Learning-design-patterns-singleton-logger.cs

public class Logger
{
  public void Success(string message)
  {
    Console.Write($"SUCCESS {message}");
  }
  public void Error(string message)
  {
    Console.Write($"ERROR {message}");
  }
}

public class SingletonLogger {
  private Logger instance = null;
  private Logger CreateInstance() => new Logger();
  public Logger GetInstance()
  {
    if (this.instance == null)
    {
      this.instance = this.CreateInstance();
    }

    return this.instance;
  }
}