//引入命名空间
using System;
using System.Collections;
using System.ComponentModel;
using System.Security.Permissions;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

// The DropDownNavigationPath is a class that extends the SiteMapPath
// control and renders a DropDownList after the CurrentNode. The
// DropDownList displays a list of pages found further down the site map
// hierarchy from the current one. Selecting an item in the DropDownList
// redirects to that page.
//
// For simplicity, the DropDownNavigationPath assumes the
// RootToCurrent PathDirection, and does not apply styles
// or templates the current node.
//
[AspNetHostingPermission(SecurityAction.Demand, Level=AspNetHostingPermissionLevel.Minimal)]
public class DropDownNavigationPath : SiteMapPath {
    // Override the InitializeItem method to add a PathSeparator
    // and DropDownList to the current node.
    protected override void InitializeItem(SiteMapNodeItem item) {

        // The only node that must be handled is the CurrentNode.
        if (item.ItemType == SiteMapNodeItemType.Current)
        {
            HyperLink hLink = new HyperLink();

            // No Theming for the HyperLink.
            hLink.EnableTheming = false;
            // Enable the link of the SiteMapPath is enabled.
            hLink.Enabled = this.Enabled;

            // Set the properties of the HyperLink to
            // match those of the corresponding SiteMapNode.
            hLink.NavigateUrl = item.SiteMapNode.Url;
            hLink.Text        = item.SiteMapNode.Title;
            if (ShowToolTips) {
                hLink.ToolTip = item.SiteMapNode.Description;
            }

            // Apply styles or templates to the HyperLink here.
            // ...
            // ...

            // Add the item to the Controls collection.
            item.Controls.Add(hLink);

            AddDropDownListAfterCurrentNode(item);
        }
        else {
            base.InitializeItem(item);
        }
    }
    private void AddDropDownListAfterCurrentNode(SiteMapNodeItem item) {

        SiteMapNodeCollection childNodes = item.SiteMapNode.ChildNodes;

        // Only do this work if there are child nodes.
        if (childNodes != null) {

            // Add another PathSeparator after the CurrentNode.
            SiteMapNodeItem finalSeparator =
                new SiteMapNodeItem(item.ItemIndex,
                                    SiteMapNodeItemType.PathSeparator);

            SiteMapNodeItemEventArgs eventArgs =
                new SiteMapNodeItemEventArgs(finalSeparator);

            InitializeItem(finalSeparator);
            // Call OnItemCreated every time a SiteMapNodeItem is
            // created and initialized.
            OnItemCreated(eventArgs);

            // The pathSeparator does not bind to any SiteMapNode, so
            // do not call DataBind on the SiteMapNodeItem.
            item.Controls.Add(finalSeparator);

            // Create a DropDownList and populate it with the children of the
            // CurrentNode. There are no styles or templates that are applied
            // to the DropDownList control. If OnSelectedIndexChanged is raised,
            // the event handler redirects to the page selected.
            // The CurrentNode has child nodes.
            DropDownList ddList = new DropDownList();
            ddList.AutoPostBack = true;

            ddList.SelectedIndexChanged += new EventHandler(this.DropDownNavPathEventHandler);

            // Add a ListItem to the DropDownList for every node in the
            // SiteMapNodes collection.
            foreach (SiteMapNode node in childNodes) {
                ddList.Items.Add(new ListItem(node.Title, node.Url));
            }

            item.Controls.Add(ddList);
        }
    }

    // The sender is the DropDownList.
    private void DropDownNavPathEventHandler(object sender,EventArgs e) {
        DropDownList ddL = sender as DropDownList;

        // Redirect to the page the user chose.
        if (Context != null)
            Context.Response.Redirect(ddL.SelectedValue);
    }
}