Hi Guys I have done this with the help of one of my friend &
appreciate 'Ron Bayer' guidance.
for (int nIndex = 0; nIndex < FilterData.Length; nIndex += 3)
{
DataRow drow = dt.NewRow();
drow["ProductItem"] = FilterData[nIndex];
var cost = FilterData[nIndex + 1];
var qty = FilterData[nIndex + 2];
drow["Cost"] = cost;
drow["Quantity"] = qty;
double Total =
Convert.ToDouble(cost.Remove(cost.Length - 1)) *
Convert.ToInt32(qty);
drow["Total"] = Total;
dt.Rows.Add(drow);
}