Refresh iframe inside ajax tab container

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C#

ASP.NET

Hello,

I am working with ajaxToolkit:TabContainer. In this every tab will have one iframe inside. When navigating through the tabs its loading the pages in iframe. But on second click on that tab its not refreshing the page. Its just displaying old page. Is there any solutions to reload the page again?

<ajaxToolkit:TabContainer runat="server"
         ID="StartTabContainer"
        Height="100%"
        Width="100%"
        ActiveTabIndex="0"
        OnDemand="true"
        AutoPostBack="false"
        TabStripPlacement="Top"
        CssClass="ajax__tab_xp"
        ScrollBars="None"
        UseVerticalStripPlacement="false"
        VerticalStripWidth="30px"
        >

    <ajaxToolkit:TabPanel runat="server"
            HeaderText="Site"
            Enabled="true"
            ScrollBars="Auto"
            OnDemandMode="Once"
            ID="SiteTabId">

            <ContentTemplate>
                <uc:UCPageViewer runat="server" id="SitePageViewer" Title="Site" Src="../Pages/Site.aspx" />
            </ContentTemplate>
        </ajaxToolkit:TabPanel>
    <ajaxToolkit:TabPanel runat="server"
            HeaderText="Pipe Segment"
            Enabled="true"
            ScrollBars="Auto"
            OnDemandMode="Once"
            ID="PipeTabId"
             >

            <ContentTemplate>
                <uc:UCPageViewer runat="server" id="PipePageViewer" Title="Pipe Segment" Src="../Pages/PipeSegment.aspx" />

            </ContentTemplate>
        </ajaxToolkit:TabPanel>

UCPageViewer content:

<div>

    <iframe id="PageViewerFrame" runat="server" width="100%" height="640px">


    </iframe>
</div>

Thanks