Linq/C#：从分组结果中选择项目并求和？

Question

我有一个这样的列表：

City   Total
Sydney 11
Dublin 9
London 12
Dublin 3
London 9
Sydney 12

I first of all need to Group By City & Sum Total so I have

Sydney 23
Dublin 12
London 21

接下来，我需要过滤那些总数 > 的条目。 20

Sydney 23
London 21

我最终需要的是这些条目的总数，例如 44

我真的想在 1 个 LINQ 语句中完成它，可能吗？

谢谢，

Answer 1

int cityTotals = cities
    .GroupBy(c => c.City)
    .Select(grp => new { City = grp.Key, Total = grp.Sum(c => c.Total) })
    .Where(c => c.Total > 20)
    .Sum(c => c.Total);

Answer 2

Lee 的几种替代方法：

int cityTotals = cities
    .GroupBy(c => c.City)
    .Select(grp => grp.Sum(c => c.Total))
    .Where(total => total > 20)
    .Sum();

或

int cityTotals = cities
    .GroupBy(c => c.City, (key, grp) => grp.Sum(x => x.Total))
    .Where(total => total > 20)
    .Sum();