小白求教，在将 varchar 值转换成数据类型 int 时失败。该如何处理

SqlConnection conn = new SqlConnection("server=.\\sqlexpress;integrated security=true;database=MobileSale");
            
            string orderid = this.textBoxOrderId.Text;
            string manid = this.textBoxManId.Text;
            string mobileid = this.textBoxMobileId.Text;
            string cusname = this.textBoxCusName.Text;
            string sex=null;
            if (this.radioButtonFemale.Checked == true)
                sex = "女";
            else
                sex = "男";
            int price = Convert.ToInt32(this.textBoxPrice.Text);
            int num = Convert.ToInt32(this.textBoxSaleNum.Text);
            int sum = price * num;
            string datetime=Convert.ToString(System.DateTime.Now);
            string sqlStr=("insert into Orderr(orderId,manId,mobileId,cusName,cusSex,salePrice,saleNum,saleSum,saleTime)values('orderid','manid','mobileid','cusname','sex','price','num','sum','datetime')");
            conn.Open();
            SqlCommand cmd = new SqlCommand(sqlStr, conn);
            cmd.ExecuteNonQuery();
            conn.Close();

string sql=string.Format("insert into Orderr(orderId,manId,mobileId,cusName,cusSex,salePrice,saleNum,saleSum,saleTime)values('{0}','{1}','{2}','{3}','{4}',{5},{6},{7},'{8}')",orderid,manid,mobileid,cusname,sex,price,num,sum,datetime)