Linq Groupby 不在c#分组

Question

Below i have a snippet of code which outputs a list of Appointments based on clients, some clients can have more than one appointment but the latest one is the one that needs to be outputted for said client

the output is not grouping at all and for some reason i cannot figure why the heck not

foreach (ClientRecord client in clients)
                {
                    List<ReturnRecord> records = db.Appointments
                        .AsNoTracking()
                        .Include(rec => rec.Property)
                        .Include(rec => rec.Property.Address)
                        .Include(rec => rec.AppointmentType)
                        .ToList()
                        .Where(rec => rec.ClientID == client.ID)
                        .Select(rec => new ReturnRecord
                        {
                            ClientName = $"{client.FirstNames} {client.Surnames}",
                            PropertyAddress = $"{rec.Property.Address.FormattedAddress}",
                            AppStatus = $"{rec.AppointmentStatus.Name}",
                            StockStatus = $"{rec.Property.Stocks.FirstOrDefault().StockStatus.Name}",
                            LastUpdated = rec.LastUpdated
    
                        })
                        .ToList();
    
                    returnList.AddRange(records);
    
                }
                returnList.GroupBy(rec => rec.PropertyAddress);
    
                return Ok(returnList);

here is an attachment of the screen grab of the output

Answer 1

You need to assign result of GroupBy() to variable:

returnList = returnList.GroupBy(rec => rec.PropertyAddress).ToList();

Answer 2

Make sure to actually use the new IEnumerable that the .GroupBy() Method returned.

If you want to return a List you need to use a workaround:

1. Get the IEnumerable<IGrouping<int, ReturnRecord>> from the .GroupBy()
2. Use .SelectMany() to select all elements and save them into an IEnumerable
3. Now you can convert your IEnumerable into a List with .List()

Example:

// Longer Alternative
IEnumerable<IGrouping<int, ReturnRecord>> groups = resultList
    .GroupBy((rec => rec.PropertyAddress);
IEnumerable<ReturnRecord> result = groups.SelectMany(group => group);
List<ReturnRecord> listResult = result.ToList();
return Ok(listResult);

// Shorter Alternative
IEnumerable<IGrouping<int, ReturnRecord>> groups = resultList
    .GroupBy((rec => rec.PropertyAddress);
IEnumerable<ReturnRecord> result = groups.SelectMany(group => group);
return Ok(result.ToList());