javascript - 新手菜单/子菜单问题

Question

我对 ASP.NET Web 编程还是新手，所以希望有人可以帮助我。我有一个水平主菜单和位于其正下方的另一个水平子菜单。

我将这些从数据库加载到 MenuCollection Session 变量中，该变量是 SubMenu 的字典及其 ParentId。

当用户单击主菜单项时，我想交换并显示正确的子菜单。

当 MainMenu.MenuItemClick 事件发生时，会发生回发，然后我尝试将正确的菜单从字典放入子菜单中，但它没有显示。

我是否需要另一个回发来加载子菜单或需要执行一些 JavaScript？还是我以错误的方式处理这个问题？

下面是我的代码。谢谢。

Imports System.Data
Imports System.Data.SqlClient
Imports System.Collections.Generic

Public Class RootMaster
  Inherits System.Web.UI.MasterPage

  Private ReadOnly connection As String = System.Configuration.ConfigurationManager.ConnectionStrings("ConnectionString").ConnectionString

  Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    If Not IsPostBack Then
      Session("MenuData") = GetMenuData()
      AddTopMenuItems(Session("MenuData"))
    End If
  End Sub

  Private Function GetMenuData() As DataTable
    Using con As New SqlConnection(connection)
      Dim cmd As New SqlCommand("Select * from MenuData", con)
      Dim dtMenuItems As New DataTable()
      Dim sda As New SqlDataAdapter(cmd)

      sda.Fill(dtMenuItems)
      cmd.Dispose()
      sda.Dispose()

      Return dtMenuItems
    End Using
  End Function

  Private Sub AddTopMenuItems(menuData As DataTable)
    Dim view As DataView = Nothing
    Dim MenuDictionary As New Dictionary(Of Integer, Menu)

    view = New DataView(menuData)
    view.RowFilter = "ParentId IS NULL"
    For Each row As DataRowView In view
      'Adding the menu item'
      If row("IsActive") Then
        Dim RowId As Integer = row("Id")
        Dim newMenuItem As New MenuItem(row("Text").ToString(), RowId.ToString())
        newMenuItem.NavigateUrl = row("NavigateUrl").ToString()
        MainMenu.Items.Add(newMenuItem)

        'Create all sub menus for each main menu item, add to dictionary'
        Dim SubM = CreateSubMenus(menuData, newMenuItem)
        If SubM.Items.Count > 0 Then
          MenuDictionary.Add(RowId, SubM)
        End If
      End If
    Next

    Session("MenuCollection") = MenuDictionary
    MainMenu.Items(0).Selected = True
    view = Nothing
  End Sub

  Private Function CreateSubMenus(menuData As DataTable, parentMenuItem As MenuItem) As Menu
    Dim view As DataView = Nothing
    Dim Result As New Menu

    view = New DataView(menuData)
    view.RowFilter = "ParentId=" & parentMenuItem.Value

    For Each row As DataRowView In view
      If row("IsActive") Then
        Dim newMenuItem As New MenuItem(row("Text").ToString(), row("Id").ToString())
        newMenuItem.NavigateUrl = row("NavigateUrl").ToString()
        Result.Items.Add(newMenuItem)
      End If
    Next

    Return Result
  End Function

  Protected Sub MainMenu_ItemClick(source As Object, e As MenuEventArgs) Handles MainMenu.MenuItemClick
    If Not Session("MenuCollection") Is Nothing Then
      Dim MenuDictionary As Dictionary(Of Integer, Menu) = DirectCast(Session("MenuCollection"), Dictionary(Of Integer, Menu))

      If MenuDictionary.ContainsKey(e.Item.Value) Then
        SubMenu = MenuDictionary.Item(e.Item.Value)
      End If
    End If
  End Sub
End Class

Answer 1

是否可以在 PreRender 事件上重绘子菜单。因此，例如:

Protected Sub MainMenu_ItemClick(source As Object, e As MenuEventArgs) Handles MainMenu.MenuItemClick
If Not Session("MenuCollection") Is Nothing Then
  Dim MenuDictionary As Dictionary(Of Integer, Menu) = DirectCast(Session("MenuCollection"), Dictionary(Of Integer, Menu))

  If MenuDictionary.ContainsKey(e.Item.Value) Then
    SubMenu = MenuDictionary.Item(e.Item.Value)
  End If
 End If
End Sub

可能会变成:

Protected Sub MainMenu_PreRender(ByVal sender As Object, ByVal e As EventArgs) Handles MainMenu.PreRender
If Not Session("MenuCollection") Is Nothing Then
   Dim MenuDictionary As Dictionary(Of Integer, Menu) = DirectCast(Session("MenuCollection"), Dictionary(Of Integer, Menu))

        If MenuDictionary.ContainsKey(e.Item.Value) Then
        SubMenu = MenuDictionary.Item(e.Item.Value)
        End If
End If 
End Sub

如果这不起作用，那么恐怕除此之外我没有什么帮助，只是一个想法。我想如果您的问题是您需要再次预加载菜单，那么使用预渲染也许可以解决它。