Question

我有以下代码来更新一些库存值...

private static void UpdateInventory(int prodId, int qty)
    {
        using (var context = new uStore7_1Entities())
        {
            //Get the catalogNo and ProductUnitID of the product passed in so we can find all identical products that might just be boxed differently
            var currProdItem = context.Products.Where(c => c.ProductID.Equals(prodId))
                                       .Select(c => new {c.CatalogNo, c.ProductUnitID}).FirstOrDefault();

            //Get the units per box factor for calculating total product ordered
            var prodIdAmount =
                context.ProductUnits.Where(pa => pa.ProductUnitID.Equals(currProdItem.ProductUnitID))
                       .Select(pa => pa.Amount)
                       .FirstOrDefault();

            //Calculate the total number of units for this item
            var prodUnits = qty*prodIdAmount;

            //Get the entire list of products with the specified catalog number excluding the product passed in
            var uStoreProducts =
                context.Products.Where(p => p.CatalogNo.Equals(currProdItem.CatalogNo) && !p.ProductID.Equals(prodId))
                       .Select(p => p.ProductID);


            //Loop through each product in the uStoreProductsList
            foreach (var uStoreProduct in uStoreProducts)
            {
                var currentProduct = uStoreProduct;

                //Get the current product's ProductUnitId to get the 'pieces' per "box"
                var currentUnitId =
                    context.Products.Where(u => u.ProductID.Equals(currentProduct))
                           .Select(u => u.ProductUnitID)
                           .FirstOrDefault();

                //Use the ProductUnitId to get the "Amount" from the ProductUnits table.
                var inventoryFactor =
                    context.ProductUnits.Where(i => i.ProductUnitID.Equals(currentUnitId))
                           .Select(i => i.Amount)
                           .FirstOrDefault();

                //Divide the quantity passed 
                var qtyInUnits = prodUnits/inventoryFactor;

                var inventory =
                    context.ProductInventories.Where(pi => pi.ProductID.Equals(currentProduct))
                           .Select(pi => pi.InventoryQuantity)
                           .FirstOrDefault();

                /*var inventory = (from i in context.ProductInventories
                                where i.ProductID == currentProduct
                                select i).FirstOrDefault();
                */


                if (inventory != null)
                {
                    var newinv = inventory - qtyInUnits;
                    inventory = newinv;
                    //context.SaveChanges();
                }
            }
            context.SaveChanges();

        }

    }

SaveChanges()似乎没有更新任何内容。我调试了它，库存值变为所需的值，但由于某种原因它没有更新。我已经在循环内部和循环外部尝试过，两者都没有变化。有任何想法吗？我在这里缺少什么？

Answer 1

您的code不会更新任何内容。您所做的只是收集实体并在局部变量中分配计算值。但是，您实际上从未更改过property。{/ p>之一的entities

请注意，选择实体的属性，将它们存储在变量中并替换此变量的值不起作用。如果要修改实体，则需要选择实体。

Answer 2

您的问题是对象替换，而不是重新分配。创建“newinv”时，它与您的上下文分离，而“inventory”是附加对象。当“newinv”被分配给“库存”时，它就会失去与上下文的关联。

试试这个：

    var prodInventory =
                   context.ProductInventories
                   .Where(pi => pi.ProductID.Equals(currentProduct))
                   .FirstOrDefault();

                if (prodInventory != null)
                {
                    var newinv = prodInventory.InventoryQuantity - qtyInUnits;
                    prodInventory.InventoryQuantity = newinv; // This updates the actual context object now.
                }

实体框架savechanges（）不工作EF5，.Net4

2 个答案: