Problem with shopping cart, asp.net c#

Question

I have built a simple shopping cart. The problem is that the first time i try to add an item nothing happens. If i click the buy button a second time an item is added. What is the cause if this problem?

Thanx!

.aspx

<asp:Content ContentPlaceHolderID="main" runat="server">
White lily
<asp:Button ID="button" runat="server" OnClick="buy_Click" />
</asp:Content>

<asp:Content ContentPlaceHolderID="rightBar" runat="server">
    <UserControl:ShoppingCart id="shoppingCart" runat="server" />
</asp:Content>

.ascx

public partial class UserControls_ShoppingCart : System.Web.UI.UserControl
{
    private List<Flower> FlowerList 
    {
        get
        {
            List<Flower> tmp = Session["FlowerList"] as List<Flower>;
            if (tmp == null)
            {
                tmp = new List<Flower>();
            }
            return tmp;
        }
    }

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            FillRepeater();
        }

    }

    public void ShoppingCart_ItemDataBound(object sender, RepeaterItemEventArgs e)
    {
        if (e.Item != null)
        {
            Label itemLabel = e.Item.FindControl("itemLabel") as Label;
            Flower flower = e.Item.DataItem as Flower;
            if (flower != null)
            {
                itemLabel.Text = flower.getName(flower);
            }
        }
    }

    private void FillRepeater()
    {
        shoppingCartRepeater.DataSource = FlowerList;
        shoppingCartRepeater.DataBind();
    }

    public void AddFlower(Flower flower)
    {
        FlowerList.Add(flower);
        Session["FlowerList"] = FlowerList;
        FillRepeater();
    }
}

Answer 1

Pursuant to my comment on the first answer.. try this

 private List<Flower> FlowerList 
    {
        get
        {
             return(_FlowerList);
        }
        set
        {
            _FlowerList = value;
        }

    }
    protected List<Flower> _FlowerList = new FlowerList();
    protected void Page_Load(object sender, EventArgs e)
    {
       if (Session["FlowerList"]!= null) {
           FlowerList = (List<Flower>)Session["FlowerList"];
       }
        if (!Page.IsPostBack)
        {
            FillRepeater();
        }
    }

It should work with everything else the same. A better way would be to use ViewState though, and save the value of _FlowerList in SaveViewState()

Answer 2

好的，我在这里是基于略读代码的猜测，所以我可能是错的，但是也许第一次不是回发，并且不会调用FillRepeater。