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Editorial Team
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Asked: 2026-06-10T16:03:09+00:00

I have tried below code but it didn’t work: DropDownList1.SelectedIndexChanged += new EventHandler (

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I have tried below code but it didn’t work:

    DropDownList1.SelectedIndexChanged += new EventHandler ( doSub );
  1. It is in C# not VB
  2. When I type DropDownList1. intellisense doesn’t bring the SelectedIndexChanged method
  3. And last it complains about SelectedIndexChanged is an event and must be called by RaiseEvent

I’m trying to make ddls dynamically based on SelectedValue of each other, so I need to set the OnSelectedIndexChanged values programmatically instead of declarativly like this:

    <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="true" OnSelectedIndexChanged="DoSub">
    </asp:DropDownList>

Thanks in advance.

Tip: Remove the AutoEventWireup=”false” in @Page section to get solution to work.

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1 Answer

  1. Editorial Team

    Use AddHandler to attach an event handler.

    Syntax:

    AddHandler obj.EventName, AddressOf HandlerName

    Example:

    <script runat="server">
    Protected Sub Page_Load(sender As Object, e As System.EventArgs)
        AddHandler DropDownList1.SelectedIndexChanged, AddressOf DoSub
    End Sub
    Sub DoSub(sender As Object, e As System.EventArgs)
        Response.Write(DropDownList1.SelectedValue)
    End Sub
</script>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>

        <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True">
            <asp:ListItem>Foo</asp:ListItem>
            <asp:ListItem>Bar</asp:ListItem>
        </asp:DropDownList>

    </div>
    </form>
</body>
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