C# LINQ to DATASET Grouping with a total -

i have datatable in data set. table has 3 columns , not grouped.

 table1  field1  string  field2  datetime  field3  decimal 

i need grouped on field1, field2, totaled on field3

tring accomplish in linq results not coming out correctly.

i want original data table in dataset (in foreach?) if not possible know easy remove/add table.

here have far not quite working;

  var newsort = row in objecttable.asenumerable()         group row new {                 fullname = row.field<string>("fullname"),                attenddate = row.field<datetime>("attenddate"),          } grp         select new              {              fullname = grp.key.fullname,              attenddate = grp.key.attenddate,              sumdayshours = grp.sum(r => r.field<double>("dayshours"))               };    foreach (var row in newsort)         {             dstemp.tables["groupeddata"].rows.add(fullname, row.attenddate, row.sumdayshours);         }