Panel pnlDropDownList;

protected void Page_PreInit(object sender, EventArgs e)

{

    //Create a Dynamic Panel

    pnlDropDownList = new Panel();

    pnlDropDownList.ID = "pnlDropDownList";

    pnlDropDownList.BorderWidth = 1;

    pnlDropDownList.Width = 300;

    this.form1.Controls.Add(pnlDropDownList);

    //Create a LinkDynamic Button to Add TextBoxes

    LinkButton btnAddDdl = new LinkButton();

    btnAddDdl.ID = "btnAddDdl";

    btnAddDdl.Text = "Add DropDownList";

    btnAddDdl.Click += new System.EventHandler(btnAdd_Click);

    this.form1.Controls.Add(btnAddDdl);

    //Recreate Controls

    RecreateControls("ddlDynamic", "DropDownList");

}

Private pnlDropDownList As Panel

Protected Sub Page_PreInit(ByVal sender As Object, ByVal e As EventArgs) Handles Me.PreInit   'Create a Dynamic Panel

   pnlDropDownList = New Panel()

   pnlDropDownList.ID = "pnlDropDownList"

   pnlDropDownList.BorderWidth = 1

   pnlDropDownList.Width = 300

   Me.form1.Controls.Add(pnlDropDownList)

   'Create a LinkDynamic Button to Add TextBoxes

   Dim btnAddDdl As New LinkButton()

   btnAddDdl.ID = "btnAddDdl"

   btnAddDdl.Text = "Add DropDownList"

   AddHandler btnAddDdl.Click, AddressOf btnAdd_Click

   Me.form1.Controls.Add(btnAddDdl)

   'Recreate Controls

   RecreateControls("ddlDynamic", "DropDownList")

End Sub

protected void btnAdd_Click(object sender, EventArgs e)

{

    int cnt = FindOccurence("ddlDynamic");

    CreateDropDownList("ddlDynamic-" + Convert.ToString(cnt + 1));

}

Protected Sub btnAdd_Click(ByVal sender As Object, ByVal e As EventArgs)

    Dim cnt As Integer = FindOccurence("ddlDynamic")

    CreateDropDownList("ddlDynamic-" & Convert.ToString(cnt + 1))

End Sub

private int FindOccurence(string substr)

{

    string reqstr = Request.Form.ToString();

    return ((reqstr.Length - reqstr.Replace(substr, "").Length)

                      / substr.Length);

}

Private Function FindOccurence(ByVal substr As String) As Integer

   Dim reqstr As String = Request.Form.ToString()

   Return ((reqstr.Length - reqstr.Replace(substr, "").Length) & _

                                           / substr.Length)

End Function

private void CreateDropDownList(string ID)

{

    DropDownList ddl = new DropDownList();

    ddl.ID = ID;

    ddl.Items.Add(new ListItem("--Select--", ""));

    ddl.Items.Add(new ListItem("One", "1"));

    ddl.Items.Add(new ListItem("Two", "2"));

    ddl.Items.Add(new ListItem("Three", "3"));

    ddl.AutoPostBack = true;

    ddl.SelectedIndexChanged += new EventHandler(OnSelectedIndexChanged);

    pnlDropDownList.Controls.Add(ddl);

    Literal lt = new Literal();

    lt.Text = "<br />";

    pnlDropDownList.Controls.Add(lt);

}

Private Sub CreateDropDownList(ByVal ID As String)

   Dim ddl As New DropDownList()

   ddl.ID = ID

   ddl.Items.Add(New ListItem("--Select--", ""))

   ddl.Items.Add(New ListItem("One", "1"))

   ddl.Items.Add(New ListItem("Two", "2"))

   ddl.Items.Add(New ListItem("Three", "3"))

   ddl.AutoPostBack = True

   AddHandler ddl.SelectedIndexChanged, AddressOf OnSelectedIndexChanged

   pnlDropDownList.Controls.Add(ddl)

   Dim lt As New Literal()

   lt.Text = "<br />"

   pnlDropDownList.Controls.Add(lt)

End Sub

protected void OnSelectedIndexChanged(object sender, EventArgs e)

{

    DropDownList ddl = (DropDownList)sender;

    string ID = ddl.ID;

    ClientScript.RegisterClientScriptBlock(this.GetType(), "Alert",

                 "<script type = 'text/javascript'>alert('" + ID  +

                  " fired SelectedIndexChanged event');</script>");

    //Place the functionality here

}

Protected Sub OnSelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs)

    Dim ddl As DropDownList = DirectCast(sender, DropDownList)

    Dim ID As String = ddl.ID

    'Place the functionality here

    ClientScript.RegisterClientScriptBlock(Me.GetType(), _

    "Alert", "<script type = 'text/javascript'>alert('" & ID _

    & " fired SelectedIndexChanged event');</script>")

End Sub

private void RecreateControls(string ctrlPrefix, string ctrlType)

{

    string[] ctrls = Request.Form.ToString().Split('&');

    int cnt = FindOccurence(ctrlPrefix);

    if (cnt > 0)

    {

        for (int k = 1; k <= cnt; k++)

        {

            for (int i = 0; i < ctrls.Length; i++)

            {

                if (ctrls[i].Contains(ctrlPrefix + "-" + k.ToString())

                    && !ctrls[i].Contains("EVENTTARGET"))

                {

                    string ctrlID = ctrls[i].Split('=')[0];

                    if (ctrlType == "DropDownList")

                    {

                        CreateDropDownList(ctrlID);

                    }

                    break;

                }

            }

        }

    }

}

Private Sub RecreateControls(ByVal ctrlPrefix As String, ByVal ctrlType As String)

  Dim ctrls As String() = Request.Form.ToString().Split("&"c)

  Dim cnt As Integer = FindOccurence(ctrlPrefix)

  If cnt > 0 Then

      For k As Integer = 1 To cnt

         For i As Integer = 0 To ctrls.Length - 1

             If ctrls(i).Contains((ctrlPrefix & "-") + k.ToString()) _

                  AndAlso Not ctrls(i).Contains("EVENTTARGET") Then

                 Dim ctrlID As String = ctrls(i).Split("="c)(0)

                 If ctrlType = "DropDownList" Then

                      CreateDropDownList(ctrlID)

                 End If

                 Exit For

             End If

         Next

     Next

  End If

End Sub