如何实现VB.NET DropDownList？
我正在VS2008中开发一个VB.NET ASPX文件。但是，检索所选输入参数时遇到问题。这是一个非常简单的问题。这是我目前的代码：如何实现VB.NET DropDownList？,vb.net,drop-down-menu,Vb.net,Drop Down Menu,我正在VS2008中开发一个VB.NET ASPX文件。但是，检索所选输入参数时遇到问题。这是一个非常简单的问题。这是我目前的代码： <html> <SCRIPT LANGUAGE="VB" RUNAT="Server"> Sub Page_Load(ByVal Sender As Object, ByVal E As EventArgs) If Not IsPostBack Then Ma
<html>
<SCRIPT LANGUAGE="VB" RUNAT="Server">
Sub Page_Load(ByVal Sender As Object, ByVal E As EventArgs)
If Not IsPostBack Then
Main()
Else
Main2()
If part_transfer.Value.Trim() <> "" Then
ShowChart()
Panel1.Visible = False
Panel2.Visible = True
End If
End If
End Sub
Sub Main()
'*** Query database and get arrays for the chart and bind query results to datagrid
Dim YearDate As Date = "1/1/2010"
Dim arrYear As New ArrayList()
While YearDate <= Today
arrYear.Add(YearDate.ToString("yyyy"))
YearDate = YearDate.AddYears(1)
End While
dYear.DataSource = arrYear
dYear.DataBind()
dYear.SelectedValue = Today.ToString("yyyy")
Dim ListMonth As Date = "1/1/2010"
Dim arrListMonth As New ArrayList()
While ListMonth <= "12/1/2010"
arrListMonth.Add(ListMonth.ToString("MMM"))
ListMonth = ListMonth.AddMonths(1)
End While
dEndMonth.DataSource = arrListMonth
dEndMonth.DataBind()
dEndMonth.SelectedValue = Today.ToString("MMM")
Response.Write("Main " & dEndMonth.SelectedValue & "<br>")...
End Sub
Sub Main2()
'*** Query database and get arrays for the chart and bind query results to datagrid
Dim YearDate As Date = "1/1/2010"
Dim arrYear As New ArrayList()
Dim TextSearch As String
TextSearch = dTextSearch.Text
While YearDate <= Today
arrYear.Add(YearDate.ToString("yyyy"))
YearDate = YearDate.AddYears(1)
End While
dYear.DataSource = arrYear
dYear.DataBind()
Dim ListMonth As Date = "1/1/2010"
Dim arrListMonth As New ArrayList()
While ListMonth <= "12/1/2010"
arrListMonth.Add(ListMonth.ToString("MMM"))
ListMonth = ListMonth.AddMonths(1)
End While
dEndMonth.DataSource = arrListMonth
dEndMonth.DataBind()
Response.Write("Main2 " & dEndMonth.SelectedValue & "<br>")
...
<form runat="Server" method="post" id="Form1">
<div style="font-size:18pt; font-family:verdana; font-weight:bold; color:#336699">
Parts Watch List
</div>
<br />
<br />
<table>
<tr><th>Year</th><th>Ending Month</th></tr>
<tr>
<td><ASP:DROPDOWNLIST id="dYear" runat="Server" autopostback="true" /></td>
<td><ASP:DROPDOWNLIST id="dEndMonth" runat="Server" autopostback="true" width="75"/></td>
<td><ASP:TEXTBOX id="dTextSearch" OnTextChanged="dBtn_TextChanged" columns="2" MaxLength="30" Text="" runat="Server" autopostback="true" Width="150" /></td>
<td><ASP:BUTTON id="dBtn" Text="Search" OnClick="dBtn_Click" runat="Server" autopostback="true" width="100"/></td>
</tr>
</table>
子页面加载（ByVal发送方作为对象，ByVal E作为事件参数）
如果不是的话，我会回来的
Main（）
其他的
main 2（）
如果部分_transfer.Value.Trim（）“”则
图表（）
面板1.可见=错误
Panel2.Visible=True
如果结束
如果结束
端接头
副标题（）
'***查询数据库并获取图表的数组，并将查询结果绑定到datagrid
Dim YearDate As Date=“2010年1月1日”
作为新的ArrayList（）的一年
当YearDate时，您也在Main2
（回发）中绑定DropDownList。防止触发事件并覆盖SelectedValue的
如果在重新绑定数据之前查找dEndMonth.SelectedValue
，您会发现SelectedValue
是正确的
为什么不为DropDownList的-event使用事件处理程序而不是Main2
-方法
<ASP:DropDownList id="dEndMonth" OnSelectedIndexChanged="EndMonthChanged" autopostback="true" runat="Server" width="75"/></td>
你应该对用户的行为做出反应，而不是你认为用户可以做什么，因此使用事件处理程序。非常感谢你，Tim！你的解决方案立刻对我起了作用。而且节省了我很多时间！
Protected Sub EndMonthChanged(sender as Object, e as EventArgs)
Dim dEndMonth = DirectCast(sender, DropDownList)
'get selected value etc. and DataBind it AFTERWARDS when needed or whatever...'
End Sub