List becomes empty when ordered

List becomes empty when ordered

I have the following method:
public List<Vehicle> Vehicles
{
get { return _vehicles; }
}
Which will return data. If I do the following;
public List<Vehicle> Vehicles
{
get { return _vehicles.OrderBy(v => v.Year).ToList(); }
}
It becomes empty. If I call the orderby outside this method myList =
vehicleList.Vehicles.OrderBy(x => x.Year) the list will contain all needed
data.
I am confused as to why.