问加速性能- LINQ可以获取一个列表中的项目，而不是另一个列表中的项目

EN

var hashSet = new HashSet<T>(ListTwo.Select(x => Tuple.Create(x.EmployeeNum, x.Sched)));
var results = ListOne.Where(x => !hashSet.Contains(Tuple.Create(x.EmployeeNum, x.Sched)));

var results = ListTwo.Except(ListOne, new EmployeeComparer());

public class EmployeeComparer : IEqualityComparer<Employee>
{
    public int GetHashCode(Employee co)
    {
        if (co == null)
        {
            return 0;
        }

        return co.EmployeeNum.GetHashCode();
    }

    public bool Equals(Employee x1, Employee x2)
    {
        if (object.ReferenceEquals(x1, x2))
        {
            return true;
        }

        if (object.ReferenceEquals(x1, null) || object.ReferenceEquals(x2, null))
        {
            return false;
        }

        return x1.EmployeeNum == x2.EmployeeNum && x1.Sched == x2.Sched;
    }
}

var Results = ListOne.AsParallel().Where(x => ListTwo.All(a => a.EmployeeNum != x.EmployeeNum && a.Sched != x.Sched)).ToList();