how can add data using for loop

Question

I want to insert some array data into the database. Here using for loop. The problem is - I want to keep the InvoiceNO related to the OrderNumber change. For example, if the OrderNumber changes, the InvoiceNO  will also change. I have shown it in the picture.
I would appreciate it if someone could help.

 public IActionResult addtoSelltable(int[] _ORderid, int[] _productid, string[] _OrderNumber)
 {
     for (int i = 0; i < _ORderid.Count(); i++)
     {
         int inv = 10001;
         var pro = new tbl_Sell();
         pro.Date = DateTime.Now;
         pro.productID = _productid[i];
         pro.OrderNumber = _OrderNumber[i];
         pro.InvoiceNO = Convert.ToString( inv+1);//my problem is here
         _context.tbl_Sells.Add(pro);
         _context.SaveChanges();
     }
     return View("SeleDetails");
 }

Untitled.png

Answer 1

as stated just move the initial invoice value out of the loop. you also need to use array indexing. a rename of orderNum to lastOrderNum would help reader of code:

     string lastOrderNum = ""; 
     int inv = 10001;
     for (int i = 0; i < _ORderid.Count(); i++)
     {
         var pro = new tbl_Sell();
         pro.Date = DateTime.Now;
         pro.productID = _productid[i];
         pro.OrderNumber = _OrderNumber[i];
         if(lastOrderNum == _OrderNumber[i])
         {
            pro.InvoiceNO = Convert.ToString(inv);
         }
         else
         {
            pro.InvoiceNO = Convert.ToString(++inv);
            lastOrderNum = _OrderNumber;           
         }
         _context.tbl_Sells.Add(pro);
     }
     _context.SaveChanges();

note: this code will only work if the _product, _OrderNumber arrays are at least as large as _ORderid array. also it will fail, if the _OrderNumber array is not in order. if the _OrderNumber is not sorted, then use a dictionary.

     var orderInvoiceNumber = new Dictionary<string,int>(); 
     int inv = 10001;
     for (int i = 0; i < _ORderid.Count(); i++)
     {
         var pro = new tbl_Sell();
         pro.Date = DateTime.Now;
         pro.productID = _productid[i];
         pro.OrderNumber = _OrderNumber[i];
         if(orderInvoiceNumber.ContainsKey(_OrderNumber[i]))
         {
            pro.InvoiceNO = orderInvoiceNumber[_OrderNumber[i]];
         }
         else
         {
            pro.InvoiceNO = Convert.ToString(++inv);
            orderInvoiceNumber[_OrderNumber[i]] = inv;           
         }
         _context.tbl_Sells.Add(pro);
     }
     _context.SaveChanges();

Answer 2

Hi @jewel,

You could try below code:

            int inv = 10001;
            for (int i = 0; i < _ORderid.Count(); i++)
            {
            
                var pro = new tbl_Sell();
                pro.Date = DateTime.Now;
                pro.productID = _productid[i];
                pro.OrderNumber = _OrderNumber[i];
                inv = inv + 1;
                pro.InvoiceNO = Convert.ToString(inv);//my problem is here

                _context.tbl_Sells.Add(pro);
                _context.SaveChanges();
            }

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