LINQ return expression if expression does not match

Question

I'm not sure the title explains the problem well, so here is the code. I want to return an anonymous object to bind my grid to. In that grid, I want to change usernames to fullnames, but only if I HAVE the fullname to match the username. In the query below, I get CreatedFullname IF CreatedUsername exists in userModels. If it does not exists then I don't get the record at all. What I wnat is to get the record, show UserFullname if it is available in userModels, if it is not I want to return x.CreatedUsername.

var inf = (from ev in db.Events
       where (ev.StartDate >= beginDate && ev.StartDate <= endDate)
       orderby ev.StartDate descending
       select new
       {
           EventID = ev.EventID,
           EventTitle = ev.Title,
           EventDate = ev.StartDate,
           StudentCount = ev.EventStudents.Count(),
           CreatedUsername = ev.CreatedUsername
           }).AsEnumerable().Select(x => new {EventID = x.EventID,
                                    EventTitle = x.EventTitle,
                                    EventDate = x.EventDate,
                                    StudentCount = x.StudentCount,
                                    CreatedUsername = x.CreatedUsername,
                                    CreatedFullname = 
                                      userModels.Where(u => u.Username == x.CreatedUsername).FirstOrDefault().UserFullName
            });

userModels is a custom object that has Username, UserFullname, Department, etc. It was collected from ActiveDirectory on pageload, based on beginDate and endDate.

p.s.w.g · Accepted Answer · 2013-06-07T00:41:03.080

You can do this:

CreatedFullname = 
    userModels.Where(u => u.Username == x.CreatedUsername)
              .Select(x => x.UserFullName)
              .FirstOrDefault() ?? x.CreatedUsername

Or this:

var inf = 
    (from x in
        (from ev in db.Events
         where (ev.StartDate >= beginDate && ev.StartDate <= endDate)
         orderby ev.StartDate descending
         select new
         {
             EventID = ev.EventID,
             EventTitle = ev.Title,
             EventDate = ev.StartDate,
             StudentCount = ev.EventStudents.Count(),
             CreatedUsername = ev.CreatedUsername
         })
         .AsEnumerable()
     let model = userModels.FirstOrDefault(u => u.Username == x.CreatedUsername)
     select new 
     {
         EventID = x.EventID,
         EventTitle = x.EventTitle,
         EventDate = x.EventDate,
         StudentCount = x.StudentCount,
         CreatedUsername = x.CreatedUsername,
         CreatedFullname = (model != null)
             ? x.modelUserFullName 
             : x.CreatedUsername
     });

LINQ return expression if expression does not match

1 Answers1