Passing parameter to inline SqlCommand insert query using C# in ASP.Net

I later got the answer, see the answer below

protected void btnSave_Click(object sender, EventArgs e)
        {
            //   string name = ddlcustomername.Text.Trim();
            // string address = customeraddress.Text.Trim();
            string productName = ddlProducts.SelectedItem.Text.Trim();
            string name = ddlcustomername.SelectedItem.Text.Trim();
            string address = ddlcustomeraddress.SelectedItem.Text.Trim();
            decimal unitPrice = Convert.ToDecimal(lblProductPrice.Text.Trim());
            int availableQuantity = Convert.ToInt32(lblQuantityAvailable.Text.Trim());
            int quantity = Convert.ToInt32(txtQuantity.Text.Trim());
            int inserted = 0;

            //  int availableInventoryQty = AvailableInventoryQty();
            if (lblProductPrice.Text.Length > 0 && txtQuantity.Text.Length > 0)
            {

                double stock = Convert.ToDouble(txtQuantity.Text);
                double customerqty = Convert.ToDouble(txtQuantity.Text);
                double tqty = stock - customerqty;
                double gqty = tqty;
                {
                    if (lblProductPrice.Text.Length > 0 && txtQuantity.Text.Length > 0)
                    {

                        double unitprice2 = Convert.ToDouble(lblProductPrice.Text);
                        double customerqty2 = Convert.ToDouble(txtQuantity.Text);
                        double grandtotal = unitprice2 * customerqty;
                        double total = grandtotal;
                        {
                            // if (txtunitprice.Text.Length > 0 && txtdiscount.Text.Length > 0)
                            {

                                //   double unitprice = Convert.ToDouble(txtunitprice.Text);
                                // double discount = Convert.ToDouble(txtdiscount.Text);
                                // double sum = grandtotal - discount;
                                //  double sumb = sum;




                                if ((availableQuantity != 0) && (quantity != 0) && (quantity < availableQuantity))
                                {
                                    using (SqlConnection con = new SqlConnection())
                                    {
                                        con.ConnectionString = str;
                                        using (SqlCommand cmd = new SqlCommand())
                                        {
                                            cmd.CommandType = CommandType.Text;
                                            cmd.Connection = con;
                                            //Change the query like below
                                            //Make sure the column name matches the with the name provided in code as per your table
                                            cmd.CommandText = "INSERT INTO Sells (UserName,CustomerName,ProductName,Ordered,UnitPrice,TotalAmount,OrderDate) VALUES(@UserName,@CustomerName,@ProductName,@Ordered,@UnitPrice,@TotalAmount,@OrderDate)";
                                            cmd.Parameters.AddWithValue("@UserName", Session["userName"]);
                                            cmd.Parameters.AddWithValue("@CustomerName", ddlcustomername.Text.Trim());
                                            cmd.Parameters.AddWithValue("@ProductName", ddlProducts.Text.Trim());
                                            cmd.Parameters.AddWithValue("@Ordered", txtQuantity.Text.Trim());
                                            cmd.Parameters.AddWithValue("@UnitPrice", lblProductPrice.Text.Trim());
                                            cmd.Parameters.AddWithValue("@TotalAmount", grandtotal);
                                            cmd.Parameters.AddWithValue("@OrderDate", DateTime.Today);
                                            con.Open();
                                            inserted = cmd.ExecuteNonQuery();
                                            con.Close();
                                        }
                                    }
                                }
                                else
                                {
                                    ClientScript.RegisterClientScriptBlock(this.GetType(), "", "alert('No of Quantity entered is not available in Stock')", true);
                                }
                            }
                        }
                    }
                }
            }
        }

 cmd.CommandText = "INSERT INTO Sells (UserName,CustomerName,ProductName,Ordered,UnitPrice,TotalAmount,OrderDate) VALUES(@UserName,@CustomerName,@ProductName,@Ordered,@UnitPrice,@TotalAmount,@OrderDate)";