Distinct Records

Question

Hi

In below linq query i want to get only distinct records

public List<View_SessionDeliveryCalendarDetails_Student> GetStudentsByMentor(Int32 MentorId)
        {
            List<View_SessionDeliveryCalendarDetails_Student> Result = (from t in context.View_SessionDeliveryCalendarDetails_Students
                                                                        where (MentorId != 0 ? t.MentorID == MentorId : 1 == 1)
                                                                        select t).ToList();
            
            return Result;
        }

Thanks

Jignesh Kumar · Answer

Hello Ramco, Have you created below as extension method and build your solution, public static IEnumerable DistinctBy (this IEnumerable source, Func keySelector) { HashSet seenKeys = new HashSet (); foreach (TSource element in source) { if (seenKeys.Add(keySelector(element))) { yield return element; } } } And try below one after that, public List GetStudentsByMentor(Int32 MentorId) { List Result = (from t in context.View_SessionDeliveryCalendarDetails_Students where (MentorId != 0 ? t.MentorID == MentorId : 1 ==1) select t).DistinctBy(d => new { d.StudentId }).ToList(); return Result; }

Jignesh Kumar · Answer

Hello Ramco, If you want to do distinct by multiple column then you can create extention method as below, public static IEnumerable DistinctBy (this IEnumerable source, Func keySelector) { HashSet seenKeys = new HashSet (); foreach (TSource element in source) { if (seenKeys.Add(keySelector(element))) { yield return element; } } } You can use as below in your code, public List GetStudentsByMentor(Int32 MentorId) { List Result = (from t in context.View_SessionDeliveryCalendarDetails_Students where (MentorId != 0 ? t.MentorID == MentorId : 1 ==1) select t).DistinctBy(d => new { d.MentorId, d.MentorName }).ToList(); return Result; }

Amit Mohanty · Answer

Try this public List GetStudentsByMentor(Int32 MentorId) { List Result = (from t in context.View_SessionDeliveryCalendarDetails_Students where (MentorId != 0 ? t.MentorID == MentorId : 1 == 1) select t).Distinct().ToList(); return Result; }

Ramco Ramco · Answer

Hi Jignesh It is givine error DistinctBy does not exist in current context. I want distinct by Student id. I want to display studentid,name,mobileno Thanks

Ramco Ramco · Answer

Hi It is giving error - Cannot implicitly convert system.collections.gereric.list to system.collections.gereric.list public List GetStudentsByMentor(Int32 MentorId) { List Result = (from t in context.View_SessionDeliveryCalendarDetails_Students where (MentorId != 0 ? t.MentorID == MentorId : 1 == 1) select t.StudentID).Distinct().ToList(); foreach (View_SessionDeliveryCalendarDetails_Student item in Result) { item.Name = item.Name + " - " + item.MobileNo; } return Result; } Thanks

Amit Mohanty · Answer

public List GetDistinctStudentIdsByMentor(int mentorId) { var result = (from t in context.View_SessionDeliveryCalendarDetails_Students where (mentorId != 0 ? t.MentorID == mentorId : 1 == 1) select t.StudentID).Distinct().ToList(); return result; }

Ramco Ramco · Answer

Hi Amit Sorry i want distinct to be by StudentId Thanks