Project project = ...
OccNbInsulator occurrence = ...

ActiveLibraryConnection activeLibrary = null;
try
{
	activeLibrary = project.ActiveConnection;
	if (activeLibrary == null)
	{
		Console.WriteLine("The active library is not available.");
	}
	else
	{
		HatchInfo hatch = activeLibrary.GetHatches().FirstOrDefault(h => h.Name.Value == "My favourite hatch");
		if (hatch == null)
		{
			Console.WriteLine("Active library does not contain this hatch.");
		}
		else
		{
			occurrence.Hatch = hatch;
		}
	}
}
catch (API.Exceptions.NoActiveLibraryException ex)
{
	Console.WriteLine("There is no active library connection in this project.");
}