Provider pattern

public static class Note 
{
  private static NoteProvider provider; 
  static Note() 
  {
    string providerName = ConfigurationManager.AppSettings["noteProvider"]; 
    Type providerType = Type.GetType(providerName); 
    provider = (NoteProvider)Activator.CreateInstance(providerType); 
  }
  public static string GetNote() 
  {
    return provider.GetNote(); 
  }
}
 
public abstract class NoteProvider 
{
  public abstract string GetNote(); 
}
 
public class FirstNoteProvider : NoteProvider 
{
  public override string GetNote() 
  {
    return "első note"; 
  }
}
 
  
public class SecondNoteProvider : NoteProvider
{
  public override string GetNote() 
  {
    return "második note"; 
  }
}