Linq Query on Group By and Sum

[ppr (Peter Preuss)]

@tmond
Welcome to the forum

We can do it with folloing flow:

(From d In dtData.AsEnumerable
Group d By k=d("Col3").toString.Trim Into grp=Group
Let gs = grp.Sum(Function (x) CInt(x("Col2").toString))
Let raa = grp.Select(Function (g,i) If(i=0,g.ItemArray.Append(gs).toArray,g.ItemArray.Append(Nothing).toArray)).toarray
From m In raa
Select dtResult.Rows.Add(m)).CopyToDataTable

And will get:

Find starter help here:
GroupBy_1Col_AddSumToFirstMember.xaml (9.0 KB)

Also have a look here:

[HowTo] Overview on different options for grouping data and processing the groups

This HowTo introduces on the different options for grouping data from a datatable in order to process the grouped data. Introduction Grouping data and processing the grouped data is a common scenario e.g. when the grouped data is to aggregate like summing up, find maximum, get the average or concatening items. Lets have a look on following data: [grafik] A possible scenario could be: Create a report containing following information: the region code the sum of CaseCount per RegionCode t…