我在PreInit事件期间向我的内容页面添加了一些动态控件，但是在回发后没有自动维护Viewstate，尽管在PreInit事件期间声明了添加控件。我的下拉列表和文本框重置。我做错了什么？
Mark Up
<%@ Page Title="" Language="VB" MasterPageFile="~/ContentPages/MasterPage.master" AutoEventWireup="false" CodeFile="ElktonOEE.aspx.vb" Inherits="ContentPages_OEE_ElktonOEE" %>
<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="asp" %>
<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder_Head" Runat="Server">
<link rel="stylesheet" href="http://flexweb/MES/css/UserControls/FlexGridView.css" type="text/css"/>
<link rel="stylesheet" href="http://flexweb/MES/css/LabelTexbox.css" type="text/css"/>
<link rel="stylesheet" href="http://flexweb/MES/css/OEE.css" type="text/css"/>
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder_PageContentTitle" Runat="Server">
<div class="PageContentTitle">OEE Report</div>
</asp:Content>
<asp:Content ID="Content4" ContentPlaceHolderID="ContentPlaceHolder_Content" Runat="Server">
<asp:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server">
</asp:ToolkitScriptManager>
<script type="text/javascript">
</script>
<div class="MESContentDiv" id="SqlQueryContentDiv">
<div id="ContentLabelDiv">
<asp:Label ID="PanelLabel" runat="server" CssClass="ContentLabel"></asp:Label>
</div>
<br />
<asp:Panel ID="Panel1" runat="server">
<!-- Controls dynamically generated in the code-behind and inserted here -->
</asp:Panel>
<br />
<br />
<asp:Panel ID="Panel2" runat="server">
<asp:Table ID="Table1" runat="server">
</asp:Table>
</asp:Panel>
</div>
</asp:Content>
背后的代码
Imports ASP 'Allows User Control to be dynamically loaded onto page
Imports System.Data 'Allows namespace access to the DataSet class
Imports System.Web.UI.UserControl
Imports MES_Class_Library
Partial Class ContentPages_OEE_ElktonOEE
Inherits System.Web.UI.Page
Protected Sub Page_PreInit(sender As Object, e As System.EventArgs) Handles Me.PreInit
'Call this to avoid null result when searching for controls on a content page
CommonFlexwebFunctions.PrepareChildControlsDuringPreInit(Page)
'Add Dynamic Controls, Dyanimc Controls Must be given ID in order for the viewstate to work.
LoadSearchPrompt()
End Sub
Protected Sub Page_Load(sender As Object, e As System.EventArgs) Handles Me.Load
Label_Debug.Visible = False
'Prompt for parameters
PanelLabel.Text = "Select OEE Parameters"
'Check for empty Query String
If (Request.QueryString("Type") IsNot Nothing) And (Request.QueryString("Date") IsNot Nothing) Then
Select Case Request.QueryString("Type")
Case "Daily"
LoadDailySummary()
Case "Weekly"
'LoadWeeklySummary()
Case "Monthly"
'LoadMonthlySummary()
End Select
Else
Panel2.Visible = False
End If
End Sub
Private Sub LoadSearchPrompt()
Dim lb1, lb2 As New Label
Dim ddl As New DropDownList
Dim tb As New TextBox
Dim ce As New AjaxControlToolkit.CalendarExtender
Dim validation_groupname As String = "ValidDate"
'Report Label
lb1.CssClass = "LabelName125 Twelve"
lb1.ID = "lbType"
lb1.Text = "Report Type:"
'Report DDL
ddl.CssClass = "ML5"
ddl.ID = "ddlReportType"
ddl.Items.Add("--")
ddl.Items.Add("Daily")
ddl.Items.Add("Weekly")
ddl.Items.Add("Monthly")
'Start Date Label
lb2.CssClass = "LabelName125 Twelve"
lb2.ID = "lbDate"
lb2.Text = "Start Date:"
'Start Date Textbox
tb.CssClass = "TextboxValue125 ML5"
tb.ID = "textboxStartDate"
tb.ValidationGroup = validation_groupname
'Calendar Extender
ce.ID = "ceDate"
ce.TargetControlID = "textboxStartDate"
'Valiation
Dim cv As New CompareValidator
Dim vs As New ValidationSummary
cv.ControlToValidate = "textboxStartDate"
cv.ID = "cv1"
cv.Display = ValidatorDisplay.None
cv.ErrorMessage = "Date must be in the mm/dd/yyyy format."
cv.Operator = ValidationCompareOperator.DataTypeCheck
cv.Type = ValidationDataType.Date
cv.ValidationGroup = validation_groupname
vs.ID = "vs1"
vs.HeaderText = "The data you entered contains an error."
vs.ShowMessageBox = True
vs.ShowSummary = False
vs.ValidationGroup = validation_groupname
'Submit
Dim btn As New Button
btn.CssClass = "Button100 LeftMargin25"
btn.ID = "btnSubmit"
btn.CausesValidation = True
btn.ValidationGroup = validation_groupname
btn.Text = "Submit"
'add handler
AddHandler btn.Click, AddressOf MyBtnClick '' this is the method to call
'Add Controls
Panel1.Controls.Add(lb1)
Panel1.Controls.Add(ddl)
Panel1.Controls.Add(lb2)
Panel1.Controls.Add(tb)
Panel1.Controls.Add(ce)
Panel1.Controls.Add(cv)
Panel1.Controls.Add(vs)
Panel1.Controls.Add(btn)
End Sub
Private Sub MyBtnClick(ByVal sender As Object, ByVal e As EventArgs)
Dim btn As Button = CType(sender, Button) ''Gets the button that fired the method
Dim ReportType As String = ""
Dim StartDate As String = ""
'Access the ddl
Dim ddl As DropDownList = CType(CommonFlexwebFunctions.RecursiveFindControl(Page, "ddlReportType"), DropDownList)
'If the proper ddl was found, set its value
If ddl IsNot Nothing Then
'Set the value
ReportType = ddl.SelectedItem.ToString()
End If
'Access the tb
Dim tb As TextBox = CType(CommonFlexwebFunctions.RecursiveFindControl(Page, "textboxStartDate"), TextBox)
'If the proper ddl was found, set its value
If tb IsNot Nothing Then
'Set the value
StartDate = tb.Text
End If
Response.Redirect("ElktonOEE.aspx?Type=" + ReportType + "&Date=" + StartDate)
End Sub
Private Sub LoadDailySummary()
Panel2.Visible = True
End Sub
End Class
类函数
Public Class CommonFlexwebFunctions
Public Shared Function RecursiveFindControl(container As Control, name As String) As Control
If Not (container.ID Is Nothing) AndAlso (container.ID.Equals(name)) Then
Return container
End If
For Each c As Control In container.Controls
Dim ctrl As Control = RecursiveFindControl(c, name)
If Not ctrl Is Nothing Then
Return ctrl
End If
Next
Return Nothing
End Function
Public Shared Sub PrepareChildControlsDuringPreInit(page As Page)
' Walk up the master page chain and tickle the getter on each one
' Run this so you can see the controls on content pages
Dim master As MasterPage = page.Master
While master IsNot Nothing
master = master.Master
End While
End Sub
End Class
答案 0 :(得分：0)
问题可能与ToolkitScriptManager默认使用主机aspx页面url引用它的控件脚本有关。因此，页面的PreInit事件被执行两次。
为了避免它 - 只需按照下面提供的说明指示ScriptManager使用它的处理程序而不是页面的URL