linqtosql，时间跨度，聚合..能做到吗

SELECT City, SUM(DATEDIFF(minute,StartDate,Completed)) AS Downtime
FROM Incidents
GROUP BY City

using System.Data.Linq.SqlClient;

db.Incidents
  .GroupBy(i => i.City)
  .Select(g => new
  {
    City = g.Key,
    DownTime = g.Sum(i => SqlMethods.DateDiffMinute(i.StartDate, i.Completed))
  });