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嗯，我有一個奇怪的問題。DropDownList當異步回發發生時觸發AutoPostback
我有一個頁面上有2個DropDownLists和一個自定義的Web用戶控件。自定義Web用戶控件在其中包含一個UpdatePanel，並且在UpdatePanel中有一個Ajax Timer控件，用於定期更新一系列內容。
當DropDownList中的一個DropDownList並將鼠標懸停在（而不是點擊）某個選項上時，UpdatePanel中的Timer控件異步回發到服務器，DropDownList將「autopostbacks」傳遞給服務器！
我想弄清楚爲什麼異步回發會導致DropDownList的行爲，就像我選擇/點擊一個選項，以便我可以找到解決此問題的方法。
現在很容易重現此問題。 創建一個名爲「TimerUpdatedListing」 Web用戶控制......這是Web用戶控件的代碼ASPX標記：
<%@ Control Language="vb" AutoEventWireup="false" CodeBehind="TimerUpdatedListing.ascx.vb" Inherits="MyNamespace.TimerUpdatedListing" %>
<div style="width: 150px; height: 150px; overflow: auto; border: solid 1px navy;">
<asp:UpdatePanel ID="anUpdatePanel" runat="server">
<ContentTemplate>
<asp:Repeater ID="aRepeater" runat="server">
<ItemTemplate>
<div style="border-bottom: solid 1px #EEC900; margin: 3px; padding: 2px;">
Id:
<%#Eval("Id")%>
<br />
Time:
<%#Eval("Time")%>
</div>
</ItemTemplate>
</asp:Repeater>
<asp:Timer ID="aTimer" runat="server" Interval="2000">
</asp:Timer>
</ContentTemplate>
</asp:UpdatePanel>
</div>
這是Web用戶控件VB.NET服務器端代碼：
Public Partial Class TimerUpdatedListing
Inherits System.Web.UI.UserControl
Private _aListOFThings As List(Of Things)
Private Sub aTimer_Tick(ByVal sender As Object, ByVal e As System.EventArgs) Handles aTimer.Tick
If Session("_aListOfThings") Is Nothing Then
_aListOFThings = New List(Of Things)
Else
_aListOFThings = CType(Session("_aListOfThings"), List(Of Things))
End If
If _aListOFThings.Count > 9 Then
_aListOFThings = New List(Of Things)
End If
_aListOFThings.Add(New Things((_aListOFThings.Count + 1).ToString, Now.ToString("hh:mm:ss")))
Session("_aListOfThings") = _aListOFThings
aRepeater.DataSource = _aListOFThings
aRepeater.DataBind()
End Sub
Private Class Things
Private _time As String
Private _id As String
Public Property Time() As String
Get
Return _time
End Get
Set(ByVal value As String)
_time = value
End Set
End Property
Public Property ID() As String
Get
Return _id
End Get
Set(ByVal value As String)
_id = value
End Set
End Property
Public Sub New(ByVal id As String, ByVal time As String)
_id = id
_time = time
End Sub
End Class
End Class
現在，在名爲WebForm1.aspx的一個ASPX頁面，加入2個DropDownLists和Web用戶控件：
<%@ Page Language="vb" AutoEventWireup="false" CodeBehind="WebForm1.aspx.vb" Inherits="MyNamespace.WebForm1" %>
<%@ Register Src="TimerUpdatedListing.ascx" TagName="TimerUpdatedListing" TagPrefix="uc1" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Test</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="true">
<asp:ListItem Text="1" Value="1" />
<asp:ListItem Text="2" Value="2" />
<asp:ListItem Text="3" Value="3" />
<asp:ListItem Text="4" Value="4" />
<asp:ListItem Text="5" Value="5" />
</asp:DropDownList>
<asp:Label ID="selectedValue1" runat="server"></asp:Label>
<br />
<asp:DropDownList ID="DropDownList2" runat="server" AutoPostBack="true">
<asp:ListItem Text="a" Value="a" />
<asp:ListItem Text="b" Value="b" />
<asp:ListItem Text="c" Value="c" />
<asp:ListItem Text="d" Value="d" />
<asp:ListItem Text="e" Value="e" />
</asp:DropDownList>
<asp:Label ID="selectedValue2" runat="server"></asp:Label>
<br />
<br />
<uc1:TimerUpdatedListing ID="TimerUpdatedListing1" runat="server" />
</div>
</form>
</body>
</html>
下面是WebForm1.aspx的VB.NET的服務器端代碼頁：
Public Partial Class WebForm1
Inherits System.Web.UI.Page
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If String.IsNullOrEmpty(Request.Params("ddl1")) = False Then
selectedValue1.Text = Request.Params("ddl1")
End If
If String.IsNullOrEmpty(Request.Params("ddl2")) = False Then
selectedValue2.Text = Request.Params("ddl2")
End If
End Sub
Private Sub DropDownList1_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles DropDownList1.SelectedIndexChanged
Response.Redirect(Request.Url.LocalPath + "?ddl1=" + DropDownList1.SelectedValue.ToString, True)
End Sub
Private Sub DropDownList2_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles DropDownList2.SelectedIndexChanged
Response.Redirect(Request.Url.LocalPath + "?ddl2=" + DropDownList2.SelectedValue.ToString, True)
End Sub
End Class
感謝，
-Frinny
你能發表一些你的代碼嗎？ – 2010-08-26 19:08:52
說真的很簡單。我在頁面上有2個DropDownLists。我有一個UpdatePanel的用戶控件...在UpdatePanel中有一個Repeater和一個Timer控件（當計時器滴答時更新的中繼器）... *嘆*用簡單的代碼更新我的原始帖子。 – Frinavale 2010-08-26 19:16:01
您意識到更新面板內的所有內容都會「回傳」給對方嗎？如果你需要單獨控制，我建議使用像[Telerik RadAjaxManager]（http://demos.telerik.com/aspnet-ajax/ajax/examples/manager/firstlook/defaultcs.aspx） – 2010-08-26 19:28:29