好的，如果你需要跨日期或多个日期的工作段，这个答案需要更多的工作。这里假设所有的工作段都在同一天。
以下代码按员工对所有段进行分组，然后将每个段的总分钟数相加。然后，仅当最后一个段在午夜结束时才返回总分钟数。
此测试代码返回以下内容：

Staff A: 15
Staff B: 20
Staff C: 0
Staff D: 2

下面是代码：

void Main()
{
    var segments = GetTestData();
    DateTime midnight = DateTime.Now.AddDays(1).Date;
    var results = segments
        .GroupBy(s => s.Name)
        .Select(grp => 
            new {
                Name = grp.Key, 
                Total = grp.Max(g => g.EndDate) == midnight 
                    ? grp.Sum(g => g.EndDate.Subtract(g.StartDate).TotalMinutes) 
                    : 0
            });

    foreach (var result in results)
    {
        Console.WriteLine($"{result.Name}: {result.Total/60F:#,##0}");
    }
}

class Segment
{
    public string Name { get; set; }
    public DateTime StartDate { get; set; }
    public DateTime EndDate { get; set; }
}

Segment[] GetTestData()
{
    return new[]
    {
        new Segment { Name = "Staff A", StartDate = new DateTime(2023, 1, 18, 9 , 0, 0), EndDate = new DateTime(2023, 1, 18, 15, 0, 0) },
        new Segment { Name = "Staff A", StartDate = new DateTime(2023, 1, 18, 15, 0, 0), EndDate = new DateTime(2023, 1, 18, 22, 0, 0) },
        new Segment { Name = "Staff A", StartDate = new DateTime(2023, 1, 18, 22, 0, 0), EndDate = new DateTime(2023, 1, 19, 0 , 0, 0) },
        new Segment { Name = "Staff B", StartDate = new DateTime(2023, 1, 18, 3 , 0, 0), EndDate = new DateTime(2023, 1, 18, 21, 0, 0) },
        new Segment { Name = "Staff B", StartDate = new DateTime(2023, 1, 18, 22, 0, 0), EndDate = new DateTime(2023, 1, 19, 0 , 0, 0) },
        new Segment { Name = "Staff C", StartDate = new DateTime(2023, 1, 18, 3 , 0, 0), EndDate = new DateTime(2023, 1, 18, 21, 0, 0) },
        new Segment { Name = "Staff D", StartDate = new DateTime(2023, 1, 18, 22, 0, 0), EndDate = new DateTime(2023, 1, 19, 0 , 0, 0) }
    };
}