input string was not in a correct format error

try
            {
                //Declaration
                string desc, aType, loc, manuf, bay, model, condtn, vendor, notes, status;
                int serialNo, aCode;
                DateTime warrantyExpiry, dateOfPurchase;

                //Assigning the values with variables
                desc = Convert.ToString(textBoxDesc.Text);
                aType = Convert.ToString(comboBoxAType.SelectedItem);
                loc = Convert.ToString(comboBoxLocation.SelectedItem);
                manuf = Convert.ToString(textBoxManuf.Text);
                bay = Convert.ToString(textBoxBay.Text);
                model = Convert.ToString(textBoxModel.Text);
                condtn = Convert.ToString(comboBoxCondition.SelectedItem);
                vendor = Convert.ToString(comboBoxVendor.SelectedItem);
                notes = Convert.ToString(textBoxNotes.Text);
                status = Convert.ToString(comboBoxStatus.SelectedItem);
                //Date time Variables
                warrantyExpiry = dateTimePickerWarranty.Value.Date;
                dateOfPurchase = dateTimePickerDOP.Value.Date;

                serialNo = Convert.ToInt32(textBoxSerialNo.Text);
                
                if (rdBtnAutomatic.Checked == true)
                {
                    aCode = 123;
                    textBoxAcode.ReadOnly=true;
                }
                else if (rdBtnManual.Checked == true)
                {
                    textBoxAcode.ReadOnly = false;
                    textBoxAcode.BackColor = Color.White;
                    aCode = Convert.ToInt32(textBoxAcode.Text);
                }
                else { aCode = 1; }

                con.Open();
                OleDbCommand cmd = new OleDbCommand("INSERT INTO Assets(Description,AssetType,Location,Manufacturer,Bay,Model,SerialNumber,Status,Condition,WarrantyExpiry,AssetCode,Dateofpurchase,Vendor,Notes,Picture) VALUES(@Description,@AssetType,@Location,@Manufacturer,@Bay,@Model,@SerialNumber,@Status,@Condition,@WarrantyExpiry,@AssetCode,@Dateofpurchase,@Vendor,@Notes,@Picture)", con);

                //Saving the image                
                MemoryStream memoryStream = new MemoryStream();
                pictureBoxAssets.Image.Save(memoryStream, System.Drawing.Imaging.ImageFormat.Jpeg);
                byte[] imgArray = new byte[memoryStream.Length];
                memoryStream.Read(imgArray, 0, imgArray.Length);

                cmd.Parameters.AddWithValue("@Description", desc);
                cmd.Parameters.AddWithValue("@AssetsType", aType);
                cmd.Parameters.AddWithValue("@Location", loc);
                cmd.Parameters.AddWithValue("@Manufacturer", manuf);
                cmd.Parameters.AddWithValue("@Bay", bay);
                cmd.Parameters.AddWithValue("@Model", model);
                cmd.Parameters.AddWithValue("@SerialNumber", serialNo);
                cmd.Parameters.AddWithValue("@Status", status);
                cmd.Parameters.AddWithValue("@Condition", condtn);
                cmd.Parameters.AddWithValue("@WarrantyExpiry", warrantyExpiry);
                cmd.Parameters.AddWithValue("@AssetCode",aCode);
                cmd.Parameters.AddWithValue("@Dateofpurchase", dateOfPurchase);
                cmd.Parameters.AddWithValue("@Vendor", vendor);
                cmd.Parameters.AddWithValue("@Notes", notes);
                cmd.Parameters.AddWithValue("@Picture", imgArray);


                int result = cmd.ExecuteNonQuery();

                if (result == 1)
                {
                    MessageBox.Show("Successfull");
                }
                else
                    MessageBox.Show("Notsuccessfull");
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }