nedash says:
Line 573: decimal SeP1 = dtFiles.Rows[0][24];
Line 574: decimal SeP2 = dtFiles.Rows[0][28];
Line 575: decimal SeP3 = dtFiles.Rows[0][32];
Replace the above with the below code.
decimal SeP1 = Convert.ToDecimal(dtFiles.Rows[0][24]);
decimal SeP2 = Convert.ToDecimal(dtFiles.Rows[0][28]);
decimal SeP3 = Convert.ToDecimal(dtFiles.Rows[0][32]);