我想ListBoxes根据主要类别和子类别创建动态添加，它们可以是无限数量的子类别。我整个星期都在研究这个问题，但无法弄清楚。
我希望它像 Ebay 类别选择一样。当页面加载时，将有一个包含所有主要类别的列表框。当用户在列表框中选择一个项目时，应该动态添加另一个列表框，以便每个列表框都具有选定的项目。因此，在第一个列表框中选择第一项后，应该有两个列表框，第二个列表框显示属于所选列表的所有子类别。请看截图。
Ebay 类别选择示例 http://www.aquariumbids.com/Images/ebayCat.JPG
每个请求的代码 - 我认为它接近工作。
public partial class WebForm2 : System.Web.UI.Page
{
private Int32 controlCount = 0;
Panel _panel;
private Panel PanelPlaceholder
{
get
{
if (_panel == null && Master != null)
_panel = pnlContainer;
return _panel;
}
}
protected void Page_PreInit(Object sender, EventArgs e)
{
this.EnsureChildControls();
if (IsPostBack)
{
// Re-create controls but not from datasource
// The controlCount value is output in the page as a hidden field during PreRender.
controlCount = Int32.Parse(Request.Form["controlCount"]); // assigns control count from persistence medium (hidden field)
for (Int32 i = 0; i < controlCount; i++)
{
CreateDynamicControlGroup(false);
}
}
}
protected void Page_Load(Object sender, EventArgs e)
{
// create from data query.
// only if not postback
if (!IsPostBack)
{
int cc = controlCount;
DataTable dt = null;
Dictionary<string, string> Params = new Dictionary<string, string>();
dt = Globals.g_DatabaseHandler.GetRecords(StoredProcedures.GetMainCategories, Params);
// create a set of dynamic controls for the Row, incrementing counter and
// getting a reference to the new controls via their common parent (Dynamic PlaceHolder)
CreateDynamicControlGroup(true);
ListBox lb = (ListBox)PanelPlaceholder.Controls[controlCount - 1];
// On reload you will see that child ListItems are persisted by the DropDownList
lb.DataSource = dt; // use the same table
lb.DataValueField = "ID";
lb.DataTextField = "Name";
lb.DataBind();
}
}
protected void Page_PreRender(Object sender, EventArgs e)
{
// persist control count
ClientScript.RegisterHiddenField("controlCount", controlCount.ToString());
}
private void ListBox_SelectedIndexChanged(Object sender, EventArgs e)
{
ListBox lb = sender as ListBox;
Dictionary<string, string> Params = new Dictionary<string, string>();
Params.Add("parentID", lb.SelectedValue);
DataTable Categories = Globals.g_DatabaseHandler.GetRecords(StoredProcedures.GetChildCategories, Params);
if (Categories.Rows.Count > 0)
{
// create a set of dynamic controls for the Row, incrementing counter and
// getting a reference to the new controls via their common parent (Dynamic PlaceHolder)
CreateDynamicControlGroup(true);
ListBox newLb = (ListBox)PanelPlaceholder.Controls[controlCount - 1];
// On reload you will see that child ListItems are persisted by the DropDownList
newLb.DataSource = Categories; // use the same table
newLb.DataValueField = "ID";
newLb.DataTextField = "Name";
newLb.DataBind();
}
}
private void CreateDynamicControlGroup(Boolean incrementCounter)
{
// Create one logical set of controls do not assign values!
ListBox lb = new ListBox();
lb.AutoPostBack = true;
lb.CssClass = "panel";
PanelPlaceholder.Controls.Add(lb);
// wire event delegate
lb.SelectedIndexChanged += new EventHandler(ListBox_SelectedIndexChanged);
if (incrementCounter)
{
controlCount += 1;
}
}
}
标记：
<div class="Column12" id="Form_NewListing">
<h2 class="h2row">Create Your Listing - Step 1 of 2)</h2>
<h3 class="h3row">Select a category</h3>
<div class="panel">
<asp:Panel ID="pnlContainer" runat="server"></asp:Panel>
</div>
</div>