c# - Perform calculations on a set using only LINQ

Question

I'd like to perform the following using only LINQ.

I have a list of time sheet entries with user's in and out times. The class looks like this:

public class TimeSheetLog
{
   public Guid EmployeeId { get; set; }
   public DateTime ClockInTimeStamp { get; set; }
   public DateTime ClockOutTimeStamp { get; set; }
}

I'm passing a List<TimeSheetLog>() which contains all logs from the beginning of the year to date.

I'm trying to calculate the total work time -- regardless of employee -- for the month of January. Please also notice that I have a function named GetTimeDifferenceInMinutes() which calculates the number of minutes between two date/time values.

Here's what I currently have but I feel the whole thing can be done using LINQ only.

public static int GetTotalTimeWorked(List<TimeSheetLog> logs, DateTime startDate, DateTime endDate)
{
   // I'm passing 1/1/2018 for startDate and 1/31/2018 for endDate to this function
   var totalTimeWorkedInMinutes = 0;

   var januaryLogs = logs.Where(x => x.ClockInTimeStamp >= startDate && 
   x.ClockOutTimeStamp <= endDate);

   foreach(var item in januaryLogs)
   {
      totalTimeWorkedInMinutes += GetTimeDifferenceInMinutes(item.ClockInTimeStamp, itemClockOutTimeStamp);
   }

   return totalTimeWorkedInMinutes;
}

Answer 1

var logsFilteredByDate = logs.Where(x => x.ClockInTimeStamp >= startDate &&
    x.ClockOutTimeStamp <= endDate);
var totalTimeWorkedInMinutes = logsFilteredByDate.Sum(x => 
    GetTimeDifferenceInMinutes(x.ClockInTimeStamp, x.ClockOutTimeStamp));

Or, to combine it all into one query, which is unnecessary and harder to read,

var totalTimeWorkedInMinutes = logs.Where(x => x.ClockInTimeStamp >= startDate &&
    x.ClockOutTimeStamp <= endDate)
    .Sum(x => 
        GetTimeDifferenceInMinutes(x.ClockInTimeStamp, x.ClockOutTimeStamp));