如何在不覆盖先前值 ASP / VB.NET 的情况下将新项目插入会话

Question

我正在使用 ASP 和 VB.net 制作一个网站（我有一个 mysql 数据库，其中存储了所有产品），我需要创建一个添加到购物车按钮，以便稍后在购物车中显示它。

为此，我决定将数据库中的商品 ID 存储到会话变量中，并在购物车页面上检索它以显示有关该产品的其他信息。但是每次用户单击按钮将商品添加到购物车时，我都需要向会话数组添加一个新变量。但我无法弄清楚每次单击时如何将变量添加到数组中。

    Private _cmd As MySqlCommand
    Private _adapter As MySqlDataAdapter
    Dim myCookie As HttpCookie = New HttpCookie("Cart")
    Dim item As Integer
    Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
        ViewProduct()
    End Sub

    Private Sub ViewProduct()
        Dim Cart(10) As String
        Dim QueryStr As String
        _conn = New MySqlConnection
        _conn.ConnectionString = ConfigurationManager.ConnectionStrings("ProductConn").ConnectionString
        Dim _reader As MySqlDataReader
        _conn.Open()

        QueryStr = "SELECT * FROM products.items "
        _cmd = New MySqlCommand(QueryStr, _conn)
        _reader = _cmd.ExecuteReader()

        For index As Integer = 0 To 48 Step 1
            _reader.Read()
            If Request.RawUrl = "/ZTY_Fashion/Scripts/Viewproduct.aspx?id=" + _reader("productID").ToString Then
                ImageButton1.ImageUrl = _reader("productImg").ToString
                name.Text = _reader("productName").ToString
                product.Text = _reader("productDisc").ToString
                price.Text = _reader("productPrice").ToString
                addtocart.Text = "Buy Now"
                quantity.Text = "Quantity in stock" + " " + _reader("Instock").ToString
                quantitytxt.Text = "Quantity"
                similar.Text = "Similar Items in stock"
                ID.Text = _reader("productID").ToString

            End If
        Next index

        _reader.Close()

        Dim rnd = New Random()
        Dim nextValue = rnd.Next(48) / 1

        QueryStr = "SELECT * FROM products.items WHERE productID='" & nextValue & "'"
        _cmd = New MySqlCommand(QueryStr, _conn)
        _reader = _cmd.ExecuteReader()

        For i As Integer = 0 To 48 Step 1
            _reader.Read()
            Select Case i
                Case 0
                    imgdisplay.ImageUrl = _reader("productImg").ToString
            End Select
        Next i

        _reader.Close()
        _conn.Close()
    End Sub

    Protected Sub addtocart_Click(sender As Object, e As EventArgs) Handles Button20.Click

    //This is where i would like to add the code
    End Sub
End Class

Answer 1

您可以在会话中存储自己的自定义对象列表，然后只需将这些对象的集合存储在您的会话中，例如List<CustomerCartItem>。将其转换为 VB.net，就像在 c# 中一样

创建一个类

public class CustomerCartItem
{
   // add what you need here, if you dont need quantity or name, just remove 
   // both, and only take Product ID
   public int ProductID {get;set;}
   public int Quantity {get;set;}
   public int Name {get;set;}
}

当您要在购物车中添加新产品时

if(Session["customerCartItem"] != null){
   List<CustomerCartItem> items = (List<CustomerCartItem>)Session["customerCartItem"];
   items.Add(new CustomerCartItem() { ProductID = 1, Quantity = 2, Name = 'Prod1' }) 
   Session["customerCartItem"] =   items ;
}
else
{
List<CustomerCartItem> items = new List<CustomerCartItem>();
items.Add(new CustomerCartItem() { ProductID = 1, Quantity = 2, Name = 'Prod2' })
Session["customerCartItem"] =   items ;
}