How to filter only last value in 2 columns grouping in LINQ C#-CodePudding

Lets say I have the following data:

EntryID     |      ColValueText
1113                20
1113                19
1024                20
1113                20
1024                21
1113                23

So In C# using LINQ or any method I want to filter the data like this

EntryID     |      ColValueText
1113               23
1024               21

That is: group by both columns but get only the last value of colvaluetext against each entryid. I am attaching my code but I am unable to get the last colvaluetext against entryid.

var groupSalesPersonData = (from  r in sp
                                    group r by new { r.EntryID, r.ColValueText } 
                                    into  results
                                    select new GroupByCommonDto
                                    {
                                        ParentGroupById = results.Select(a => a.EntryID).LastOrDefault(),
                                        FieldValue = results.Select(a => a.FieldValue).LastOrDefault(),
                                        Order = results.Sum(x => x.Order),
                                        VehicleProfit = results.Sum(x => x.VehicleProfit),
                                        ColValueText = results.Select(a => a.ColValueText).LastOrDefault()
                                    })
                                    .ToList();

CodePudding user response：

I wouldn't use Linq to solve this problem. You could potentially do it with Aggregate as this is an aggregation problem. I would use a simple foreach and a dictionary

CodePudding user response：

var groupSalesPersonData = (from  r in sp
                                group r by new { r.EntryID} 
                                into  results
                                select new GroupByCommonDto
                                {
                                    ParentGroupById = results.Select(a => a.EntryID).LastOrDefault(),
                                    ColValueText = results.Select(a => a.ColValueText).LastOrDefault() //Assuming this is a text value and you always want last in the collection.
                                })
                                .ToList();

ColValueText if this are numbers using the correct type with correct sort order give you always the right value