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Editorial Team
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Asked: 2026-05-24T09:02:34+00:00

I am developing a VB.NET ASPX file in VS 2008. I am having trouble

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I am developing a VB.NET ASPX file in VS 2008. I am having trouble retrieving the selected input parameters however. This is real simple problem. Here is my current code:

<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>

…This is a really basic question. This code currently sets the dropdownlist like I want, but just doesn’t return selected month and year. How can I fix this?Note that Main2 sub is for PostBack = True.

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1 Answer

  1. Editorial Team

    You are binding the DropDownList also in Main2(in PostBack). That prevents events from being triggered and overwrites the SelectedValue.

    If you would look for dEndMonth.SelectedValue before you DataBind it again, you would see that the SelectedValue is correct.

    Why aren’t you using an event-handler for the SelectedIndexChanged-Event of the DropDownList instead of your Main2-method?

    <ASP:DropDownList id="dEndMonth" OnSelectedIndexChanged="EndMonthChanged" autopostback="true" runat="Server" width="75"/></td>

    and in codebehind:

    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

    You should react on the user’s action and not on what you think what the user could have done, therefore use event-handlers.

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