我有一个页面,其中包含一些动态创建的控件(TextBox和DropDownList).发生回发时,TextBox会保留其值,但DropDownLists会丢失其ListItem.
这非常令人困惑,因为页面级DropDownList也保留其ListItems.任何人都可以看到下面的代码有什么问题吗？
这非常令人困惑,因为页面级DropDownList也保留其ListItems.任何人都可以看到下面的代码有什么问题吗？
任何帮助解决这个问题将不胜感激.
<%@ Page Language="VB"%>
<script runat="server">
Protected Sub Page_Init(ByVal sender As Object,ByVal e As System.EventArgs)
If Not Page.IsPostBack Then
ddlFixed.Items.Add(New ListItem("12","13"))
ddlFixed.Items.Add(New ListItem("14","15"))
End If
Dim i As Integer
For i = 0 To 3
Dim ddl As New DropDownList
ddl.ID = "ddlPage" & i
ddl.EnableViewState = True
If Not Page.IsPostBack Then
ddl.Items.Add(New ListItem("12","13"))
ddl.Items.Add(New ListItem("14","15"))
End If
pnlDynamic.Controls.Add(ddl)
Dim txtBx As New TextBox
txtBx.ID = "txtPage" & i
If Not Page.IsPostBack Then
txtBx.Text = "Preset"
End If
pnlDynamic.Controls.Add(txtBx)
Next
End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server" enableviewstate="true">
<div>
<br />
<br />
<a href="Default.aspx">Get-Request</a>
<br />
<br />
<asp:Panel runat="server" ID="pnlDynamic" EnableViewState="true" />
<br />
<br />
<asp:DropDownList runat="server" ID="ddlFixed" />
<asp:Button runat="server" ID="btn" Text="Postback"/>
</div>
</form>
</body>
</html>
解决方法
我找到了一个解决方案,可以让我在回发中保持视图状态.
它是调用ItemCollection的TrackViewState.
它是调用ItemCollection的TrackViewState.
CType(ddl.Items,IStateManager).TrackViewState()
感谢大家的帮助.
这是工作解决方案：
<%@ Page Language="VB"%>
<script runat="server">
Protected Sub Page_Init(ByVal sender As Object,"15"))
End If
Dim i As Integer
For i = 0 To 3
Dim ddl As New DropDownList
ddl.ID = "ddlPage" & i
CType(ddl.Items,IStateManager).TrackViewState()
If Not Page.IsPostBack Then
ddl.Items.Add(New ListItem("12","15"))
End If
pnlDynamic.Controls.Add(ddl)
Dim txtBx As New TextBox
txtBx.ID = "txtPage" & i
If Not Page.IsPostBack Then
txtBx.Text = "Preset"
End If
pnlDynamic.Controls.Add(txtBx)
Next
End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server" >
<div>
<br />
<br />
<a href="Default.aspx">Get-Request</a>
<br />
<br />
<asp:Panel runat="server" ID="pnlDynamic" />
<br />
<br />
<asp:DropDownList runat="server" ID="ddlFixed" />
<asp:Button runat="server" ID="btn" Text="Postback"/>
</div>
</form>
</body>
</html>
