Tutorial :User Control Postback



Question:

I am working on rendering a set of cart items using a user control. Each cart item can be removed via a button in the user control. When a cart item is removed I need to visually show it's removal. However, since the cart item existed during the loading of the page it remains until the page is refreshed again. What I am after is a means to refresh the page after the work to remove the cartitem has been completed.

The code behind cart.aspx.cs looks like:

protected void Page_Init(object sender, EventArgs e)  {      CreateCartItemControls();  }    private void CreateCartItemControls()  {      foreach (CartItem ci in Profile.Cart.Items)      {          ASP.CartItemControl cic = new ASP.CartItemControl();          cic.ItemName = ci.Name;            cic.CartID = ci.ID;          cic.Cost = ci.BaseCost.ToString("c");          cic.ItemComponents = ci.Components;            cic.CartItemRemoved += new EventHandler(CartItemRemoved);            Content.Controls.Add(cic);      }  }    void CartItemRemoved(object sender, EventArgs e)  {      Master.UpdateCartItemCount();  }  

Markup for CartItemControl.ascx

<%@ Control Language="C#" ClassName="CartItemControl" AutoEventWireup="true"      CodeFile="CartItemControl.ascx.cs"      Inherits="UserControls_CartItemControl" %>  <fieldset id="FieldSet" runat="server">      <legend>          <asp:HyperLink ID="ItemLink" runat="server" />      </legend>      <asp:ImageButton ID="RemoveCartItem" AlternateText="Remove Item"           ImageUrl="~/img/buttons/remove_4c.gif" runat="server"          CommandName="Remove" OnCommand="RemoveCartItem_Command" />      <asp:Label ID="TotalItemCost" runat="server" Text="$0.00" />      <ol>          <li runat="server" id="ComponentsLI" visible="false">              <fieldset id="ComponentsFieldSet" runat="server">                  <legend>Item Components</legend>                  <asp:CheckBoxList ID="ItemComponentsCheckList"                      runat="server" />              </fieldset>          </li>      </ol>  </fieldset>  

Code behind for the UserControl CartItemControl.ascx.cs

public partial class UserControls_CartItemControl  : System.Web.UI.UserControl  {  public string ItemName { get; set; }  public int CartID { get; set; }  public string Cost { get; set; }  public IDictionary<int, SoftwareComponent> ItemComponents { get; set; }    protected void Page_PreRender(object sender, EventArgs e)  {      SetCartItemControlAttributes();  }    private void SetCartItemControlAttributes()  {      ItemLink.Text = ItemName;      TotalItemCost.Text = Cost;        RemoveCartItem.CommandArgument = CartID.ToString();        if (!ItemComponents.Count.Equals(0))      {          ComponentsLI.Visible = true;          foreach (KeyValuePair<int, ItemComponent> kvp in              ItemComponents)          {              ItemComponentsCheckList.Items.Add(                  new ListItem(string.Format("{0} {1}",                      kvp.Value.ComponentName,                      kvp.Value.ComponentCost.ToString("c")),                      kvp.Key.ToString()));          }      }  }    public event EventHandler CartItemRemoved;    protected void RemoveCartItem_Command(object sender, CommandEventArgs e)  {      int itemID;        if (int.TryParse(e.CommandArgument.ToString(), out itemID))      {          Profile.Cart.RemoveCartItem(itemID);          CartItemRemoved(sender, e);          Parent.Controls.Remove(this);      }  }  }  


Solution:1

Just as you add CartItemControls to Content's Controls collection on init, you need to remove them on RemoveCartItem_Command. Do so by either exposing your own ItemRemoved event and handling it in the main page or by calling Parent.Controls.Remove(this) inside the RemoveCartItem_Command.

Or am I missing something?


Solution:2

Response.Redirect back to the page after you do the work to remove the cart item.


Solution:3

Try Server.Transfer to the same page.

That said, consider using Ruslan approach, by exposing an ItemRemoved event and handling it on the main page. You can do Content.Controls.Clear and call CreateCartItemControls again.


Solution:4

Just rebind the everything on the main page on every postback.


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