sum problem of decimal value

Question

I am getting output for single number when I use decimal value then the following code does not work. Please help me.

 

string Charge = (Convert.ToInt32(_product.Where(x => x.SoinikNo.ToLower() == row.Cells[2].Value.ToString().ToLower()).Select(x => x.Charge).FirstOrDefault()) + Convert.ToInt32(row.Cells[21].Value.ToString())).ToString();