C#

public struct Header
{
  public int count;
  public FileHeader[] headers;
}
public struct FileHeader
{
  public string Filename;
  public long Offset;
  public long Length;
}

[DllImport("wininet.dll")]
public static extern bool InternetGetConnectedState(out int flags, int reserved);

int flags;
if (InternetGetConnectedState(out flags, 0))
{
  // Make your connection.
}

public sealed class Singleton
{
  private static Singleton instance;
 
  private Singleton() {}
  // Makes sure that only one instance exists.
  private static Singleton Instance
  {
    get
    {
      // Thread-safe initialization.
      if (instance == null)
        lock (typeof(Singleton))
          if (instance == null)
            instance = new Singleton();
      return instance;
    }
  }
  private void doSomething()
  {
    Console.WriteLine("Something done.");
  }
  public static void DoSomething()
  {
    Instance.doSomething();
  }
}

if (instance == null)
  lock (typeof(Singleton))
    if (instance == null)
      instance = new Singleton();