我的问题如下:我有两个ListBoxe
。首先,我存储可以订购的产品,第二个是客户的购物车。因此,产品具有Quantity属性,并且我有一个NumericUpDown
,客户可以在其中更改订购产品的数量。
private void button2_Click(object sender, EventArgs e) //puts selectedproduct to the cart
{
if (listBox1.SelectedItem == null || (int)numericUpDown1.Value == 0 ||
(listBox1.SelectedItem as Product).Quantity < (int)numericUpDown1.Value) return;
foreach (Product item in listBox2.Items)
{
if (item.ID == (listBox1.SelectedItem as Product).ID)
{
return;
}
}
listBox2.Items.Add(new Product { Name = (listBox1.SelectedItem as Product).Name,
Price = (listBox1.SelectedItem as Product).Price,
Quantity = (int)numericUpDown1.Value});
(listBox1.SelectedItem as Product).Quantity -= (int)numericUpDown1.Value;
}
这很好用,除了它在我的Products表中添加了一个新项目。我想要做的是向客户添加所选产品的选定数量,而不是向产品表添加新商品,并使用numericupdown1.value减少订购的产品数量。我正在使用EF Code First Database,如下所示:
public class Order
{
public int ID { get; set; }
public bool Status { get; set; }
public virtual Account account { get; set; }
public virtual List<Product> products { get; set; }
}
public class Product
{
public int ID { get; set; }
public string Name { get; set; }
public long Price { get; set; }
public int Quantity { get; set; }
public virtual List<Order> orders { get; set; }
}
以下是保存方法:
private void button1_Click(object sender, EventArgs e)
{
List<Product> p = new List<Product>();
foreach (Product item in listBox2.Items)
{
p.Add(item);
}
Variables.Db.orders.Add(new Order { account = Variables.Currentuser, products = p });
Variables.Db.SaveChanges(); //Variables.Db is my CodeFirst Database
}
我尝试了很多方法,例如:
int q = (listBox1.SelectedItem as Product).Quantity;
(listBox1.SelectedItem as Product).Quantity = (int)numericUpDown1.Value;
listBox2.Items.Add(listBox1.SelectedItem);
(listBox1.SelectedItem as Product).Quantity = q - (int)numericUpDown1.Value;
但最后一行将listbox2对象的数量更改为与listbox1s相同。
答案 0 :(得分:3)
您使用相同的实体(Product
)用于两个不同的目的(产品和订单商品),这是错误的。
您看到的第一个行为是为任何订单创建新Product
个对象的结果,第二个行为是因为您在两个列表框中使用相同的产品对象。
执行此操作的正确方法是为订单商品创建新实体:
public class Product
{
public int ID { get; set; }
public string Name { get; set; }
public long Price { get; set; }
public int Quantity { get; set; }
public virtual List<OrderItem> ordersItems { get; set; }
}
public class Order
{
public int ID { get; set; }
public bool Status { get; set; }
public virtual Account account { get; set; }
public virtual List<OrderItem> Items { get; set; }
}
public class OrderItem
{
public int ID { get; set; }
public int Quantity { get; set; }
public virtual Product Product { get; set; }
public long TotalPrice { get; set; } // It is better to hold the price. What if you later changed the product price?
}
然后您可以轻松处理购买:
private void button2_Click(object sender, EventArgs e) //puts selectedproduct to the cart
{
Product p = listBox1.SelectedItem as Product;
int q = (int)numericUpDown1.Value;
if (p == null || q == 0 || p.Quantity < q)
return;
foreach (Product item in listBox2.Items)
{
if (item.ID == p.ID)
{
return;
}
}
listBox2.Items.Add(new OrderItem { Product = p, Quantity = q, TotalPrice = p.Price * q });
p.Quantity -= q;
}
private void button1_Click(object sender, EventArgs e)
{
Order o = new Order() { account = Variables.Currentuser, Items = new List<Order>() };
foreach (OrderItem item in listBox2.Items)
{
o.Items.Add(item);
}
Variables.Db.orders.Add(o);
Variables.Db.SaveChanges(); //Variables.Db is my CodeFirst Database
}
您是否也注意到清洁代码? :)
还有一件事:请始终为控件和类字段使用有意义的名称:btnSave
,btnAddToCart
和numQuantity
是不错的候选人。