Good day! There's a question on vb forums on how to apply LINQ grouping and aggregate function sum to a datatable object. This can be achieved by familiarizing on IGrouping which is a key/value pair interface. Here's how i did it. VB.NET 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Dim dt As New DataTable( "tblEntTable" ) dt.Columns.Add( "ID" , GetType ( String )) dt.Columns.Add( "amount" , GetType ( Decimal )) dt.Rows.Add( New Object () { "1" , 100.51}) dt.Rows.Add( New Object () { "1" , 200.52}) dt.Rows.Add( New Object () { "2" , 500.24}) dt.Rows.Add( New Object () { "2" , 400.31}) dt.Rows.Add( New Object () { "3" , 600.88}) dt.Rows.Add( New Object () { "3" , 700.11}) Dim result = (From orders In dt.AsEnumerable Group orders By ID = orders.Field( Of String )( "ID" ) Into g = Group Select New With { Key ID, .Amount = g.Sum(Function(r) r