How can I edit an .ini file passing the data through a textbox?

public class IniFile
{
	private readonly string _inifile;

	[DllImport("kernel32", CharSet = CharSet.Unicode)]
	private static extern int GetPrivateProfileString(string section, string key,
		string defaultValue, StringBuilder value, int valueSize, string filepath );

	public IniFile( string inifile )
	{
		_inifile = new FileInfo( inifile ).FullName;
	}

	public string Read( string section, string key )
	{
		var value = new StringBuilder(255);
		GetPrivateProfileString( section, key, "", value, 255, _inifile );
		return value.ToString();
	}

	public bool KeyExists(string section, string key )
	{
		return Read(section, key ).Length > 0;
	}
}