我希望通过动态更新来更新我的 DDL 功能之一，这样如果用户添加更多文件，下拉列表就会选择它。
目前我的下拉列表是从VB代码后面拉出来的，如下所示：
Public Sub DDL_SelectedIndexChanged(sender As Object, e As EventArgs)
Dim ddl As DropDownList = CType(sender, DropDownList) 'item is already dropdownlist
Dim ctl As TextBox = DirectCast(ddl.NamingContainer.FindControl("eTemplate"), TextBox)
If ddl.SelectedValue = 1 Then
ctl.Text = File.ReadAllText("e:Documents\Visual Studio 2013\Projects\Web\Templates\Down.txt")
ElseIf ddl.SelectedValue = 2 Then
ctl.Text = File.ReadAllText("e:Documents\Visual Studio 2013\Projects\Web\Templates\Up.txt")
Else
ctl.Text = ""
End If
End Sub
目前，我已经对 VB 的功能进行了硬编码以获取特定的 .txt 文件，如何才能从 .txt 文件的文件夹中动态更新它？
感谢您的关注。
这是一些示例代码。该演示使用UpdatePanel and a Timer每 5 秒刷新一次 DropdownList。
将新的 aspx 文件添加到您的 Web 应用程序并添加以下代码：
<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Demo.aspx.vb" Inherits="Zpk_Test2" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html dir="ltr" xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Asynchronous Update Demo</title>
</head>
<body>
<form id="form1" runat="server">
<asp:ScriptManager runat="server" ID="ScriptManager1" />
<asp:UpdatePanel runat="server" ID="UpdatePanel1">
<ContentTemplate>
<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="true" /><br />
<asp:Timer runat="server" ID="Timer1" Interval="5000" Enabled="true" />
</ContentTemplate>
<Triggers>
<asp:PostBackTrigger ControlID="DropDownList1" />
</Triggers>
</asp:UpdatePanel>
<asp:TextBox ID="TextBox1" runat="server" TextMode="MultiLine" Width="300" Height="250" />
</form>
</body>
</html>
这是背后的代码：
Partial Class Demo
Inherits System.Web.UI.Page
Private Const FolderName As String = "C:\Temp" '<-- replace with your folder name
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Not IsPostBack Then
RefreshDropDownList()
OpenSelectedFile()
End If
End Sub
Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
' this event is fired everytime a timer ticks.
' refresh your dropdown list here.
RefreshDropDownList()
End Sub
Protected Sub DropDownList1_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles DropDownList1.SelectedIndexChanged
OpenSelectedFile()
End Sub
Private Sub RefreshDropDownList()
Dim currentSelected As String = DropDownList1.SelectedValue
DropDownList1.DataSource = IO.Directory.GetFiles(FolderName, "*.txt").Select(Function(f) IO.Path.GetFileName(f)).ToList
DropDownList1.DataBind()
DropDownList1.SelectedValue = currentSelected
End Sub
Private Sub OpenSelectedFile()
Dim fileName As String = IO.Path.Combine(FolderName, DropDownList1.SelectedValue)
TextBox1.Text = IO.File.ReadAllText(fileName)
End Sub
End Class
本文内容由网友自发贡献，版权归原作者所有，本站不承担相应法律责任。如您发现有涉嫌抄袭侵权的内容，请联系:hwhale#tublm.com(使用前将#替换为@)
