創建或更新項目是否存在

Question

我有一個創建表格，如果存在特定的Medicine ，其供應量將更新或添加新的條目，但是如果不存在特定的Medicine ，它將創建新的一批數據。

我在了解更新如何在MVC中工作時遇到了麻煩。

這是錯誤：

存儲更新，插入或刪除語句影響了意外的行數（0）。 自加載實體以來，實體可能已被修改或刪除。

這是我的控制器：

public ActionResult Create([Bind(Include = "SupplyID,MedicineID,Expiration,NumberOfSupply")] Supply supply)
    {
        if (ModelState.IsValid)
        {
            bool supplyExsist = db.Supplies.Any(x => x.Expiration == supply.Expiration && x.MedicineID == supply.MedicineID);

            if (supplyExsist)
            {
                var currentSupply = (from x in db.Supplies //get current supply
                                     where x.MedicineID == supply.MedicineID
                                     && x.Expiration == supply.Expiration
                                     select x.NumberOfSupply).First();

                db.Entry(supply).State = EntityState.Modified;
                supply.NumberOfSupply = currentSupply + supply.NumberOfSupply;
                db.SaveChanges();
                return RedirectToAction("Index");
            }
            else
            {
                db.Supplies.Add(supply);
                db.SaveChanges();
                return RedirectToAction("Index");
            }
        }

        ViewBag.MedicineID = new SelectList(db.Medicines, "MedicineID", "MedicineName", supply.MedicineID);
        return View(supply);
    }

模型：

public class Supply
{
    [Key]
    public int SupplyID { get; set; }

    [ForeignKey("Medicine")]
    public int MedicineID { get; set; }
    public Medicine Medicine { get; set; }

    [DataType(DataType.Date)]
    public DateTime Expiration { get; set; }

    [Display(Name = "Quantity")]
    [Range(1, int.MaxValue, ErrorMessage = "The value must be greater than 0")]
    public int NumberOfSupply { get; set; }
}

Answer 1

試試這個

db.Supplies.AddOrUpdate(h => h.medicineID,supply));

它將檢查db中是否存在具有相同葯品ID的行，否則將添加新的行，並對其進行更新

Answer 2

您應該使用以下命令更改if塊：

if (supplyExsist)
            {
                var currentSupply = (from x in db.Supplies //get current supply
                                     where x.MedicineID == supply.MedicineID
                                     && x.Expiration == supply.Expiration
                                     select x.NumberOfSupply).First();

                db.Supplies.Attach(supply);
                db.Entry(supply).State = EntityState.Modified;
                supply.NumberOfSupply = currentSupply + supply.NumberOfSupply;
                db.SaveChanges();
                return RedirectToAction("Index");
            }