DropDownList SelectedIndexChanged within Gridview not firing!

Question

I have been looking for a solution to this for a while though and seen many posts that show me how to do it but yet I cannot get my SelectedIndexChanged event to fire when the DropDownList is changed.

The DropDownList AutoPostBack is set to True, i've followed code in the below post also: Link to post

Here is my code:

.ASPX

    <asp:GridView ID="gvCases" DataKeyNames="UserId" runat="server" AutoGenerateColumns="False" 
    BorderWidth="0px" CssClass="gridList" GridLines="None">
    <AlternatingRowStyle BackColor="#F7F7F7" />
    <Columns>

        <asp:BoundField DataField="id" HeaderText="Case Ref" />

        <asp:TemplateField HeaderText="Name">
            <ItemTemplate>
                <asp:Label ID="clientName" runat="server" Text="Label"></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>

        <asp:BoundField DataField="company" HeaderText="Company" />

        <asp:TemplateField HeaderText="Order Date">
            <ItemTemplate>
                <asp:Label ID="dateTime" runat="server" Text="Label"></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>

        <asp:TemplateField HeaderText="Case Owner">
            <ItemTemplate>
                <asp:DropDownList ID="iconUsers" runat="server" OnSelectedIndexChanged="iconUsers_SelectedIndexChanged">
                </asp:DropDownList>
            </ItemTemplate>
        </asp:TemplateField>

        <asp:TemplateField ShowHeader="False">
            <ItemTemplate>
                <asp:Button ID="btnDetails" runat="server" CausesValidation="False" Text="Details" />
            </ItemTemplate>
        </asp:TemplateField>

        <asp:TemplateField ShowHeader="False">
            <ItemTemplate>
                <asp:Button ID="btnSchedule" runat="server" CausesValidation="False" Text="Schedule" />
            </ItemTemplate>
        </asp:TemplateField>



    </Columns>
</asp:GridView>

.VB

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load


    If (Request.IsAuthenticated = False) Then
        Response.Redirect("~/admin/default.aspx")
    End If


    Dim keypadSQL As SqlConnection = New SqlConnection()
    keypadSQL.ConnectionString = ConfigurationManager.ConnectionStrings("connKeypad").ConnectionString()


    Dim cmdActive As SqlCommand = New SqlCommand()
    cmdActive.Connection = keypadSQL
    cmdActive.CommandText = "spCasesActive"
    cmdActive.CommandType = CommandType.StoredProcedure


    Dim daCases As SqlDataAdapter = New SqlDataAdapter
    daCases.SelectCommand = cmdActive

    Dim dsCases As DataSet = New DataSet()
    daCases.Fill(dsCases, "CaseList")

    Dim CaseTotal As Integer
    CaseTotal = dsCases.Tables(0).Rows.Count

    If CaseTotal = 1 Then
        iCaseTotal.InnerHtml = CaseTotal & " Case"
    Else
        iCaseTotal.InnerHtml = CaseTotal & " Cases"
    End If

    gvCases.DataSource = dsCases
    gvCases.DataBind()
    cmdActive.Dispose()


    If Page.IsPostBack Then

    End If

End Sub

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

    If e.Row.RowType = DataControlRowType.Header Then

        gvCases.Columns(5).ItemStyle.Width() = "60"
        gvCases.Columns(6).ItemStyle.Width() = "70"

    End If

    If e.Row.RowType = DataControlRowType.DataRow Then

        Dim rowView As DataRowView = CType(e.Row.DataItem, DataRowView)

        Dim strClientName As String
        Dim clientName As Label
        strClientName = rowView("firstname") & " " & rowView("lastname")
        clientName = CType(e.Row.FindControl("clientName"), Label)
        clientName.Text = strClientName

        Dim strDateTime As String
        Dim dateTime As Label
        strDateTime = rowView("CaseSent")
        dateTime = CType(e.Row.FindControl("dateTime"), Label)
        dateTime.Text = FormatDateTime(strDateTime, DateFormat.ShortDate) & "<br />" & FormatDateTime(strDateTime, DateFormat.ShortTime)

        gvCases.Columns(3).ItemStyle.Font.Size = 8
        gvCases.Columns(5).ControlStyle.CssClass = "btnEdit"
        gvCases.Columns(6).ControlStyle.CssClass = "btnSchedule"

        Dim intUserId As String
        intUserId = Convert.ToString(gvCases.DataKeys(e.Row.RowIndex).Value)



        Dim cmd As New SqlCommand("SELECT id, Firstname, Lastname, Firstname + ' ' + Lastname As FullName FROM [users_icon] ORDER BY Firstname, Lastname", New SqlConnection(ConfigurationManager.ConnectionStrings("connKeypad").ConnectionString()))
        cmd.Connection.Open()

        Dim ddlValues As SqlDataReader
        ddlValues = cmd.ExecuteReader()

        Dim iconUsers As DropDownList
        iconUsers = CType(e.Row.FindControl("iconUsers"), DropDownList)
        iconUsers.Style.Add("font-size", "11px")
        iconUsers.DataSource = ddlValues
        iconUsers.DataValueField = "id"
        iconUsers.DataTextField = "FullName"
        iconUsers.DataBind()

        Dim ListItem1 = New ListItem("Select Case Owner", "0")
        iconUsers.Items.Insert("0", ListItem1)
        iconUsers.AutoPostBack = True
        If IsDBNull(rowView("CaseOwner")) Then
            iconUsers.SelectedValue = 0
        Else
            iconUsers.SelectedValue = rowView("CaseOwner")
        End If

        AddHandler iconUsers.SelectedIndexChanged, AddressOf iconUsers_SelectedIndexChanged

        cmd.Connection.Close()
        cmd.Connection.Dispose()


        Dim btnDetails As Button = CType(e.Row.FindControl("btnDetails"), Button)
        btnDetails.PostBackUrl = "~/admin/detail.aspx?uid=" & intUserId

        Dim LabelAddress As Button = CType(e.Row.FindControl("btnSchedule"), Button)
        LabelAddress.PostBackUrl = "~/admin/schedule.aspx?uid=" & intUserId

    End If

End Sub

Protected Sub iconUsers_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs)

    Response.Write("Function Called")

End Sub

Thanks for any help. J.