c# - Using Linq to GroupBy and Sum datatable

Question

Hi, I have a Datatable like this:

Id             Amount 1        Amount 2        Amount 3  
1              2               2               2  
12             4               6               4  
12             6               6               5  
22             7               2               1  
22             7               2               2

I need to get my datatable like this:

Id             Amount 1        Amount 2        Amount 3  
1              2               2               2  
12             10              12              9    
22             14              4               3

I originally tried to do it in an anonymous method but I need to return it to another class which cannot be done with anonymous method. My second attempt was to do this so it can be returned:

DataTable ddt = dt.AsEnumerable()
        .Sum(g => g.Field<int>("Amount 1"))
        .GroupBy(g => new { Col1 = g["ID"] })
        .Select(g => g.OrderBy(r => r["ID"]).First())
        .CopyToDataTable();

This code definitely wont compile but Any help/advice if possible would be really appreciated. I'm very new to linq.

Answer 1

You can GroupBy first, then project the groups to DataRows, then create the DataTable using CopyToDataTable extension:

var newDt = dt.AsEnumerable()
              .GroupBy(r => r.Field<int>("Id"))
              .Select(g =>
              {
                  var row = dt.NewRow();

                  row["Id"] = g.Key;
                  row["Amount 1"] = g.Sum(r => r.Field<int>("Amount 1"));
                  row["Amount 2"] = g.Sum(r => r.Field<int>("Amount 2"));
                  row["Amount 3"] = g.Sum(r => r.Field<int>("Amount 3"));

                  return row;
              }).CopyToDataTable();