LEFT JOINS and DefaultIfEmpty Operator in LINQ

Suppose you have a tblRoom and tblUserInfo. Now, you need to select all the rooms regardless of whether the room has user information or not. This calls for a LEFT JOIN which will select everything from the LEFT side (the room side) regardless of the join on the right side. Here is the example.

 var list = from r in dc.tblRooms
                           join ui in dc.tblUserInfos
                           on r.UserName equals ui.UserName into userrooms
                           where r.CourseID == 1848

                           from ur in userrooms.DefaultIfEmpty()

                           select new
                           {
                               FirstName = (ur.FirstName == null) ? "N/A" : ur.FirstName,
                               LastName = (ur.LastName == null) ? "N/A" : ur.LastName,
                               RoomName = r.Name
                              
                           };

The anonymous type replaces the "null" FirstName and LastName with "N/A" (not available).