ASP.net Dropdowlist added in runtime - event handler not getting fired

THis event does not get fired - not sure why

Protected Sub ddl_selectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs)
    Dim a As String = ""
    'this does not get fired
End Sub


<asp:GridView ID="GridViewAssignment" runat="server" BackColor="White" BorderColor="White"
                                    BorderStyle="Ridge" BorderWidth="2px" CellPadding="3" CellSpacing="1" GridLines="None"
                                    Width="100%">
                                    <RowStyle BackColor="#DEDFDE" ForeColor="Black" />
                                    <FooterStyle BackColor="#C6C3C6" ForeColor="Black" />
                                    <PagerStyle BackColor="#C6C3C6" ForeColor="Black" HorizontalAlign="Right" />
                                    <SelectedRowStyle BackColor="#86A4CA" Font-Bold="True" ForeColor="White" />
                                    <HeaderStyle BackColor="#808080" Font-Bold="True" ForeColor="#E7E7FF" />
  </asp:GridView>

Protected Sub GridViewAssignment_RowDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewRowEventArgs) Handles GridViewAssignment.RowDataBound

    Dim dateApplicationCreatedCell As TableCell = e.Row.Cells(0) 'app created on
    Dim typeOfReview As TableCell = e.Row.Cells(7) 'type
    Dim QCCell As TableCell = e.Row.Cells(8) 'qc
    Dim dateReviewAssignedCell As TableCell = e.Row.Cells(9) 'date assigned
    Dim reviewerNameCell As TableCell = e.Row.Cells(10) 'reviewer
    Dim dateReviewCompletedCell As TableCell = e.Row.Cells(11) 'date completed review

    Dim ddl As DropDownList

    If e.Row.RowIndex <> -1 Then
        If dateReviewAssignedCell.Text.Trim = "&nbsp;" Then
            dateReviewAssignedCell.Text = Now.Date
        End If


        Dim sqlCondition As String = String.Empty
        If dateReviewCompletedCell.Text.Trim = "&nbsp;" Then
            Dim nameToSelect As String

            If reviewerNameCell.Text.Trim <> "&nbsp;" Then
                Dim dateReviewAssigned As Date = dateReviewAssignedCell.Text
                Dim elapsedSinceAssigned As Long = DateDiff(DateInterval.Day, dateReviewAssigned.Date, Now.Date, Microsoft.VisualBasic.FirstDayOfWeek.Monday, FirstWeekOfYear.Jan1)
                If elapsedSinceAssigned <= 3 Then
                    dateReviewAssignedCell.BackColor = Drawing.Color.LightGreen
                ElseIf elapsedSinceAssigned > 3 And elapsedSinceAssigned <= 5 Then
                    dateReviewAssignedCell.BackColor = Drawing.Color.Yellow
                ElseIf elapsedSinceAssigned > 5 Then
                    dateReviewAssignedCell.BackColor = Drawing.Color.OrangeRed
                End If
                nameToSelect = reviewerNameCell.Text.Trim
            Else
                nameToSelect = String.Empty

            End If


            If QCCell.Text.ToLower.Contains("qc") Then
                If typeOfReview.Text.ToLower.Contains("bca") Then
                    sqlCondition = "where [QCRole_Level1] = 1 and [BCA] = 1"
                ElseIf typeOfReview.Text.ToLower.Contains("ehp") Then
                    sqlCondition = "where [QCRole_Level1] = 1 and [EHP] = 1"
                ElseIf typeOfReview.Text.ToLower.Contains("eligibility") Then
                    sqlCondition = "where [QCRole_Level1] = 1 and [ProgramEligibility] = 1"
                ElseIf typeOfReview.Text.ToLower.Contains("engineering") Then
                    sqlCondition = "where [QCRole_Level1] = 1 and [Engineering] = 1"
                End If
            ElseIf QCCell.Text.ToLower.Contains("initial") Then
                If typeOfReview.Text.ToLower.Contains("bca") Then
                    sqlCondition = "where [BCA] = 1"
                ElseIf typeOfReview.Text.ToLower.Contains("ehp") Then
                    sqlCondition = "where [EHP] = 1"
                ElseIf typeOfReview.Text.ToLower.Contains("eligibility") Then
                    sqlCondition = "where [ProgramEligibility] = 1"
                ElseIf typeOfReview.Text.ToLower.Contains("engineering") Then
                    sqlCondition = "where [Engineering] = 1"
                End If
            ElseIf QCCell.Text.ToLower.Contains("letter") Then
                sqlCondition = "where [FinalLetter] = 1"
            End If


            ddl = New DropDownList
            ddl.EnableViewState = True
            ddl.AutoPostBack = True

            AddHandler ddl.SelectedIndexChanged, AddressOf ddl_selectedIndexChanged

            ddl.Width = New Unit(110, UnitType.Pixel)
            dropDownListSelect(ddl, nameToSelect, sqlCondition)
            reviewerNameCell.Controls.Add(ddl)



        End If
    End If
End Sub

Protected Sub GridViewAssignment_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles GridViewAssignment.SelectedIndexChanged

End Sub


Protected Sub dropDownListSelect(ByVal ddlist As DropDownList, ByVal valueToSelect As String, ByVal sqlFilterString As String)

    Dim sqlQuery As String = "SELECT [ReviewerName],[Specialty],[Tiger],[Triage]" + _
    ",[ProgramEligibility],[Engineering],[BCA],[EHP],[QCRole_Level1],[QCRole_Overall]" + _
    ",[FinalLetter] FROM [SubApplicationTracker].[dbo].[ReviewerResources] " + _
    sqlFilterString + " order by ReviewerName asc"


    Dim connStr As String = System.Configuration.ConfigurationManager.ConnectionStrings("SubAppTrackerConnString").ConnectionString
    Dim sqlconnection As SqlConnection = New SqlConnection(connStr)
    sqlconnection.Open()
    Dim sqlCommand As SqlCommand = New SqlCommand(sqlQuery, sqlconnection)
    Dim dr As SqlDataReader = sqlCommand.ExecuteReader
    ddlist.Items.Clear()
    ddlist.Items.Add("")
    Do While d开发者_如何学运维r.Read

        Dim itemToAdd As New ListItem
        itemToAdd.Text = dr("ReviewerName")
        itemToAdd.Value = dr("ReviewerName")
        ddlist.Items.Add(itemToAdd)
    Loop

    'if we find no reviewer then combo should be at the blank item
    If valueToSelect = String.Empty Then
        ddlist.Items(0).Selected = True
    Else 'if we find a matching value then combo should selected at that value
        If ddlist.Items.FindByValue(valueToSelect) IsNot Nothing Then
            ddlist.Items.FindByValue(valueToSelect).Selected = True
        Else 'if we find a non empty value but it doesnt exist in the combo list then - add that item to combo list and select it
            Dim newItem As New ListItem
            newItem.Text = valueToSelect
            newItem.Value = valueToSelect
            ddlist.Items.Add(newItem)
            ddlist.Items.FindByValue(valueToSelect).Selected = True
        End If
    End If


End Sub

You need to be data binding the gridview on every postback, in order to get the event to fire?