Drop Down Select Index Change with Ajax Update Progress

--Update Panel with Update Progress

.aspx page

<div title="Update Panel with Update Progress">

    <asp:UpdateProgress AssociatedUpdatePanelID="upMainPracticeCountry" runat="server" ID="UpdateProgress2">

                    <ProgressTemplate>

                        <img src="images/pbar2.gif" alt="loading..." />ProgressTemplate>

     asp:UpdateProgress>

                <asp:UpdatePanel ID="upMainPracticeCountry" runat="server">

                    <Triggers>

                        <asp:AsyncPostBackTrigger ControlID="ddlPostalCountry" EventName="SelectedIndexChanged" />

                    Triggers>

                    <ContentTemplate>

                        <asp:DropDownList ID="ddlPostalCountry" runat="server" AutoPostBack="True" OnSelectedIndexChanged="ddlMainPracticeState_SelectedIndexChanged">

                        asp:DropDownList>

                    ContentTemplate>

                asp:UpdatePanel>

            <asp:UpdateProgress runat="server" ID="up2" AssociatedUpdatePanelID="upPostalCountry" DisplayAfter="2000" DynamicLayout="true">

                <ProgressTemplate>

                    <img src="images/progressbar3.gif" alt="loading..." />ProgressTemplate>

            asp:UpdateProgress>

            <asp:UpdatePanel ID="upPostalCountry" runat="server" UpdateMode="Conditional">

                <Triggers>

                    <asp:AsyncPostBackTrigger ControlID="ddlPostalCountry" EventName="SelectedIndexChanged" />

                Triggers>

                <ContentTemplate>

                    <asp:DropDownList ID="ddlPostalState" runat="server">asp:DropDownList>

                ContentTemplate>

            asp:UpdatePanel>

    div>

--Update Panel without Update Progress

<div title="Update Panel without Update Progress">

   

                <asp:UpdatePanel ID="upMainPracticeCountry" runat="server">

                   

                    <ContentTemplate>

                        <asp:DropDownList ID="ddlPostalCountry" runat="server" AutoPostBack="True" OnSelectedIndexChanged="ddlMainPracticeState_SelectedIndexChanged">

                        asp:DropDownList>

                    ContentTemplate>

                asp:UpdatePanel>

            <asp:UpdatePanel ID="upPostalCountry" runat="server">

                <ContentTemplate>

                    <asp:DropDownList ID="ddlPostalState" runat="server">asp:DropDownList>

                ContentTemplate>

            asp:UpdatePanel>

    div>

.aspx.cs page

    protected void ddlMainPracticeState_SelectedIndexChanged(object sender, EventArgs e)

    {

        //System.Threading.Thread.Sleep(3000);

        ddlPostalState.Items.Clear();

        BindState ();

    }

  protected void BindState ()

    {

        Do your code here…
    }