples on these functions, you can refer to these sources

•  #CSharp

•  #INIFiles

•  #WindowsAPI

•  #PInvoke

•  #Configuration

•  #Settings

•  #Programming

•  #Coding

•  #Tutorial

•  #HowTo

•  #DotNet

•  #Kernel32

•  #WritePrivateProfileString

•  #GetPrivateProfileString

•  #CodeExample style="color: red;">What's INI file?

• INI file is common system config files. 
• INI files are text files that store name=value pairs.
• INI files can be used to save basic user settings easily. 

This topic will be focus to how to read, write INI files in CSharp.

 

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I'm using two functions: Read, Write INI files

Read function:
- Using GetPrivateProfileStringAPI for get key values in INI files
- Using StringBuilder to stored value from file.

Write function:Using WritePrivateProfileString API for write key values in INI files

Source Code

 /* ************************************************************************
       * Author: VịLH - Zidane (huuvi168@gmail.com)
       * Last Modified: 20141215 
       * clsIniFile.cs
       * ************************************************************************
       */
      
      using System;
      using System.Collections.Generic;
      using System.Runtime.InteropServices;
      using System.Text;
      
      /* 
       * How to use: clsIniFile
       * 
       * --> Write file 
       * clsIniFile inif = new clsIniFile("D:\\config.ini");
       * inif.Write("Database", "Devs", "sa");
       * 
       * => [Database]
       *    Devs=sa;
       * 
       * --> Read file
       * clsIniFile inif = new clsIniFile("D:\\config.ini");
       * Console.WriteLine("The Value is:" + inif.Read("Database", "Devs"));
       * => sa
       * 
       */
      
      namespace IniFileCommons
      {
          public class clsIniFile
          {
              private string filePath;
               
              [DllImport("kernel32")]
              private static extern long WritePrivateProfileString(string section,
                                          string key,
                                          string val,
                                          string filePath);
       
              [DllImport("kernel32")]
              private static extern int GetPrivateProfileString(string section,
                                          string key,
                                          string def,
                                          StringBuilder retVal,
                                          int size,
                                          string filePath);
      
              public clsIniFile(string filePath)
              {
                  this.filePath = filePath;
              }
       
              public void Write(string section, string key, string value)
              {
                  WritePrivateProfileString(section, key, value.ToLower(), 
                      this.filePath);
              }
       
              public string Read(string section, string key)
              {
                  StringBuilder SB = new StringBuilder(255);
                  int i = GetPrivateProfileString(section, key, "", SB, 255, 
                      this.filePath);
                  return SB.ToString();
              }
               
              public string FilePath
              {
                  get { return this.filePath; }
                  set { this.filePath = value; }
              }
          }
      }
      

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