C#

private Extension {...}
 
public ExtensionForm
{
   public AddExtension(Extension myExt) {...}
}

public class MyFile
{
   private string artist;
   private string album;
   private string year;
   private string song;
 
   public MyFile()
   {
   }
 
   public string Artist
   {  
      get
      {
          return this.artist;
      }
      set
      {
          this.artist = value;
      }
   }
 
   public string Album
   {  
      get
      {
          return this.album;
      }
      set
      {
          this.album = value;
      }
   }
 
   public string Year
   {  
      get
      {
          return this.year;
      }
      set
      {
          this.year = value;
      }
   }
 
   public string Song
   {  
      get
      {
          return this.song;
      }
      set
      {
          this.song = value;
      }
   }
}

   System.IO.TextReader reader = new System.IO.TextReader(Application.StartupPath + "\\myfile.txt");
   try
   {
      MyFile customClass = new MyFile(); //Create an instance of the custom class above

      while(true)
      {
         string line = reader.ReadLine();
         if(line == null) //End of file
         {
             break;
         }
         ParseText(line,ref customClass);
      }
   }
   finally
   {
      if(reader != null)
      {
         reader.Close(); //Don't forget to ALWAYS close the file
      }
   }
 
   //Now customClass should be populated with all of the values from the file

public void ParseText(string text, ref MyFile customClass) //Parse the text and fill the MyFile attr
{
      if(customClass == null)  // Make sure it's been instantiated
      {
          customClass = new MyFile();
      }
      if(text.IndexOf(":") > -1) //Make sure this is a line we should read
      {
          string[] temp = text.Split(':');
          if(temp.Length > 1) //Make sure we have at least two values
          {
              select(temp[0].Trim().ToLower()) //Lets check on the left value with no whitespace and as lowercase
              {
                   case "artist":
                      customClass.Artist = temp[1];
                      break; // In c# you MUST break each case unless you want it to trickle down
                                    
                   case "album":
                      break; // In c# you MUST break each case unless you want it to trickle down
                      customClass.Album = temp[1];
 
                   case "year":
                      break; // In c# you MUST break each case unless you want it to trickle down
                      customClass.Year = temp[1];
 
                   case "song":
                      break; // In c# you MUST break each case unless you want it to trickle down
                      customClass.Song = temp[1];
              }
          }
      }
 
}