Grouping of Data from DataTable and Assign to GridView

var result = dtTable.AsEnumerable().GroupBy(c => c.Field < string > ("GroupbyField")).Select(g => new
{
    GroupbyField = g.Key,
        SumField1 = g.Sum(c => Convert.ToDecimal(c.Field < string > ("Field1"))).ToString("N0"),
        SumField2 = g.Sum(c => Convert.ToDecimal(c.Field < string > ("Field2"))).ToString("N0"),
});
DataTable dtSummary = new DataTable();
dtSummary.Columns.Add("Column1");
dtSummary.Columns.Add("Column2");
dtSummary.Columns.Add("Column3");
using(var enumerator = result.GetEnumerator())
{
    while (enumerator.MoveNext())
    {
        dtSummary.Rows.Add(enumerator.Current.GroupbyField, enumerator.Current.SumField1, enumerator.Current.SumField2);
    }
}
GridView1.DataSource = dtSummary;
GridView1.DataBind();