Input string was not in a correct format. Filtering from combobox

public partial class Form1 : Form
     {

        public ProductsBL productBL;
        public ArrayList prodList;
        ArrayList list;
        public Form1()
        {
            InitializeComponent();
             productBL = new ProductsBL();
             prodList = new ArrayList();
             prodList = productBL.getProducts();
             
             dataGridView1.DataSource = prodList;
             dataGridView1.Columns[0].Visible = false;
             prodList = productBL.loadComboboxProductID();
             comboBox1.DataSource = prodList;
             //prodList = new ArrayList();
            
        }
    }
   private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            Products products = productBL.getSpecificProducts(Convert.ToInt32 
            (comboBox1.SelectedValue));
            dataGridView1.DataSource = products;

        }

Below is my Business Layer


 public Products getSpecificProducts(int productID)
        {
            using (SqlConnection con = new SqlConnection(ConnectionString))
            {
                SqlCommand cmd = new SqlCommand("procGetSingleRowOnProducts", con);
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.Add(new SqlParameter("@productID", SqlDbType.Int));
                cmd.Parameters["@productID"].Value = productID;
                
                con.Open();
                SqlDataReader reader = cmd.ExecuteReader();
                reader.Read();
                               
                    Products products = new Products(Convert.ToInt32(reader["ProductID"]), Convert.ToString(reader["productName"]), Convert.ToInt32(reader["supplierID"]), Convert.ToInt32(reader["categoryID"]), Convert.ToString(reader["quantityPerUnit"]), Convert.ToDouble(reader["unitPrice"]), Convert.ToInt16(reader["UnitsInStock"]), Convert.ToInt16(reader["UnitsOnOrder"]), Convert.ToInt16(reader["ReorderLevel"]), Convert.ToBoolean(reader["Discontinued"]));
                    
                               return products;
            }//End 
        }