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         


        

Answer 1

You are making your calls out of order. The code below wont put the data into a table, but it will give you data you could put into a table easily.

dt.AsEnumberable()
    .GroupBy(g => g["ID])
    .Select(g => new {
        Id = g.Key, 
        Amount1 = g.Sum(s => s.Amount1), 
        Amount2 = g.Sum(s => s.Amount2), 
        Amount3 = g.Sum(s => s.Amount3)});

Answer 2

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();

Answer 3

This works for me. A slight Change to Arturo's code to help with cast issues if you have decimal values and use a datatable as a datatable not a variable. (Note that r[15] is the column you will be summing)

                  dt = dt.AsEnumerable()
                    .GroupBy(r => r["fldReportCode"])
                    .Select(g =>
                     {
                        var row = dt.NewRow();

                      row["fldReportCode"] = g.Key;
                      row[15] = g.Sum(r => (decimal)r[15]);
                      //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();