class SomeData
    {
        public string tabl_name;
        public decimal? zn_term;
        public decimal? zn_osn;
        public Int64? ko;
        public Int64? st;
        public Int16? gr;			
    }
	
static void PrintColumns(DataTable dt)
	{
		foreach (DataColumn column in dt.Columns)
		{
			column.Dump(column.ColumnName);
		}	
	}
	
static DataTable GetDataTable(SomeData[] sd)
        {
            DataTable table = new DataTable(); 
            table.Columns.Add("tabl_name",typeof(string));
            table.Columns.Add("zn_term",typeof(decimal));
            table.Columns.Add("zn_osn",typeof(decimal));
            table.Columns.Add("ko",typeof(Int64));
            table.Columns.Add("st",typeof(Int64));
            table.Columns.Add("gr",typeof(Int16));			
			
            foreach (SomeData d in sd)
            {
                table.Rows.Add(d.tabl_name, d.zn_term, d.zn_osn, d.ko, d.st, d.gr);
            }
            return (table);

        }	
		
void Main()
{
			SomeData[] samples = {
									new SomeData { tabl_name = "t1", zn_term = 12.589M, zn_osn = 34534.0M, ko = 10, st = 20, gr = 3},
									new SomeData { tabl_name = "t1", zn_term = 12.589M, zn_osn = 34534.0M, ko = 10, st = 20, gr = 3},
									new SomeData { tabl_name = "t1", zn_term = null, zn_osn = null, ko = 10, st = 20, gr = 3}
                                 };
								 					 
								
            DataTable dt_samples = GetDataTable(samples);	
			
			PrintColumns(dt_samples);
						
			IEnumerable query = (from t in dt_samples.AsEnumerable()
											group t by new { test1 = t.Field<string>("tabl_name"), test2 = t.Field<Int64?>("ko"), test3 = t.Field<Int64?>("st"), test4 = t.Field<Int16?>("gr") }
												into grp
												select new
												{
													grp.Key.test1,
													grp.Key.test2,
													grp.Key.test3,
													grp.Key.test4,
													Quantity1 = grp.Sum(t => t.Field<decimal?>("zn_term")),
													Quantity2 = grp.Sum(t => t.Field<decimal?>("zn_osn"))                                        
												}).ToList();			
			query.Dump();
			
}