Question

My Log class has 2 properties.

List<LogDetails>
string Title

And my LogDetails class has 2 properties:

string Message
LogStatus LogStatus  //enum

During this objects life time, it receives many messages which are stored for logging at a later stage. The LogStatus Enum has a few states, but simply it is either “in progress”, “file not found error”, “success” or “failed”.

I am trying to use Linq to match only those which failed, but I can’t build the new type.

List<Log> filteredLogs = (from a in logs
                          from b in a.LogDetailsList
                          where b.Status == LogDetails.LogStatus.Failed
                          select new Log()
                                  {
                                     Title = a.Title,
                                     LogDetailsList = a.LogDetailsList
                                  }).Distinct().ToList();

My filteredLogs returns to me the full list as if the where clause hadn’t worked.

I tried

 List<Log> filteredLogs = (from a in logs
                           from b in a.LogDetailsList
                           where b.Status == LogDetails.LogStatus.Failed
                           select new Log()
                                  {
                                       Title = a.Title,
                                       LogDetailsList = new LogDetails() { Message = b.Message, Status = b.Status }
                                  }).Distinct().ToList();

This doesn’t work either as it appears I can’t call the ToList() method from within the Linq query.

EDIT

Does any one have any suggestions on how to overcome this issue? My goal is to have a List which only lists those which failed.

Answer 1

Use Enumerable.Any on your “nested” LogDetails list.

List<Log> failedLogs = logs
            .Where(l => l.LogDetails.Any(ld => ld.LogStatus==LogStatus.Failed))
            .ToList();

This returns all logs where at least one log-detail has LogStatus.Failed.

Here’s a Demo.