How To Filter First in Last Out record In LINQ-CodePudding

I have Data In List It is the employee's entry and exit information.

Datetime                 User_id              UserName              Tna
--------------------------------------------------------------------------------
2022-03-15 08:30:23      01                   John                  null
2022-03-15 09:43:40      01                   John                  null
2022-03-15 10:16:52      01                   John                  null
2022-03-15 13:45:23      01                   John                  null
2022-03-15 15:38:23      01                   John                  null
2022-03-15 17:36:23      01                   John                  null
2022-03-15 08:31:23      02                   Eva                   null
2022-03-15 10:16:52      02                   Eva                   null
2022-03-15 13:45:23      02                   Eva                   null
2022-03-15 15:38:23      02                   Eva                   null
2022-03-15 17:30:23      02                   Eva                   null

Information in List retrieved from API.

I would like to know how to filter the items in the list. First check-in and last check-out by filtering by time , How to get output like this using LINQ?

Datetime                 User_id              UserName              Tna
--------------------------------------------------------------------------------
2022-03-15 08:30:23      01                   John                  IN
2022-03-15 17:36:23      01                   John                  OUT
2022-03-15 08:31:23      02                   Eva                   IN
2022-03-15 17:30:23      02                   Eva                   OUT

CodePudding user response：

You may want group by person, then select first and last of each group.

Assumption
Every person has at least one in and out entry.

pseudocode

   var result = lst.GroupBy(x => x.User_id)
                   .Select(g => g.OrderBy(x => x.Datetime))
                   .Select(g => new[] { g.First() }.Concat(new[] { g.Last() }));